INTRODUCTION

The youngest author of this article, Matthew Muldavin, who was 14 years old at the time, was inspired to increase his vertical leap for enhanced performance in basketball. The senior author, Daniel B. Muldavin, BS, DC, and a member of the International Society of Clinical Rehab Specialists (ISCRS), encouraged his son to perform research on muscle fiber type physiology and EMG analysis of muscles involved in order to develop his own scientifically based vertical leap program. The willingness to perform this research project belies his inquisitive nature of anatomy and physiology of the musculoskeletal system, spawned by a severe orthopedic injury occurring when he was nine years old, combined with his passion for physical training. Consequently, this comprehensive research review spawned the development of a new model of pre-participation functional and strength screening (PPFSS), which we hypothesize will safely place adolescent athletes in our scientifically based training program which allows an effective, safe enhancement of fast twitch muscle fiber (type IIa and IIx) in adolescent athletes.

Fast twitch fibers (type IIa and IIx) are predominate in anaerobic type activities including forceful muscle actions such as vertical leap and sprints which rely on anaerobic energy metabolism.16,19 Fast Twitch Fibers (FTF) enable rapid energy generation for powerful action 3-5 times faster than slow twitch fibers.16,19 Two major subdivisions characterize FTF’s, the intermediate type IIa fiber, also known as Fast Oxidative Glycolytic (FOG), exhibit characteristics and capacity for energy transfer from both aerobic and anaerobic sources. The other subdivision, the type IIx muscle fiber, is known as the “true fast glycolytic fiber” (FG) and has the greatest anaerobic potential which creates the most power through its rapid shortening velocity.

Our project was designed to enhance type IIa and type IIx muscle fiber in adolescent athletes and was based on well documented studies showing the effects of physical training on fiber composition in human skeletal muscle. Initial classic studies performed by Gollnick and Saltin in the early 1970’s led to an explosion of research showing fiber type alterations with specific training stimulus.14,15 Dawson, et al, found that 4-6 weeks of anaerobic sprint training increased the amount of FTF percentage and decreased Slow Twitch Fiber (STF) percentage.10 Furthermore, studies have shown the importance of exercise specificity and load stimulus with changes and enhancements in fiber type activity and growth. Tesch and Karlson showed that considerable hypertrophy of predominantly fast twitch fibers occur in power and Olympic type weight-lifters who train over many years.35,36 Similar training effects from plyometric and power training have correlated with adolescent youth.12 Unfortunately, there has been a lack of research studies pertaining to proper placement of adolescent athletes in a safe, effective, plyometric/power training program.

Therefore, we felt one of the most important aspects of training adolescent athletes (especially with regard to plyometric/power training) was to find an appropriate training program for their “developmental age” and functional capabilities. Balyi and Way have developed the gold standard for training young athletes with the concept of Long Term Athletic Development (LTAD). 4 In their research and papers they indicate that although growth and development is a natural process, the timing of the maturation process can vary widely. In Borms article (1982), it states that “a child with a

chronological age of twelve years may possess a biological age of between nine and fifteen years.” 5 The problem is that these young athletes are trained in the same way which may benefit an “early maturer” but stifle or injure a late maturer. In Bayli and Way’s articles, it breaks down strategies to ascertain maturity levels by Peak Height Velocity (PHV) which is the fastest rate of growth during the adolescent growth spurt and is “usually” about twelve years in girls and about two years later in boys. Importantly, the Peak Strength Velocity (PSV) comes 12-18 months after PHV. Both stamina and strength should be trained at all stages, but the emphasis should be based on developmental age not chronological age.3 Consequently, part of our screening/study asks not only the chronological age but seeks to determine the developmental age as well. Although developmental age is crucial, it does not ensure a young athlete will have adequate flexibility, strength and fundamental movements to perform plyometric/power training at the highest level. Consequently, we developed a new Pre-Participation Functional and Strength Screening (PPFSS) specifically designed to place our young athletes at an appropriate functional “developmental age level” to enhance fast twitch muscle fiber growth safely and effectively. Our new model of the PPFSS was based on a synthesis of several sources including Gray Cooks Functional Movement Screen (FMS), Dr. Craig Liebenson’s Magnificent 7, and tests in the plyometric literature. Please see Methods for details of tests.

Finally, to enhance safety and efficiency of training for adolescents, our extensive review of the literature yielded a program that would safely and effectively train adolescent athletes in power and plyometric training including the concepts of periodization, introduced by Russian Scientist Leonid Mateyeev in 1972.26 Rhea and Alderman, in their December 2004 article, a meta-analysis of periodized vs. non periodized strength and power training programs, found in their statistical review of the literature that periodized training is more effective than non periodized training for men and women, all ages, and all training levels.32 Studies have shown plyometric training to be effective in young athletes.12 In addition to the plyometrics, we utilized sprint training, as studies have shown that sprints can have a similar effect on jump height and power as plyometric training. A Croatian study showed similar increases in both the sprint group and the plyometric group in drop jump and isometric strength changes as compared to the control group.25 Furthermore, there appears to be a strong correlation among maximum squat strength, sprint performance, and vertical jump height. A study was performed on elite soccer players in 2004 which showed maximum strength in half squats determines sprint performance and jumping height in high level soccer players. This study showed a significant relationship between One Repetition Maximum (1RM) in ½ squats and both sprinting and jumping.38

In summary, the purpose of our training program was to develop a safe and effective training protocol to enhance type IIa and type IIx muscle fibers in adolescent athletes. Our training program was scientifically based on the periodization concept (see Methods for details) utilizing a six week mesocycle with variation of the weekly microcycle. We utilized plyometrics, sprints, and limited ½ squat training to increase power and thus increase type IIa and type IIx muscle fiber. We will discuss specifics of the workouts which also included pre and post warm up drills, including Nordic lowers which have been shown to reduce hamstring injuries.1 Furthermore, we developed a new model of functional screening in our PPFSS along with Long Term Athletic Development

(LTAD) to allow adolescents to be properly placed in a plyometric and power training program to reduce injury and increase efficiency.

METHODS

Experimental Approach to the Problem

Our study design was developed to test our hypothesis that adolescent athletes age 12-18 can be placed in a safe, appropriate and effective training program to increase fast twitch muscle fiber growth (type IIa and IIx) through plyometric and power training. First, the subjects or prospective adolescent athletes developmental age and peak height velocity (PHV) are ascertained by questionnaires and growth charts. Based on Bayli and Way’s Long Term Athletic Development (LTAD) research, the young athletes’ optimum training sensitivity can be determined which allows accelerated adaptation and specific training.3,4 Although developmental age is crucial, it does not ensure a young athlete will have adequate flexibility, strength and fundamental movements to perform plyometric/power training at the highest level. Consequently, we developed a Pre-Participation Functional and Strength Screening (PPFSS) specifically designed to place our young athletes at an appropriate functional “developmental age level” to enhance fast twitch muscle fiber growth safely and effectively. The new model of our PPFSS was based on a synthesis of several sources including Gray Cooks Functional Movement Screen (FMS), Dr. Craig Liebenson’s Magnificent 7, and tests in the plyometric literature.8,9,22,29,39 After the PPFSS tests are performed, the subjects are put in categories of physical training consistent with their functional developmental age level. (Please see Procedures.) To test the effectiveness of the training program for increased fast twitch fiber growth, baseline testing was performed prior to commencement of the training, which included the vertical jump test, 2 step, 1 leg vertical jump, 2 step, 2 leg vertical jump, and 30 yard sprint. A 6 week training program at 3 days per week was utilized based on literature review. Shortly after the training, testing was performed to determine the results of the baseline tests. Furthermore, safety was evaluated by the ability of the subject to successfully complete the training with no injuries or effects of overtraining.

Subjects

The Institutional Review Board (IRB) guidelines regarding experimental procedures were adopted from the Editorial Board of Medicine and Science in Sports and Exercise. The subject and one of the authors of the paper, Matthew Muldavin (M.M.) who was 14 years,7 ½ months at the commencement of the training, gave his informed consent and willingly performed all procedures and protocols listed in the case study.

Procedures

A.) Determination of Peak Height Velocity/Based on Long-term Athletic development

Based on the concepts of Long Term Athletic Development ( LTAD ) by Bayli and Way we calculated Peak Height Velocity ( PHV ) to have occurred at approximately 13 years, 6 months for Matthew Muldavin ( M.M ). At the time of the PPFSS and training, M.M. was age 14 years, 7 ½ months. Based on the concepts of LTAD, strength training sensitivity occurs 12-18 months after PHV and the literature indicates this should be a priority3,4 Consequently, M.M. was in the proper training sensitivity for plyometric/power training and thus was ready for the PPFSS to determine which category he should be placed in.

B. Development of the Pre-Participation Functional and Strength Screening (PPFSS)

This was developed as a guideline in concert with the “LTAD protocols” by Balyi and Way.3,4 It analyzes and assesses kinesiological, proprioceptive and biological readiness for young athletes to perform the strength and plyometric training. Our Pre-Participation Functional and Strength Screening (PPFSS) is based on seven distinct tests. Four of our tests check fundamental movements requiring a sound kinetic chain or linking system showing proper proximal to distal sequence.8,9 One of our tests assesses proprioception and balance and two tests assess overall body and core strength.22,29,39

We had a total of seven tests in our PPFSS with each test worth three points, for a total of 21 points. Please see video for a demonstration of our PPFSS at www.youtube.com/watch?v=lWjmEcooqEI.

Description of Tests and Grading Scale

1.) Deep Squat with Dowel Overhead

We felt this was extremely important as this is the position needed in most athletic events – especially vertical jump.

The deep squat assesses bilateral, symmetrical, functional mobility of the hips, knees, and ankles and assesses posterior chain strength shown to be critical for vertical leap18,31 The dowel overhead assesses symmetrical mobility of the shoulders and thoracic spine.

3 pts - Perfect form, straight back, femur below horizontal, knees and dowel aligned over feet.

2 pts - Relatively good form with slight compensation.

1 pt. - Unable to perform squat or major compensations.

0 pts - Pain occurs during squat.

2.) Hurdle Step Down with Dowel behind the Back

We felt this was important as this movement requires proper coordination and stability between the hips and torso during stepping motion and single leg stance stability – important in sprints and jumping on and off plyo boxes. Description: Hurdle set to heights of tibial tuberosity with dowel across back. The subject is asked to step over hurdle and touch heel to floor while maintaining stance extended. You have three times to do this. If able to do it once as described below a three is given.

3 pts. - Hips, knees and ankles remain aligned in sagittal plane. Minimal movement in the lumbar spine and dowel and string remain

parallel.

2 pts - Alignment lost between hips, knees and ankles. Movement in spine. Dowel, string not parallel.

1 pt - Contact between feet and string occurs. Loss of balance.

0 pts – Pain.

3.) Lunge with Dowel Overhead

This is another fundamental movement that we felt was very important to assess for our training which consisted of sprinting and cross-over drills. Description: With dowel overhead, subject lunges forward as far as possible – touches the opposite knee to the ground, comes up and back into standing position.

3 pts - Deep lunge with back straight and knee over toes in good balance.

2 pts – Able to perform lunge but with slight compensations.

1 pt. – Loss of balance, unable to touch back knee, back bent over.

0 pts – Pain.

4.) One Leg Balance Test

We felt this was extremely important with the plyo box jumping and 180 degree turnaround jumps. Lack of excellent balance/proprioception is a predictor of future ankle

injury and presage compensations proximally up the kinetic chain into the knees, hip, low back and neck 22 This also checks to see if there are any old ankle injuries or weakness. Description: Standing straight with arms folded across chest, bring up one leg in a flexed position and look straight ahead. You are given 4 tries to do this. The test is the best attempt out of 4 tries.

3 pts - Ability to balance for 60 seconds with eyes open and 30 seconds with eyes closed.

2 pts – Ability to do with eyes open between 45- 60 seconds and eyes closed between 15 and 30 seconds.

1 pt. – Ability to do with eyes open for 30-45 seconds and less than 15 seconds with eyes closed.

0 pts – Pain during tests.

5.) Angel Wall

Description: Stand with back against wall with heels 1-2″ from wall. Bring arms up against wall in 90 degree abduction and elbows bent to 90 degrees and external rotation in 90 degrees. Then lift arms overhead. The External Occipital Protuberance (EOP) should touch the wall with the full thoracic spine touching the wall. This test helps determine the stability between the lower body and upper body and assesses shoulder and thoracic posture.

3 pts – Able to do angel wall with EOP touching wall and full thoracic spine pressing against wall.

2 pts – Slight compensations. Unable to bring whole thoracic spine against wall.

1 pt – EOP does not hit wall. Unable to externally rotate shoulder.

0 pts – Pain.

6.) Plank

Description: Pushup position on toes with elbows and forearms touching ground. The goal is to hold position with back straight. Cook utilizes the traditional push up,

testing the ability to stabilize the spine in an anterior to posterior plane doing a closed plane upper body movement.9 However, we utilize the plank position as McGill does in his progressions of the big three stabilization exercises as this activates the abdominal muscles and is an easy, measurable test of core strength.29 Powerful jumping requires a strong fixed core for optimum leverage of both the upper and lower extremities.

3 pts – 75 seconds or above with straight legs and back

2 pts – 60-75 seconds – straight legs and back

1 pt – Less than 60 seconds

0 pts – Pain

7.) One Repetition Maximum (1RM) Half Squat

This is maybe the most important test we added to our functional screening testing, especially for adolescent athletes who might not be “developmentally ready” to perform box plyometrics. Concern for musculoskeletal injury stems partly from the estimation that plyometric drop jumping generates external skeletal loads up to 10 x body mass.27 The National Strength and Conditioning Association suggests that athletes first achieve lifts of 1.5x body weight in the squat exercise before initiating high intensity plyometric training.39 We recommend initial testing be done on a machine such as the “body master squat” which is safer to determine ½ squat max.

3 pts – one rep (1RM) ½ squat 2x more than body weight

2 pts – 1.5 – 2x body weight

1 pt – less than 1.5 x body weight

Categories and Training Programs based on results of PPFSS

Gold: Greater than 17/21 on screenings with a three on the 1RM ½ squat test. This group can fully participate in unlimited power/plyometrics program – able to use 12″ and 18″ boxes. Can also participate in squat training if desired.

Silver: 15/21 – 17/21 on screenings with a minimum of two on the 1RM ½ squat test able to utilize plyos – only able to use 12 ″ plyo box.

Bronze: 10/21 – 14/21 on screening with a minimum of a two on the 1RM ½ squat test. This group will work on ground plyometrics only and will utilize part of training to

perfect fundamental movements and proprioception and as they improve and retest, may be able to utilize some box plyos.

Crystal: Less than 10 on screenings and only one on 1RM ½ squat test. No box plyos – work on prescreening tests that they were deficient in as a large part of their training so as to build core strength, balance and fundamental movements to correct compensated motor patterns and prevent injury.

Score of PPFSS for M.M.

1. Deep squat with dowel overhead scored 3/3 2. Hurdle step down with dowel across shoulder scored 2/3 3. Lunge with dowel across shoulder (below neck) scored 3/34. 1 leg balance test scored 3/35. Angel Wall scored 3/36. Plank scored 3/37. 1 RM – 380 lbs scored 3/3

M.M. scored 20/21 pts on our PPFSS and since he was in the proper strength training sensitivity based on LTAD, (see page 5) this placed him in the Gold category. Consequently, we developed an unlimited power/plyo training program utilizing both 12″ and 18″ plyometric boxes. M.M. also elected to augment his program with the 2x per week, ½ squat protocols described under Training Protocols.

Baseline Testing

Subsequent to the PPFSS and prior to the commencement of training, the following baseline tests were performed as follows:

A. Vertical jump test. This test is performed to measure peak anaerobic power output (PAPO) utilized by Sayers, et al. 34 The test we used is described in McArdle and Hatch and is as follows:28 PAPO is correlated with fast twitch fiber growth.

1.) Establish standing reach height. Standing flat footed with preferred shoulder against wall, the subject reaches

as high as possible to touch wall. This starting point is known as the standing reach height and is recorded in centimeters.

2.) Next, with both feet stationary, bend knees to about 90 degree angle while moving arms back in a winged position.

3.) Thrust forward and upward touching as high as possible on the wall. In our study, we used chalk on the distal 3rd phalanx (top of middle finger) onto painters tape to mark the tape.

4.) The subject is allowed three trials of the jump test. We utilized the highest score on the vertical leap.

5.) We computed vertical jump heights in cm as the difference between standing reach height and vertical height achieved in the jump.

6.) To predict peak anaerobic power output, we used the following equation: as outlined by Sayers.34

PAPw = 60.7 (VJcm) + 45.3 (BMkg) – 2055

PAPw = peak anaerobic power in watts VJcm = vertical jump height in centimetersBMkg = body mass in kilograms

This same protocol was utilized post plyometric/strength training.

B.) 2 Step, 1 Leg Vertical Leap

In this baseline test, 3 trials were performed and the highest touch point was recorded. The same measuring system was utilized with chalk

dust being affixed to the distal 3rd phalanx and the mark was on painters tape which extended vertically from 8 ½ ′ to 10 ½.′ The same protocol was utilized post plyometric/strength training.

C.) 2 Step, 2 Leg Jump

The same protocol was utilized as above. 3 jumps were recorded and the highest jump taken for baseline levels. This protocol was utilized

post plyometric/strength training.

D.) 30 Yard Sprint

30 yards were measured using a 30 yard ruling tape secured and marked at the beginning and end. 3 sprints were performed with the fastest time

recorded. This was repeated and recorded post training.

E.) ½ Squat Maximum (1RM)

We include this here in our baseline tests and it is also #7 of the PPFSS. Research shows that ½ squat resistance training 2x per week for 2

months in junior soccer players increased peak power output, vertical jump performance, and speed in sprints.6 We start this extra

training at a weight that can be performed with near maximum effort for 5 reps. This is optional only if the subject is in the gold category.

Baseline Tests for M.M. (taken prior to training)

Subsequent to the PPFSS, and prior to the commencement of training, M.M. performed baseline tests as described above in Methods. At the start of training, M.M. was 5’ 7 1/2″ (67 ½″) (172 cm) and weighed 137 lbs (62.27 kg). To determine Peak Anaerobic Power (PAP), we had following measurements:

1. Standing reach height: 87 5/8″ (223 cm)2. He performed 3 trials of vertical jump test as described in Methods. His

highest vertical jump recorded was 9′ ¾ ″ (276 cm.) This was a net vertical leap of 53 cm. (Please see graph #1 in Results)

Using these stats, the formula was utilized as follows:

PAPw = 60.7 (VJcm) + 45.3 (BMkg) – 2055

60.7 (53cm) + 45.3 (62.27 kg) – 20553,217 + 2,820 – 20556,037-2,055=3982wAnaerobic Power output 3,982w (Please see graph #2 in Results)

3. 2 Step, 1 Leg Vertical Leap

In this baseline test, 3 trials were performed and the highest touch point was recorded, which was 9′ 3 ″ (282 cm) for a net 59cm. (Please see graph #2 in Results)

4. 2 Step, 2 Leg Vertical Leap

The same protocol as the previous test was utilized but off two legs. The highest touch point was 9′3″ (282cm) for a net 59cm. ( Please see graph #2 in Results)

5. 30 Yard Sprint

3, 30 yard sprint times were measured with the lowest time of 4.43 seconds.

6. 1/2 Squat Max

As stated above, in PPFSS, the 1/2 squat measurement was 380lbs. (173 kg)

Principles and Description of Training

Materials used for training:

- 2 plyo boxes, one 12″ and one 18″ - A Body Fit balance board- A large size and small size 8 lb medicine ball- A small graded hill about 30′ was used for our medicine

ball jumps.- A Body Masters Squat machine (at the gym) was

utilized for brief 2x week squat training.- A notepad was used charting every workout in all

microcycles.- Another person (not the subject) was required to help

subject perform Nordic lowers.

Principles: Our research showed that plyometric training of four days per week was

no more efficient than two days per week and that a four week training period is not as effective as a seven week program, four weeks post training.11,24 The program was designed with the principles of periodization whose maximum mesocycle is six weeks with variations in volume, duration and intensity in our three day per week training sessions (microcycles).7,26

Consequently, we utilized a six week mesocycle training period consisting of three days per week training in concert with the literature and periodization principles. The literature relating to plyometric box height parameters is somewhat inconsistent with one study showing that .3 meters ( m ) ( 11.81″ ) produce greater jumps than .6m ( 23.62″ ) or .9 m ( 35.43″ ).37 One study found the optimum height to be .4m ( 15.74″ ) and others found it to be .5m ( 19.68″ ) for females and .6m ( 23.62″ ) for males.2,20 Conversely, some studies have found heights as low as .12m ( 4.72″ ) were as effective as the higher boxes.17,21 Consequently, our plyo boxes were 12″ and 18″ based on the synthesis of the above research articles which showed diminishing returns and possible injuries with the higher boxes. Furthermore, our 18″ box is reserved for our gold group and the 12″ box is utilized with care for our groups below silver (see Methods).

Description of Training for M.M.

1.) Warm-up. This consists of three-five minutes of light jogging. This is followed by 100 – 150 hops. These are quick 1-2″ hops with straight stiff legs. This was followed by 12-15 Nordic lowers which has shown to be more effective than stretching to reduce hamstring strains and injury.1 These were performed prior to each workout by M.M. and is appropriate for all categories.

2.) Training. The training program was based on periodization principles employing a 6 week mesocycle varying the parameters of volume, duration, and intensity. Each week consisted of three workouts

(microcycles) and these workouts varied from light and medium to heavy/super heavy workouts. The training was broken down into the following categories:

a) Non Box Plyometrics. These consisted of hopping in the athletic position and the 180 deg. squat plyometrics.23 These could be utilized by categories, Gold, Silver, Bronze and some Crystal subjects.

b) Plyometric Box Jumps. This consisted of depth jumps, rebound jumps, and multiple set depth drop, rebound, and 180 deg. jump sets. Depending on whether they were in the Gold or Silver category, either 12″ or 18″ boxes, or both were/are utilized. In M.M.’s training, which was the Gold category, both the 12” and 18” plyo boxes were used and the volume of jumps of combined non-box and box plyos varied from 220 jumps on a light day to 604 jumps on a super heavy day. If the subject is in the Silver category, only a 12” box is used. If in the Bronze category, only non-box plyos will be used until the new PPFSS yields a score of 15 or greater.

c) Medicine Ball Jumps. With an 8 lb medicine ball at chest level position, and elbows straight out, on an uphill slope, continuous broad jumps are performed. In M.M.’s training, sets of 5 jumps were performed from 4 sets on a light day to 7 sets on a heavy day. This can be utilized with less intensity (no hill) by the Silver category. This is not to be utilized by categories Bronze or Crystal.

d) Sprints and Cross-over Drills. 30 yard sprints were performed and 2-3 second 10 yard power cross-over drills were utilized. In M.M.’s training, the 30 yard sprints varied from 4 on a light day to 10 on a super heavy day. Eight, 10 yard cross-over sprints were performed on light days and up to 20 on super heavy days. These cross-over drills are not mandatory but can be used by all groups.

e) In Between Set Exercises. Geared for basketball, the following drills were/can be added:

1.) While on balance board, chest, overhead and underhand passes were thrown to subject

while keeping balance on board with 8 lb. medicine ball. In M.M.’s training, passes varied from 20 on a light day to 60 on a super heavy day.

2.) Fingertip Pushups (FP). In between sets, FP’s were performed to help

rebounding, and grip strength. M.M.’s

training consisted of 20 on a light day and up to 90 on a super heavy day. f) Cool Down. 100-150 easy athletic hops followed by 5-7

minutes of stretching were performed. This can and should be utilized by all categories.

g) Optional for gold category: 1/2 squat training performed 2x per week. This is separate from the above workouts and 5 reps. are performed in one set with progressions weekly 38 M.M. did elect to perform the ½ squat training, This is optional for Gold categories only.

Variation in Duration

M.M.’s training duration was varied in time in near direct proportion to the volume of training (total number of jumps, sprints, etc.) as described above. M.M.’s workouts varied from 28 minutes for a light workout to 67 minutes during a super heavy workout.

Variation in Intensity

The intensity was varied through the use of decreased rest intervals between sets.Following the six week workout, the post tests were performed after three days of no training.

Statistical Analysis

As we had only one subject, there was no specific statistical analysis performed. Percentage of improvements were compared from initial baseline testing and post training testing.

RESULTS

M.M. was able to complete the three day per week, six week training program at the highest level (Gold category) with no missed training sessions, injuries, or effects of overtraining. The post training baseline tests were performed three days subsequent to the final workout. The results of the baseline tests were as follows:

Standing Two Leg Vertical Leap

Just prior to the final baseline testing, we again measured the height and weight of M.M. Height was 5′ 7 ½ ″ (172 cm) and weight was 138 lbs. (62.72 kg). The standing reach height was 87 5/8 ″ (223 cm). The 2 leg standing vertical jump was performed 3 times with the highest touch point at 9′ 3 ½ ″ (111 ½ ″) (283 cm). His vertical jump in cm was 60 cm. (see graph #2)

GRAPH #1

60.7 (60) + 45.3 (62.72) – 2055

PAP 3,642 + 2,841.21 – 20556,483 – 2055 = 4428 watts10% increase in PAPO (see graph #1)

Utilizing Sayers equation above and comparing PAPO before and after training, we see a 10% increase post training.

Two Step, One Leg Vertical Leap

The highest attempt out of 3 trials in the two step, one leg vertical leap post plyo/strength training was 9′ 5 4/5 ″ (289 cm). This led to a 66cm vertical leap and elicited nearly a 3″ increase (7cm) post training. This was an increase of 11%. (see graph # 2 )

Two Step, Two Leg Vertical Leap

The highest attempt out of 3 tries in the two step, two leg vertical leap was 9′ 7 ½″ (293.5 cm).This led to a 70.5 cm vertical leap and elicited a 4.5 ″ increase (11cm) post training. This was an increase of 19%. (see graph # 2)

GRAPH #2

Thirty Yard SprintOut of three trials of 30 yard dash sprints post plyo/strength training, the fastest

time was 4.18 seconds. This was a decrease of .25 seconds over the pretest time of 4.43 seconds.

DISCUSSION

There are an expanding number of plyometric/strength training programs available online or by local “trainers” and so called “experts” that promise to increase power, speed and vertical leap in our young athletes which are not only costly but may cause injury. Unfortunately, our review of the scientific literature yielded no specific research studies or models pertaining to proper placement of adolescent athletes in a safe, effective,

plyometric/power training program. Consequently, we developed a new model of screening young athletes based on concepts of Long Term Athletic Development (LTAD) by Bayli and Way and our Pre-Participation Functional and Strength Screening ( PPFSS ) we created from aspects of Gray Cooks Functional Movement Screen (FMS), as well as material from Dr. Liebenson., Dr. McGill and from tests in the plyometric literature. 8,9,22,29,39 In our case study M.M. was placed in the gold category based on findings related to his peak height velocity (PHV) and score on the PPFSS allowing him placement in unlimited power and plyometric training. No injuries or overtraining effects were noted during or subsequent to the six week training program. Furthermore, M.M. increased his fast twitch muscle fiber growth inferred by a 10% increase in the peak anaerobic power output (PAPO) based on calculations of Sayers Formula. 34 Increases were also shown in the two step, one leg (11%) and two step, two leg vertical leap (19%). There was also a .25 second decrease in 30 yard sprint time which is supported by the literature correlating speed with vertical leap. 25

Furthermore, to enhance safety and effectiveness in our training program we emphasized concepts of periodization, introduced by Mateyeev in 1972 which have been validated as more effective in the scientific literature.26,32,13 Our microcycles (individual workouts) varied from light to super heavy with respect to duration, volume and intensity. To further enhance safety for subjects cleared for plyometric box training (Gold and Silver categories) our literature review yielded box height parameters of 12″ for the Silver category and 12″ and 18″ boxes only for the Gold category as the “ research review” shows diminishing returns and safety issues with the higher box heights.37,2,20,17,21 Also, Nordic lowers were implemented in our warm up protocols which are more effective than hamstring stretches to reduce hamstring strains and injuries. 1

Our new PPFSS and categorized training programs fill a void in the literature for a model to safely place adolescent athletes in a safe, comprehensive and effective plyometric/power training program. Some weaknesses of M.M.’s specific training program need to be addressed. Because of the young author’s desire to enhance vertical leap/power, along with his high level of physical readiness, we (he) decided to augment the plyometric training with sprint training and a limited ½ squat resistance training referenced in protocols and descriptions of training.6,25,38 However, studies have shown that combining strength and plyometric training, as well as complex and compound training programs, do not necessarily increase vertical jump height or power output as compared to performing plyometric/resistance training alone.30,33

PRACTICAL APPLICATIONS

Youth sports today is “big business” with high pressure on young athletes to perform at their highest potential to obtain college scholarships, and perhaps propel them to a professional career. Consequently, this has ignited a “cottage industry” of so-called experts in the plyometric and power training of adolescent athletes which may not be based on scientific literature or the best interest of the young athletes’ safety. Consequently, our new screening model (PPFSS) and category based training program was developed so coaches and trainers have a scientifically based protocol for a safe, effective way to enhance fast twitch muscle fiber (type IIa and type IIx) growth in adolescent athletes. The PPFSS can be seen in this paper and in our video (see page 5)

and can be used by coaches and trainers, as well as health professionals. Ultimately, this model was designed for practical use by coaches, trainers and allied health professions to optimally train adolescent athletes to increase speed, power and vertical leap, which are so vital for youth sports today. This new model of functional screening will allow them to find an appropriate training program for the individual athlete’s “developmental age” and functional capabilities to ensure safety and efficiency in plyometric and power training. The concepts of long term, athletic development are also outlined in great detail and can be utilized in the references. In addition, the specific basketball drills (balance board passes, fingertip pushups, crossover drills) can be utilized specifically for basketball trainers and coaches to enhance quickness, balance, and strength for rebounding. Please contact the authors directly for any further information regarding the study.

References:

1. Arnason, A., Anderson, T.E., et al. (2007) Prevention of hamstring strains in elite soccer: an intervention study. Scand J Med Sci Sports.

2. Asmussen, E., & Bonde-Peterson, F. (1974). Storage of elastic energy in skeletal muscles in man. Acta Physiologica Scandinavia, 92, 385-392.

3. Balyi, Istvan, Way, Richard. The Role of Monitoring Growth in Long-Term Athlete Development. Canadian Sport for Life.

4. Balyi, I., Way, R., Norris, S., Cardinal, C. & Higgs, C. (2005). Canadian sport for life:Long-term athlete developement resource paper. Vancouver, BC: Canadian Sport Centres.

5. Borms, J. (1986). The child and exercise: An overview. Journal of Sports Sciences, 4, 3-20.

6. Chelly, MS., Fathloun, M., Cherif, N., Ben Amar, M., Tabka, Z., Van Praagh, E. (2009) Effects of a back squat training program on leg power, jump, and sprint performances in junior soccer players.. J Strength Cond Res. 23(8):2241-9

7. Cole, Matt (1999) The Theory & Methodology of Periodization. The Straight Dope: Journal of Conditioning. Research Reviews, (2009)

8. Cook, Gray, PT, OCS, Burton, Lee, MS, ATC, Hoogenboom, Barb. (2006) Pre-Participation Screening:The Use of Fundamental Movements as an Assessment of Function – Part 1. North American Journal of Sports Physical Therapy, Volume 1, Number 2.

9. Cook, Gray, PT, OCS, Burton, Lee, MS, ATC, Hoogenboom, Barb, PT, EdD, SCS, ATC. (2006) Pre-Participation Screening: The Use of Fundamental Movements as an Assessment of Function – Part 2. North American Journal of Sports Physical Therapy, Volume 1, Number 3.

10. Dawson, B., et al. (1998) Changes in performance, muscle metabolites, enzymes and fibre types after short sprint training. Eur J Appl Physiol. 78:163.

11. de Villarreal ES, Gonzalez-Badillo, JJ, Izquierdo, M. Low and moderate plyometric training frequency produces greater jumping and sprinting gains compared with high frequency. May 2008: J Strength Cond Res. 22(3):715-25.

12. Diallo, O., Dore, E., Duche, P., Van Praagh, E. (2001) Sep: Effects of plyometric training followed by a reduced training programme on physical performance in prepubescent soccer players. J Sports Med Phys Fitness. 41(3):342-8.

13. Fleck, SJ. (1999) Periodized strength training:a critical review J Strength Cond Res. 13:82.

14. Gollnick, PD., Armstrong, RB., Saubert, CW IV, Piehl, K, and Saltin, B. (1972) Enzyme activity and fiber composition in skeletal muscle of untrained and trained men. J Appl Physiol 33: 312-319.

15. Gollnick, PD, Armstrong, RB, Saltin, B., Saubert, CW IV, Sembrowich, WL., and Shepherd, RE. (1973) Effect of training on enzyme activity and fiber composition of human skeletal muscle. J Appl Physiol 34: 107-111.

16. Gollnick, PD, et al. (1983) Fiber number and size in overloaded chicken anterior latissimus dorsi muscle. J Appl Physiol. 54:1292.

17. Gulick, Dawn T., Fagnani, James, Long, Matthew, Morris, Kenneth, and Hartzell, Brian. Parameters That Influence Vertical Jump Height. United States Sports Academy – “America’s Sports University” The Sport Journal – ISSN: 1543-9518.

18. Hubley, C.L., Wells, R.P. (1983) A work-energy approach to determine individual joint contributions to vertical jump performance. European Journal of Applied Physiology and Occupational Physiology. Springer Berlin/Heidelberg. Volume 50, Number 2.

19. Karlsson, JB., et al. (1975) LDH isozymes in skeletal muscles of endurance and strength trained athletes. Acta Physiol Scand. 93:150.

20. Komi, P.V., & Bosco, C. (1978). Utilization of stored elastic energy in leg extensor muscles by men and women. Medicine and Science in Sports and Exercise. 10, 261-265.

21. Lees, A., & Fahmi, E. (1994) Optimal drop heights for plyometric training. Ergonomics, 37(1), 141-148.

22. Liebenson, Craig, DC. (2001) Sensory-motor training. Self-Help Advise for the Clinician. Journal of Bodywork and Movement Therapies.

23. Liebenson, Craig, DC. (2009) The ABC’s of movement literacy. Self-Management: Patient Section. Journal of Bodywork and Movement Therapies.

24. Luebbers, PE, Potteiger, JA, Hulver, MW, Thyfault, JP., Carper, MJ, Lockwood, RH. (2003) Effects of plyometric training and recovery on vertical jump performance and anaerobic power. J Strength Cond Res. 17(4):704-9.

25. Markovic, G., Jukic, I., Milanovic, D., Metikos, D. (2007) Effects of sprint and plyometric training on muscle function and athletic performance. J Strength Cond Res. 21(2):543-9.

26. Mateyeev, L. (1972) Periodisierang des sportlichen training. Berlin: Berles & Wernitz.

27. McArdle, William D., Katch, Frank I., Katch, Victor L., (2007) Muscular Strength:Training Muscles to Become Stronger. Exercise Physiology Energy, Nutrition & Human Performance Sixth Edition. Lipincott Williams & Wilkins. 22:537.

28. McArdle, William D., Katch, Frank I., Katch, Victor L., (2007) Skeletal Muscle: Structure and Function. . Exercise Physiology Energy, Nutrition & Human Performance Sixth Edition. Lipincott Williams & Wilkins. 18:384.

29. McGill, Stuart M., PHD, Karpowicz, Amy, BSc, MPT. (2009) Exercises for Spine Stabilization: Motion/Motor Patterns, Stability Progressions, and Clinical Technique. Arch Phys Med Rehabil Vol 90.

30. Mihalik, J., Libby, JJ, Battaglini, CL, McMurray, RG. (2008) Comparing short-term complex and compound training programs on vertical jump height and power output. J Strength Cond Res. 22(1):47-53.

31. Pereira, Rafael, Machado, Marco, Miragaya dos Santos, Marcelo, Pereira, Lucas N., Sampaio-Jorge, Felipe. (2008) Muscle Activation Sequence Compromises Vertical Jump Performance. Serbian Journal of Sports Sciences. 2(3): 85-90.

32. Rhea, Matthew R., Alderman, Brandon L. (2004) A meta-analysis of periodized versus nonperiodized strength and power training programs. (Physiology). Research Quarterly for Exercise and Sport.

33. Ronnestad, BR., Kvamme, N., Sunde, A., Raastad, T. (2008) Short-term effects of strength and plyometric training on sprint and jump performance in professional soccer players. J Strength Cond Res. 22(3):773-80.

34. Sayers, S., et al. (1999) Cross validation of three jump power equations. Med Sci Sports Exerc. 31:572.

35. Tesch, PA., Karlsson, J. (1985) Muscle fiber types and size in trained and untrained muscles of elite athletes. J Appl Aphysiol.59:1716.

36. Tesch, PA, et al. Muscle capillary supply and fiber type characteristics in weight and power lifters. J Appl Physiol 1984; 56:35.

37. Voigt, M., Simonsen, E.B., Deyhre-Poulsen, P., & Klausen, K. (1995). Mechanical and muscular factors influencing the performance in maximal vertical jumping after different prestretch loads. Journal of Biomechanics, 28, 293-307.

38. Wislofff, U., Castagna, C., Helgerud, R., Jones, R., Hoff, J. (2004) Strong correlation of maximal squat strength with sprint performance and vertical jump height in elite soccer players. Br J Sports Med. 38:285-288.

39. Wilson, G., et al. (1997) Performance benefits from weight and plyometrics training: effects of initial strength level. Coach Sport Scienct J. 2:3.