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UNIVERSITY OF HAWAII LIBRARY

OPTIMIZING FREESTYLE FLIP-TURN TECHNIQUE

A"THESIS SUBMITTED TO THE GRADUATE DIVISION OF THE UNIVERSITY OF HA WAI'! IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE

DEGREE OF

MASTER OF SCIENCE

IN

KINESIOLOGY AND LEISURE SCIENCE

DECEMBER 2005

By AmyE. Patz

Thesis Committee:

Jan Prins Coop De Renne

Paul Kingery

• We certify that we have read this thesis and that, in our opinion, it is satisfactory in scope

and quality as a thesis for the degree of Master of Science in Kinesiology.

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THESIS COMMITTEE

" . Chairperson

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Gi:d*l'~~

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Table of Contents

Acknowledgements .................................................................. iv Abstract ................................................................................. v List of Tables and Figures ............................................................ vi Chapter 1: Introduction ............................................................... 1

Statement of the Problem .... .'; ............................................. 5 Need for the Study ........................................................... 5 Operational Definitions ..................................................... , 5

Independent V ariab I es .............................................. 5 Dependent Variables ................................................ 6

Delimitations ...................................... ~ ................... : ....... 6 Limitations .................................................................... 7

Chapter 2: Review of Literature .................................................... 8 Literature Review Overview ....................................... .' ........ 8 Importance of Turns ................................................... : ..... , 8 Turning Time ........................ c ....................... , ................ 11 Push-off velocity as the Criterion Value ................... ~ .............. 12 Overview of the Phases of a Flip-Tum .................................... 14 The Approach ................................................................ 14 TbeTurn ...................................................................... 16 Push-Off ...................................................................... 16

Tuck Index .......................................................... 17 Foot Plant Position ........... : ..................................... 18 WaH Contact Time ................................................. 19

Glide ........................................................................... 23 PUll out/Initiation of Kick .................................................. 25 Review Summary ............................................................ 26

Chapter 3: Methods ................................................................... 28 Subjects ....................................................................... 28 . Subject Preparation ......................................................... 28 Protocol ....................................................................... 28 Kinematic Data Collection ................................. , ............... 29 Analysis of Data ............................................................. 29

Chapter 4: Results .................................................................... 31 Chapter 5: Discussion ................................................................ 39

Tuck Index .................................................................... 39 Foot-Plant Index ............................................................ 42 Wall Contact Time ...... ' ............. .' ...................................... 43"

Chapter 6: Practical Applications ........................................................ 44 Appendices ......................................... .' ................................... 45

Appendix A .................................................................. 45 Appendix B .................................................................. 47

References ............. , ................................................................. 48

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Acknowledgements

My most sinc~re thanks go to Dr. Prins for his initiative with this project, his

professionalism, and his encouraging "can-do" attitude. I especially appreciated his

hands-on work With the data collection, including coUntless hours spent at the aquatic .

complex'in the hot sun.

( , Without the help of Dr. Uyeno, the statistical analysis would have not been nearly as

thorough and professional. His'support in this area was invaluable. ,-,

., I'd also like to acknowledge Coach Mike Anderson, as well as the UH swimmers who

participated in the study. The project wouldn't have been possible without ilieml 1 r •.

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Coop provided constructive editing throughout the writing process. My sister Ellen

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provided valuable editing feedback from the point of view of a non-swimmer.

I'd finally like to thank Steven for encouraging me and supporting me through the final

phase of this project.

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Abstract .

The purpose ofthis study was to examine the effect of three vanables on the push-off

velocity ofthe freestyle flip-turn. These variables are: (l)The distance from the wall a

swimmer's hips are at foot contact (tu'ck index); (2) The depth of the foot plant on the , wall during push-off (fodt plant index); and c:h The jJercentage of wall-contact time

spent in an active push-off phase (%WCT active). The flip-turns of twenty-three

University (Divison I) swimmers performed at race pace were captured using underwater

videography and analyzed for kinematic data. Simultaneous regression analysis was

conducted using the push-off velocity as a dependent variable to determine the overall

predictive characteristics of the variables. The mean push-off velocity was 2.47 ms·!.

The minimum velocity ~as 1.3 ms·! and the maximum push-off velocity was 3.29 ms·!.

The mean tuck index of all turns was 0.57 +0.14, indicating that the hips were a mean

distance from the wall that was approximately 57% of the length of the swimmer' s l~gs .

The study found a significant, negative correlation between push-off velocity and tuck •

index, indicating that the more tucked position (lower tuck index) predicted higher push-, , .

off velocity. By using a curvilinear model, a tuck index of.46 was suggested to produce

the maximum push-off velocity. Neither'foot plant index nor %WCT active was found to

signifi~antly predict push-off velocity.

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List of Tables and Figures

Table "

1. Importance of Turns in Races ..... ; ................................ : .......... '10

2. Push-Off Segment of Turns ................................................... 23 I

3. Means, Maximums, Minimums for Individual Variables ................ 31 '.,

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4. Skewness and Kurtosis of Data Distribution. . . . . . .. .. . .. .... .. . .. .. . . ..... 31

5. Pearson Product Moment Correlation Matrix ................. : ............. 32

6. Full-Model Simultaneous Regression Analysis Model .................... 32

7. Results of Simultaneous Regression .......................................... 33 •

8. F-Test Full Model ............................................................... 33

9. Coefficients for Push-Off Velocity ............................................ 34.

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10. Collinearity Statistics .............................................. .' ............ 34

11: Results of Simple Regression ................................................... 34

12. Analysis Using Tuck Index as Sole Independent Variable ................. 35

'Oc 13. Coefficients for Tuck Index ................................................... 35

14. Descriptive Statistics: Centered and Squared Centered Tuck Index .... ; 36

, 15. Linear and Quadratic Models ................................................. 36

., , 16. Coefficients for Models 1 and 2 ...... : ....................................... 37

17. Results Using a Curvilinear Model ........................................... 37

Figure

1. Tuck Index and Push-Off Velocity .......................................... 36

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• Introduction

The turning techniques used in swimming competitions playa critical role in the

final outcome of the race. Turns comprise up to one'-third of the total race time in

Collegiate Short-Course events (Thayer & Hay, 1984). Due to the performance of twice ..

as many turns in short course events, the world records for short-course meter events are

considerably faster than the records for,the same distance in a long-course format.

Investigations of turris during Olympic swimming competitions demonstrate,the

importance of turns in the long course format as well. An analysis of swimmers in the

" 1992 Olympic Games has shown that the tu~ing phase of the race is strongly correlated

to swimming performance of the 100 and 200 meter Freestyle events (Arrellano, Brown,

Cappaert, & Nelson, 1994). In the 2000 Olympic Games in Sydney, Australia, the

performances of finalists and semi-fmalists' in the 200 meter events were studi~d for start

phase, velocity, stroke frequency, stroke lengths, and turns. The final event times were

related to the velocity of the second and_third length, as well as the velocities of all three

turns. The velocity of the final tum was a factor differentiating between medallists and . ,

non-medallists. (Chatard, Girold, Caudal, Cossor, & Mason, 2003)

The portion of swimming excluding the start and turns is known as "mid'pool

swimming." While mid-pilolswimming velocity is the primary determinant of race

performance at the elite level (Thayer & Hay, 1984; Mason, 1999; Thompson, Haljand,

& MacLaren, 2004), it does not necessarily indicate a similar proficiency in turning

technique (Mason & Cossor, 2000). Consequently, turns have the potential to determine

a winner among swirrn.ners with ,the same mid-pool swimming velocity.

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In recent studies, the examination of kinematic measures have included such ,

parameters. as the velocity of the swimmer when approaching the wall, the body position

at wall contact, time spent on the wall, body position upon pushing off the wall, initiation

of the kick and arm stroke, and the total time taken to complete the turn. For example,

investigation of the turns at the 2000 Olympic Games (Mason & Cossor, 2000) revealed

that the underwater phase, including the action of pushing off the wall, was the most

significant aspect of the turn performance for elite'swimmers. Consequently, analysis of

the'kinematic variables associated with the freestyle flip-turn requires the use of

underwater videography and a motion analysis system which includes pertinent software.

The push-off phase of the turn has several ~omponents, including Tuck Index,

Foot Plant Position, and Wall Contact Time (WCT). Tuck Index, described by Blanksby

in 1996, measures how close a swimmer's hips are to the wall, at the start of push-off,

• relative to leg length. Tuck index is defined as the distance of the greater trochanter of

the femur from the wall at foot contact, divided by the actual trochanteric height; a higher

number indicates straighter legs at wall contact. Analyses of freestyle and backstroke ,

turns have indicated that higher tuck;indices (straig~ter legs at wall contact) are

correlated with faster turns (Blanksby, Gathercole, & Marshall, 1996; Blanksby,

Hodgkinson, & Marshall, 1996; Blanksby, Skender, Elliott, McElroy, & Landers; 2004).

Takahashi (1983) found that peak forces were generated when the knee was flexed at'120

degrees. However, a turn performea with the legs in an excessively straight position at

wall contact (very high tuck index) would not allow the leg muscles the opportunity to

generate optimal muscular force.

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A second component of the push-off phase is the depth of fo~t plant below the

surface of the water. No research published to date has examined the effect of the foot

plant position on the ensuing push-off. The foot plant position has the potential to alter

the trajectory of the body upon push-off. Positioning the feet too high on the wall may

result in a push-off with a deep trajectory. While positioning the feet too far below the

surface may result in the swimmer surfacing too quickly. Utilizing a force platform to

study backstroke turns, BlaIlksby et al. (2004) found that a trajectory that emphasized

more vertical component during wall contact (greater peak Y forces) contributed to a

• faster tum. However, the position of the foot plant, position was not evaluated. •

If the position of the foot plant affects the resulting depth of the swimmer's . . trajectory during the streamlined glide off the wall, then it is important to know the ideal

glide depth. Utilizing an underwater towing system, Lyttle et al. (1998) measured the

drag forces present when a male swimmer was towed at several different velocities and

depths. At velocities'between 2.2 and 3.l'ms·1, the drag at the .02 meter depth was

significantly higher than that recorded at the 0.4 meter and 0.6 meter depths, where no

significant difference was found. This is a typical range of push off velocities for

experienced swimmers, as indicated by thirty experienced adult male swimmers who had.

an average push-off velocity of 2.75 ms·1 (Lyttle et a!., 1999). It has been suggested that ,

experienced swimmers perform their post -tum glides at 0.4 meters underwater to reduce

drag and reach the surface optimally. (Lyttle et al., 1998) Manipulating the foot plant

position may possibly allow swimmers to push off at the ideal depth for reducing wave

drag.

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Total wall contact time (WCT) is the third component of the push-off phase. We

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have chosen to divide the WCT into two segments, a "preparatory" segment and an

"active" segment. The preparatory segment occurs prior to forward motion, beginning

when feet make contact with the wall and ending at the moment before the hips make

their first forward displacement.

The "active" segment of WCT begins at the first forward displacement of the hips

" and ends when the feet leave the wall. In freestyle and backstroke turns, shorter overall

WCT resulted in faster turns, higher peak forces, and faster peak velocities upon push-off

(Blanksby, Gathercole, & Marshall, 1996; Blanksby, Hodgkinson, & Marshall, 1996; , 1

Blanksby et ai., 2004). The improved turns resulting from shorter wall contact times may

result from optimizing the use of stored elastic energy in the muscles. Wilson et al.

(1991) found that when a pre-stretch is followed by a large concentric muscular . .

contraction, there is maximal use of the stored elastic energy: An exponential dissipation

of the energy occurs with time, with half the stored energy lost every 0.85s. They

concluded that swimmers may use momentum into the wall to pie-stretch the leg muscles

and store elastic energy. The elastic energy could then be recovered during a sufficiently

rapid concentric push-off. (Wilson et ai., 1991)

Longer wall contact times are associated with slower turns and slower push-off •

velocities particularly if the swimmer has an extended "preparatory" segment with no

forward displacement. Conversely, a longer "active" segment of WCT is associated with . .

• • faster velocities upon push-off (Lyttle, Blanksby, Elliott, & Lloyd, 1999). Exploring the

ideal percentage of total WCT spent in the "active" phase of pushing off may help

optimize turning-technique. In Lyttle's 1999 study, the "active" push-off segment of elite

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swimmers ranged from 33% - 94% of the total WCT. Values have not yet been

determined for ideal push-off time, expressed as a percentage of overall WCT. .' '

In summary, the kinematic factors of tuck index, foot plant position, and •

percentage of wall contact time spent in the active phase are kinematic factors which

have the potential to affect the turn outcome. Since turns have been shown to be a critical"

element of race performance, these factors may ultimately influence race outcome.

Statement of the Problem

The purpose of this study is to examine the effect of three variables on the freestyle , .

flip-turn performance. More specifically, the study seeks to investigate:

a. the optimal distance from the wall a swimmer's hips should be at foot contact.

b. the depth of the foot plant on the wall during push:off for optimal results

c. the optimal percentage of wall contact time spent pushing off the wall.

Needfor the Study

Currently there are no formal recommendations for swimmers regarding the

following aspects of the flip-turn: tuck index, depth of foot plant, and the time spent in I

the "active phase" of wall contact time .

Operational Definitions

Independent Variables Measured:

.' Tuck Index: the distance of the hips from the wall at foot contact divided by the

trochanteric height.

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• Foot Plant Position: the dist~ce from the ankle to the surfac'e of the water,

divided by trochanteric height.

• Total Contact Time ofthe feet with the wall (WCT), which is subdivided into the •

following segments:

o "Preparatory" Segment: Contact time of feet with wall with no forward

displacement of the hips.

o "Active" Segment: Contact time offeet with wall while hips move

forward.

o Percentage of WCT spent in the active segment. •

Dependent Variable Measured:

• Push-off velocity: the average value taken to cover the first 60 centimeters upon

leaving the wall, as measured by displacement of the hips.

Delimitations

1. The study participants were 23 healthy volunteers ~etween the ages of 18 and 25 . .

years old. To ensure similar swimming experience level, thc"subjects were all

members of the University of Hawaii Varsity swim team.

2. There are several ways to assess ihe per~ormance of the flip-turn. Certain studies

measure round trip times, which include a set -distance (2.5 or 5 meters) before

and after the wall. In this study, flip-turns were evaluated by measuring the push-,

off velocity. Push-off velocity has been shown in the literature to correlate

negatively with 50 meter swimming times, as well as 5 and 2.5 meter round trip •

times. (Blanksby, 2004). Measuring the swimmer's velocity immediately after

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the feet leave the wall may help determine the effect of variations among trials

while minimizing confounding fact6rs.

Limitations

1. The subjects were required to make modifications to their normal turning

technique. Because the study required alterations in turning mechanics, it is

anticipated that these changes may have affected the turn performance in a

manner other than the factors studied. The major change when executing the

different turn requirements is that the swimmers may have slowed down due to

the change. in technique.

2. Using a repeated-measures design introduces the possibility that the swimmers

modified their technique based on the previous trial. They were asked to perform

one modification at a time, but each trial may have influenced subsequent trials.

3. The results of this study are limited to the subject population used .

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Review of the Literature

Literature Review Overview

Swimming turns represent an important factor in determining the results of

swimming races, and consequently, improved turning performance could lead to

improvement'in event times and race outcomes, Freestyle flip-tu~s involve multiple

factors and require complex and specific movements for optimal performance. This

review of the literature examines the importance of turns in swimming events, exami~es

the aiscussions on different ways of measuring turning performance, and looks at the

individual components of freestyle turning performance. Particular attention will be

given to the literature relating to the push-off phase of the tum, since three specific . ,

, aspects of the push-off are the focus of this study. The review will focus mainly on the

freestyle flip-tum; but relevant research pertaining to turns from other stokes will also be

included.

Importance of Turns •

Although several studies have shown that race performance is most strongly

determined by "mid-pool" or "free" swimming, the portion of swimming events that

excludes the start, turns, and finish (Mason, 1999; Thayer & Hay, 1984; Chatard et til.

2000; Thompson, Haljand, & MacLaren, 2000), the importance of turns has been noted

and analyzed for several decades. Utilizing 12 timers with stopwatches during a short-

course swimming competition, Thayer and Hay (1984) determined the percentage of race

time spent turning. For the 50 yard freestyle, 20.5% of the race was spent turning, while

for the 1000 yard freestyle, 36.5% of race time was spent in the turning phase. For all

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races of 200 yards or longer, over one-third of race time was spent turning (Thayer and

Hay, 1984).

Chow et al. (1984) used video cameras during the 1982 British Commonwealth ,

" g.Jnes to detennine if a relationship'couldbe found between turn kinematics and both

race times and finishing order. Turning times were found to correlate positively with

final event times. In accordance with results from Thayer and Hay (1984), a swimmer's

• turning proficiency was found to be progressively more important as the distance of the

event increased.

More recently, Chatard et al. (2000) compared medalists and non-medalists

among the 16 [mali.sts in the 200 meter freestyle in the 2000 Olympic Games, In addition

.. to exaininingstart time, turn time, and mid-pool swimining velocity, the researchers also

looked ~t the kinematic variables of stroke length and stroke frequency. They found the

final turn velocity was second only to mid-pool swimming velocity in importance for

winning a medal in the men's race, and that stroke length and frequency were not

significantly related to perfonnance. ,

Blanksby et al. (1996b) looked for the strongest predictor of 50 meter short-

course swimming times among Australian National freestyle finalists. Using force plates

mounted on the turning surface, researchers were able to examine kinetic variables as •

well as kinematic and anthropometric variables during three maximum effort 50 meter ,

freestyle swims. Upon analyzing the effect of 17 variables, the flip-turn, measured as 5,

meter round trip time, most str~ngiy predicted 50 meter time for females. Thi~ was not

the case for males, for whom height, mass, and impulse most strongly predicted the 50

meter time.

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Table 1. Importance of Turns in Races

AuthorfY ear Subjects Relevant Factors Studied Methods Results/Conclusions Blanksby, 10 male and 9 Wall contact time, RTf 2 video cameras, force plates, For females, 5m RTI was the Hodgkinson, female Australian (50m, 25m and 5m), strongest predictor of som et all996 National freestyle tuck index, distance-in, time. For males, 50m time best SA Journal for fmalists. velocity-in, swim predicted by height. mass, Research in Freestyle resumption dist and vel. impulse and velocity-in at Spon, PE, & Also: peak force and ; 2.5m. Recreation. impulse.

, Chatard et al. 16 finalists in Comparison of 12 video cameras In the men's 200m freestyle, 2000 200m freestyle, medalists and non- the final turn velocity was the Conference 2000 Olympic medalists for start, tum second most important factor of proceedings Games. and fmish times, the race (first was mid-pool

Freestyle velocity of each length, swimming velocity). stroke length and frequency.

Chowet al. Finalists in 19 I.Determine selected 2 video cameras located Turning times correlate 1984 individual kinematic , above and horizontal to positively with fmal event time. Journal of swimnting events characteristics of , swimmers. For the longest freestyle events, Sports in the 1982 British turning techniques;

, Vanguard Motion Analyzer exit velocity was significantly

Sciences Commonwealth 2.Detennine if there is used to analyze data. related to the event time and Games. relationship btw tum order of finishing. All4 strokes kinematics and (I) race A swimmer's turning technique

times and (2) finishing assumes a progressively greater order importance as the distance of

the event increases. Mason 16 finalists of Identify any • Pearson correlation, with Free swimming velocity related

every event of relationships the result times the dependent to race perfonnance in all Goriference 1998 World following variables variable. Doesn't necessarily events. proceedings Swimming (independent variables) imply causation. ·HiKe t!er!ormaCkJ;;: in:

Championships may have had with race Back and breast were related to All 4 strokes perfonnance (dependent both start and turn perfonnance

variable): Free swim Butterfly: tum performance velocity, start time, tum Sprint free: start time, fmish time, stroke Mid-dist free: tum length, stroke Dist free: only free swim vel. frequency, and 1M: twn perfonnance • efficiency index. Stroke length, stroke frequency,

efficiency index not significantly related to race performance except for men's lOOfree.

Mason & Top 16 fmalists at Identify characteristics Total tum time was 705m Turning phase is strongly Cossor, 2000 2000 Syduey of elite tum . RTf. related to swimming Conference Olympic Games. performance. S video cameras and split performance. Proceedings All 4 strokes times from the pool's official

timin.!!: system. Thayer & Hay, Division I men's Quantify amount of Times obtained by 12 timers % of race time somt hlmjng: 1984 swimming team total race time spent with stopwatc~es. 50 free: 20.5% Swimming All 4 strokes starting and turning. 1000 free: 365% Technique 200 breast: 39%

'. Over 113 of race time in all events of 200 yds or longer.

Thompson et A and B fmalists Evaluate the inter- S panning cameras placed Non-swinuning elements al. 2000 in men's and relationship between along the course of the pool (starts, turns, fmish) constituted

women's 100m & swimming and non- filmed each race. Digital 35% of 100m and 32.5% of Journal of 200m breaststroke swimming (starts, turns, analysis using software 200m breaststroke raceS. Sports events in 12 finish) variables and designed by one of the Strong relationships between Sciences world, national performance for researchers. mean turning time and

and international breaststroke. • finishing time in both the 100 championships. m and 200 m events, but Breaststroke strom:er for the 200 m.

RTT: round trip time (usuaJly for SOm, sin, and/or 2.Sm)

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Analyses of the finalists of all four strokes in the 1998 World Swimming

Championships revealed that turns were most important for the middle-distance freestyle, . ,

butterfly, and individual medley events (Mason, 2000). Both start and turn performance.

were most critical in backstroke and breaststroke events, but start pelformance was most

related to sprint freestyle events. In contrast to the 1984 studies by !hayer and Hay and

Cho~ et al., performance in long distance freestyle events related solely to mid-pool

swimming velocity and not significantly to turning perfo~ance. Similar to results from

Chatard et al., stroke length and stroke frequency were not significantly related to most

race performances.

In addition, a study of breaststroke finalists at several international championship

! events revealed strong relationships ,between mean turning time and finishing time in

both the' 100 meter and 200 meter events, supporting Mason's breastStroke results

(Thompson et al., 2000). A stronger relationship between turning time and finishing

time was seen in the 200 meter breaststroke, reflecting an increased proportion of the race

spent turning in the longer 200 meter event.

Turning Time .~

The lack of consistency in the methods used in measuring turning times has made

comparisons between studies difficult. Researchers have established set distances into

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and out of the wall, measuring such times as the 2.S meter round-trip time (RTT)

(Blimksby et al., 1996a; Blanksby'et al. 1996b; B1anksby et al., 1998; B1anksby et al.,

2004; Cossor et al. 1999), Smeter RTT (B1anksby et al., 1996a; B1anksby et al. 1996b;

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Blanksoy et al., 1998; Blanksby et al., 2004; Cossor, Blanksby & Elliot, 1999; Lyttle et .-•

al., 1999) and 7.5 meter RTf (Chatard et al., 2001; Lyttle & Mason, 1997, Mason &

Cossor, 2001; Thompson et aI., 2000). Thayer and Hay m~asured from 3 meters before ,

the wall and 6.5 meters after the wall for freestyle turn time, and different distance's for .. butterfly, backstroke and breaststroke (1984). The 5 meter RTf is often used as the

, . criterion value for tum time because it represents 20% of a 50 meter event, is relatively

easy to determine, and allows direct comparison to be made between swimmers. In •

addition, it is a practical measure since it is the same distance as the backstroke flags.

Additional methods have utilized significant events performed by the swimmer to

determine the turn time. Chow and Hay (1984) measured the tum time from the instant •• •

• the swimmer's forward nand entered the water during the last stroke until the swimmer •

• : completed the first stroke follow~g the tum. Another method termed "Kinex turn speed"

calculated the average speed from the submersion of the head before the wall until the

end of the first complete stroke cycle (Lyttle & Mason, 1997). These types of

measurements provide a more specific measure of. the individual's tum, since they

. elimimite the "free" swimming phase, but they make comparisons between swimmers

difficult. I

Push-off velocity as the Criterion Value

Another method of evaluating turns is by measuring the v~locity of the swimmer

after the turn. Chow et al. (1984) calculated the average speed from the push-off until the

finishing of the first stroke cycle. "Speed out" significantly correlated with both the

event time and the order of finishing, with the greater speed out correlating with reduced

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event time and higher placing. In addition Lyttle et al. (1997) measUred "glide speed,"

the average speed of the glide phase from the toe-off until the initiation of the first stroke.

More recent researchers have used "push-off velocity" to measure the average

velocity of the swimmer for 60 centimeters after the toes leave the wall. This measure

may minimize the effect of variations among trials in both the gliding position and the

initiation of the underwater kick in a repeated-measure design. It measures how

efficiently the turn is translated into velocity off the wall before kicking and stroking

commences, and therefore can more accurately reflect the effect of small changes in

push-off technique. While investigating kinetics of the freestyle push-off, Lyttle (1999) ,

used push"off velocity as the criterion variable to reduce confo~ding factors associated

with using the 5 meter RTT. He concluded that the swimmer's velocity immediately

after the fe,et leave the wall is the mo~t relevant measure to any investigation of the wall

push-off during a turn.

Blanksby et al. (2004) found that push-off velocity was second only to ",'

trochanteric height (a measure of leg length) as the best predictor of 5 meter RTT. They

also found that push-off velocity correlates negatively with 50 meter swimming times, as

well as 2.5 and 5 meter round trip times, Cossor et al. (1999) used push-off velocity to

evaluate the effect of a plyometrics training piogr~m on the freestyle turn. Significant

correlations were found between the push-off velocity and 2.5 meter RTT, 5 meter RTT,

• and 50 meter times.

While studies have shown that mid-pool swimming ,velocity is the most important

factor in race outcomes, the turns playa critical role in swimming performance.

Improvement in turning has the potential to positively affect race performance, especially • !

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at the elite level where the ability to improve performance is quite limited. Certain

aspects of turns have a more important role than others, with the push-off phase a critical ..

component. While researchers eV,aluate turns using several different criteria, measuring

the push-off velocity has been found to be the most useful method to study push-off I

technique. By eliminating the confounding factors of the streamline glide, first kick and

arm stroke, the push-off velocity provides the most specific measure of push-off

effectiveness. The next section will review the phases of the freestyle flip-tum, the ,

optimal mechanicS of each phase, and its significance for turning performance.

Overview of the Phases of a Flip-Turn

The freestyle tum can be divided into the approach, tum, push-off, glide, and pull- •

ou~ phases (~aglisco, 2003). While all segments of the tum will be addressed, special

attention will be given to the push-off phase .

Phases of the tum: 1. approach 2. tum 3. push-off

• tuck • foot plant • wall contact time (WCT)

4. glide S. pull-out and initiation of kick.

The Approach

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The approach into the tum includes the swimming, final arm stroke, and gliding

that occurs before the tum begins. A few studies have examined the kinematic factors

associated with freestyle as swimmers approach the wall to determine their significance

in the overall tum. The two parameters evaluated are "velocityCin" and "distance-in."

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, " ~easuring each swimmer's velocity at 5 meters before the wall, Blariksby et al. (l9~6b)

found tha~ velocity-in at 5 meters did not significantly correlate with the 5 meter round- •

trip time for male or female elite swimmers during three maximum effort turns. Mason

and Cossor (2000) measured the velocity-in of the top 16 finalists at the 2000 Olympic

• Games. Rather than using an instantaneous measure of,velocity, they measured the

swimmer's pre-turn velocity from a 25 meter distance before the wall until the

commencement of the turn. Total turn time was measured from 7.5 meters into and out

of the wall. They found that for men, the pre-turn velocity was not related to total turn

time during individual events. For women, pre-turn velocity was only related to total turn ,

time in the 200 meter freestyle. For both genders, it was concluded that the "out" phaSe, . •

including the push-off, was more related to total turn performance than the "in" phase.

The researchers noted that the fastest mid-pool swimmers were not necessarily the fastest

turners.

A second measure of the approach is "distance-in". While most swimmers begin

their final arm stroke 1.7 to 2.0 meters from the wall (Chow et aI., 1984), "distance-in"

typically measures when the head moves downward to initiate the turn (Blanksby et ai.,

1996b; Lyttle,"1997). Elite swimmers were found to initiate freestyle turns at slightly

less than a meter from the wall (Lyttle & Mason, 1997). Distance-in has limited value

because it does not take into account the height of the swimmer. Not surprisingly,

• Blanksby et al. (1996b) found that distance-in correlated significantly with both the

• height and tuck index of male swimmers. Tuck index measures hoi.\' close a swimmer's

hips are to the wall at foot contact relative to the individual's leg length, but is considered , -

more relevant to the push-off phase of the turn. While lack of consistency makes

15

c?mparisons between studies difficult, the approach phase has not been shown to be the

most significant aspect of the flip-turn.

The Turn •

The turning phase includes all aspects of the somersault utilized during the flip-

turn. Swimmers typically perform a small dolphin kick during the final arm stroke to

assist in pushing the hips over the water during the turn and usually maintain a tuck

• position until foot contact with the wall (Maglisco, 2003). Lyttle (1997) measured flip-

turn "rotation time" as the elapsed time from when the head submerges until the feet

touch the wall.

There are wide variations among swimmers regarding the degree of longitudinal

rotation that occurs before wall contact. According to Maglisco, swimmers should be

mostly on their backs when their feet reach the ,wall and rotate to a prone position during

the push-off and glide. In 1955 Counsilman, in contrast, reported higher passive drag

forces when rotating about the longitudimil axis than when gliding in a prone or lateral

. position (as cited in Lyttle et al., 2000). Lyttle and Mason (1997) noticed that swimmers

who tended to push off the wall on their backs had a high push-off speed (speed while

pushing off the wall) but low glide speed phase. They suspected that the nearly 1800

rotation required during the glide resulted in an increased hydrodynamic drag and lower

glide speed.

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push.Off

The underWater push-off phase has been found to be a critical aspect of

swimming turns. While analyzing the turns of the top 16 fmalists in all four strokes at the

2000 Olympic G.ames, Mason and Cossor (2000) aimed to'identify the characteristics of

elite !.,.urning performance. r; their analysis, the most significant aspect of the turn

performance was the underwater phase including the action of pushing off the wall. •

Underwater distance and time were significantly related to the total turn times. ,

According to Mason and Cossor (2000), a good underwater phase includes three

.parts: pushing off the wall effectively, maintaining good streamlining during the glide, . -. •. "

and initiating the kick at the approp?ate time. The first part, the push-off segment, has

several components. Two important factors have to do with body position at wall

contact: the amount the body is in a tuck position and the foot plant position. A third

r

component of the push-off is ~all contact time.

Tuck Index

A critical variable regarding body pOSition at foot contact is how far the swimmer

is from the wall. This has been measured in two ways: the degree of knee flexion; and

tuck index. Maglisco (2003) recommends that the legs be flexed nearly 90 degrees at the -. it'

hips and beyond 90 degrees at the knees. Takahashi (1983) determined that three highly •

trained swimmers had greater maximum knee flexion than recreational swimmers. Using

. \

an electrogoniometer, it was found that these trained swimmers ranged from 98 to 49 . , degrees of knee flexion (average 76 degrees), and that peak force was found at 120

degrees of knee flexion.

• 'I

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More recent literatUre measures tuck index, a term introduced by Blanksby to

describe the distance of the hlp from the wall at foot contact relative to leg length. Iris . ~

measured as the distance of the greater trochanter of the femur from the wall at foot

• < contact, divided by the actual trochanteric height. Trochanteric height is measured from

the floor to the "greater trochanter. A high tuck index indicates straighter legs. ,

In studies investigating the role of tuck index on freestYle and backstroke turns, a . . 4 ....

higher tuck index (straighter legs) at wall contact resulted in faster round trip times.

(B1anksby el al.. 2004; B1anksby et al., 1996a; B1anksby et al., I 996b; Cossor et aI., " , ,

" , 1999). Two possible factors explain why the higher tuck index results in faster flip !WTIs.

First, the center of mass is' farther from the wall upon foot contact. Th~s rela~es to the

distance-in measurement 'because ultimately the swimmer covers less distallce over the

course of a race. The second ~actor is that the push-off with straighter h:gs may produce

less water resistance due to the swimmer's body position. The straighter legs reduce the

form drag created by the swimnier during the pushcoff,"while legs in. a very bent position

would result in an increased cross sectional area Of the body while pushing off .

• ' The use ofthe tuck index illustrates a major difference between the somersault-

style freestyle and backstroke tUrns, and the pivot-style butterfly and breaststroke turns~

Somersault-style turns involve making a subjective determination of ideal distance from

the wall. In pivot-style turns the arms must reach the wall in order to initiate the turn, and

consequently there is no possibility of reducing the distance swum. As expected, the

degree of tuck was not significantly correlated with peak velocity 'or average velocity for

breaststroke tUrns: (B1anksby el al., 1998)

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Foot plant position •

A second component ofthe turning position is the extent to which the feet are

. l ' sUbmerged below the surface of the water upon foot contact. While no published

research to date has explored the depth o~ foot plant, a flip-tum with the feet too high on

the wall may result in a push-off that is too deep, and allowing the feet to drop lower on

the wall may result in surfacing too quickly. MagJisco (2003) recommends that feet hit

the wall at a depth of approximately 30 to 40 centimeters to ensure a horizontal push-off.

This recommendation does not take into account individual variations in torso height. ;

While studying backstroke turns, Blanksby et at: (2004) found that greater peak Y forces

contributed to a faster tum. The greater peak Y forces result from the swimmer pushing

up on the wall in an effort to maximally submerge for the backstroke strearriline.

However, position of the feet at wall contact, relative to trochanteric height has not been

evaluated in any study.

Examining how the position of the foot plant position affects the depth ofthe

J

,glide off the wall, Lyttle et at (! 998) found that gliding at a depth of 0.4 meters under the

water surface mosteffectively reduced wave drag. Foot plant position -may be a practical

tool for swimmers and coaches since planting the feet in the ideal position could "

potentially assist the swimmer in achieving the optimal glide depth. Optimal glide depth

will be discussed in further detail in the glide section.

Wall Contact Time

The time spent with the feet on the wall transitions the swimmer from the

somersault rotation to the push-off phase. The overall wall contact time (Wen can be

.<

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divided into the "preparatory" segment and the "active" segment. The preparatory

segment occurs prior to forward motion, begirui.ing when feet make contact with the wall

and ending at the moment before the hips make their first forward displacement. This

• phase includes the feet hitting the walland the eccentric contractions of the lower limbs

during any countermovement. The "active" segmeht of WeT begins at the first forward

displacement of the hips and ends when the feet leave the wall.

In both freestyle and backstroke flip turns, shorter ovenill WeT has been found to

result in faster turns and higher peak forces. In the backstroke turn analysis, reduced

WCT also resulted in faster peak exit velocities off the wall. (Takahashi eta!., 1983;

Blanksby et al., I 996a; Blanksby et al., 1996b; Blanksby et al., 2004). A similar

phenomenon has been noted in high jumpers, for whom a shorter ground contact resulted •

in improved vertical impulse and jump neight (Duda 1988; Hay, 1992; Schmidtbleicher

1988 as cited in Bobbert, Gerritsen, Litjens, and Van Soest, 1996), possibly due to

optimizing the stretch-shorten refl~x. A comparison of two subjects with almost the same

7.5 meter round-trip time (1.90 vs. 1.91 seconds) and exactly the same rotation time (.75

second) helps to illustrate the importance of the WCT. One subject had a higher

~ . approach speed while the other had a shorter WCT, higher maximum force and higher

push-off and glide speed. (Lyttle & Mason, 1997) .

An important distinction between overall weT and the "active" push-off segment

must be made. While a longer overall weT is associated with slower turns, a relatively ..

longer "active" segment is ~sociated with faster velocities upon leaving the wall (Lyttle,

Blanksby, Elliott, & Lloyd, 1999). Too Iowa percentage ofWCT spent generating the

push-off force is likely to negatively affect the push-off velocity. Exploring the ideal

20

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percentage oftcital WCT spent in the "active" phase of pus bing off may help optimize

turning technique. The "active" push-off segment of elite swimmers ranged from 33% -

94% of the total WCT (Lyttle et al., 1999). Positive correlation indicated that longer

active segments resulted in faster final push-off velocities. It was not determined whether

or not this extended active push-off segment was detrimental to the overall turn time.

One factor may expl;Un why shorter wall contact times and relatively short

"preparatory" segments produce faster peak velocities off the wall. This factor is the

stretch-shorten cycle of muscles in the lower body. Several investigators have considered , the role of the stretch-shorten cycle when considering flip-turn performance (B1~by et

, al., ,1996a; Blanksby et al., 1996b; Cossor et al., 1999; Tourney-Chollet, et aI., 2001)

Stretch-shorten cycle (SSC) activities involve an eccentric contraction followed by a

concentric contraction. Using SSC has been shown to improve performance in the

concentric phase through the storage and release of elastic energy in the tendons and

" muscles (Wilson, Elliott & Wood, 1991). The crucial contribution of the , countermovement is that it allows the muscles to build up a high level of active state and

force before the start of shortening so that they are able to produce more work over the • •

first part of their shortening distance (Bobbert M., Gerritsen K., Litjens M. &Van Soest . .

A., 1996).

The freestyle flip-turn incorporates a SSC tYpe of movement and could potentially'

derive benefits from the sto~ed elastic e";ergy. As wall contact occurs, the leg muscles

undergo ecc~ntric contraction due to the body's continuing forward momentum. Elastic

energy is stored during the eccentric phase and a portion of the stored energy could be : . .. . "

" recovered and used during ~e push-off. However in contrast to typical jumping sports,

•

21

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, the flip-turn hasa critical time element, and performing a countermovement could

potent~ally cost the swimmer valuable time.

Looking at butterfly turns can help illustrate another important concept. In an

exploratory analysis of seven e.lite swimmers,. it was found that butterfly ~ have a

longer rotation time, higher average impulse (force per unit of time), and greater peak

. force compared with freestyle turns. The researchers concluded that the optjmal

positioning before the push-off contributed to these resul.ts. Like freestyle turns, longer

time with feet on the wall led to a slower push-off speed (average velocity during the

push-off phase), as well as slower glide and shorter glide distance. (Lyttle & Mason,

1997)

The result of the butterfly and freestyle research may be explained by another

principle of the stretch-shorten cycle. Wilson et al. (1991) showed that there is an

exponential dissipation of elastic energy as a function of pause time,implying that the

• longer the delay the less performance is enhanced in the subsequent concentric

contraction. Therefore, a sse activity must be performed with a minimal delay between

the eccentric and concentric phases.

An examination of 22 butterfly swimmers at French National championships had

different results. "Push-off speed" was measured as the velocity during the fust 5 meters

after the wall, which includes both the push-off phase and a portion of the glide phase.

A significant correlation was' found between foot contact and push-off speed. In contrast • w

to Lyttle & Mason's (1997) results, the longer the duration offoot-to-wall contact, the

greater the push-off speed. Itwas suggested that sufficient contact is required for optimal

push-off. Interestingly and in support of Lyttle and Mason's results, an examination of

' .

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the 200 meter European champion revealed that he .had significantly shorter foot contact

time than the other swimmers (TournY-Ch611et, Chollet, Hogie & Papparodopoulos, __ L

2002). Table f sums up some important findirigs regarding t1ilpush~off segment of

turns.

Table 2: Push-Off Segment of Turns

AuthorlVear Subiects Relevant Factors Studied . Method. Results/CobClusioDI Lyttle et al. 30 experienced The effect ofwall push- Underwater force plate and Low peak drag force. high peak 1999 adult mal. off time, peak videogmphy propulsive force, and increased

swimmers with propulsive force. total wall push-offtime produced Journal of similar propulsive impulse, the fastest tinal push-off Applied anthropometry to peak drag f()ll;e lUld velocity.

Biomechanics elite swimmers. total Wag impulse on the velocity of .

Freestyle swimmer's eG. Mason & Top 16 fmalists at Swim turn performance 5 overhead cameras The most significant aspect of

Coss?r, 2000 2000 Olympics analyzed to identifY the AIS Biomechanics start and. the tum performance was the better characteristics of tum analysis program to underwater phase including the

Conference All 4 strokes elite performance. digitize head. Computes action of pushing offlhe wall. Proceedings swimmer's time. distance. Underwater distance and time

and velocity for push-off, were significantly related to under water, and above water total tum time. ' sub phases. Good underwater phase . includes pushing offlhe wall

effectively, maintaining good . -'streamlining during the glide, and initiating kick at appropriate time.

Tournya 22 fmalists and Butterfly turns: "Turn time" 7.5 m before and Significant correlation between Choll,t et al. semi-finalists at determine if wall after wall. foot contact time and push-off 2002 the French • contact times are related Turns videotaped by 3 above- speed for butterfly turns.

National Champs to swim speed; compare water cameras 10m and Sm Longer contact times ofthe feet Journal oJ in I99S & 1999. tum variables of before wall andjust above on the wall were associated Sports European Champion wall. with a faster push-(dl speed. Sciences Butterflv with national swimmers ~

'.' .

, Glide

In a review of the forces involved in swimming, it haS been advocated that

, swimming actions first be oriented to minimizing resistance and second to developing

" propulsive forces. Attention to the details of drag reduction is especially important at

higher speeds (Rushall, Holt, Sprigings, Cappae.rt, 1994). Lyttle et'al (1999) examined

the role of peak drag force, peak propulsive force, and wall push-off time on push-off

23 ,

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velocity, and found that the peak drag force carried the highest weighting of the three

variables. ,

While eyaluating forces in swiinming, frictional, form, and wave drag can be ,.

considered .. Frictional drag is developed when water pa,sses over a rough'surface

(Rushall et ai., 1994). Skin roughness,"hair and swimsuit fabric are examples of the . . . ' roughness that creates friction as a swimmer moves through the water. The relationship

,?ffrictional drag to velocity is linear, and frictional drag can be reduced by shaving body

hair~wearing a bathing cap, and using a tight swim suit with modern fabrics (Rushall et

ai., 1994). ,.

Form drag is caused by the shape of the swinuner, with the largest factor being . ,

cross-sectional area (frontal resistance) .?fthe body. Form drag incriases by the square of

the ,velocity and has an increasingly important role the faster a swimmer tra'vels (Rushall

et ai., 1994). Form drag c~ be disadvantageous when the swimmer's position in·the

water is not fully streamlined and the iricorrect swimming alignment produces extra

resistance (Rushall et ai., 1994). A towing syst~m was utilized in an attempt to establish

• the most efficient gliding position and kicking technique for the reduction of form drag

among male swinuners. At typical swimming speeds, no significant difference was

found between the.prone fre~style kick, prone dolphin kick, or lateral doll'hin kick. ~.n

addition, no significant difference was found between the prone and lateral streamline

glide at any velocity (Lyttle et al., 2000). .' Wave drag occurs when a swimmer creates waves, wakes and turbulence. Since

waves carry energy, a swimmer's energy that could be applied to productive force is lost

by unnecessary wave production. According to Rushall (1994), body position can

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contribute to wave drag by increasing turbulence ("eddy resistance"),_ and exaggerated

vertical or lateral movements also contribute to wave drag. Wave drag is the most costly ..

form of drag for fast swimmers because it is reported to increase as the cube of

swimming velocity (Rushall et a/., 1994).

Wave drag is also affected by the depth of the swimmer below the surface of the

• water. A swimming flume was used to determine the passive drag of female swimmers

in a prone streamline position at both the water surface and 0.5 meters underwater

(Maiello, Sabatini, Demarie, Sardella & Del Monte, 1998, as cited in Lyttle, 2000).

Lower passive drag values'were reported at two different velocities (i~76 ms·1 and 1.91

ms·l) d::mng the 0.5 meter ~def\vater compared with the surface meilsuremen~. As

towing velocities increased, th~ passive drag force increased by 23% on the surface and

17% underwater. The results of the study suggest that gliding at 0.5 meters underwater is

more economical than gliding at the water surface ~ue to reduced passive drag force.

A very thorough investigation of glide depth was performed by Lyttle et aI.

(1998). They utilized a motorized winch and pulley system to tow male swimmers of

similar body shape in a streamlined position at predetermined depths and velocities. A

load cell was used to measure drag at the surface, 0.2, 0.4, and 0.6 meters deep, and at

several different velocities: For all velocities, drag was highest at the surface. At

velocities between 2.2 and 3Jms·l, the drag at the 0.2 meters depth was significantly'

higher than that recorded at the 0.4 and 0.6 meter depths, where no significant difference

was found. Since experienced swimmers push off at this range of velocities, it was

'suggested that swimmers should perform theirpost-turn glides at 0.4 metersundeiwater

to gain maximum drag reduction.

25

Pull outlinitiation of kick I

Lyttle et al. (2000) attempted to establish the appropriate velocity for initiating

the underwater kick. 16 male experienced swimmerswere towed at a depth of 0.5 meters

underwater at five different velocities. At each velocity, the s~bjects performed a prone

streamline glide, a lateral streamline glide, prone freestyle kick, prone dolphin kick, and

lateral dolphin kick. All kicking trials were performed at maximal effort. Net force was

recorded using a uni-directionalload cell. During kicking, net force represented the total

propulsive force produced by kicking minus the active drag fo~ce resisting towing.

During the streamline glide trials; the'net force consisted' solely of the negative passive

drag forces. At 3,1 ms·], the prone streamline position demonstrated significantly lower

net forces than kicking positions which indicate that kicking at this velo~ity would be

detrimental to the swimmer. At 2.2 ms·], the prone streamline position was not

, significantly differentfr?m the kicking conditions, indicating that there is no advantage

for the swimmers iIi kicking at this velocity. At some point, the swimmer creates more •

propulsive force while kicking than the active drag force created by deviating from the

streamline glide position. From these results, the researchers concluded that swimmers

should start underwater kicking velocities of 1.9 ms·1 and 2.2 ms·] off the wall.

Review Summary

The swimming turn is a critical aspect of swimming performance and holds the

potential for improved times a(alileveis of competition. Among the severalco~ponents

of the freestyle flip-turn, the push-off phase ~s been shown to play an important role in

26

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overall turlling performance. The push-off phase involves both reducing drag and

creating propulsion, with drag reduction the more important aspect. . There are several , ... ways to evaluate turns. Many studies have measured round-trip times at either 5 meters

or"2.5 meters into and out ofthe"wall. When assessing the push-off phase of turns, ~ .

~easuring the resulting push-off velocity. is most appropriate since it minimizes the

~ J-

confounding factors of the streamline position and initiation of the kick and stroke.

Three components of the push-off phase will be examined in this study.

(1) Tuck index, which indicates how close a swimmer's hips are to the wall prior -!!-' •

to push-off, lias been shown to affect turning performance. However, no study has yet •

identified the upper limit of the benefits associated with straight legs,

(2) The depth of the foot plant is another important component of the push-off,

since it affects the resUlting glide~fter the push-off. The optimal depth for the glide has

been reported to be at a depth of 0.4 meters below the surface of the' water. Although the

t depth of foot plant has not yet been studied, it has the potential to link the research done

on optimal depth with practical advice for swimmers and coaches.

(3) Wall contact time is the third component of the push-off that will be examined

in this study. While a shorter overall ~all contact time has been shown to correlate with

faster turning times, a relatively longer propulsive segment ("active" phase) of the wall

contact has been shown to positively affect velocity upon push-off. One aim of this

investigation is to examine the percentage ofWCT spent in the active phase and

'determine how this relates to the factors of tuck index and foot plant position.

27

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Methods

Subjects

Twenty three members of a Division I swim team participated as subjects for the

study. Twelve were male and eleven were female, ranging in age from 19 to 25. The

study was approved by the University Institutional Review Board for the Study of Human

Subjects. Each subject was required to sign a written informed consent form prior to

testing.

Subject Preparation

Prior to video taping the pertinent joints on each subject were marked 'using Duct

tape. Trochanteric height was measured using a stedometer (Seca, Country Technology

Inc/Gays Mills, WI, Model # 67032), with trochanteric height measured from the ground , .'

to the superior border of the greater trochanter of the femur. (Blanks by, Gathercole, &

.Marshall, 1996).

Protocol .J

For the purpose of data collection, each subject was required to perform eleven trials,

• each' consisting of a 50 yard freestyle swim over a 25 yard course. Each trial took place

within a time interval of 1 minute and 30 seconds. Subjects were instructed to perform

, the flip tum at race pace, swimming at maximum speed for 5 meters before and after the

• flip tum. Theremaining 40 yards were swum at a moderate pace. The rest interval

provided adequate recovery and promoted a maximum effort on each tum. The swimmer

,. was asked to perform the turns in the following manner:

28

1. Turns 1 and 2: the swimmer's usual turning technique.

2. Turns 3 and 4: hips too far from the wall .

• ' 3. Turns 5 and 6: hips too close to the wall.

4. TUrns 7 and 8: foot plant too high on the wall

5. Turns 9 and 10: foot plant too low on the wall

6. Turn 11: usual turning technique.

After each turn, swimmers were asked to ev~luate their turn using a self-rating scale.

Kinematic Data Collection

Video images of the turns were recorded by a digital video camera (Sony !R950)

" placed in a custom-designed underwater housing. The camera was at a depth of half a

meter, and located 2 meters from the end of the pool and 7 meters lateral to the turning . surface. A four-point calibration rod was used as a scaling factor for the kinematic

analysis. ,2D analyses in the saggital plane were made l!sing motion analysis software

(Motus, ViconIPEAK Performance Systems, Denver, CO).

Analysis of Data

The push-off, velocity has been chosen as the criterion measure of the push-off

performance. Independent variables include:

1. tuck index <

2. foot plant position

3. percentage of-WCT spent in the "active" segment of the push-off phase.

,

29

The purpose of this study was to examine th~ effect of these three variables on push-

, off velocity. The initial objective was to analyze 115 flip-turns, since 23 swimmers each

performed five different types ofturns (normal, high, low, close, far). For each swimmer,

the most representative turn from each category was chosen for analysis. If the swimmer

was not able to achieve the desired tum, then the turn was eliminated from analysis. Six

swimmers were unable to achieve a tum where the feet were planted either "too low" or

"too high." Each of these turns was eliminated because the feet were not planted lower •

or higher than the swimmer's "normal" turn. As a result, a total of 109 turns were •

selected, digitized, and analyzed. The dependent and independent variables for each of

these turns was calculated using Microsoft Excel (Microsoft Corporation, Redmond,

W A) and 'chosen for statistical analysis.

. . 1. A Pearson correlation coefficient matrix was constructed to identify the

relationship between variables.

2. Independent variables were checked for collinearity.

3. A full-model simultaneous regression analysis was conducted using the push-off

• velocity as a dependent variable to determine the overall predictive characteristics

of the variables.

4. The scatterplots were analyzed for the possibility that a curvilinear eq~ation be

used to calculate the line of best fit.

All statistical procedures were performed on the SPSS software package version 12

(SPSS Inc., Chicago, IL).

30

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Results

Following the statistical analysis, the means, maximum and minimum values, and

standard deviations for all variables are reported in Table 3. The mean push-off velocity

was 2.47 ±.40 ms· l. The mini!llum velocity was 1.3 ms· l and the maximum push-off

velocity was 3.29 ms· l .• The mean tuck ind:x was 0.57 ± 0.14. The mean foot plant

index was 0.45 ± 0.10. The mean percentage of the wall contact spent in the "active"

push-off phase was 74.31 %. The minimum percentage was 35%, and the maximum was

95%.

Table 3: Means, maximums, minimums, and standard'deviations for individual variables." .

N Minimum Maximum Mean Std. Siatistic Statistic Statistic Siatistic Siatistic

Push:Off Velocity (ms") 109 1.3 . 3.29 2.4749 0.40294 Tuck Index 109 0.23 0.89 0.5718 0.14236

Foot Plant Index 109 0.274 , 0.812 0.45082 0.100524 % WCT Active 109 35 95 74.31 11.578

Valid N (listwise) 109

The distribution of data was checked for skewness and kurtosis, and appears to be

within normal ranges (Table 4).

Table 4: Skewness and kurtosis of data distribution

. Skewness . Kurtosis. -

Statistic Std. Error Statistic Std. Error Push-Off Velocity (ms') -0.355 0.231 0.546 0.459 Tuck Index 0.238 0.231 . -0.392 0.459 Foot Plant Index 0.682 0.23\ 0.953 0.459 %WCTActive -0.888 0.231 1.394 0.459 Valid N (Iistwise)

A correlation matrix was established to investigate the strength of the bivariate

• l. association between the variables (Table 5). A significant, neg~tive correlation was

31

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found between push-off velocity imd tuck index. No significant correlations existed

between P?sh-off velocity and foot-plant index and between push-off velocity and

• % WCT Active. The possibility of correlations between each independent variable was

~ , examined, and they were not found to be significantly correlated with each other.

Table'S: Pea~on Product Moment Correlation matrix determining strength of relationship between. variables.

. . Foot - Push-Off Tuck Plant %WCT . Velocity Index Index Active

Pearson Correlation Push-Off Velocity 1.000 -All * -0.142 0.211 Tuck Index 1.000 0.185 -0.393 Foot Plant Index 1.000 0.119 . % WCT Active 1.000 ..

*Slgmflcant at the ~0.05 level. .

• A full-model simultaneous regression analysis was then conducted using the

push-off velocity as a dependent variable to determine the overall predictive

Table 6: Full-model simultaneous regression analysis model

Vatiables EnteredlRemove<P

Variables Variables Model Entered Removed Method 1 %WCT

Active, Fool Enter Piant Inde><:. Tucl! Index

O. All requested vanables entered.

b. Dependent Variable: pusn·OffVelo<:ity

characteristics of the variables (Table 6). Results of the simultaneous regression

(Table 7) indicate that these independent variables predicted approximately 18% of the

variance (R2 = .178).

32

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Table 7: Model summary; results of sim~ltaneous regression •

Adjusted R Std. Error of Model R RSquare Square the Estimate 1 .422" .178 .155 . . a. PredIctors: (Constant), % WCT ActIve, Foot Plant Index, Tuck Index

The results in Table 8 indicate that the full model accounts for a significant

amount of variance in push-off velocity (F=7 .597, P$O.05). '.

Table 8: F-test of full model

Sum of Model Squares df Mean SQuare 1 Regretsion 3.127 3 1.042

Residual 14.406 105 .137 Total 17.535 106

•. PredIctors: (Constant), % WCT Active. Foot Plant Index, Tuck Index

b. Depend,,", Variable: Push-OffVeloeily

F SiQ. 7.597 .000'

.37043

In summary, the significance of the F-value indicates that this statistical model

works; the R2 demonstrates that 18% of the variation is expla~ed. Next, the contribution

of each independent variable will be examined.

Table 9 provides information on the individual predictor variables in the full

model. Based on the raw regression coefficients, we can derive the following equation

for predicting push-off velocity:

POV';; 3.017 + (-1.033)(tuck index) - (.338)(foot plant index) + (.003)(%WCT Active~:

,However, tuck index has been found to be the only significant predictor of push-off

velocity at the p~O.05Ievel, as indicated by the value oft = -3.669. The other

independent variables (foot-plant inuex and%WCT Active) did not significantly predict . push-off velocity.

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Table 9. Coefficients for push·otT velocity

UMtandardized Standardized . CoefficlentB Coefflclents 95% Confidence Intefvalfor B ,

Model B Std. Error Bela t SKI. lowerBoond UooerBound , (Constant) '.017 _351 6.602 .000 2.322 3.713 Tuck Index .1.033 .282 ·.365 -3.669 ,1lOO ~1.591 -.475 Foot Plant Index ·.338 .369 ·.084 ·..915 .362 ., .070 .394 % weT Active .003 .003 .076 ]88 .433 -.004 .009

"

The predictors were checked for problems related to collinearity, According to

the standard that VIF ~ 10 indicates serious multicollinearity (Cohen, Cohen, West,

Aiken, 2003), the results indicated that there is not a problem with correhition among the

predictors.

Table 10. CoIlinearity statistics

. coirelations Collinearit Slati;tics

Model Zero-order Partial Part ToJerance VIF 1 (Constant)

Tuck Index ·.411 -.337 -.325 .791 1.264 Foot Plant Index ·.142 -.089 -.081 .922 1.084 %WCTAdive .211 ,011 .070 .807 1.239

a. Dependent Vanable: Push-OffVelocily

, , Since ~eithedoot-plant index nor %WCT Active was significant, the tuck index

was rerun as the sole predictor of push-off velocity in a simple regression. Results of the

simple regression (Table 11) indicate that tuck index predicted approxi~ately 17% of the

variance (R2 '" .169). Approximately 17% of the variance in the dependent variable can

be accounted for by tuck index alone.

Table 11. Results of the simple regression using tuck index as the sole independent variable' . -

ModeISlI11mary

a. Predictors: (Constant), Tuck

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The results in Table 12 indicate that the model using only tuck index' accounts for

a significant amount of variance in push-off velocity (F=21.745, p~O.05).

Table 12: Analysis of variance accounting for change in push-off velocity using tuck index as the sole independent variable

AJroVAD

Sumaf Model <If Mean Square 'F Sia. I ",,_on 2.962 1 2962 21.745 .000"

Residuol 14.573 107 .136 Toial 17.535 108

•. Predictln; (Constant), Tuck Index b. Oepe<_tlVari8IlIe: Push--OffVetoci\y

Using the coefficient -1.163 for tuck'index (Table 13), the resulting linear

relationihip can be written ~s: POV= 2.475 -1.163(tuck index).

Table 13: Coefficients for tuck index

Unstandardized StandaJdiZed CoeIIi<:iems Coefliciems

Model B SId. EJror Bela t Sig. 1 3.140 .147 21.368 .000

Tuck Index . -1.163 .249 • .• 11 -".663 .000

Logic suggests that the relationship between tuck and push-off velocity may be

curvilinear. That is, there may be an optimal range of tuck index for maximizing push-

off velocity, and indexes below and above that range will result in lower velocities. This

relationship was tested using the following quadratic model:

POV = bltuck index) + b2(tuck inde~) + a. .

Descriptive statistics of the centered and the squared center tuck index are ~ -i

indicated in Table 14. Figure 1 shows the data scatterplofwith both linear and quadratic

equations used for regression.

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Table 14. Descriptive statistics: centered and squared center~ tuck index

Mean Std. Deviation N Push-Off Velocity 2.4749 .40294 109 Centered Tuck Index .00000 .14236 109 Squared Centered .0201 .02529 109 Tuck Index

. Figure 1. Tuck index and push-otT velocity

0 0 0 0 0

0 0 0

0 8 3.00 00 0 0 0° 0 is' 0

~86>0 000 0

~ o 0 0_ o If' 0 0 0 0

~ ,.sa -0 'b ocg .0 0 0 0

~ 0 0' ~ 0

~ 0 0 0> 00

0 0 .c .. 0 ~ '.00 0 0

0 0 0 0

0 0

HiD A SqQu-*'Wc -00''iNI

0

0 RSqLNat-O.1et

0 •

020 030 0.-40 0.'" o.eo 0.10 oso 0"

Tuck In<flx

In order to see if using the quadratic equation helps to predict push-off, the original

~odel is entered first, followed by the model using the quadratic equation (Table 15) .

• Table 15. Variables enteredlremovedb

; linear (1) and quadratic (2) models

Model Variables Variables Method Entered Removed • .

1 Centered Tuck . Enter, Index· • .

2 Squared . Enter Centered Tuck Index .

a. All requested variables entered. b. Dependent Variable: Push-Off Velocity

•

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The coe.fficients for both models are shown in Table 16. Based on the regression -. coefficients, we can derive the following quadratic equation for predicting push-off

velocity: POV = -1.074(tuck index) - 2.682(tuck inde~) + 2.529

Table 16. Coefficients for models 1 and 2 ~ ~

Unstandardized Standardized Coefficients Coefficients

Std. -Model B Error Beta t Sig.

1 (Constant) • 2.475 .035 70.013 '.000 Centered Tuck Index '1~163 ~249 .~ ~ -.411 -4.663 .000

2 (Constant) 2.529 0.045 56.204 .000 Centered ,Tuck

'''.4.281 Index ·1.074 .251 ·~379 .000 Squared Centered -2.682 1.412 -.168 -1.899 .060 Tuck Index • .

Results indicate (Table 17) that using the quadratic equation allows for the explanation'

Table 17. Results using a Curvilinear Model .

Change Statistics

Adjusied Std. Error of R R R the Square F Sig. F

Model R Square Square Estimate Change Change df1 df2 Change

1 .411" ~169 ~ 161 .36905 ~ 169 21 ~745 1 107 .000

2 .443" ~ .196 ~ 181 ~36464 .027 3.606 1 106 .060

of 19.6% of the variance in push-off velocity, versus 16.9% when using a linear equati~n.

However, using the quadratic equation does not improve the push·off velocity prediction

at the p~0.05 level.

Using the following model (Cohen et aI., 2003), an optimal tuck index can be

suggested for generating ,maximum push·off velocity: Xm = -b 1/2b2• The following

. ~

equation is used: Xm = 1.074/·5.364 = -.2, indicating that a mean x of ·.2 would generate

" the maximum push-off. Since the tuck index was centered for use in the quadratic

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equation, .26 needs to be ,added to the mean value. The resulting figure of .46 can be

suggested to produce the maximum push-off velocity .

•

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Discussion 1 .•

The purpose of this study was to examine the effect cif three different variables on

push-off velocity. The mean push-off velocity for all turns analyzed was 2.47 ±.40 ms'!.

The minimum velocity was l.3 ms'! and the maximum push-off velocity was 3.29 ms· l.

The swimmers were asked to provide feedback after every turn regarding their

positioning on the wall. For only six swimmers, the fastest push-off velocity was

,!chieved after a turn rated "normal." For nine swimmers, the fastest push-off velocity . was achieved during a turn rated "too close." Three swimmers each achieved the highest . ,

velocity during a turn rated "too far" and "too high." Two achieved peak push·off

velocity after a turn rated "too low." The mean velocity of all "normal" turns was 2.?6

ms· l, slightly fasterthan the mean velocity of all turns. . .

When Lyttle (1999) measured the push-off velocity of30 experienced male

swimmers with a mean age of 19.8, the mean push-off velocity was 2.75 ± .25 ms· l. The

, mean push-off velocity for males in the present study was 2.69 ± .34.· Other studies

which measured push-off velocity were conducted on children. Th~ mean push-off

velocities of trained young swimmers aged 10 to 14 years old were found to be 1.14 ms'!

(Cossor, 1999). StUdying the same age group, Blanskby (2004) found the mean push-off

velocity during backstroke turns to be 1.7 ms .1. The slow~st push-off velocity recorded

in this present study (l.3rns·l ) fell within the range of trained children.

Tuck Index

Tuck index is the ratio measurement used to indicate how close a swimmer is to

the wall.' A higher tuck index indicates straighter legs. In the present study, the mean

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-tuck index of all turns was 0.57 ± 0.14, indicating that~he hips were a mean distance

from the wall that was approximately 57% of the length of the swimmer's.Jegs. For the

, ~, . 23 turns that the swimmers rated as "normal," the average tuck index was also 0.57.

The tuck index of elite freeStyle swimmers with a mean age of 20.1 for males and

15.6 for females wascexamined by Blanksby (l996b). All were Australian national

finalists' in freestyle events. The mean tUck index was 0.65, indicating that these elite • ..

• swimmers had straighter legs than the swimmers in the present study.

Tuck index was measured on trained childr~n aged 10 to 14 years old in three

separate studies. Mean tuck index for freestyle tUrns waS 0.65 (<:;ossor, 1999). and 0.566

(Blanksby, 1996a), and 0.6 for backstroke turns (Blanksby, 2004).

,,' Tuck index was the only significant predictor of push-off velocity in the present

study. Tuck index was negatively correhited with push-off velocity. indicating tliat the

more tucked position (lower tuck index) predicted higher push-off velocity. This result

appears to contrast with two studies of tuck index, which indicate that a higher tuck index

results in a faster turn. (Blanksby et al:, 2004; Blanksby et ai" I 996a; Blanksby et aI.,

1996b; Cossor et al., 1999) .• However, all of these studies measured round-trip time

(either 2.5 or 5 mJrom the wall) as the dependent variable. I? these caSes, the round trip

time is shorter, possibly due to the center of mass being further from the wall upon foot

contact.. These studies did not look at the velocity upon push-off or at certain distances

after push-off.

While no research to date' has explored the curvilinear relationship between tuck

index and push-off velocity. the relationship is a logical one. Performing a flip-turn with

40

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'j

the hips either extremely close to the wall or in an excessively straight position would not

allow the leg muscles the opportunity to generate optimal muscular force. '"" ,

This concept was illustrated by Linthome (2000), who examined optimal take-off

range in vertical jumping by having track athletes perform squat jiimps and

countermovement jumps using a force platform. Trained swimmers perform their flip-

turns with very little coUntermovement, so it may be more appropriate to examine squat

jump rather than countermovement jumps when making comparisons between jumping "

and flip-turns.

When the track athletes began squat jumps from the deepest squat positions (-0.5

to -0.6 m vertical position from stahding), these jumps had a "two"phase" vertical force

~ profile and they generated approximately 30% less vertical ground reaction force when

compared to more moderate veT!ical starting positions (-.2 to -.25 m). It was speculated ,

that the reduced force production resulted from the sharp decrease i? knee extensor

strength in a deep squat, due to compromised force-length, force-velocity, and moment. . ' arm relations of the many muscles in the lower body. Squat jumps performed with'legs

close to full extension (-~012 m vertical position from standing) prodU:c~d ~pproximately 'I ,.J

25% less vertical ground'reaction force than those with the more optimal starting

"" position. (Linthome, 2000) While these numbers do not take into account possible

variations in leg length, they provide general support for the concept that the relationship

between tuck index and push-off velocity may be a curvilinear one. , *

, , Using a quadratic equation for the regression suggested an optimal tuck index of

.46. At this tuck index, the swimmer's hips are a distance from the wall approximately I

46% of the leg length.' It is important to note that both methods of evalUating flip-turn ..

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perfonnance have their weaknesses .. When using either round-trip' time, the important

factor <!f velocity upon push-off is eliminated. When using push-off velocity, the overall

time it takes to perfonn the turn is not taken into account. As a result, the optimal tuck

index value of .46 is specifically for optimizing push-off velocity, and may not result in '. .

an optimal round-trip time.

Foot-Plant Index'

Foot plant index w~s developed by Dr. Jan Prins in 2004 specifically for this

study. It is a way to measure the distance of the feet from the water's surface while

taking into account the le!lgth of the swinuner's leg. A higher number for foot plant

index indicates a deeper foot plant. The mean foot plant index in the present study was

0.45 ± 0.10, indicating that the mean foot plant was approximately 45% of the swinuners'

leg length below the water. When only the swinuners' "nonnal" turns were taken into

account, the mean foot plant was 0.46. There was not a significant relationship between ,

foot plant index and push-off velocity. No other research has been conducted to date

examining the depth of foot plant and possible implications for flip-turn perfonnance .

Lyttle (1998) found that gliding at a depth of 0.4 meters under the water surface most

effectively reduced wave drag. Thirty-three of the 109 tufns.in the present study resulted

in glides·that were perfonned above the 0.40 meter optimal depth, indicating a turn that

results in a glide that is too s,haIlow. Of those 33, 6 were rated "nc:)nnal" while 10 were

rated as feet positioned "too low." While no significant relatio~ship was found between

foot plant index and push-off velocity, further examination of the present data could

examine tlie link between foot plant index and push-off depth. An analysis examining

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the relationship between foot-plant index (independent variable) and push"off depth

(dependent variable) might provide insight into optimal foot-plant index for achieving the

0.4 m - 0.6m depth range upon push-off.

Wall Contact Time

The mean WCT of turns rated "normal" was .2817 seconds. ,The WCT of all

-swims was 0.31367. This wall contact time,is among the shortest of those who have been

" studied.

Table 18. Comparisons of mean waif contact times among normal freestyle turns

Stud lY S b' t P I ti U )leC ODU a on. T IWCT ota Current Study 23 Division I Collegiate Swimmers 0.28 -(2005) Lyttle and Mason 3 International-Level males 0.29 . (1997) Lyttle et al. 30 experienced male adult swimmers 0.32 (1999) • •

. Blanksby et al. 36 competitive age group swimmers (19 0.58 (1996a) female, 17 male) ,

.. . The mean percentage of the wall contact spent in the "active" push-off phase was

74.31 %. The minimum percentage was 35%, and the maximum was 95%. For turns that

were rated "normal" by the swimmers, the percent "active" jumped to 78.21 %.

Surprisingly, Lyttle 1999 found that the active push-off segment of elite swimmers

ranged from 33% to 94% of the total WCT. Mean was 67.5% ± 15.2%. In that study,

positive correlations indicated that longer active segments resulted in faster final push-off

velocities. In the present study, no significant relationship was found between % WCT

active and push-off velocity.

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Practical Applications and Future Research

The purpose of this study was to examine the effeCt of three variables on the

push-off velocity of the free~tyle flip-turn. In this study, no signi~,cant relationships we.re

found between push-off velocity and neither foot-plant index nor % WCT active. While

no significant relationship was found between foot plant index and push-off velocity,

further examination of the present data could examine the lifik between foot plant index

and push-off depth.

. . A significant, negative correI~tion was found betweenyush-offvelocity and tuck

index, indicating that the more tucked position (lower tuck index) predicted higher push-

off velocity. By using a curvilinear model, a tuck index of .46 was suggested to produce

the maximum push-offvelocitY~ At this tuck index, the swimmer's hips are a distance ,

from the wall approximately 46% of the leg length. It is important to note that using

push-off velocity as the dependent variable may have yielded different results thail using

a measure that includes an element of time for performing the entire turn, such as 2.5 or 5

meter round-trip time. When using push-off velocity, the overall time it takes to perform

the tum is not taken into account. As 'a result, the optimal tuck index value of .46 is

• specifically for optimizing push-off velocity, and may not result in an optimal round-trip

"

time. Researchers in the future may want to conduct a more complex analysis that

compares results using both push-off velocity and a timed round-trip distanc~.

In this study, Motus, ViconIPEAK Performance Systems (Denver, CO) was used

for data analysis. This system allowed for precise analysis of the kinematic aspects

freestyle flip-tum. In future studies of swimming kinematics, such sophisticated motion

analysis software should be used to maximize acc.uracy an~ precision.

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•

Appendix A: Consent Form

'. AGREEMENT TO PARTICIPATE IN

A Kinematic Analysis of the Freestyle Flip-Turn

AmyPatz Graduate Student

University of Hawaii, Department of Kinesiology and Leisure Science 1337 Lower Campus Road, PEIA Complex, Room 223

Honolulu, Hawaii 96822 808-741-0326 or 808-956-7421

'\

1) Description

The purpose of this research study is to investigate the kinematics of the flip-turn push­off during freestyle swimming via high speed video analysis. The principle investigator is a graduate student pursuing a Master's degree in Kinesiology and Leisure Science (KLS). The turning phase of comprises approximately one-third of the total race time in swimming events and a relationship has been observed between turri performance and " final event time. The push-off phase is pne of the most significant aspects of turn performance. To date, no research has been conducted on the effect of foot-plant position and hip and knee flexion on the swimmer's velocity after the push-off. You will be asked to perform 12 freestyle flip-turns while an underwater camera is used to capture digital images of your turns. During several turns, you may be asked to make slight changes your turning technique. You may be asked to return for one or two additional video data collection sessions, with at least one week between sessions.

2) Procedures

Calibratiou a'ud measurement. Before beginning flip-turns, you will be asked to position yourself in the pool next to our calibration and measurement frame while the underwater camera is used to capture the video. This will take less than five minutes and it allows us to determine distance during our analysis of the video.

Flip-turn performance. You will be asked to perform 12 flip-turns while video data are collected. During some of the turns, you may be asked to make slight changes to your turning technique. You will be allowed to rest in-between flip turns. Performing the flip turns should require approximately 10 minutes.

3) Confidentiality

All results and data will be held confidential. You will be assigned a subject number and the video data collected will be held in the Department of Kinesiology and Leisure Science Biomechanics Laboratory for no longer than'five years. Your name will not be shown or indicated on any report of these data.

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4) Benefits

You may not receive any direct benefit from participation in this study other than the experience of being part of a scientific experiment. The results of this research may provide coaches with guidelines for flip-turn technique.

5) Risks

Protocols involved in this research involve minimal risk to the participants. Although the activities used in this study are only rarely associated with injury, the possibility does exist that the person can injure himself or herself. You should understand that if you are injured in the course of this research procedure that you alone may be responsible for the costs of treating your injuries.

6) Right to Withdrawal

Participation in this data collection is strictly voluntary and you may withdraw your participation at any time without prejudice or penalty.Uyou have any questions or concerns regarding your participation in this research, you may feel free to contact Amy Patz at 741-0326.

7) Certification

I certify that I have read and that I understand the foregoing, that I have been given satisfactory answers to my inquiries concerning project procedures and that I have been advised that I am free to withdraw my consent and to discontinue participation in the project or activity at any time without prejudice.

I understand that if I am injured in the course of this research procedure, I alone may be responsible for the costs of treating my injuries. .

I herewith give my consent to participate in this project with the uncterstanding that such consent does not waive any of my legal rights: nor does it release the principle investigator or the institution or any employee or agent thereof from the liability for negligence .

Signature of Participant: _____________ Date: ____ _

Signature of Investigator: _______ --' _____ Date: ____ _

If you cannot obtain satisfactory answers to your questions or have comments or complaints about your treatment in this study. please contact:

Committee on Human Studies University of Hawaii

2540 Maile Way Honolulu, HI 96822

Phone: (808) 956-5007

46

Appendix B: Swimmer Self-Rating Scale

• Flip-Turn Self-Ratlng Scale Swimme, Participant Number.

Turn 1 2 3 4 5 6 7

much too dose too COSEt almost right just right almost right too far much too far to the waIl to the wall (a bit too;' close) (a bit too- far) frnm the wan from the waif

Tuml 2 3 4 5 6 7

much too close too close almost right just right almost right too far much too far to the wall to the wall (a bit too close) {a bit too far) from the waH from the wall

Tum3 2 3 4 5 6 7

much too close too close aim ost right j .... right almost right too fat much too far to the waH to the wall (a bit too close) (a bit too far) from the wan from the wall

Tum" 2 3 • 5 6 7

mue h too close toocbse almost right rust tight almost right too far mum too far to the wall to the wall (a bit too close) {a bit too far) from the wal from the wall

Tum 5 2 3 4 5 6 7

much too dOH too close almost right just right almost right too far much too far to the wan to th-e wall (3 bit too close) {a hit too far) from the wail from the wall

Tum 6 2 3 • 5 6 7

much too clOH too close almost right jlBt right almost right too far much too far to th-e wall to the wall (a bit too close) (a bit too far) frOm the waH from the wall

Tum7 2 3 • 5 6 7

much too close too close almost right just right almost right too far mud'! too far to thews" to the wall (a bit too close) (a bit too far) from the wall from the waN

Turn 8 2 3 • 5 6 7

much too high too high almost right just fight almost right too low much too low on the wall on the wal (a bittoo high) {a bit too lowl on the wall on the-wal

Turn 9 2 3 4 5 6 7

much too high too high almost right just right almost right too low much too low on the wall on the walt (3 bit teo high) (3 bit too low) on the waU on thewa.

Tum 10 1 2 3 4 5 6 7

much too high too high' aim ost right just right almost right too-law much too low on IhewaH on the wall (a bit too high) (a bit too low) on the wall on thewa.

Turn 11 1 2 3 4 5 6 7

muc.h 100 high too high • almost right just right almost right 100 low much too low on the waH on the waff (a bit too hiJh) (a bit too low) on Ihe wall onthewal

~

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References Blanksby, B.A., Gathercole, D.G, Marshall, R.N. (1996). Force plate and video analysis of the tumble turn by age-group sw'immers. Journal of Swimming Research, 11,40-45.

Blanksby, B.A., Hodgkinson, J.N., & Marshall, R.N. (1996). Force-time characteristics of freestyle tumble turns by elite swimmers. South African Journal for Research in Sport, Physical Education and Recreation, 19, 1-15.

Blanksby, B.A.:Simpson, 1.R:, Elliott, B.C., & McElroy, G.K. (1998). Biomechanical factors influencing breaststroke turns by age-group swimmers. Journal of Applied Biomechanics, 14, 180-189 .

•

Blanksby, B.A., Skender, S., Elliott, B.C., & McElroy, G.K., Landers, G. (2004) An analysis of the rollover backstroke turn by age-group swimmers. Sports Biomechanics, 3, 1-14. .

Bobbert, M.F.; Gerritsen, K.G., Litjens, A, &'yan Soest, AJ. (1996). Why is countermovement jump hei~t greater than 'squat jump height? Medicine and Science in Sports and Exercise, 1402-1412. .

Chatard, J., Girold, S., Cossor, J.M., Mason, B. (2003). Analysis of the 200m events in the Sydney Olympic games. In 1. Chatard (EdJ, Biomechanics and Medicine in Swimming (pp. 261C264). Saint-Etienne: I'Universite de Saint-Etienne.

"

Cohen; 1., Cohen, P., West,S.G., & Aiken, L.G. (2003). Applied multiple regressiOn/correlation analysis for the behavioral sciences, 3rd ed. Mahwah, NJ: Lawrence Erlbaum Associates, Publishers. •

, Cossor, J .M., Blanksby, B.A, & Elliot, B.C. (1999). The influence of plyometric training on the freestyle tumble turn. Journal of Science and Medicine in Sport, 2, 106-116. .

Linthorne, N.P. (2000). Optimum take-off range in vertical jumping. In R. Barrett, R. Simeoni, and C. D'Helon (Editors): Book of Abstracts, 3rd Australian Biomechanics Conference, 31 January -1 February 2000 (pp. 49-50). Gold C.oast: Griffith University.

Lyttle, A D~, Blanksby B. A, Elliott,.B.C., & Lloyd, D.G. (1999). Investigating kinetics in the freestyle flip turn. Journal of Applied Biomechanics 15,242-252.

Lyttle, AD. & Blanksby, B.A. (2000). A look a gliding and underwater kicking in the swim turn. XYIIllnternational Symposium on Biomechanics in Sports, Hong Kong, China, The Chinese University Press.

Lyttle, AD., Blanksby, B.A., Elliott, B.C., & Lloyd, D.G. (2000). Net forces during tethered simulation of underwater streamlined gliding and kicking techniques of the freestyle turn. Journal of Sports Science, 10,801-807.

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Lyttle, A.D., Blanksby, B.A., Elliott, B.C., & Lloyd, D.G. (1998). The effect of depth'and velocity on drag during the streamlined glide. Journal of Swimming Research,13, 15-22.

Lyttle, AD. and Mason, B. (1997). A kinematic and kinetic analysis of the freestyle and butterfly turns. Journal of Swimming Research. 12,7-11..

Mason, B. (1999). Where are races won (~d lost)? In R. Sanders and J. Linsten (Eds.). Swimming: Applied Proceeoings of the XVII International Symposium on Biomechanics in Sports (1 ed. Vol. 1. pp.l-lO). Perth, Western Australia: School of Biomedical and Sports Science. • .

Mason, B., & Cossor, J.M. (2001) Swim tum performance at the Sydney 2000 Olympic games. Edinbugh: Moray House School of Education, The University of Edinburgh .

• Thayer, AL. & Hay, J.G. (1984). Motivating start and tum improvement. Swimming Technique, 20, 17-20.

Thompson, K.G., Haljand, R., & MacLaren, D.P. (2000). An analysis of selected kinematic variables in national and elite male and female l00-m and200-m breaststroke swimmers. Journal of Sports Sciences. 18, 421-431.

Tourny-Chollet, C., Chollet, D.;Hogie, S., & Papparodopoulos; C. (2002). Kinematic analysis of butterfly turns of international and national swimmers. Journal of Sports Sciences, 20,383-390. . •

Wilson, GJ.; Elliott, B.C.; Wood, G.A (1991). The performance augmentation achieved from use of the stretch-shorten cycle; The neuromuscular contribution. Australian Journal of Science and Medicine in Sport, 23, 97-101.

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