APPLEBY ET AL (2011) - Changes in Strength Over a Two Year Period in Professional Rugby Union Players

8/3/2019 APPLEBY ET AL (2011) - Changes in Strength Over a Two Year Period in Professional Rugby Union Players

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Journal of Strength and Conditioning Research Publish Ahead of Print

DOI: 10.1519/JSC.0b013e31823f8b86

Changes in Strength over a Two Year Period in Professional Rugby Union Players

Brendyn Applebya, Robert U. Newton

band Prue Cormie

b

aWestern Force, Rugby WA, Perth, AustraliabSchool of Exercise, Biomedical and Health Sciences, Edith Cowan University, Perth, Australia

Corresponding author: Brendyn ApplebyRugby WA

PO 146 FloreatWA 6014

Phone: (+61 8) 9387 0754Email: [email protected]


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ABSTRACT

The purpose of this study was to assess the magnitude of upper and lower body strength

change in highly trained professional rugby union players following two years of training. An

additional purpose was to examine if the changes in strength were influenced by starting strength

level, lean mass index or chronological age. This longitudinal investigation tracked maximal strength

and body composition over three consecutive years in 20 professional rugby union athletes. Maximal

strength in the bench press and back squat as well as body composition was assessed during pre-

season resistance training sessions each year. Athletes completed a very rigorous training program

throughout the duration of this study consisting of numerous resistance, conditioning and skills

training sessions every week. The primary findings of this study were: (1) maximal upper and lower

body strength was increased by 6.5-11.5% following two years of training (p = 0.000-0.002 for bench

press; p = 0.277-0.165 for squat); (2) magnitude of the improvement was negatively associated with

initial strength level (r = -0.569 to -0.712; p 0.05); (3) magnitude of improvement in lower body

maximal strength was positively related to the change in LMI (an indicator of hypertrophy; r = 0.692-

0.880; p 0.05); and (4) magnitude of improvement was not associated with the age of professional

rugby union athletes (r = -0.068 to -0.345). It appears particularly important for training programs to

be designed for continued muscle hypertrophy in highly trained athletes. Even in professional rugby

union athletes this must be achieved in the face of high volumes of aerobic and skills training if

strength is to be increased.

Key Words: resistance training, long term adaptations, diminishing returns, bench press, squat


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INTRODUCTION

Rugby union is a collision based field sport, intermittent in nature, requiring high levels of

endurance, strength, power, agility and speed, as well as proficiency in match related skills (1, 13, 14).

Match analysis has detailed a highly varied and intermittent game, with a wide degree of physical

situations utilising all energy systems (13). Forwards in particular have been identified as requiring

high levels of strength for scrumming and contact/wrestling activities whilst backs perform a higher

frequency of sprints per match compared to forwards. In rugby league, player sprint performance has

been related to strength and power (4) whilst muscular strength has been frequently demonstrated to

discriminate playing levels within many collision-based field sports (2, 6, 18, 19). Whilst these

findings highlight the importance of high strength development as a critical requirement for rugby

union players, the need for development of other physical characteristics and the training structure of

professional rugby (i.e. limited time for physical conditioning and the need for concurrent training)

can affect maximum strength development.

Whilst maximising the long-term development of strength is one of the primary goals of

conditioning programs, much of what we know about the neurological and morphological adaptations

to resistance training arise from short-term (i.e. commonly 8-12 week interventions) investigations

involving relatively untrained or inexperienced participants. This is a serious limitation of current

knowledge as the principle of diminished returns dictates that initial improvements in muscular

function are easily invoked and further improvements are progressively harder to achieve (28). Very

few studies have examined the magnitude of changes in strength over relatively longer periods of time

and even fewer have done so with very well trained athletes (3, 5, 7, 20, 21). An investigation


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rugby league athletes with at least 3 years of resistance training experience were reported to improve

maximal lower body strength by 14% across a four year period (7) and maximal upper body strength

by 11% across a six year period (3). Furthermore, a comparison of upper body strength development

between elite and sub-elite rugby league athletes illustrated considerable difference in the magnitude

of change over a 6 year period with increases of 6% and 24% observed respectively (3). Finnish

national champion weightlifters were observed to show small, non-statistically significant

improvements in maximal strength following one year of training (20), and a significant improvement

of 2.8% in total weight-lifting result after two years of training (21). Collectively, these results

illustrate that highly trained athletes have a limited potential for further strength development even

over long-term periods of intense training and highlight the importance of effective program design.

While these findings provide indirect observations about the theoretical construct of the principle of

diminished returns, to date there is a paucity of research empirically testing this hypothesis (28),

especially in highly trained athletes.

Maximising the long-term strength development of team sport athletes is a primary goal for

strength and conditioning coaches. Despite this, there is very limited research investigating long-term

strength development in highly trained professional team sport athletes, especially rugby union

athletes. While extensive research has examined the magnitude of change in strength expected over

short periods of time in relatively untrained subjects, little scientific evidence exists regarding the

magnitude of change in strength that can be expected over a long-term period in highly trained

athletes (5, 7, 20, 21). Importantly, no such evidence is available for professional rugby union

athletes. Furthermore, very limited evidence is available regarding the factors that may influence the

ability to adapt to resistance training, and thus the magnitude of change in strength, in highly trained

rugby union athletes (i.e. can the older and/or very strong athletes still significantly improve their


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training. An additional purpose was to examine if the changes in strength were influenced by starting

strength level, lean mass index or chronological age.

METHODS

Approach to the Problem

This longitudinal investigation tracked maximal strength and body composition over three

consecutive years in highly trained, professional rugby union athletes in order to examine the long-

term adaptations to resistance training. Maximal strength in the bench press and back squat as well as

body composition was assessed using a one repetition maximum (1RM) test during pre-season

resistance training sessions each year. Participants completed 1RM assessments at the same time of

day (i.e. 1st

training session of the day), with squat and bench press 1RM tests conducted on separate

days every three to four weeks throughout the pre-season period each year. Assessment of body

composition was performed at the same time of day (i.e. prior to the 1st

training session of the day)

every two weeks throughout the pre-season period each year. All participants were highly experienced

athletes from the same professional club that completed a very rigorous training program throughout

the duration of this study consisting of numerous resistance, conditioning and skills training sessions

every week.

Subjects

Twenty professional rugby union athletes (12 forwards and 8 backs) with extensive resistance

training experience fulfilled all the requirements of this investigation (Table 1). Only athletes who had

a minimum of two years of full-time employment in a professional rugby union club in 2007 were


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the lower body strength assessments. Participants gave their written informed consent and voluntarily

completed the requirements of this investigation as part of their normal club training sessions and.

This study was approved by the universitys human research ethics committee.

- insert Table 1 here -

Procedures

Training Program.Throughout the duration of the study participants completed a periodised

training program consisting of between 4-12 training sessions per week. The average number of

resistance, conditioning and skills sessions as well as matches per week is outlined in Table 2.

Resistance training programs were individualised based on each athletes physical strengths and

weaknesses and the presence of any injury. The resistance training program was designed to maximise

the long-term development of strength and power. During the pre-season phase, the resistance training

sessions were typically categorised as hypertrophy (i.e. 60 to 75% 1RM, 20 to 25 sets of 10 to 15

reps) hypertrophy-strength (i.e. 65 to 90% 1RM, 20 to 25 sets of 3 to 15 reps), strength (i.e. 80 to

100% 1RM, 15 to 20 sets of 1 to 6 reps) or power (i.e. 50 to 85% 1RM, 15 to 20 sets of 1 to 6 reps)

and cycled in three week blocks with a recovery or lighter week being the last week of each cycle.

The pre-competition phase was characterised by lower volume (i.e. 15 to 20 sets of 1 to 10 reps),

higher intensity (i.e. 75 to 100% 1RM) strength and power sessions while the competition phase

consisted primarily of maintenance programming (i.e. 80 to 100% 1RM, 20 to 25 sets of 3 to 12 reps).

At the completion of the season, athletes involved with their national representative team followed the


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methodical, progressive overload outlook. Recovery and off-season programs were general in

prescription.

A typical upper body training session commenced with one to three shoulder warm-up

exercises targeting rotator cuff and scapular stability. In general, the number of sets ranged from 15 to

25, depending on the individual requirements. Between three to four sets of progressively increasing

load were performed prior to two to three sets at maximal intensity for that sessions required load.

Only multi-joint exercises were used and the ratio of push-pull movements was prescribed

individually to ensure muscular balance in each athlete. Typical exercises included chin-ups, bent-

over rows, bench pull, flat, incline and shoulder press, using barbells or dumbbells.

A typical lower body session commenced with one to two lower body stability or technique

orientated warm-up exercises of sub-maximal intensity. The number of work sets was generally less

than the upper body sessions, ranging from 15 to 20. Similar to upper body strength training sessions,

between three to four sets of progressively increasing load were performed prior to two to three sets of

maximal intensity at that sessions required load. Only multi-joint exercises were prescribed with the

exception of supplementary hamstring and gluteal isolation exercises, completed towards the later

stages of the program. Typical multi-joint exercises included deadlifts, squats, clean pulls, step-ups,

incline leg press and power cleans.

Conditioning sessions involved a variety of aerobic and anaerobic conditioning training

modalities during the duration of the study period. During the pre-season phase, conditioning

sessions were comprised predominately of running, although bike, cross-training, swimming and

boxing sessions were also utilised. Individuals were prescribed between two and four conditioning

sessions per week of varying intensity (i.e. 6 to 9 rating of perceived exertion [RPE] using the


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prescribed on an individual player basis in accordance to their needs analysis. The in-season

conditioning sessions were of a similar intensity (i.e. 6 to 9 RPE), but much shorter duration

(maximum 30 minutes).

Skill sessions involved components of individual player skill development, unit training (i.e.

position specific specialist small team technique and tactics), full team training, simulating match play

with varying levels of physical contact ranging from no contact, to pads, to full contact drills. The

number of sessions per week ranged from two to four, of varying lengths (45 to 120 minutes) and

intensity (RPE of 3 to 7). In-season, post-match recovery and travel were factors that influenced the

frequency (between 2 and 3), duration (30 to 60 minutes) and intensity (RPE of 2 to 7) of skill

sessions.

- insert Table 2 here -

Maximal Strength Assessment. The bench press and back squat 1RM were used to assess

maximal upper body and lower body strength respectively. Regular assessments were conducted

throughout the pre-season period each year with testing occurring at the same time of the day, on the

same day of the week for each exercise every year. The 1RM protocol involved participants

completing a series of 3-4 warm up sets of increasing load each separated by 3 minutes of recovery. A

series of maximal lift attempts were then performed until a 1RM was obtained. No more than five

attempts were permitted with each attempt separated by 5 minutes of recovery. This protocol has been

used frequently in previous research for the assessment of maximal dynamic strength (8, 10, 11) and

reliability of these protocols have been established previously (24-26). A free weights bench press

rack was used to test bench press 1RM Only trials in which participants lowered the barbell to their


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successful. This depth was monitored during testing using a linear position transducer (GymAware,

Kinetic Technology, Canberra, Australia) attached to the barbell as well as visually by the same

experienced tester. All participants were very experienced with the bench press and squat 1RM

protocols, having performed the assessments frequently for a minimum of 2 years prior to 2007.

Assessment of 1RM occurred frequently throughout the pre-season phase each year and only the

highest 1RM of the year was included in the analysis (i.e. comparisons were made between the

highest strength level achieved during the pre-season of three consecutive years in order to determine

the long-term changes in strength rather than short-term fluctuations due to de-conditioning during the

off-season etc.).

Body Composition Assessment. The same experienced, International Society for the

Advancement of Kinanthropometry accredited anthropometrist performed skinfold thickness

assessments in accordance with standard methods throughout the duration of this study. The following

seven sites were measured using calibrated skinfold callipers (Harpenden Skinfold Callipers) triceps,

subscapular, biceps, supraspinale, abdomen, thigh and calf. Body mass was assessed using the same

set of calibrated electronic scales. The between test technical error for sum of seven skinfolds and

body mass was 2mm (i.e. 3.0%) and 0.01kg (i.e. 0.01%) respectively based on repeated measurements

of 10 athletes. The lean mass index (LMI) was calculated using methods described by Duthie et al.

(15) as an indicator of fat-free mass (LMI = mass/sum of 7 skinfoldsx; where x is 0.13 for forwards

and 0.14 for backs). Urine specific gravity was assessed regularly to ensure a consistent level of

hydration.

Statistical Analyses


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represent a small, moderate and large effect respectively. Relationships between the changes in

strength and starting strength level, LMI as well as age were evaluated using Pearsons correlation

coefficient (r). The strength of the correlation coefficient was determined based on classifications

outlined by Cohen (9) where r = 0.10 0.29 has a small effect, r = 0.30 0.49 has a moderate effect

and r 0.5 has a large effect. Statistical significance for all analyses was defined by p 0.05 and

results were summarized as means standard deviations.

RESULTS

Statistically significant differences between 2007, 2008 and 2009 were observed in a number

of variables (Table 1). Statistically significant changes in LMI, bench press 1RM and bench press

1RM:BM were observed in both 2008 and 2009 (Table 3). Practically relevant improvements in squat

1RM and squat 1RM:BM were also observed in 2008 and 2009 but these changes did not reach

statistical significance (Table 3). Significant negative relationships that had a large effect were

observed between strength level in 2007 and the percent change in strength in 2008 and 2009 for both

the bench press and squat (Figure 1). This data indicates that 32-51% of the variance in maximal

upper body strength percent change and 41-46% of the variance in maximal lower body strength

percent change was explained by starting strength level. Significant positive relationships that had a

large effect were also observed between the percent change in LMI and percent change in lower body

strength but not upper body strength (Figure 2). This data indicates that 6-10% of the variance in

maximal upper body strength percent change and 44-77% of the variance in maximal lower body

strength percent change was explained by the percent change in LMI. No relationship was observed

between age in 2007 and the percent change in either upper body or lower body strength (Figure 3).


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clear understanding of the multitude of factors that affect adaptation in professional team sport

athletes.

Influence of Initial Strength Level on Long-Term Changes in Strength. Significant

negative relationships were observed between initial strength level and the magnitude of change in

both upper and lower body strength following two years of training (r = -0.569 to -0.712 i.e. 32-51%

and 41-46% of the variance in maximal upper and lower body strength change respectively was

explained by starting strength level). These results provide some of the first data and certainly the

strongest evidence to date for elite athletes supporting the theoretical construct of the principle of

diminished returns which dictates that initial improvements in muscular function are easily invoked

and further improvements are progressively harder to achieve (i.e. the magnitude of potential for

training-induced improvement decreases as strength and training experience of the athlete increases)

(7, 29).It is theorised that despite all participants being exposed to a similar volume of resistance

training, the relatively weaker athletes had a greater capacity for adaptation within the neuromuscular

system (i.e. a larger window of adaptation). If similar rates of improvements are to be achieved, the

stronger participants may require a greater stimulus due to the smaller window of adaptation for

strength improvement these athletes have as a result of their highly developed neuromuscular system.

It is unknown if this can be achieved through sophisticated program design or if the time necessary to

devote to a greater rate of improvement in these athletes limits the ability for development in other

important performance areas and increases the risk of overtraining.

Influence of Lean Mass on Long-Term Changes in Strength. It has been well documented

that increases in muscle cross-sectional area are strongly associated with increased strength (16, 17,

23). The current study reflects these results in an applied setting with significant correlations

b d b h i d f l b d h i d h h i ( 0 692 0 880


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the lower body compared to upper body musculature. Although not a direct measure of muscle mass

or cross-sectional area, the LMI can be considered an indicator of muscle hypertrophy. The significant

relationship between strength and LMI gain demonstrates the importance of hypertrophy to enhancing

lower body maximal strength in professional rugby union players. Therefore, if further improvements

in strength are to be achieved in such highly trained athletes, training programs need to be designed

for continued muscle hypertrophy and this can be achieved despite high volumes of aerobic and skills

training. The significant 2.8% increase in LMI observed in the current investigation illustrates that

muscle hypertrophy is still achievable under these circumstances.

Influence of Age on Long-Term Changes in Strength. The average age of participants in

the current study was higher than other long-term studies involving highly trained athletes (5, 7, 27).

Despite this, the results indicate that older athletes were still able to increase strength. Specifically,

there were no statistically significant relationships observed between the athletes age at the start of

the investigation and the magnitude of change in maximal strength following two years of training.

Although there were non-significant trends towards a negative relationship between initial age and

upper body strength gain (r = -0.313 to -0.345; p = 0.148-0.191, i.e. 10-12% of the variance in upper

body strength change was explained by initial age), changes in lower body strength showed no

association with initial age (r = -0.068 to -0.152; p = 0.655-0.842, i.e. 0-2% of the variance in lower

body strength change was explained by initial age). Interestingly, in 2007 there was a trend towards a

positive relationship between age and upper body strength level (r = 0.389, p = 0.100) and no

relationship observed between age and lower body strength level (r = -0.289, p = 0.388). These

observations suggest that the higher initial upper body strength level of older athletes may have a

strong confounding impact on the correlations observed between age and change in strength.

Nevertheless, it is clear that changes in lean muscle and an athletes initial strength level are more


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Time Course of Long-Term Changes in Strength. Another interesting observation worthy

of discussion is the timing of improvements over the two year training period. Increases of 7.3% (p =

0.001, ES = 0.66) and 10.6% (p = 0.198, ES = 0.50) in bench press and squat 1RM strength

respectively were observed during the first year of training (i.e. 2007-2008). In contrast, increases of

only 4.0% (p = 0.099, ES = 0.38) and 0.4% (p = 0.857, ES = 0.02) in bench press and squat 1RM

were observed during the second year of training (i.e. 2008-2009), leading to improvements of 11.5%

and 10.8% across the two years of training (i.e. 2007-2009). These figures quite clearly demonstrate a

far more pronounced yearly increase in strength during the first year of the training period observed,

especially with lower body strength. There are many factors that may have contributed to these

observations (i.e. less effective program design, increased quantity of match time leading to more

match related soreness (27), increased prevalence of injury, shift in program emphasis, player

motivation etc.) but the primary driver was theorised to be associated with differences in the training

load performed between the first and second year of training. The number of resistance training

sessions involving the bench press remained relatively similar from 2007 (17.1 7.7) to 2008 (16.3

6.4; p = 0.627) and 2009 (14.6 8.5; p = 0.307). However, the number of resistance training sessions

involving the squat showed a trend towards increasing from 2007 (10.9 6.6) to 2008 (13.0 6.4; p =

0.275) and was significantly lower in 2009 (6.3 4.4; p = 0.021). Similar results were observed in

the number of work sets performed of the bench press (2007 51.4 25.5; 2008 51.3 23.2, p =

0.981; 2009 40.8 26.0, p = 0.197) and the squat (2007 40.7 25.4; 2008 51.6 30.2, p =

0.244; 2009 21.6 15.4, p = 0.018). While this data doesnt capture all exercise that target the

prime movers in the bench press and squat, it provides a strong indication of the changes in upper and

lower body resistance training volume throughout the duration of the study. These differences in the

volume of resistance training performed were due to injury and/or a shift in training emphasis for


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and are associated with an increase in lean mass (squat only). Given the strong relationship between

increases in lean mass index and increases in strength it appears particularly important for training

programs to be designed for continued muscle hypertrophy. Even in elite level rugby union athletes

this must be achieved in the face of high volumes of aerobic and skills training. Furthermore, the

degree of strength improvement is related to initial strength level with larger improvements observed

in athletes with relatively lower levels of strength regardless of age.

PRACTICAL APPLICATIONS

Improvement in strength is highly related to increased lean muscle mass in highly trainedathletes. Strength and conditioning coaches should be mindful to include a level of hypertrophy

training in resistance training programs for highly trained athletes requiring increases in

strength.

The magnitude of strength improvement is related to initial strength level with greaterimprovements observed in relatively weaker athletes. Strength and conditioning professionals

should be aware of the greater programming detail required for continued development of

strength in highly trained athletes compared to relatively weaker athletes even within the same

professional organisation.

Age does not appear to limit the potential to adapt to strength training within a group of highlytrained professional rugby union athletes.

ACKNOWLEDGEMENTS


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FIGURE LEGENDS

TABLES

Table 1. Participant characteristics throughout the duration of the study. * Significantly (p 0.05)

different than 2007.

Table 2. Average duration and number of resistance training, conditioning and skills sessions as well

as the number of matches per week during each of the phases of the year.

Table 3. Percent change in body composition and strength from 2007. The magnitude of effect is

indicated by the effect size with 0.20 representing the smallest worthwhile change. * Significant (p

0.05) change from 2007.

FIGURES

Figure 1. Relationship between maximal strength level in 2007 and the percent change in maximal

strength in 2008 (A bench press and C - squat) and 2009 (B bench press and D - squat). The

correlation coefficient (r) is indicated for each of the graphs. * Significant (p 0.05) correlation.

Figure 2. Relationship between percent change in maximal strength and percent change in lean massindex between 2007-2008 (A bench press and C - squat) and 2007-2009 (B bench press and D -

squat). The correlation coefficient (r) is indicated for each of the graphs. * Significant (p 0.05)

correlation.

Figure 3. Relationship between age in 2007 and the percent change in maximal strength in 2008 (A

bench press and C - squat) and 2009 (B bench press and D - squat). The correlation coefficient (r) is

indicated for each of the graphs.


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Copyright National Strength and Conditioning Association Unauthorized reproduction of this article is prohibited.

2007 2008 2009

Age (years) 24.4 3.4 25.4 3.4* 26.4 3.4*

Body Mass (kg) 103.8 7.6 104.7 8.2 106.0 8.4*

Sum of 7 Skinfolds (mm) 71.1 16.9 65.7 16.1* 68.0 16.4

Lean Mass Index 58.7 4.3 59.8 4.3* 60.3 4.3*

Bench Press 1RM (kg) 132.5 14.0 141.6 12.6* 146.8 11.5*Bench Press 1RM:BM 1.28 0.13 1.36 0.13* 1.39 0.14*

Squat 1RM (kg) 164.6 31.5 178.6 26.1 179.1 26.7

Squat 1RM:BM 1.55 0.24 1.68 0.22 1.67 0.19

Table 1. Participant characteristics throughout the duration of the study. * Significantly (p 0.05) different than 2007.


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Phase of YearAverage

Duration

Resistance Sessions Conditioning

SessionsSkills Sessions Matches

Upper Body Lower Body

Pre-Season 8-10 weeks 4 4 3-4 4 0

Christmas Break 2 weeks 1-2 1-2 2 0 0

Pre-Competition 5 weeks 1-2 1-2 2 2-3 0-1

Super 14 Competition 14 weeks 1-2 1-2 1-2 2-3 1

Recovery 1-3 weeks 0 0 0 0 0

International or Club Season 13-16 weeks 1-2 1-2 1-2 2 1

Off-Season 2-4 weeks 1 1 1-2 0 0

Table 2. Average duration and number of resistance training, conditioning and skills sessions as well as the number of matches per week

during each of the phases of the year.


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2008 2009

% Change P-value Effect Size % Change

P-

value Effect Size

Body Mass 0.8 1.6 0.147 0.11 Trivial 2.1 2.4* 0.003 0.28 Small

Sum of 7 Skinfolds -7.2 10.7* 0.028-

0.33Small -3.9 12.5 0.586 -0.19 Trivial

Lean Mass Index 1.9 1.9* 0.002 0.25 Small 2.8 2.2* 0.000 0.37 Small

Bench Press 1RM 7.3 7.2* 0.001 0.66Moderat

e

11.5 10.0* 0.000 1.04 Large

Bench Press

1RM:BM6.5 7.6* 0.005 0.56

Moderat

e9.2 9.0* 0.001 0.81 Large

Squat 1RM 10.6 17.0 0.198 0.50Moderat

e10.8 17.6 0.206 0.52

Moderat

e

Squat 1RM:BM 9.5 14.6 0.165 0.59Moderat

e9.2 16.4 0.277 0.53

Moderat

e

Table 3. Percent change in body composition and strength from 2007. The magnitude of effect is indicated by the effect size with

0.20 representing the smallest worthwhile change. * Significant (p 0.05) change from 2007.


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Figure 1. Relationship between maximal strength level in 2007 and the percent change in maximal strength in 2008

(A bench press and C - squat) and 2009 (B bench press and D - squat). The correlation coefficient (r) is indicated for each of the graphs.

* Significant (p 0.05) correlation.


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Figure 2. Relationship between percent change in maximal strength and percent change in lean mass index between 2007-2008 (

A bench press and C - squat) and 2007-2009 (B bench press and D - squat).

The correlation coefficient (r) is indicated for each of the graphs. * Significant (p 0.05) correlation.


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Figure 3. Relationship between age in 2007 and the percent change in maximal strength in 2008 (A bench press and C - squat) and 2009 (

B bench press and D - squat). The correlation coefficient (r) is indicated for each of the graphs.

Documents

APPLEBY ET AL (2011) - Changes in Strength Over a Two Year Period in Professional Rugby Union Players