Original Research
Training and game loads and injury risk in elite Australian footballers

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Abstract

Objectives

To examine the relationship between combined training and game loads and injury risk in elite Australian footballers.

Methods

Forty-six elite Australian footballers (mean ± SD age of 22.2 ± 2.9 y) from one club were involved in a one-season study. Training and game loads (session-RPE multiplied by duration in min) and injuries were recorded each time an athlete exerted an exercise load. Rolling weekly sums and week-to-week changes in load were then modelled against injury data using a logistic regression model. Odds ratios (OR) were reported against a reference group of the lowest training load range.

Results

Larger 1 weekly (>1750 AU, OR = 2.44–3.38), 2 weekly (>4000 AU, OR = 4.74) and previous to current week changes in load (>1250 AU, OR = 2.58) significantly related (p < 0.05) to a larger injury risk throughout the in-season phase. Players with 2–3 and 4–6 years of experience had a significantly lower injury risk compared to 7+ years players (OR = 0.22, OR = 0.28) when the previous to current week change in load was more than 1000 AU. No significant relationships were found between all derived load values and injury risk during the pre-season phase.

Conclusions

In-season, as the amount of 1–2 weekly load or previous to current week increment in load increases, so does the risk of injury in elite Australian footballers. To reduce the risk of injury, derived training and game load values of weekly loads and previous week-to-week load changes should be individually monitored in elite Australian footballers.

Introduction

Playing Australian football requires repeated physical contact and movements involving endurance, speed and acceleration1 over match durations of 100+ min.2 Recently, Australian Football League (AFL) interchange rates have dramatically increased, allowing players additional breaks throughout games, possibly contributing to higher mean game speeds.3 With greater player physical demands,[1], [4] injury incidence and prevalence rates have also increased.3 During 2010, each AFL club (on average) experienced 38.6 new injuries, causing a player to miss one or more games. Overall, player injuries resulted in an average of 153.8 missed games per club.3

Understanding potential mechanisms of sporting injuries is important to AFL medical and conditioning staff, as they manage their players to be fit for matches. Training and game overload is one possible cause of injury, therefore monitoring these loads in players is important. Measuring training and game loads exerted by athletes can be done by multiplying session rating of perceived exertion5 (Borg CR10 RPE) and duration (min). Previous studies have analysed the relationship between load exerted and injury risk in team sports including sub-elite6 and professional rugby league,7 soccer,8 basketball9 and cricket.10

Gabbett and Domrow6 analysed training loads and injuries of 183 sub-elite rugby league players, finding increases in odds of injury in pre-season (OR = 2.12, p = 0.01), early competition (OR = 2.85, p = 0.01) and late competition (OR = 1.50, p = 0.04) phases, for each increase in a log (150 arbitrary units) of training load. Orchard et al.10 reported cricket bowlers completing more than 50 overs in a match had a significantly increased risk (1.77 times) of injury in the next 14–21 days compared to bowlers completing less than 50 overs. The delayed effect of the load of previous weeks is important to consider when analysing load and injury relationships.

Piggott et al.11 analysed the relationship of injury and illness with weekly training load in 16 AFL players across a 15-week pre-season training phase. No significant relationships were reported between injuries or illness and training load across this period. However, studies using a larger sample and conducted over a longer time period may provide a more comprehensive understanding of the relationship between training load and injury in AFL players.

Each year approximately 4–8 new rookie players are drafted into AFL clubs, coming primarily from junior competitions and State leagues. Senior AFL players have significantly more lean body mass and bone mineral density than State junior players,12 which is likely a result of physical maturation from previous training and game loads within the elite system. Greater movement demands in the AFL compared to State leagues13 further highlights the increased physical demands required of junior or sub-elite players in making the transition into the professional AFL game and training environment. Therefore, exploring the training and game load tolerance of players with different years of experience at an elite level is important.

To date, studies of the training load-injury relationship of AFL players are limited, with the only study performed restricted to a small sample of AFL players over a pre-season period.11 Therefore, the aim of the present study was to examine the relationship between training and game loads and injury risk in AFL players from a full club squad, across an entire season. Identifying a relationship between load and injury may allow club staff to make more objective decisions on when players are at increased risk of injury.

Section snippets

Methods

Elite (n = 46) Australian footballers were involved in this prospective study. Their mean ± SD age, stature and body mass were 22.2 ± 2.9 years, 187.7 ± 7.5 cm and 85.4 ± 8.9 kg, respectively. All were from one AFL club and competed in matches in the AFL or Western Australian Football League (WAFL) during 2010. The AFL team played 22 competition matches but did not qualify for finals. All players provided informed written consent prior to participation and all data were obtained anonymously. Ethics

Results

Additional data pertaining to classifications of pre-season and in-season injuries are provided in (online) Supplementary Table A.

Injury incidence increased (χ2 = 9.37, df = 1, p = 0.002) from pre-season (21.9 per 1000 h) to in-season (32.8 per 1000 h) (Supplementary Table B). The thigh (7.3 per 1000 h, 22.2%) and hip/groin (5.9 per 1000 h, 18.1%) were the most common sites of injuries in-season, with the most common types of injuries being muscle strains (10.7 per 1000 h, 32.6%) and haematomas/contusions

Discussion

The purpose of this study was to examine whether a relationship existed between training and game loads and injury in AFL players. These results indicate injury risk is significantly higher for players who exert larger 1 (>1750 AU) and 2 weekly loads (>4000 AU) or a large previous to current week increment (>1250 AU) in comparison to lower training and game load ranges (<1250 AU, <2000 AU, <250 AU), respectively. These findings suggest that the training and game loads of elite Australian football

Conclusion

During an elite Australian football in-season, larger 1 (>1750 AU) and 2 weekly loads (>4000 AU) and substantial previous to current week change in load (>1250 AU) were found to significantly increase injury risk when compared to lower training and game load ranges (<1250 AU, <2000 AU, <250 AU), respectively. As a method to reduce the risk of injury, derived training and game load values of weekly loads and previous week-to-week load changes should be monitored individually in elite Australian

Acknowledgement

No external financial support was received for this study.

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