This presentation highlights the key points from a paper that was published in 2018 on Journal of Australian Strength and Conditioning. https://www.researchgate.net/publication/329884639_Fitness_Testing_Battery_Battery_for_Rugby_League_Obtraining_Meaningful_Information_From_Data

1. Fitness Testing Battery for
Rugby League: Obtaining
Meaningful Information
from the Data
By
Norbert Keshish Banoocy, MSc, ASCAL2,
CSCS, USAW

2. The Purpose of this Presentation
• Provide background information on Rugby League (RL) football
• Propose a testing battery that is both valid and reliable
• Show different methods that S&C coaches can use to gain deeper insight into
the underlying physical qualities of the athletes they work with
• What if we don’t have the resources?
• And……
• Hopefully, provoke some conversation and critical thinking!

3. Why Test?!
• Players possess numerous physical and
physiological qualities; therefore, it is
important to:
• Track training progress and athlete
development process
• Compare players within the squad
and amongst different positions
(Figure 1)
• Compare to normative/descriptive
data (Table 1)
• Monitor player fitness and fatigue
• Assess strengths and weaknesses
• Design individualized training
programs
• Aid the decision-making process

4. Figure 1: Within Squad Player
Comparison
-2.0
-1.5
-1.0
-0.5
0.0
0.5
1.0
1.5
Mass
Σ7 Skinfold
CMJ
0-5
0-5 Sprint Momentum1RM Squat
Squat: Mass Ratio
Peak Power
VIFT
Player 1 vs. Player 2
Player 1 Player 2 Squad Mean

5. Table 1: Physical and Physiological Characteristics of Rugby League Players of Different
Playing Standards and Positions a
Variables Reported Values Based on Playing Level, Age, and Standard
Height (cm)
Senior elite ugby league players (183.9-184.2)
Junior elite rugby league players (171.0-182.0)
Body Mass (cm)
Elite NRL and Junior-elite NYC (U20) (96.1±9.6 (93.8±98.5))
Professional Rugby League Forwards (97.47±8.69)
Professional Rugby League Backs (85.15±6.69)
Senior elite rugby league players (94.0-97.6)
Junior elite rugby league players (75.2-95.1)
∑7 Skinfold (mm)
Elite NRL and Junior-elite NYC (U20) (71.1±18.9 (66.4-75.7))
Senior elite rugby players (47.0-60.8)
Junior elite rugby players (64.3-68.5)
Lean Mass Index
(kg)
Elite NRL and Junior-elite NYC (U20) (54.3±5.2 (53.0-55.5))
Vertical Jump (cm)
Senior elite rugby league players (37.3-64.7)
Junior elite rugby league players (43.5-52.8)
Eccentric Utilization
Ratio (EUR)
Rugby Union Athletes based on Jump Height (Off-season: 1.13±0.14)
(Pre-season: 1.33±0.23)
Rugby Union Athletes based on Peak Power (Off-season: 1.01±0.20)
(Pre-season: 1.19±0.09)

6. 5-0-5 Agility Test (s)
Elite NRL and Junior-elite NYC (U20) (2.33±0.15 (2.29-2.37))
First grade rugby league players (2.34±0.20)
Second Grade rugby league players (2.39±0.15)
L-Run (s)
First Grade rugby league players (6.36±0.53)
Second Grade rugby league players (6.49±0.40)
5-meter Sprint (s)
First Grade rugby league players (1.14±0.06)
Second Grade rugby league players (1.20±0.11)
10-meter Sprint (s)
NRL (1.61±006)
SRL (1.60±005)
Elite NRL and Junior-elite NYC (U20) (1.66±0.07 (1.65-1.68))
First Grade rugby league players (1.90±0.09)
Second Grade rugby league players (2.00±0.14)
40-meter Sprint (s)
NRL (5.15±024)
SRL (5.13±017)
Elite NRL and Junior-elite NYC (U20) (5.17±0.19 (5.13-5.22))
Professional rugby league forwards (5.27±0.19)
Professional rugby league backs (5.08±0.20)
Sprint Momentum
(Kg.m/s)
NRL 10-meter Sprint Momentum (610±51)
SRL 10-meter Sprint Momentum (570±46)

7. 1RM Squat (kg)
NRL (175.0±27.3)
SRL (149.6±14.3)
Professional rugby league players 3RM full squat (157.9±18.8)
Professional rugby league players before pre-season training (170.6±21.4)
Professional rugby league players after pre-season training (200.8±19.0)
1RM Bench Press (kg)
Professional rugby league forwards (123±11.76)
Professional rugby league backs (114±17.03)
Relative Squat 1RM
Strength (kg/kg)
Professional rugby league players before pre-season training (1.78±0.27)
Professional rugby league players after pre-season training (2.05±0.21)
VO2max (ml/kg/min)
Elite NRL and Junior-elite NYC (U20) VO2max estimated from 30-15IFT (50.0±3.2 (49.3-
50.3))
VO2max (predicted) for senior elite rugby league players (54.9-55.9)
VO2max (predicted) for junior elite rugby league players (46.4-51.7)
30-15IFT (VIFT) (km/h)
Combined average data from 2 trials for U20, U18, U16 (18.45±1.0)
Elite NRL and Junior-elite NYC (U20) (18.4±0.9 (18.2-18.6))

8. • Data adapted from previous publications (3, 4, 8, 15, 17, 21, 25, 31, 32)
• NRL = National Rugby League, SRL = State Rugby League, NYC = National Youth
Competition
• a Data are presented as mean±SD or means (95% CI)

9. Introduction
• Rugby league football (RL) is played over two 40-minute halves
separated by a 10 minute half-time.
• Intermittent Sport : Periods of high intensity activity separated by
periods of low intensity activity (11, 12, 17).
• Each team has 13 players on the field that are grouped into
forwards and backs.
• Forwards are involved in more collisions (11, 12, 17).
• Backs are involved in more running (11, 12, 17).

10. Demands of the Game
• Total Distance (TD) (2, 14, 17, 23, 24, 40) :
• Average Distance of ~4,000-8,000 m based on playing position and level of
play
• Outside backs: ~5,500-8,000 m
• Adjustables: ~6,000-7,000 m
• Forwards: ~3,500-6,000 m

11. Demands of the Game (Cont’d)
• Average Heart Rate (%HRmax) (17, 40):
• Backs: 83.5±1.9%
• Adjustables: 81.5±4.1%
• Forwards: 84.1±8.2%
• Relative Distance (m/min) (14, 17, 23, 39, 40) :
• 90-100 m/min
• Can vary based on ball being in play and the level of the play

12. Demands of the Game (Cont’d)
• High-Speed Running (HSR) Distance (17, 40):
• Outside Backs: 926±291 m
• Adjustables: 907±255 m
• Forwards: 513±298 m

13. What is important to test?
• The testing battery needs to include :
• Anthropometry (height, body mass, body composition)
• Acceleration and Top speed
• Agility and Change of Direction Speed (CODS)
• Muscular Strength and Power
• High-Intensity Running and Aerobic power

14. Anthropometry
• Players engage in collisions throughout the games and practices; hence, it is
important to keep track of different measures of anthropometry (i.e. lean mass
vs. fat mass)
• Increased amounts of body fat (BF) decreases power-to-body-mass ratio (P:BM),
thermoregulation, aerobic power (VO2max) (9, 25).
• Also, a reduction in acceleration capabilities is also evident when increase in
non-functional mass requires players to move a heavier body (9, 25).
• It has been shown body composition changes throughout a RL season in
Australia where players tend to gain fat mass and lose lean mass (7).
• More reasons as to why coaches need to keep track!

15. Anthropometry: Recommendations
• 7-site skinfold assessment by International Society for the Advancement in
Kinanthropometry (ISAK) (37):
• Measurements of skinfold thickness from triceps, subscapular, biceps, supraspinale,
abdominal, front of thigh, and calf.
• Use the ∑7 skinfold to calculate body density (Db), then convert to %body fat (%BF).
• Standard error of estimate of the prediction equations for Db is 2-5%.
• 3 Steps:
Step 1: Bd = 1.112 – 0.00043499 (sum of 7 sites) + 0.00000055 (sum of 7 sites)2 – 0.00028826 (age)
(26).
Step 2: %BF= (5.21 / Db) – 4.78 (29).
Step 3: Fat Mass = body mass x % Fat → Fat Free Mass = body mass – fat mass (20).

16. Anthropometry: Recommendations
(Cont’d)
• Lean Mass Index (LMI)
• Tracks intra-subject proportional changes in body mass considering changes
in skinfold thickness (36).
• Correlated to dual-energy x-ray absorptiometry (DXA) (r=0.95, SEE=1.89 kg)
(10).
• A strong predictor of fat-free mass compared to bioelectrical impedance
analysis (BIA) (BIA 97% vs. Skinfold 63%) likelihood to track changes in lean
mass within RL players (10).
• LMI is calculated:
• LMI = M/Sx
• Where, M is the athlete’s body mass in (kg), S is the ∑7 skinfolds in (mm), and
x is the exponent which is (0.13 for forwards and 0.14 for backs) (10, 36).

17. Acceleration and Top Speed
• Sprinting patterns of National Rugby League Competition (NRL) players (13) :
• Majority of the sprints occurred across distances of <20 m (67.5%, ES= 1.7)
• Sprints between 6-10 m had the highest frequency (39.7%) (13).
• Distances between 11-20 m (27.8%) (13).
• About (85%) of the sprints occurred over <30 m (ES=1.6).
• Hit-up forwards over 6-10 m (46.4%) , distances >21 m occurred (18.4%), and (5.0%) for >40 m (13).
• Outside backs, wide running forwards, and adjustables for distances >21 m:
• (33.7%), (26.0%), and (17.3%), respectively (13).
• Sprints >40 m occurred (5.0%), (7.4%), (5.0%), and (9.7%) for hit-up forwards, wide
running forwards, adjustables, and outside backs, respectively (13).
• Although a lesser proportion of sprints occurred at distances >40 m, it still
highlights the importance of top speed amongst various positions.

18. Acceleration and Top
Speed: Recommendations
• 40-m speed test
• Intraclass correlation coefficient
(ICC): 0.97 (13).
• Typical Error (TE): 1.2% (13).
• “first step quickness” and acceleration:
• Can be obtained from 0-5, 0-10 or 0-
20-m split times.
• Top-speed:
• 20-40 or 30-40-m split times
• Flying start

19. Sprint Momentum (SM)
• NRL players possessing similar
velocities as State Rugby League
(SRL) players (4).
• Distinguishing factor was BM
(kg) of the NRL (4)
• 7% greater SM (4)
• SM (kg.m/s) = Velocity (m/s) x BM
(kg) (4, 5).

20. Agility and Change of Direction Speed
(CODS)
• Agility is defined as “a whole-body movement with change of velocity or direction
in response to a stimulus” (35).
• Composed of : perceptual and decision-making factors (i.e. visual scanning,
anticipation, knowledge of situation, pattern recognition) and change of direction
speed (CODS) (35).
• The sport-specific reactive agility test (RAT) using a rugby specific video-based
stimulus:
• (ICC=0.82) for agility time (33).
• Human-based stimulus :
• Movement time (ICC=0.92) (15).
• Decision time (ICC=0.95) (15).
• Response accuracy (ICC=0.93) (15).

21. CODS
• CODS tests are unable to discriminate between players of different skill levels and
performance and reactive agility tests have been poorly correlated with the 5-0-5
and L-run COD test performance (15).
• Measure of total time masks the true ability to change direction due to its
dependence on linear sprinting ability (27).
• Angle of direction change (45 ̊, 90 ̊,180 ̊) (27).
• Entry velocity (i.e. run-up distance and speed) will influence the test (27).
• Validity Questioned!!

22. CODS: Recommendations (Cont’d)
• L-Run test: maneuverability and ability to maintain velocity
• (ICC=0.94, 95%CI=0.90-0.95, CV%=1.96, and SEM =0.17) (27, 38).
• T-test : Forward, Lateral, Backward movements
• (ICC=0.95, 95%CI=0.92-0.97, CV%=1.96, and SEM=0.21) (38).
• 5-0-5 Agility test: 180 ̊ COD
• (ICC=0.88, 95%CI=0.81-0.93, CV%=2.40, and SEM=0.06) (38).
• COD Deficit: Isolating the Ability to Change Direction
• Not correlated with sprint time (r= -0.11-0.10) but be correlated to 5-0-5 (r=0.74-0.81)
(28).
• COD Deficit = COD Test completion time (s) – Completion time of a similar
distance (s) (27).

23. Muscular Strength and Power
• Muscular force and power generation are critical in tackling, lifting, pushing, and
pulling opponents during the game, as well as fast play-the-ball speed and having
an effective leg drive during tackles (12, 25).
• Relative measures of strength and Power to Body Mass Ratio (P:BM) expressed via
3RM squat and 3RM power clean from the hang and loaded jump squats are
significantly related to 10- and 40-m sprint as opposed to absolute measures in
professional RL players (r= -0.52 to r= -0.76 (p≤0.05)) (3).
• Improvement in both relative and absolute measures of strength assessed via 1RM
squat resulted in significant improvement in 5-,10-,20-m sprint performance in RL
players (8).

24. Muscular Strength: Recommendations
• 1RM Squat and Bench Press as a measure of lower and upper body strength
• ICC values of (0.97) and (0.98) (22, 34).
• Use absolute measures to gain insight into relative strength:
• Relative Strength (kg/kg) = 1RM (kg)/BM (kg)
• To account for the different body sizes and obtain an index that is independent of
body size, you need to allometrically scale the data (16).
• Sn=S/m0.67 (16).
• Where S is the load lifted, and m represents the body mass of the athlete.

25. Muscular Power: Recommendations
• Countermovement jump test (CMJ), and the squat jump test (SJ):
• Test-retest reliability for the jump heights measured (ICC=0.98 for CMJ, and
ICC=0.96 for SJ) (19).
• Jump height = (g x flight time x flight time)/8 (19).
• Peak power (PP) using Sayers power equation (30):
• Peak Power (W) = 60.7x (jump height (cm) +45.3x (body mass (kg))-2055.
• Express PP in relative terms (i.e. PP/BM) and/or allometrically scale.

26. Muscular Power: Stretch-Shortening Cycle
(SSC)
• % pre-stretch augmentation: assesses the effect of a pre-stretch on a movement (21).
• % pre-stretch augmentation = [(CMJ-SJ) X SJ-1] x 100
• Reactive strength: assesses the ability to use the pre-stretch during the CMJ (21).
• Reactive Strength=CMJ-SJ
• Eccentric Utilization Ratio (EUR): ratio between the CMJ and SJ jump height and/or
PP data (21).
• EUR = CMJ/SJ
• Provides information about the SSC performance
• Sensitive to the type of training being undertaken with values increasing from
off-season to pre-season for rugby athletes (off-season values using jump height
= 1.13±0.14 to pre-season = 1.33 ±0.23, and values for PP = 1.01±0.20 to 1.19±0.09) (21).

27. High-Intensity Running and Aerobic
Power
• RL players need to cover a large amount of distance during a match and engage in
various high-intensity activities (17).
• Hence, it is important for the players to have a developed VO2max to cover such
distances and to recover from the high intensity activities rapidly.
• Repeated high-intensity exercise (RHIE) bouts appear to be more common during
critical times in a match, as opposed to repeated-sprint ability (RSA) that appears to
be more common in other team sports (1, 17).

28. High-Intensity Running and Aerobic
Power : Recommendations
• 30-15 Intermittent Fitness Test (30-15IFT) developed by Martin Buchheit (6).
• TE of (0.36 km/h) and a ICC of (0.89) and a CV of (1.9%) (31).
• Large correlation with Yo-Yo IR1 (r=0.75) which is commonly used within rugby
(31).
• TE and the smallest worthwhile change (SWC) for this test is less than 1 stage or
0.5 km/h, which can be reflected as a meaningful change in performance (31).
• Valid measure of prolonged high-intensity intermittent running within rugby
league (32).

29. High-Intensity Running and Aerobic
Power : Recommendations (Cont’d)
• The test is conducted over 40-m in 30 second shuttles that is separated by 15 seconds
of active recovery that starts out at 8 km/h and is increased by 0.5 km/h after every
stage completed (6).
• The velocity achieved at the end of the 30-15IFT is referred to as VIFT which can be used
to estimate VO2max with the following formula:
• VO2max 30-15IFT (ml/min/kg) = 28.3 - 2.15G - 0.741A -0.0357W + 0.0586A x VIFT + 1.03VIFT (G
= gender (female = 2; male = 1), A=age, W=weight) (6).
• VIFT can be used to individualize interval training sessions as opposed to the more
commonly used vVO2max (6).
• VIFT is typically 2-5 km/h faster than velocities achieved at the end of continuous tests
(6).
• VIFT reflects a player’s anaerobic velocity reserve (AVR) (6).
• Considers accelerations, decelerations, ability to change direction, between effort
recoverability, and RSA which taxes aerobic, anaerobic, and neuromuscular
qualities (6) that are common in intermittent team sports such as rugby.

30. Testing Battery Sequence
Day 1: AM Session Day 1: PM Session
Anthropometry (Height and Body Mass) 40-meter sprint
CMJ 1RM Squat
SJ
5-0-5 Agility Test
Day 2: AM Session Day 2: PM Session
Anthropometry (Sum of 7 Skinfold) 30-15IFT
1RM Bench Press

31. References
1. Austin DJ, Gabbett TJ, and Jenkins DJ. Repeated high-intensity exercise in a professional rugby league. Journal of strength and
conditioning research / National Strength & Conditioning Association 25: 1898-1904, 2011.
2. Austin DJ and Kelly SJ. Positional differences in professional rugby league match play through the use of global positioning
systems. Journal of strength and conditioning research / National Strength & Conditioning Association 27: 14-19, 2013.
3. Baker D and Nance S. The Relation Between Running Speed and Measures of Strength and Power in Professional Rugby League
Players. 1999.
4. Baker DG and Newton RU. Comparison of lower body strength, power, acceleration, speed, agility, and sprint momentum to
describe and compare playing rank among professional rugby league players. Journal of strength and conditioning research /
National Strength & Conditioning Association 22: 153-158, 2008.
5. Barr MJ, Sheppard JM, Gabbett TJ, and Newton RU. Long-term training-induced changes in sprinting speed and sprint
momentum in elite rugby union players. Journal of strength and conditioning research / National Strength & Conditioning
Association 28: 2724-2731, 2014.
6. Buchheit M. The 30-15 Intermittent Fitness Test : 10 year review. 2009.
7. C Georgeson E, Weeks B, McLellan C, and Beck B. Seasonal change in bone, muscle and fat in professional rugby league players
and its relationship to injury: A cohort study. 2012.
8. Comfort P, Haigh A, and Matthews MJ. Are changes in maximal squat strength during preseason training reflected in changes in
sprint performance in rugby league players? Journal of strength and conditioning research / National Strength & Conditioning
Association 26: 772-776, 2012.
9. Coneyworth P, Turner A, and Ward N. A field based test battery for Rugby League. 2012.
10. Delaney JA, Thornton HR, Scott TJ, Ballard DA, Duthie GM, Wood LG, and Dascombe BJ. Validity of Skinfold-Based Measures
for Tracking Changes in Body Composition in Professional Rugby League Players. International journal of sports physiology and
performance 11: 261-266, 2016.

32. 11. Gabbett T. Science of rugby league football: A review. 2005.
12. Gabbett T, King T, and Jenkins D. Applied physiology of rugby league. Sports medicine (Auckland, NZ) 38: 119-138, 2008.
13. Gabbett TJ. Sprinting patterns of National Rugby League competition. Journal of strength and conditioning research / National
Strength & Conditioning Association 26: 121-130, 2012.
14. Gabbett TJ, Jenkins DG, and Abernethy B. Physical demands of professional rugby league training and competition using
microtechnology. Journal of Science and Medicine in Sport 15: 80-86, 2012.
15. Gabbett TJ, Kelly JN, and Sheppard JM. Speed, change of direction speed, and reactive agility of rugby league players. Journal of
strength and conditioning research / National Strength & Conditioning Association 22: 174-181, 2008.
16. Jaric S. Muscle strength testing: use of normalisation for body size. Sports medicine (Auckland, NZ) 32: 615-631, 2002.
17. Johnston RD, Gabbett TJ, and Jenkins DG. Applied Sport Science of Rugby League. Sports Medicine 44: 1087-1100, 2014.
18. Lees A, Vanrenterghem J, and Clercq DD. Understanding how an arm swing enhances performance in the vertical jump. Journal of
Biomechanics 37: 1929-1940, 2004.
19. M Carlock J, L Smith S, Hartman M, T Morris R, A Ciroslan D, Pierce K, Newton R, A Harman E, Sands W, and Stone M. The
Relationship Between Vertical Jump Power Estimates and Weightlifting Ability: A Field-Test Approach. 2004.
20. Malina RM. Body composition in athletes: assessment and estimated fatness. Clin Sports Med 26: 37-68, 2007.
21. McGuigan MR, Doyle TL, Newton M, Edwards DJ, Nimphius S, and Newton RU. Eccentric utilization ratio: effect of sport and
phase of training. Journal of strength and conditioning research / National Strength & Conditioning Association 20: 992-995,
2006.
22. McGuigan MR and Winchester JB. The Relationship Between Isometric and Dynamic Strength in College Football Players.
Journal of Sports Science & Medicine 7: 101-105, 2008.
23. McLellan CP and Lovell DI. Performance analysis of professional, semiprofessional, and junior elite rugby league match-play
using global positioning systems. Journal of strength and conditioning research / National Strength & Conditioning Association
27: 3266-3274, 2013.
24. McLellan CP, Lovell DI, and Gass GC. Performance analysis of elite Rugby League match play using global positioning systems.
Journal of strength and conditioning research / National Strength & Conditioning Association 25: 1703-1710, 2011.

33. 25. Meir R, Newton R, Curtis E, Fardell M, and Butler B. Physical Fitness Qualities of Professional Rugby League Football Players:
Determination of Positional Differences. 2001.
26. Miller T, ed. NSCA's guide to tests and assessments. Champaign, IL :: Human Kinetics, 27-28, 2012.
27. Nimphius S, Callaghan S, Bezodis N, and Lockie R. Change of Direction and Agility Tests: Challenging Our Current Measures of
Performance. 2017.
28. Nimphius S, Callaghan S, Spiteri T, and Lockie R. Change of Direction Deficit: A More Isolated Measure of Change of Direction
Performance Than Total 505 Time. 2016.
29. Pescatello LS, Arena R, Riebe D, Thompson PD, eds. ACSM's guidelines for exercise testing and prescription. Philadelphia ::
Wolters Kluwer/Lippincott Williams & Wilkins Health, 71, 2014.
30. Sayers SP, Harackiewicz DV, Harman EA, Frykman PN, and Rosenstein MT. Cross-validation of three jump power equations.
Medicine and science in sports and exercise 31: 572-577, 1999.
31. Scott TJ, Delaney JA, Duthie GM, Sanctuary CE, Ballard DA, Hickmans JA, and Dascombe BJ. Reliability and Usefulness of the
30-15 Intermittent Fitness Test in Rugby League. Journal of strength and conditioning research / National Strength &
Conditioning Association 29: 1985-1990, 2015.
32. Scott TJ, Duthie GM, Delaney JA, Sanctuary CE, Ballard DA, Hickmans JA, and Dascombe BJ. The Validity and Contributing
Physiological Factors to 30-15 Intermittent Fitness Test Performance in Rugby League. The Journal of Strength & Conditioning
Research 31: 2409-2416, 2017.
33. Serpell BG, Ford M, and Young WB. The development of a new test of agility for rugby league. Journal of strength and
conditioning research / National Strength & Conditioning Association 24: 3270-3277, 2010.
34. Sheppard JM, Cronin JB, Gabbett TJ, McGuigan MR, Etxebarria N, and Newton RU. Relative Importance of Strength, Power, and
Anthropometric Measures to Jump Performance of Elite Volleyball Players. The Journal of Strength & Conditioning Research 22:
758-765, 2008.
35. Sheppard JM and Young WB. Agility literature review: classifications, training and testing. J Sports Sci 24: 919-932, 2006.
36. Slater GJ, Duthie GM, Pyne DB, and Hopkins WG. Validation of a skinfold based index for tracking proportional changes in lean
mass. British Journal of Sports Medicine 40: 208-213, 2006.

34. 37. Stewart A, Marfell-Jones M, Olds T, and De Ridder J. International Standards for Anthropometric Assessment. 2011.
38. Stewart PF, Turner AN, and Miller SC. Reliability, factorial validity, and interrelationships of five commonly used change of
direction speed tests. Scandinavian Journal of Medicine and Science 24: 500-506, 2014.
39. Varley M, Gabbett T, and Aughey R. Activity profiles of professional soccer, rugby league and Australian football match play.
2013.
40. Waldron M, Twist C, Highton J, Worsfold P, and Daniels M. Movement and physiological match demands of elite rugby league
using portable global positioning systems. J Sports Sci 29: 1223-1230, 2011.
Images obtained from Google Images.