RESEARCH REPOSITORY.

Transcription

1 RESEARCH REPOSITORY This is the author s final version of the work, as accepted for publication following peer review but without the publisher s layout or pagination. The definitive version is available at: Elseworthy, N., Burke, D., Scott, B.R., Stevens, C.J. and Dascombe, B.J. (2014) Physical and Decision-Making Demands of Australian Football Umpires During Competitive Matches. Journal of Strength and Conditioning Research, 28 (12). pp Copyright: 2014 National Strength and Conditioning Association It is posted here for your personal use. No further distribution is permitted.

2 ORIGINAL INVESTIGATION Title: Physical and decision-making demands of Australian football umpires during competitive matches Running Title: Match demands of Australian football umpires Authors: Nathan Elsworthy 1 Darren Burke 2 Brendan R. Scott 1 Christopher J. Stevens 1 Benjamin J. Dascombe 1,3 Affiliations: 1 Applied Sports Science and Exercise Testing Laboratory, University of Newcastle, Ourimbah Campus, NSW, Australia 2 School of Psychology, University of Newcastle, Ourimbah Campus, NSW, Australia 3 Priority Research Centre in Physical Activity and Nutrition, University of Newcastle, Callaghan, Australia Correspondence: Mr Nathan Elsworthy School of Environmental and Life Sciences Faculty of Science and Information Technology University of Newcastle PO Box 127 Ourimbah, NSW AUSTRALIA, 2258 Ph: Fax: Mob: Nathan.Elsworthy@uon.edu.au Submission Date: 10 April

3 PHYSICAL AND DECISION-MAKING DEMANDS OF AUSTRALIAN FOOTBALL UMPIRES DURING COMPETITIVE MATCHES 2

4 ABSTRACT The current study examined the physical and decision-making requirements of elite Australian football umpires during match play. Twenty-nine field umpires were assessed across 20 Australian Football League matches. Physical demands were monitored using global positioning system devices to record the total distance covered and high-speed running (HSR; >14.4 km h -1 ) demands across each quarter. Decision-making performance was assessed via video by three elite umpire coaches who reviewed free kick accuracy during each match. These data were further analyzed according to the position (mid-zone or endzone) of the umpire when each decision was made. The average distance covered was 10,563 ± 608 m, of which 1952 ± 494 m was HSR. Significant reductions in distance covered were observed during the third (p=0.006) and fourth (p=0.001) quarters, compared to the first. An average of 44 ± 8 free kicks awarded per match with a decision accuracy of 84 ± 6%; however, there were no significant differences (p>0.05) in these measures across a match. Significantly (p<0.05) higher physical (HSR; relative distance) and decision-making requirements were observed within the mid-zone. The current data quantifies the physical and decision-making demands of Australian football umpiring, and demonstrated that despite a high physical workload, free kick accuracy is maintained across a match. This suggests that decision-making may not be directly compromised by the intermittent running demands of Australian football umpires. Positional rotations between the mid-zone and end-zone position allow for the demands to be shared amongst all field umpires during a match. Keywords: match analysis; cognition; perception; motor skills; perceptual-cognitive 3

5 INTRODUCTION Australian football (AF) officials are responsible for enforcing the laws of the game and ensuring that matches are played in a fair and safe manner. The on-field AF officials, commonly known as field umpires, are responsible for officiating play on large fields (between m long, m wide), with 36 players on the field at one time. Given this large playing area, three field umpires are appointed to elite matches and officiate together without the benefit of being interchanged. As such, field umpires typically rotate between three main areas of the field, specifically the mid-zone and two end-zones to equally share the match demands (see Figure 1). The umpire officiating the mid-zone typically undertakes greater work demands, given that this is the largest zone and the ball frequently transitions through this region. The timing of rotations is largely determined on the field by the umpires, however they commonly occur following a goal, or during a delay in play (i.e. ball out of bounds, player injury). Previous studies have reported that field umpires cover between 10,000-11,500 m using the three umpire system, with high-speed running (HSR; >14.4 km h -1 ) accounting for ~3000 m (5, 7). However, little is known on the differences in physical demands between the separate umpiring positions. ***FIGURE 1 ABOUT HERE*** While past literature has reported upon the physical demands AF umpiring (5, 7), the other requirements of officials (i.e. decision-making requirements) are not well understood. The most important role of umpires is to determine whether the laws of the game have been breached by a player, and if so, apply the appropriate course of action by way of a free kick (8). Such decisions are made in a dynamic, multi-person environment, and during periods of intense physical work. The ability of umpires to detect law infringements from video-based 4

6 methods has concluded that elite AF umpires can correctly identify illegal acts of play on 92% of occasions (13). While video-based assessments provide valid examination of decision-making performance, they do not replicate the physical, physiological, and psychological aspects of an actual match environment. Specific to match play, soccer referees make up to 140 observable decisions, with ~45 free kicks directly related to breaches of the rules (8). Other studies have demonstrated that soccer referees correctly adjudicate between 64-86% of free kick decisions (14, 15). However, free kick decisions only account for a limited number of the total decision-making demands, and therefore when encompassing all decisions, it is likely that the accuracy would be considerably higher. With the limited information available regarding the match demands of AF umpires, this study aims to quantify the current demands of elite AF umpiring. Further, as no previous studies have compared the separate areas of the field (i.e. mid-zone versus endzone), this will be examined. These data detail the match running requirements of elite AF umpires, specifically describing the variations between different on-field umpiring positions, which is particularly important when prescribing conditioning training sessions. Lastly, the most important role of AF umpiring (decision-making) will be assessed to determine the decisionmaking performance during match play. METHODS Experimental Approach to the Problem To analyze the current physical and decision-making demands of AF field umpires during elite match play, and to examine the differences in these demands in different areas of the field. Firstly, using time motion analysis methods, the current study quantified the overall physical demands associated with match play, as well as comparing the demands of the mid- 5

7 zone and end-zone positions, typical of AF umpiring. Secondly, the study also determined the decision-making requirements by assessing the number of free kicks awarded and the accuracy of these decisions during elite AF matches. Subjects Male field umpires (n=29, age: 32.4 ± 6.1 y [range: y]; height: ± 5.7 cm; body mass: 73.6 ± 5.4 kg; Σ7 skinfolds: 49.6 ± 7.4 mm) volunteered to participate in this study. Each participant had 6.4 ± 5.4 y experience of umpiring in elite AF competition, and all were currently officiating in the Australian Football League (AFL). Prior to the commencement of any testing procedures, approval was granted by The University of Newcastle Human Ethics Committee (approval number: H ), and participants provided informed written consent. This study and its methods were supported by the AFL. Match data were collected on the three field umpires per match across 20 matches, resulting in a total of 58 files for analysis (two files were excluded due to incomplete data files). Individual AF umpires were examined between 1-4 times over the course of the data collection period. Procedures Free kick decisions were identified post-hoc by three experienced AF umpire coaches. Each AFL umpire coach had previously umpired at least 300 elite AFL matches and had been employed as an elite AFL umpire coach for between 7-12 years. Within three days following each match, coaches viewed each individual match using television broadcast footage and three additional camera angles (full field from behind the goal, wide angle side view from halfway, and close up angle vision). Only free kick situations with complete agreement between coaches was used for analysis as per Mallo et al. (14). In AF, free kicks are awarded to or against a player, as the case may be when a field umpire considers any 6

8 circumstances set out in Law 15 (1). While free kicks only represent a small portion of the overall decision-making demands, they are easily measurable and require more complex cognitive processing and rule interpretation. Other decisions such as marks, out of bounds and scoring decisions were excluded from analysis, as they represent general play scenarios that occur on a very frequent basis or are adjudicated by the boundary or goal umpires. Free kicks were assessed as either correct (i.e. field umpire awarded a free kick to a player who was infringed); missed (i.e. the umpire failed to award a free kick to a player who was infringed and a free kick should have been awarded to a player); or unwarranted (i.e. umpire awarded a free kick to a player who was not infringed and no free kick should have been awarded in these circumstances). Missed and unwarranted free kicks were further classified as incorrect decisions. The nature of the infringement, the area it occurred on the playing field (mid-zone or end-zone), time and quarter of the infringement as well as the players and umpires involved were also recorded. Free kick accuracy was calculated as the number of correct decisions divided by the total number of free kicks awarded by each umpire during each quarter of a match. To examine intra-observer reliability of the AF umpire coaches, video footage of 50 free kick scenarios separate to the data collection period was shown to each umpire coach for assessment. This assessment demonstrated a moderate level of intraobserver reliability (ICC=0.91; CV=10.2%) (9, 14). Time-motion data were collected using MinimaxX global positioning system devices (5 Hz; Catapult Innovations, Melbourne, Australia), which were fitted into an undergarment, worn underneath their normal umpiring uniform. Each device was turned on at least 20 minutes prior to the commencement of a match in an open area to ensure a satellite lock was established. Data were downloaded and analyzed following each match using the Catapult 7

9 Sprint 5.0 software (Catapult Innovations, Melbourne, Australia). Data were divided into the four quarters, according to the start time and duration obtained from official timekeepers. Non-playing data (i.e. quarter breaks) were not included in analysis. Movement data was calculated as the distance covered and time spent in six locomotor categories: [stand (<0.7 km h -1 ); walk (0.7-7 km h -1 ); jog ( km h -1 ); run ( km h -1 ); fast run (20-23 km h -1 ); sprint ( 23 km h -1 )]. The distance covered in low-intensity activity (<14.4 km h -1 ) and HSR ( 14.4 km h -1 ) were also collated in addition to the total distance covered and relative distance maintained during each quarter. These zones are consistent with previously published time-motion analysis studies, and thus allow for direct comparison with the demands of umpires and players in AF (4, 7). Previously, 5 Hz MinimaxX GPS units have demonstrated acceptable validity (SEE: 3.8 ± 0.6%), and reliability (CV: 3.6%) for measuring the total distance during simulated team sport exercise (10). However, a limitation of GPS use is the decreased reliability when assessing HSR in two change of direction courses (typical error: 2.6 m; CV: %) (10). As such, care needs to be taken when interpreting these results. Using the post-match video analysis, the time periods throughout the match that each umpire spent in the mid- or end-zone was determined. The position of each umpire and elapsed time of each rotation between the mid-zone and end-zone umpires was recorded. Rotations could occur at any time throughout a match as per the discretion of the officiating umpires. Movement data was then manually divided to determine the various physical performance measures for each rotation. 8

10 Statistical Analysis All data are presented as the mean (± standard deviation). Data were initially analyzed for normality and homogeneity of variances using the Shapiro-Wilk statistic and Levene s test, respectively. One-way repeated measures analysis of variance (ANOVA) was used to determine the differences in physical demands between the four quarters. For significant main effects, a Bonferroni post hoc comparison test was used. Further, a two-way mixed ANOVA (2 [position] x 4 [quarter] design) was used to examine the effect of umpire positioning (i.e. mid-zone and end-zone) on the physical demands across each quarter. Independent t-tests were used to identify comparisons between groups. Further, 95% Confidence Intervals (CI) were used to report mean differences between the two groups. Decision-making accuracy was analyzed by comparing the free kick decisions made within each quarter of a match. As this data was non-parametric, a Friedman s analysis of variance was used. Chi-squared goodness of fit tests (16) were applied to examine the decision-making performance between the mid-zone and end-zone umpire positions. Statistical significance was set at p<0.05 for all statistical tests and procedures were performed using SPSS Statistics (version 19, IBM Corporation, Somers, New York, USA). RESULTS The mean values for the physical and free kick decision-making demands are presented in Table 1. Significant reductions in the distance covered were observed (F3,168=6.116; p=0.001; η 2 p=0.098), with post-hoc analysis identifying that the distance covered in the third (p=0.006) and fourth (p=0.001) quarters were significantly less than that of the first quarter. A significant main effect was also observed for the HSR distance (F3,168=4.271; p=0.006; η 2 p=0.071), with the fourth quarter being significantly lower compared to the first (p=0.003). 9

11 Further reductions were observed across various speed thresholds that are collectively shown in Table 1. ***TABLE 1 ABOUT HERE*** Significant differences exist between the mid-zone and end-zone positions in regard to HSR (p=0.001, 95% CI: 641 to 895 m) and relative distance (p=0.001, 95% CI: 47 to 55 m min -1 ) covered. There was no significant difference between the two groups for the total distance covered (Figure 2). On average, a rotation between the umpires occurred every 2:38 ± 1:24 min:s, with no significant difference in rotation length across quarters (p=0.530). ***FIGURE 2 ABOUT HERE*** During the observed matches, umpires awarded a total of 779 free kicks (correct: 742; unwarranted: 37) with a further 105 free kicks categorized as missed during these matches (n=884 decisions). Subsequent analysis determined that in each match, field umpires had an overall free kick accuracy of 84 ± 6%, awarding a collective 44 ± 8 free kicks per match. Free kick accuracy (p=0.110) and number of free kicks awarded (p=0.340) were consistent across each quarter of a match. Chi-square (χ 2 ) analysis identified a non-uniform distribution in the number of free kicks with more free kicks awarded in the mid-zone area compared to the end-zone (p=0.025; χ 2 (1)=5.040). Accuracy between mid-zone and end-zone areas was uniformly distributed. Examination of incorrect free kicks highlighted no significant trend to over or under penalizing across a match (p=0.731). 10

12 DISCUSSION The current study aimed to examine the physical demands of AF umpires and quantify their free kick decision-making performance during match play. The results present novel data that examine differences in the physical demands and decision-making requirements in different regions of the field. Together, these data have important applications in the development of AF umpires, and collectively all team sport officials. Whilst there is little difference in the total distance covered by umpires in the current study, compared with Coutts and Reaburn (5), umpires performed a greater proportion of HSR. Further differences in physical demands exist compared to a sub-elite population group using similar methodology (7). This may reflect the differing standards of competition examined, with the superior ability of elite level umpires to read play and predict where to position themselves (2). Although, this may not be true for AF umpires as suggested by Larkin et al. (13) using video based play prediction methods. Similar to various AF research (4, 6, 7), within match variations exist, demonstrated by reductions in the total distance and HSR distance towards the end of matches. However, given the role of umpires, their physical demands are likely to be influenced by the running speed and ball movement of players. The significantly faster movement reported for the beginning of a match, and the subsequent decline in these demands (4), demonstrate that the physical intensity of umpires may be reduced in response the demands of play (19). While global changes occur in the movement demands across a match, perhaps more importantly, significant differences in the demands (i.e. relative distance, HSR) within the mid-zone highlight the more physically demanding region for AF umpires. It is proposed that rotating umpires between mid- and end-zone positions during match play permits umpires to 11

13 alternate periods of high-intensity work and rest, allowing them to maintain a lower physiological intensity and limit fatigue. However, while positioned within the end-zone, umpires are still required to perform their role, particularly if play transitions towards this area. As such this may limit the potential for complete physical recovery prior to rotating back into the mid-zone. While reductions in the movement demands exist, the maintenance of decision-making accuracy suggests that these activity changes are in response to game speed and structure, rather than physical fatigue. It would be expected that with increasing physical fatigue, umpires are unable to maintain the required intensity to position themselves correctly around play (11, 12) and as a result, are more likely to incorrectly adjudicate. As the majority of match play is spent in the middle of the ground, it was expected that the mid-zone umpire would make the highest number of decisions whilst undertaking the highest relative physical demands. Mental fatigue has been suggested as a mechanism for poorer decision-making performance in soccer referees (14), hence the three umpire system may assist in alleviating this reduction in performance late in matches, by allowing mid-zone umpires to rotate in order to recover in the end-zone. Therefore, this may be beneficial for umpires to help maintain decision-making accuracy throughout a match. Although decision-making performance is stable in the current study, previous research has reported conflicting findings across similar studies. Mallo et al. (14) reported that soccer referees demonstrate the greatest decision-making error rate in the final 15 minutes, suggesting that physical and mental fatigue occurs in the final stages of a match. In contrast, Masceranhas et al. (15) reported poorer decision-making performance of soccer referees during the initial 15 minutes of matches due more players being around the ball. While there 12

14 were no significant changes in decision-making within a match in the current study, a considerable number of errors (16%) in free kick judgement are committed by AF umpires. As such, other factors may facilitate errors in the decision-making performance of AF umpires, including obstructed view, distance from play (14), movement speed (17), and changes in central nervous system arousal (3). These factors are yet to be examined in AF umpires, and therefore could be a focus of future research. It is important to note that the free kick judgements made by umpires represent only a small proportion of the total decision-making demands. With respect to soccer referees, Plessner and colleagues (18) estimated that there are between potential decision-making judgements across a match. Alternatively, Helsen and Bultynck (8) determined that soccer referees make on average, 137 observable decisions per match, of which 45 related to free kick scenarios. As such, free kicks represent only a portion of the overall decision-making, with referees making numerous non-observable decisions (i.e. when the referee does not interfere with play and it continues on). Specifically, each AF match involves over 700 disposals (i.e. passing the ball to a team mate), each representing either a legal kick or handball. In these instances, the AF umpire is effectively making a decision to determine whether the method of disposal was legal. Further, body-to-body contact (i.e. tackling, marking contests) between opposing players is only permitted within specific areas of the body placing further decision-making demands on the umpire. Therefore it is likely that the total decision-making requirements of AF officiating is above and beyond the free kick judgements and likely to be upwards of 2000 decisions per match, however this remains difficult to quantify. Each of these acts of play require some assessment by the umpire, most of which occur without interference (i.e. a play-on decision when there is no illegal act of play), or obvious reaction from the umpire. As such, future studies should aim to establish 13

15 methods to identify the total decision-making demands associated with AF umpiring, and team sport officiating in general. The main findings of the current study present current information regarding the match demands of AF umpires whereby reductions in various physical performance measures existed during the fourth quarter. There were reduced physical and decision-making demands in the end-zone position, which umpires use for periods of on-field physical recovery. Further, the study demonstrated that the free kick decision-making accuracy of AF umpires remains consistent across each quarter of a match. The positional rotations of the umpires allow for physical recovery between bouts within the mid-zone, and thus the match demands are shared, enabling all umpires to complete each match whilst maintaining their decisionmaking performance. PRACTICAL APPLICATIONS The results of this study provide beneficial information for strength and conditioning coaches to apply current physical demands to AF umpire training. Important information such as comparison between the demands of mid-zone and end-zone AF umpires has never previously been quantified. Therefore, this study highlights how these positions are used for methods of on-field recovery. Further, no previous studies examined the free kick decisionmaking aspect of AF umpire performance, and as this is considered their most important role during play, these findings are important to include for future training. However, free kicks only account for a proportion of the total decision-making demands and therefore this needs to be considered during match performance assessment. 14

16 REFERENCES 1. Australian Football League. Laws of Australian Football. Melbourne (VIC): Australian Football League, Castagna C, Abt G, and D'Ottavio S. Activity profile of international-level soccer referees during competitive matches. J Strength Cond Res 18: , Chmura J and Nazar K. Parallel changes in the onset of blood lactate accumulation (OBLA) and threshold of psychomotor performance deterioration during incremental exercise after training in athletes. Int J Psychophysiol 75: , Coutts AJ, Quinn J, Hocking J, Castagna C, and Rampinini E. Match running performance in elite Australian Rules Football. J Sci Med Sport 13: , Coutts AJ and Reaburn PR. Time and motion analysis of the AFL field umpire. J Sci Med Sport 3: , Duffield R, Coutts AJ, and Quinn J. Core temperature responses and match running performance during intermittent-sprint exercise competition in warm conditions. J Strength Cond Res 23: , Elsworthy N and Dascombe BJ. The match demands of Australian rules football umpires in a state-based competition. Int J Sports Physiol Perform 6: , Helsen W and Bultynck JB. Physical and perceptual-cognitive demands of top-class refereeing in association football. J Sports Sci 22: , Hopkins WG. Measures of reliability in sports medicine and science. Sports Med 30: 1-15, Jennings D, Cormack S, Coutts AJ, Boyd L, and Aughey RJ. The validity and reliability of GPS units in team sport specific running patterns. Int J Sports Physiol Perform 5: ,

17 11. Krustrup P and Bangsbo J. Physiological demands of top-class soccer refereeing in relation to physical capacity: effect of intense intermittent exercise training. J Sports Sci 19: , Krustrup P, Helsen W, Randers MB, Christensen JF, MacDonald C, Rebelo AN, and Bangsbo J. Activity profile and physical demands of football referees and assistant referees in international games. J Sports Sci 27: , Larkin P, Berry J, Dawson B, and Lay B. Perceptual and decision-making skills of Australian Football umpires. Int J Perform Anal Sport 11: , Mallo J, Frutos PG, Juarez D, and Navarro E. Effect of positioning on the accuracy of decision making of association football top-class referees and assistant referees during competitive matches. J Sports Sci 30: , Mascarenhas DRD, Button C, O'Hare D, and Dicks M. Physical performance and decision making in association football referees: A naturalistic study. Open Sports Sci J 2: 1-9, Nevill AM, Atkinson G, Hughes MD, and Cooper S. Statistical methods for analysing discrete and categorical data recorded in performance analysis. J Sports Sci 20: , Oudejans RRD, Bakker FC, Verheijen R, Gerrits JC, Steinbrückner M, and Beek PJ. How position and motion of expert assistant referees in soccer relate to the quality of their offside judgements during actual match play. Int J Sport Psychol 36: 3-21, Plessner H, Schweizer G, Brand R, and O'Hare D. A multiple-cue learning approach as the basis for understanding and improving soccer referees' decision making. Prog Brain Res 174: ,

18 19. Weston M, Castagna C, Impellizzeri FM, Rampinini E, and Abt G. Analysis of physical match performance in English Premier League soccer referees with particular reference to first half and player work rates. J Sci Med Sport 10: , ACKNOWLEDGEMENTS There was no outside financial support for this project. The authors would like to express their gratitude to the AFL Umpiring Department for their assistance in this project. No conflicts of interest exist for this research. 17

19 Figures: Figure 1: Field coverage areas of the mid-zone ( ) and end-zone ( ) umpire positions in Australian football. Figure 2: The total distance (A), high-speed running distance (B), relative distance (C), and free kick decision-making accuracy (D) between mid-zone ( ) and end-zone ( ) positions (mean ± SD). *-significantly different between groups; a-significantly different to first quarter; b- significantly different to second quarter; c-significantly different to third quarter. DMAdecision-making accuracy. Note: Fig 2(D)-No SD as this represents DMA across all decisions (n=884) 18

20 Table 1: Physical and perceptual-cognitive performance measures of Australian football field umpires during match play (mean ± SD). Variable Quarter 1 st 2 nd 3 rd 4 th Match Distance Covered Stand (m) 18 ± 6 18 ± 4 18 ± 4 19 ± ± 19 Walk (m) 1170 ± ± ± ± ± 671 Jog (m) 1053 ± ± ± 188 a 951 ± 201 a 3933 ± 497 Run (m) 427 ± ± ± ± 100 a 1560 ± 326 Fast Run (m) 89 ± ± 52 a 79 ± ± 40 a 304 ± 149 Sprint (m) 26 ± ± ± ± ± 91 LSA (m) 2241 ± ± ± 182 a 2127 ± 258 a 8611 ± 557 HSR (m) 541 ± ± ± ± 140 a 1952 ± 494 TD (m) 2781 ± ± ± 269 a 2566 ± 317 a ± 608 Time Spent Stand (s) 325 ± ± ± ± 74 a 1381 ± 246 Walk (s) 1060 ± ± ± ± ± 341 Jog (s) 340 ± ± ± 64 a 307 ± 65 a 1270 ± 177 Run (s) 91 ± ± ± ± 21 a 334 ± 70 Fast Run (s) 15 ± ± 9 13 ± 8 11 ± 7 a 51 ± 25 Sprint (s) 4 ± 5 3 ± 5 4 ± 5 3 ± 4 13 ± 13 LSA (s) 1724 ± ± ± ± 156 c 6850 ± 241 HSR (s) 110 ± ± ± ± 28 a 398 ± 95 Decision-making demands Correct 9 ± 3 11 ± 4 9 ± 3 8 ± 3 37 ± 8 Incorrect 2 ± 1 1 ± 1 2 ± 2 2 ± 2 7 ± 2 Total 11 ± 3 12 ± 4 11 ± 4 10 ± 3 44 ± 8 Accuracy (%) 82 ± ± ± ± ± 6 Other Relative Speed (m min -1 ) 91 ± ± ± 9 84 ± 9 a 87 ± 6 Quarter Length (min:s) 30:34 ± 2:05 30:07 ± 1:13 29:41 ± 1:41 a 30:28 ± 2:35 120:49 ± 3:56 Notes: TD=Total distance; LSA=Low speed activity; HSR=High-speed running. a -significantly different to the first quarter; b -significantly different to the second quarter; c -significantly different to the third quarter (all p<0.05) 19