Relationship between interchange usage and risk of hamstring injuries in the Australian Football League

doi:10.1016/j.jsams.2011.11.250

Journal of Science and Medicine in Sport

Volume 15, Issue 3, May 2012, Pages 201-206

https://doi.org/10.1016/j.jsams.2011.11.250 Get rights and content

Abstract

Objectives

To study risk factors for hamstring injury in the Australian Football League (AFL), in particular the effect of recent changes in match participation (increased use of the interchange bench) on hamstring injury.

Design

Analysis of hamstring match injury statistics extracted from an injury database combined with match participation statistics extracted from a player statistics database.

Methods

56,320 player matches in the AFL over the period 2003–2010 were analyzed, in which 416 hamstring injuries occurred.

Results

In a Generalized Estimating Equation (GEE) analysis accounting for clustering of different teams, significant predictors of hamstring injuries were recent hamstring injury (RR 4.16, 95% CI 3.19–5.43), past history of ACL reconstruction (RR 1.69, 95% CI 1.09–2.60), past history of calf injury (RR 1.58, 95% CI 1.37–1.82), opposition team making 60 or more interchanges during the game (RR 1.38, 95% CI 1.12–1.68) and player having made 7 or more interchanges off the field in the last 3 weeks (protective RR 0.74, 95% CI 0.59–0.93).

Conclusions

These findings suggest that regular interchanges protect individual players against hamstring injuries, but increase the risk of hamstring injury for opposition players. These findings can be explained by a model in which both fatigue and average match running speed are risk factors for hamstring injury. A player who returns to the ground after a rest on the interchange bench may himself have some short-term protection against hamstring injury because of the reduced fatigue, but his rested state may contribute to increased average running speed for his direct opponent, increasing the risk of injury for players on the opposition team.

Introduction

The hamstring strain is one of the most common injuries in sports which involve sprinting, including track events (such as the 100 m sprint) and the various football codes. Hamstring injuries are the most common injury in the Australian Football League (AFL) and are responsible for the highest number of matches missed through injury.¹ Hamstring injuries generally occur acutely from a high intensity event (as per the 100 m sprinter tearing the muscle after 40 m of running) during a match or training session or, less commonly, as a gradual onset injury with specific onset hard to isolate. A slight majority of hamstring injuries in the AFL occur in matches although some occur during training sessions or are of unknown/insidious onset. Known risk factors for hamstring injury include player age,2, 3 past history of hamstring injury, strength deficits, indigenous race and past history of other injury (including calf, knee, ankle and groin injuries).4, 5, 6

The use of the interchange bench in AFL football changed over the period 2003–2010 despite fairly constant rules. In these years the game was played between two teams of 18 players, with four players on an interchange bench and with unlimited rotations (interchanges) of players allowed. In 2006, rule changes were introduced to increase the continuity of the game to improve the spectacle of the event, which had an effect of reducing the amount of rest time for players after a score or an umpiring decision. In addition to these changes, umpires have been instructed to try to increase the continuity of the game by decreasing the amount of time taken to bounce the ball and throw the ball in from the boundary line. Although there has been a basic 80 min of time ‘in play’ over these eight seasons, the continuity of the game has varied, partly because of the 2006 rule changes and partly due to changes in the number of stoppages which otherwise occur (e.g. scoring plays, boundary throw ins, ball-ups). The actual length of games is approximately 120 min due to the substantial time added for stoppages. In the background of these changes to game continuity, there was a substantial increase in the number of interchange movements being made by teams during games over the eight year period between 2003 and 2010 (online Table 4). Teams made fewer than 30 interchanges per game in 2003 but greater than 100 interchanges per game in 2010.

Fatigue has previously been cited as a risk factor for injury in team sport.7, 8 It is plausible that increased average player speed9, 10 and increased player fatigue are both independent risk factors for hamstring strain. The level of both risk factors are likely to be influenced by the number of player interchanges. The aim of this study was to assess risk factors for hamstring strain in the AFL. In particular, it was aimed to assess the impact that changes in interchange movements and game time may have had on the risk of hamstring strain in the AFL, corrected for other known risk factors.

Section snippets

Methods

The methods used in this study are similar to a previously conducted study in the AFL examining intrinsic and extrinsic risk factors for hamstring strain, although in this study a more sophisticated multivariate technique was used.³ Injury data collected between 2003 and 2010 inclusive were extracted from the AFL injury database for analysis. Match performance statistics obtained from the official statistical providers for the AFL (Champion Data, Melbourne, Australia) were also analyzed. We

Results

Over each of the eight seasons from 2003 to 2010 the total numbers of listed players at all 16 AFL clubs combined were respectively 676, 685, 692, 702, 708, 713, 738 and 742. They suffered a total of 899 hamstring strains during the home and away seasons over the eight years (Table 1). However, only 416 were confirmed as occurring during a regular season AFL grade match from rounds 2–21. The number of interchanges per match (for both teams) steadily increased by a substantial amount each year (

Discussion

Hamstring injuries in the AFL have been studied extensively. This study confirmed previous findings that recent hamstring strain, past ACL reconstruction⁵ and past calf injury³ are all risk factors for hamstring strain.2, 18 It is the first study to examine the effects of match characteristics on the risk of hamstring injury.

Increasing interchanges by the opposition increased the risk of hamstring injury in an individual, and where the opposition made more than 60 interchanges in a game there

Conclusion

This study suggests that AFL players who do not regularly interchange off the field are slightly more prone to hamstring injury over the coming weeks and that an increasing number of interchanges by the opposition also increases individual risk of hamstring injury. The protective effect of individual rest is not enough to offset the increased risk to other players on the field when there are increased numbers of interchange movements. It is plausible that a combination of increased game speed

Practical implications

•
Individual athletes are somewhat protected against hamstring injury in the AFL by having a break on the interchange bench. This suggests that fatigue may be a risk factor for hamstring injury.
•
When opposition interchanges increase, a player's risk of hamstring injury increases. This suggests that running speed (particularly running speed of one's opponent) may also be a risk factor for hamstring injury.
•
The protective effect of interchange for individuals is not enough to offset the increased

Acknowledgments

Kevin McGeechan is acknowledged for providing assistance with the SAS analysis. The Australian Football League (AFL) is acknowledged as the funding source for the AFL Injury database. Champion Data is acknowledged as the provider of match participation statistics. John Orchard is paid as a consultant to provide injury surveillance services for the AFL.

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Original researchRelationship between interchange usage and risk of hamstring injuries in the Australian Football League

Abstract

Objectives

Design

Methods

Results

Conclusions

Introduction

Section snippets

Methods

Results

Discussion

Conclusion

Practical implications

Acknowledgments

J Sci Med Sport

J Sci Med Sport

Accid Anal Prev

J Sci Med Sport

J Sci Med Sport

Epidemiology of injuries in the Australian Football League, seasons 1997–2000

Br J Sports Med

Intrinsic and extrinsic risk factors for muscle strain injury in Australian footballers

Am J Sports Med

Preseason hamstring muscle weakness associated with hamstring muscle injury in Australian footballers

Am J Sports Med

Clinical risk factors for hamstring muscle strain injury: a prospective study with correlation of injury by magnetic resonance imaging

Br J Sports Med

Predictors of hamstring injury at the elite level of Australian football

Scand J Med Sci Sports

Injury incidence and injury patterns in professional football: the UEFA injury study

Br J Sports Med

Incidence of injury in semi-professional rugby league players

Br J Sports Med

Aetiology of injuries in Australian football

Br J Sports Med

AFL Injury Report: season 2004

Sport Health

Original research
Relationship between interchange usage and risk of hamstring injuries in the Australian Football League