DETECTING DEFICITS IN CHANGE OF DIRECTION PERFORMANCE USING THE PREPLANNED MULTIDIRECTIONAL AUSTRALIAN FOOTBALL LEAGUE AGILITY TEST NICOLAS H. HART,1,2 TANIA SPITERI,1 ROBERT G. LOCKIE,3 SOPHIA NIMPHIUS,1 ROBERT U. NEWTON1
AND
1
Centre for Exercise and Sport Science Research, Edith Cowan University, Perth, Australia; 2Fremantle Dockers Football Club, Fremantle, Australia; and 3School of Environmental and Life Sciences, University of Newcastle, New South Wales, Australia
ABSTRACT
with particular leg dominance profiles and to provide a limb
Hart, NH, Spiteri, T, Lockie, RG, Nimphius, S, and Newton, RU. Detecting deficits in change of direction performance using the preplanned multidirectional Australian Football League agility test. J Strength Cond Res 28(12): 3552–3556, 2014—The Australian Football League (AFL) agility test is a preplanned multidirectional circuit involving 5 directional changes of various magnitudes that might differently assess athletes of particular leg dominance. This study served to establish whether the AFL agility test appropriately examines athletes of differing limb dominance, while also quantifying performance deficits prevalent between limbs of Australian Footballers. Fifty-eight Australian Footballers were recruited from the Western Australian Football League (age = 21.9 6 2.8 years; height = 183.7 6 5.9 cm; weight = 86.4 6 4.7 kg). Two circuits of the AFL agility test were set up in accordance with official specifications. The finish line of the second circuit was relocated to the opposite side to modify the starting direction. Footballers were randomized and counterbalanced between versions, performing 3 trials in each direction. Paired t-tests (p # 0.05) were used to examine differences between dominant and nondominant trials. Independent t-tests (p # 0.05) were used to identify differences between left and right leg dominant groups. The current version of the AFL agility test appropriately examined ;61% of footballers in this cohort. The remaining ;39% produced significantly faster times during the alternate version (0.63–0.82 seconds; p # 0.001). All footballers demonstrated a performance deficit of 5–10% between limbs (;0.72 seconds; p # 0.001). Limb dominance (directional preference) was evident for all footballers. Change of direction capabilities should therefore be examined bilaterally to eliminate bias toward athletes
deficit measure for enhanced athletic profiling outcomes.
Address correspondence to Nicolas H. Hart, [email protected]. 28(12)/3552–3556 Journal of Strength and Conditioning Research Ó 2014 National Strength and Conditioning Association
3552
the
KEY WORDS strength, imbalance, asymmetry, directional preference, athlete profiling
INTRODUCTION
T
he recruitment process of the Australian Football League (AFL) purports to examine a variety of physical and technical athletic competencies as part of a structured talent identification system (5,24). The annually operated national draft camp quantifies these attributes through a series of standardized assessments (anthropometry, vertical jumps, sprints, agility, endurance, and technical skills) that are subsequently benchmarked against historical data, fellow competitors, and reference values to assist talent scouts with their decision-making process (5,16,23). In particular, outcomes provided by this profiling system are relied on to identify talent, player strengths and weaknesses, position suitability, and assist in the optimal design of strength and conditioning programs (6,24,28), yet are only moderately predictive of early-career success (5,23). Despite this modest predictive power, information gathered by these standardized examinations continue to produce valuable athletic profiling and physical competency insights into emerging Australian Footballers for sport scientists, strength and conditioning coaches, and football coaches. The ability to pursue or evade an opponent is a critical attribute for an Australian Footballer (4,30); therefore, determining the ability of footballers to change direction effectively is of high importance to recruiters, coaches, and athletes alike (10,26). This specific physical attribute is assessed during the national draft camp through the AFL agility test; a custom preplanned circuit that involves 5 multidirectional changes of various magnitudes (3 left and 2 right). Although the AFL agility test has been previously viewed to appropriately assess a footballer’s ability to change direction, it may be biased toward athletes of particular leg dominance, and by extension
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Figure 1. A schematic overview of the original version (25) of the AFL agility test (left); with a modified version of the AFL agility test (right), adjusted to suit limb dominance.
preferred cutting direction. Specifically, the test contains more directional changes to the left, of which the first directional change is the greatest in magnitude (;2308), has the longest approach (;5 m), and therefore has the highest entry velocity. It therefore stands to reason that those who preferentially move left will score higher in this test, disadvantaging those who prefer right-side directional motion. Given the underlying importance of test scores using this measure, the evident limitation of a preferred cutting direction in the current AFL agility circuit must be recognized by recruiters, and the test modified for increased equity when assessing change of direction proficiency. The AFL agility test currently only examines the performance capacity of an athlete using a single scenario and does not seek to examine deficiencies in change of direction performance between limb dominance and directional preference profiles. However, it is of practical relevance to understand and examine the level of movement deficiency between dominant and nondominant limbs during left and right directional changes. Athletes with lower deficits across limbs and directions could be more attractive to recruiters, as this could potentially indicate a greater physical ability to respond dynamically (in any direction) within the volatile environment of Australian Football. Conversely, footballers with greater disparities between limbs may not only indicate lower quality change of direction performance (increased performance rigidity) but could also highlight a physical weakness that could predispose them to a higher risk of injury if forced, by the constraints of elite-level competition, to change direction to their undesired side.
This study therefore seeks to examine change of direction performance of Australian Footballers under left- and rightstarting conditions using the preplanned, multidirectional AFL agility test to (a) establish whether the current AFL agility test appropriately examines Australian Footballers of differing limb dominance and (b) establish whether a performance deficit exists between dominant and nondominant limbs of Australian Footballers.
METHODS Experimental Approach to the Problem
This study used an acute cross-sectional design conducted during a single testing session on an indoor wooden court surface (Figure 1). Footballers were provided with a standardized dynamic warm-up spanning 15 minutes in duration, followed by 3 submaximal runs through each agility circuit to conclude warm-up preparations. Footballers were required to perform a total of 6 AFL agility trials: 3 trials commenced with the initial, sharp directional change to the left (version 1: current), and 3 trials commenced with an initial sharp directional change to the right (version 2: additional). Trials were randomized and counterbalanced for all footballers with 2-minute recovery provided between each effort. Athletes were stratified into left direction (right foot) or right direction (left foot) dominant groups in conjunction with their fastest completion times. Subjects
Fifty-eight subelite Australian Footballers (n = 58; age = 21.9 6 2.8 years; height = 183.7 6 5.9 cm; weight = 86.4 6 4.7 kg) VOLUME 28 | NUMBER 12 | DECEMBER 2014 |
3553
Copyright © National Strength and Conditioning Association Unauthorized reproduction of this article is prohibited.
Performance Deficits During Changes of Direction reliably performed (coefficient of variation [CV] #0.3%; intraclass correlation coefficient [ICC] $ 0.993) by the same accredited exercise scientist (ESSA, Australia). Australian Football League Agility Protocol
Figure 2. Completion times for directional preference across the initial left turn (left start; current version) and initial right turn (right start; additional version) AFL agility circuits.
were recruited from the Western Australian Football League (WAFL). Athletes from all positions (forwards, midfielders, and backs) were recruited for use in this study, as the ability to change direction quickly is a required skill by all Australian Football players; therefore, no position specific bias was expected. Athletes were free from injury at the time of testing and were not permitted to perform strenuous exercise or lowerbody resistance training within 48 hours of their testing session. All athletes provided written informed consent before testing. Ethics approval was provided by the institutional review board. Procedures
Anthropometry. Stature was recorded to the nearest 0.1 cm using a wall-mounted stadiometer (Model 222; Seca, Hamburg, DE, USA), with body mass recorded to the nearest 0.1 kg using an electronic weighing scale (AE Adams CPW Plus-200; Adam Equipment, Inc., CT, USA). Shoes were not permitted to be worn during these measures. Stature was measured 3 times with the average of the 3 trials retained for analysis. All measures were
Two AFL agility circuits were created with the same specifications (dimensions and equipment) as per AFL draft camp requirements (25). Two sets of dual-beam infrared electronic timing gates (Speedlight Timing System; Swift Performance, NSW, Australia) were separated by 1 m at the start line and 2 m at the finish line of each AFL agility circuit; with 5 weighted poles (10–12 cm diameter, 25 cm base, and 1.1 m height) positioned throughout the circuit (Figure 2). Subjects were required to start from a stationary upright position with their front foot positioned on the start line, in line with the timing gates. Once in position, each participant commenced their trial when ready, and no information regarding optimal technique was issued. Subjects were instructed only to progress through the course as quickly as possible without moving or knocking the poles. Verbal encouragement was provided during each trial. Any false starts or invalid trials were repeated after a 1-minute rest period. Familiarization of each circuit formed part of their specific warm-up (3 submaximal attempts at 50, 70, and 90% of perceived maximum effort, respectively). Each version of the AFL agility circuit was randomized and counterbalanced, with 29 subjects completing 3 trials of version 1 followed by 3 trials of version 2. The remaining 29 subjects completed the opposite order of testing. Although 2-minute recovery was provided between trials within each circuit, 5-minute recovery was provided between versions of the test to minimize any effects of fatigue. Statistical Analyses
Descriptive statistics (mean 6 SD) were calculated for all results. Paired t-tests (p # 0.05) were used to determine whether significant differences existed between performance times of dominant and nondominant trials as a withinsubject measure. Independent t-tests (p # 0.05) were used to determine whether significance differences between perforTABLE 1. Descriptive characteristics of subjects and performance, stratified by mance times of left direction directional and leg dominance.* (right foot) and right direction Left direction/right foot Right direction/left foot (left foot) dominant groups (n = 36) (n = 22) were prevalent. All statistical examinations were performed Age, y 21.4 6 3.4 22.6 6 2.4 Height, cm 183.1 6 6.1 184.2 6 5.8 using statistical analysis softWeight, kg 85.3 6 4.3 87.8 6 5.4 ware (PASW, version 19.0; Completion time (left) 8.17 6 0.3†z 8.99 6 0.3†z IBM, Chicago, IL, USA). Completion time (right) Interlimb deficit, %
8.90 6 0.3†z 8.2 6 0.1
*Values are expressed as mean 6 SD. †Statistical significance (p # 0.001) between groups. zStatistical significance (p # 0.001) between left and right trials.
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8.27 6 0.3†z 8.0 6 0.1
RESULTS Limb dominance and directional preference (a preferred path to change direction) was evident for all footballers.
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Journal of Strength and Conditioning Research Thirty-six subjects were 8.2% (0.73 seconds; p # 0.001) faster during the left turn (right foot) dominant circuit when compared with the right turn (left foot) dominant circuit. Conversely, 22 of 58 athletes were 8.0% (0.72 seconds; p # 0.001) slower when using the original AFL agility test (left turn, right foot dominant). Therefore, version 1 of the AFL agility test appropriately assessed 61% of athletes, whereas 39% of athletes performed better when the starting direction was modified to suit their dominance profile in version 2. A performance disparity of approximately 8% was prevalent between dominant and nondominant COD trials for each group (Figure 2; Table 1).
DISCUSSION The AFL agility test requires footballers to always perform 3 left-side and 2 right-side changes in direction (25,30), with a rapid entry and steep initial turn to the left around the first agility pole. However, the results of this study identify potential limitations in the ability of the current version of the AFL agility test to assess all players equally within the constraints of the task. In particular, only 61% of Australian Footballers in our cohort were suited to the AFL agility test currently used in the national draft camp, with 39% better suited to the alternate version. In the absence of bilateral starting directions, the AFL agility test disadvantages athletes who are right turn (left leg) dominant, thus assisting athletes who are left turn (right leg) dominant to produce faster performance times. The AFL agility test should be broadened to include both the original version and the additional version investigated in this study. These findings not only have implications for the AFL draft camp, testing, and recruitment model but also match performance and injury risk management. Footballers displayed an evident interlimb deficit in performance of 8% (;0.7 seconds) between dominant and nondominant trials. This prevalence of an interlimb deficit could provide another useful measure of performance for recruiters to consider. An athlete with a lower performance deficit, and therefore a smaller loss of speed between conditions may indicate higher level performance or improved training status. Previous research has demonstrated an evident sacrifice in skilled performance in athletes with larger deficits in lean mass and leg strength (11,12,18), which would likely also translate to change of direction activities (2,15,22,26,29). Because of the importance of changing direction in Australian Football, with most sprints containing at least 1 directional change (8), it is important for coaches to be able to identify any performance discrepancies in their players. This could be achieved by testing players in both versions of the AFL agility test. Previous research has used direct strength assessments of imbalance through isokinetic and isometric modalities (1,13,20) to identify potential relationships with performance or injury incidence. However, a majority of these studies used single-joint movements, which fail to replicate the multijoint
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rapid muscular actions typically observed in most athletic movements (20). To address this limitation, several studies have established countermovement jumps and single-leg hop assessments as reliable screening tools to identify imbalances between limbs (3,12,20,21). Although these screening tools share similar lower-body movement strategies with change of direction movements (simultaneous flexion and extension of the hip, knee, and ankle), the AFL agility test requires an aggressive first directional change involving a greater eccentric load compared with more traditional directional changes, followed by 4 further directional changes that would further stress these capacities in the athlete. Given the importance of eccentric muscle function and stretchshorten cycle capabilities to change of direction performance, this could explain the greater intralimb imbalances for Australian Footballers during the AFL agility test. Greater asymmetries in strength and lean mass have also been reported to have greater associations with injury incidence (7,9,14,17,19). In particular, several studies have reported higher rates and greater severity of injuries in athletes with identified asymmetries extending beyond 10% between limbs (14,17,27). Therefore, quantifying performance deficits between limbs during a rapid, dynamic, and functional task under supervised conditions would seem to have direct relevance to potential recruitment decisions during the national draft camp, and provide useful information for entry-level strength and conditioning programs. Although it is beyond the scope of this study to confirm this, the injury implications of any directional performance disparities identified by the AFL agility test should be investigated further. This study provides a viable addition to a commonly used assessment as a method to examine bilateral competency during change of direction performance; however, there are limitations that require acknowledgment. Specifically, this study assumes that differences in performance times across AFL agility circuits indirectly reflect limb dominance, whereas a unilateral strength or power assessment could have provided more direct support for these findings. Future research should therefore determine whether performance disparities evident in the AFL agility test are also reflected in strength and power deficits in footballers. Despite this limitation, the impact of directional preference in Australian Footballers remains a necessary consideration for draft camp examinations. This has implications for the screening of footballers for recruiters and coaches, as well as performance for the athletes themselves. Altering the current AFL agility test using the parameters outlined in this study could provide an in-depth profile of change of direction ability and lowerbody strength deficits within this population.
PRACTICAL APPLICATIONS To ensure the national draft camp accurately and comprehensively examine the physical competency (strengths and weaknesses) of Australian Footballers, it is recommended that the AFL agility test be expanded to require all athletes VOLUME 28 | NUMBER 12 | DECEMBER 2014 |
3555
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Performance Deficits During Changes of Direction to complete 6 COD trials: 3 trials to the left and 3 trials to the right. This serves to examine limb dominance and directional preference and could also quantify the magnitude of interlimb deficit between dominant and nondominant limbs. This information can then be used to strengthen the athletic profiling and performance screening process. Australian Footballers should also train to ensure that their change of direction ability is balanced when considering turns or cuts in all directions.
REFERENCES 1. Atkins, SJ, Hesketh, C, and Sinclair, JK. The presence of bilateral imbalance of the lower limbs in elite youth soccer players of different age. J Strength Cond Res Epub May 21, 2013. 2. Baker, DG and Newton, RU. Comparison of lower body strength, power, acceleration, speed, agility, and sprint momentum to describe playing rank among professional rugby league players. J Strength Cond Res 22: 153–158, 2008. 3. Benjanuvatra, N, Lay, BS, Alderson, JA, and Blanksby, BA. Comparison of ground reaction force asymmetry in one- and two-legged countermovement jumps. J Strength Cond Res 27: 2700–2707, 2013. 4. Bradshaw, RJ, Young, WB, Russell, A, and Burge, P. Comparison of offensive agility techniques in Australian Rules Football. J Sci Med Sport 14: 65–69, 2011. 5. Burgess, D, Naughton, G, and Hopkins, WG. Draft-camp predictors of subsequent career success in the Australian Football League. J Sci Med Sport 15: 561–567, 2012. 6. Chaouachi, A, Brughelli, M, Levin, G, Boudhina, NB, Cronin, J, and Chamari, K. Anthropometric, physiological and performance characteristics of elite team-handball players. J Sports Sci 27: 151– 157, 2008. 7. Croisier, JL, Ganteaume, S, Binet, J, Genty, M, and Ferret, JM. Strength imbalances and prevention of hamstring injury in professional soccer players: A prospective study. Am J Sports Med 36: 1469–1475, 2008.
14. Jacobs, C, Uhl, TL, Seeley, M, Sterling, W, and Goodrich, L. Strength and fatigability of the dominant and non-dominant hip abductors. J Athl Train 40: 203–206, 2005. 15. Jones, PA and Bampouras, TM. A comparison of isokinetic and functional methods of assessing bilateral strength imbalance. J Strength Cond Res 24: 1553–1558, 2010. 16. Keogh, J. The use of physical fitness scores and anthropometric data to predict selection in an elite under 18 Australian Rules Football team. J Sci Med Sport 2: 125–133, 1999. 17. Knapik, JJ, Bauman, CL, Jones, BH, Harris, JM, and Vaughan, L. Preseason strength and flexibility imbalances associated with athletic injuries in female collegiate athletes. Am J Sports Med 19: 76–81, 1991. 18. Lin, CW, Su, FC, Wu, HW, and Lin, CF. Effects of leg dominance on performance of ballet turns (pirouettes) by experienced and novice dancers. J Sports Sci 31: 1781–1788, 2013. 19. Murphy, DF, Connolly, DAJ, and Beynnon, BD. Risk factors for lower extremity injury: A review of the literature. Br J Sports Med 37: 13–29, 2003. 20. Newton, RU, Gerber, A, Nimphius, S, Shim, JK, Doan, BK, Robertson, M, Pearson, DR, Craig, BW, Hakkinen, K, and Kraemer, WJ. Determination of functional strength imbalance of the lower extremities. J Strength Cond Res 20: 971–977, 2006. 21. Orchard, J, Marsden, J, Lord, S, and Garlick, D. Preseason hamstring muscle weakness associated with hamstring muscle injury in Australian footballers. Am J Sports Med 25: 81–85, 1997. 22. Peterson, MD, Alvar, BA, and Reha, MR. The contribution of maximal force production to explosive movement among young collegiate athletes. J Strength Cond Res 20: 867–873, 2006. 23. Pyne, DB, Gardner, AS, Sheehan, K, and Hopkins, WG. Fitness testing and career progression in AFL football. J Sci Med Sport 8: 321–332, 2005. 24. Pyne, DB, Gardner, AS, Sheehan, K, and Hopkins, WG. Positional differences in fitness and anthropometric characteristics in Australian Football. J Sci Med Sport 9: 143–150, 2006. 25. Sheehan, K. NAB Rising Stars, AFL Under 16 State Combines. Canberra, Australia: Australian Football League, 2011.
8. Dawson, B, Hopkinson, R, Appleby, B, Stewart, G, and Roberts, C. Player movement patterns and game activities in the Australian Football League. J Sci Med Sport 7: 278–291, 2004.
26. Spiteri, T, Cochrane, JL, Hart, NH, Haff, GG, and Nimphius, S. Effect of strength on plant foot kinetics and kinematics during a change of direction task. Eur J Sport Sci 13: 646–652, 2013.
9. Ford, KR, Myer, GD, and Hewett, TE. Valgus knee motion during landing in high school female and male basketball players. Med Sci Sports Exerc 35: 1745–1750, 2003.
27. Thomee´, R, Kaplan, Y, Kvist, J, Myklebust, G, Risberg, MA, Theisen, D, Tsepis, E, Werner, S, Wondrasch, B, and Witvrouw, E. Muscle strength and hop performance criteria prior to return to sports after ACL reconstruction. Knee Surg Sports Traumatol Arthrosc 19: 1798–1805, 2011.
10. Gabbett, TJ, Kelly, JN, and Sheppard, JM. Speed, change of direction speed, and reactive agility of rugby league players. J Strength Cond Res 22: 174–181, 2008. 11. Hart, NH, Nimphius, S, Cochrane, JL, and Newton, RU. Leg mass characteristics of accurate and inaccurate kickers—An Australian football perspective. J Sports Sci 31: 1146–1157, 2013. 12. Hart, NH, Nimphius, S, Spiteri, T, and Newton, RU. Leg strength and lean mass symmetry influences kicking performance in Australian Football. J Sports Sci Med 13: 157–165, 2014. 13. Impellizzeri, FM, Rampinini, E, Maffiuletti, N, and Marcora, SM. A vertical jump force test for assessing bilateral strength asymmetry in athletes. Med Sci Sports Exerc 39: 2044–2050, 2007.
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28. Veale, JP, Pearce, AJ, Buttifant, D, and Carlson, JS. Anthropometric profiling of elite junior and senior Australian football players. Int J Sports Physiol Perform 5: 509–520, 2010. 29. Young, WB, James, R, and Montgomery, I. Is muscle power related to running speed with changes of direction? J Sports Med Phys Fitness 42: 282–288, 2002. 30. Young, WB and Pryor, L. Relationship between pre-season anthropometric and fitness measures and indicators of playing performance in elite junior Australia Rules Football. J Sci Med Sport 10: 110–118, 2007.
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Journal of Strength and Conditioning Research
Copyright © National Strength and Conditioning Association Unauthorized reproduction of this article is prohibited.
AND
1
Centre for Exercise and Sport Science Research, Edith Cowan University, Perth, Australia; 2Fremantle Dockers Football Club, Fremantle, Australia; and 3School of Environmental and Life Sciences, University of Newcastle, New South Wales, Australia
ABSTRACT
with particular leg dominance profiles and to provide a limb
Hart, NH, Spiteri, T, Lockie, RG, Nimphius, S, and Newton, RU. Detecting deficits in change of direction performance using the preplanned multidirectional Australian Football League agility test. J Strength Cond Res 28(12): 3552–3556, 2014—The Australian Football League (AFL) agility test is a preplanned multidirectional circuit involving 5 directional changes of various magnitudes that might differently assess athletes of particular leg dominance. This study served to establish whether the AFL agility test appropriately examines athletes of differing limb dominance, while also quantifying performance deficits prevalent between limbs of Australian Footballers. Fifty-eight Australian Footballers were recruited from the Western Australian Football League (age = 21.9 6 2.8 years; height = 183.7 6 5.9 cm; weight = 86.4 6 4.7 kg). Two circuits of the AFL agility test were set up in accordance with official specifications. The finish line of the second circuit was relocated to the opposite side to modify the starting direction. Footballers were randomized and counterbalanced between versions, performing 3 trials in each direction. Paired t-tests (p # 0.05) were used to examine differences between dominant and nondominant trials. Independent t-tests (p # 0.05) were used to identify differences between left and right leg dominant groups. The current version of the AFL agility test appropriately examined ;61% of footballers in this cohort. The remaining ;39% produced significantly faster times during the alternate version (0.63–0.82 seconds; p # 0.001). All footballers demonstrated a performance deficit of 5–10% between limbs (;0.72 seconds; p # 0.001). Limb dominance (directional preference) was evident for all footballers. Change of direction capabilities should therefore be examined bilaterally to eliminate bias toward athletes
deficit measure for enhanced athletic profiling outcomes.
Address correspondence to Nicolas H. Hart, [email protected]. 28(12)/3552–3556 Journal of Strength and Conditioning Research Ó 2014 National Strength and Conditioning Association
3552
the
KEY WORDS strength, imbalance, asymmetry, directional preference, athlete profiling
INTRODUCTION
T
he recruitment process of the Australian Football League (AFL) purports to examine a variety of physical and technical athletic competencies as part of a structured talent identification system (5,24). The annually operated national draft camp quantifies these attributes through a series of standardized assessments (anthropometry, vertical jumps, sprints, agility, endurance, and technical skills) that are subsequently benchmarked against historical data, fellow competitors, and reference values to assist talent scouts with their decision-making process (5,16,23). In particular, outcomes provided by this profiling system are relied on to identify talent, player strengths and weaknesses, position suitability, and assist in the optimal design of strength and conditioning programs (6,24,28), yet are only moderately predictive of early-career success (5,23). Despite this modest predictive power, information gathered by these standardized examinations continue to produce valuable athletic profiling and physical competency insights into emerging Australian Footballers for sport scientists, strength and conditioning coaches, and football coaches. The ability to pursue or evade an opponent is a critical attribute for an Australian Footballer (4,30); therefore, determining the ability of footballers to change direction effectively is of high importance to recruiters, coaches, and athletes alike (10,26). This specific physical attribute is assessed during the national draft camp through the AFL agility test; a custom preplanned circuit that involves 5 multidirectional changes of various magnitudes (3 left and 2 right). Although the AFL agility test has been previously viewed to appropriately assess a footballer’s ability to change direction, it may be biased toward athletes of particular leg dominance, and by extension
TM
Journal of Strength and Conditioning Research
Copyright © National Strength and Conditioning Association Unauthorized reproduction of this article is prohibited.
the
TM
Journal of Strength and Conditioning Research
| www.nsca.com
Figure 1. A schematic overview of the original version (25) of the AFL agility test (left); with a modified version of the AFL agility test (right), adjusted to suit limb dominance.
preferred cutting direction. Specifically, the test contains more directional changes to the left, of which the first directional change is the greatest in magnitude (;2308), has the longest approach (;5 m), and therefore has the highest entry velocity. It therefore stands to reason that those who preferentially move left will score higher in this test, disadvantaging those who prefer right-side directional motion. Given the underlying importance of test scores using this measure, the evident limitation of a preferred cutting direction in the current AFL agility circuit must be recognized by recruiters, and the test modified for increased equity when assessing change of direction proficiency. The AFL agility test currently only examines the performance capacity of an athlete using a single scenario and does not seek to examine deficiencies in change of direction performance between limb dominance and directional preference profiles. However, it is of practical relevance to understand and examine the level of movement deficiency between dominant and nondominant limbs during left and right directional changes. Athletes with lower deficits across limbs and directions could be more attractive to recruiters, as this could potentially indicate a greater physical ability to respond dynamically (in any direction) within the volatile environment of Australian Football. Conversely, footballers with greater disparities between limbs may not only indicate lower quality change of direction performance (increased performance rigidity) but could also highlight a physical weakness that could predispose them to a higher risk of injury if forced, by the constraints of elite-level competition, to change direction to their undesired side.
This study therefore seeks to examine change of direction performance of Australian Footballers under left- and rightstarting conditions using the preplanned, multidirectional AFL agility test to (a) establish whether the current AFL agility test appropriately examines Australian Footballers of differing limb dominance and (b) establish whether a performance deficit exists between dominant and nondominant limbs of Australian Footballers.
METHODS Experimental Approach to the Problem
This study used an acute cross-sectional design conducted during a single testing session on an indoor wooden court surface (Figure 1). Footballers were provided with a standardized dynamic warm-up spanning 15 minutes in duration, followed by 3 submaximal runs through each agility circuit to conclude warm-up preparations. Footballers were required to perform a total of 6 AFL agility trials: 3 trials commenced with the initial, sharp directional change to the left (version 1: current), and 3 trials commenced with an initial sharp directional change to the right (version 2: additional). Trials were randomized and counterbalanced for all footballers with 2-minute recovery provided between each effort. Athletes were stratified into left direction (right foot) or right direction (left foot) dominant groups in conjunction with their fastest completion times. Subjects
Fifty-eight subelite Australian Footballers (n = 58; age = 21.9 6 2.8 years; height = 183.7 6 5.9 cm; weight = 86.4 6 4.7 kg) VOLUME 28 | NUMBER 12 | DECEMBER 2014 |
3553
Copyright © National Strength and Conditioning Association Unauthorized reproduction of this article is prohibited.
Performance Deficits During Changes of Direction reliably performed (coefficient of variation [CV] #0.3%; intraclass correlation coefficient [ICC] $ 0.993) by the same accredited exercise scientist (ESSA, Australia). Australian Football League Agility Protocol
Figure 2. Completion times for directional preference across the initial left turn (left start; current version) and initial right turn (right start; additional version) AFL agility circuits.
were recruited from the Western Australian Football League (WAFL). Athletes from all positions (forwards, midfielders, and backs) were recruited for use in this study, as the ability to change direction quickly is a required skill by all Australian Football players; therefore, no position specific bias was expected. Athletes were free from injury at the time of testing and were not permitted to perform strenuous exercise or lowerbody resistance training within 48 hours of their testing session. All athletes provided written informed consent before testing. Ethics approval was provided by the institutional review board. Procedures
Anthropometry. Stature was recorded to the nearest 0.1 cm using a wall-mounted stadiometer (Model 222; Seca, Hamburg, DE, USA), with body mass recorded to the nearest 0.1 kg using an electronic weighing scale (AE Adams CPW Plus-200; Adam Equipment, Inc., CT, USA). Shoes were not permitted to be worn during these measures. Stature was measured 3 times with the average of the 3 trials retained for analysis. All measures were
Two AFL agility circuits were created with the same specifications (dimensions and equipment) as per AFL draft camp requirements (25). Two sets of dual-beam infrared electronic timing gates (Speedlight Timing System; Swift Performance, NSW, Australia) were separated by 1 m at the start line and 2 m at the finish line of each AFL agility circuit; with 5 weighted poles (10–12 cm diameter, 25 cm base, and 1.1 m height) positioned throughout the circuit (Figure 2). Subjects were required to start from a stationary upright position with their front foot positioned on the start line, in line with the timing gates. Once in position, each participant commenced their trial when ready, and no information regarding optimal technique was issued. Subjects were instructed only to progress through the course as quickly as possible without moving or knocking the poles. Verbal encouragement was provided during each trial. Any false starts or invalid trials were repeated after a 1-minute rest period. Familiarization of each circuit formed part of their specific warm-up (3 submaximal attempts at 50, 70, and 90% of perceived maximum effort, respectively). Each version of the AFL agility circuit was randomized and counterbalanced, with 29 subjects completing 3 trials of version 1 followed by 3 trials of version 2. The remaining 29 subjects completed the opposite order of testing. Although 2-minute recovery was provided between trials within each circuit, 5-minute recovery was provided between versions of the test to minimize any effects of fatigue. Statistical Analyses
Descriptive statistics (mean 6 SD) were calculated for all results. Paired t-tests (p # 0.05) were used to determine whether significant differences existed between performance times of dominant and nondominant trials as a withinsubject measure. Independent t-tests (p # 0.05) were used to determine whether significance differences between perforTABLE 1. Descriptive characteristics of subjects and performance, stratified by mance times of left direction directional and leg dominance.* (right foot) and right direction Left direction/right foot Right direction/left foot (left foot) dominant groups (n = 36) (n = 22) were prevalent. All statistical examinations were performed Age, y 21.4 6 3.4 22.6 6 2.4 Height, cm 183.1 6 6.1 184.2 6 5.8 using statistical analysis softWeight, kg 85.3 6 4.3 87.8 6 5.4 ware (PASW, version 19.0; Completion time (left) 8.17 6 0.3†z 8.99 6 0.3†z IBM, Chicago, IL, USA). Completion time (right) Interlimb deficit, %
8.90 6 0.3†z 8.2 6 0.1
*Values are expressed as mean 6 SD. †Statistical significance (p # 0.001) between groups. zStatistical significance (p # 0.001) between left and right trials.
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8.27 6 0.3†z 8.0 6 0.1
RESULTS Limb dominance and directional preference (a preferred path to change direction) was evident for all footballers.
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Journal of Strength and Conditioning Research Thirty-six subjects were 8.2% (0.73 seconds; p # 0.001) faster during the left turn (right foot) dominant circuit when compared with the right turn (left foot) dominant circuit. Conversely, 22 of 58 athletes were 8.0% (0.72 seconds; p # 0.001) slower when using the original AFL agility test (left turn, right foot dominant). Therefore, version 1 of the AFL agility test appropriately assessed 61% of athletes, whereas 39% of athletes performed better when the starting direction was modified to suit their dominance profile in version 2. A performance disparity of approximately 8% was prevalent between dominant and nondominant COD trials for each group (Figure 2; Table 1).
DISCUSSION The AFL agility test requires footballers to always perform 3 left-side and 2 right-side changes in direction (25,30), with a rapid entry and steep initial turn to the left around the first agility pole. However, the results of this study identify potential limitations in the ability of the current version of the AFL agility test to assess all players equally within the constraints of the task. In particular, only 61% of Australian Footballers in our cohort were suited to the AFL agility test currently used in the national draft camp, with 39% better suited to the alternate version. In the absence of bilateral starting directions, the AFL agility test disadvantages athletes who are right turn (left leg) dominant, thus assisting athletes who are left turn (right leg) dominant to produce faster performance times. The AFL agility test should be broadened to include both the original version and the additional version investigated in this study. These findings not only have implications for the AFL draft camp, testing, and recruitment model but also match performance and injury risk management. Footballers displayed an evident interlimb deficit in performance of 8% (;0.7 seconds) between dominant and nondominant trials. This prevalence of an interlimb deficit could provide another useful measure of performance for recruiters to consider. An athlete with a lower performance deficit, and therefore a smaller loss of speed between conditions may indicate higher level performance or improved training status. Previous research has demonstrated an evident sacrifice in skilled performance in athletes with larger deficits in lean mass and leg strength (11,12,18), which would likely also translate to change of direction activities (2,15,22,26,29). Because of the importance of changing direction in Australian Football, with most sprints containing at least 1 directional change (8), it is important for coaches to be able to identify any performance discrepancies in their players. This could be achieved by testing players in both versions of the AFL agility test. Previous research has used direct strength assessments of imbalance through isokinetic and isometric modalities (1,13,20) to identify potential relationships with performance or injury incidence. However, a majority of these studies used single-joint movements, which fail to replicate the multijoint
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rapid muscular actions typically observed in most athletic movements (20). To address this limitation, several studies have established countermovement jumps and single-leg hop assessments as reliable screening tools to identify imbalances between limbs (3,12,20,21). Although these screening tools share similar lower-body movement strategies with change of direction movements (simultaneous flexion and extension of the hip, knee, and ankle), the AFL agility test requires an aggressive first directional change involving a greater eccentric load compared with more traditional directional changes, followed by 4 further directional changes that would further stress these capacities in the athlete. Given the importance of eccentric muscle function and stretchshorten cycle capabilities to change of direction performance, this could explain the greater intralimb imbalances for Australian Footballers during the AFL agility test. Greater asymmetries in strength and lean mass have also been reported to have greater associations with injury incidence (7,9,14,17,19). In particular, several studies have reported higher rates and greater severity of injuries in athletes with identified asymmetries extending beyond 10% between limbs (14,17,27). Therefore, quantifying performance deficits between limbs during a rapid, dynamic, and functional task under supervised conditions would seem to have direct relevance to potential recruitment decisions during the national draft camp, and provide useful information for entry-level strength and conditioning programs. Although it is beyond the scope of this study to confirm this, the injury implications of any directional performance disparities identified by the AFL agility test should be investigated further. This study provides a viable addition to a commonly used assessment as a method to examine bilateral competency during change of direction performance; however, there are limitations that require acknowledgment. Specifically, this study assumes that differences in performance times across AFL agility circuits indirectly reflect limb dominance, whereas a unilateral strength or power assessment could have provided more direct support for these findings. Future research should therefore determine whether performance disparities evident in the AFL agility test are also reflected in strength and power deficits in footballers. Despite this limitation, the impact of directional preference in Australian Footballers remains a necessary consideration for draft camp examinations. This has implications for the screening of footballers for recruiters and coaches, as well as performance for the athletes themselves. Altering the current AFL agility test using the parameters outlined in this study could provide an in-depth profile of change of direction ability and lowerbody strength deficits within this population.
PRACTICAL APPLICATIONS To ensure the national draft camp accurately and comprehensively examine the physical competency (strengths and weaknesses) of Australian Footballers, it is recommended that the AFL agility test be expanded to require all athletes VOLUME 28 | NUMBER 12 | DECEMBER 2014 |
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Performance Deficits During Changes of Direction to complete 6 COD trials: 3 trials to the left and 3 trials to the right. This serves to examine limb dominance and directional preference and could also quantify the magnitude of interlimb deficit between dominant and nondominant limbs. This information can then be used to strengthen the athletic profiling and performance screening process. Australian Footballers should also train to ensure that their change of direction ability is balanced when considering turns or cuts in all directions.
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