Knee flexion strength is significantly reduced following competition in semi-professional Australian Rules football athletes: Implications for injury prevention programs

Highlights

• Maximal isometric knee flexion strength is significantly reduced at 26 h following competitive match-play in semi-professional AF athletes.

• Restoration of knee flexion strength occurring by 50 h post-match may be used to monitor recovery and plan subsequent training sessions.

• Knee flexion strength recovery following match-play may be especially pertinent for monitoring athletes with past-history of hamstring strain.

Abstract

Objectives

To evaluate strength and flexibility measures pre- and post- Australian Football (AF) competition to determine their potential utility as secondary prevention measures.

Design

Cohort study.

Setting

Semi-professional AF club.

Participants

Ten male AF athletes (mean ± SD; age, 21.3 ± 2.2 years; height, 186.1 ± 6.3 cm; weight, 83.5 ± 8.6 kg).

Main Outcome Measures

Maximal unilateral isometric knee flexion strength performed in 45 degrees of hip flexion and 30 degrees of knee flexion, flexibility measures of hip and knee extension and ankle dorsiflexion. All outcome measures were evaluated pre-match to determine baseline measurements and repeated acutely post-match and at 26, 50 and 74 h following. Comparisons were made between baseline measures and all other time points.

Results

Knee flexion strength was significantly reduced at a group level acutely (−122.8N, 95%CI −156.2 to −89.4, p = 0.000) and at 26 h (−89.6N, 95%CI −122.9 to −56.2, p = 0.000) following competition. Hamstring flexibility was significantly reduced at all time periods following competition (all p < 0.05), however these values were not clinically meaningful.

Conclusions

Knowledge that unilateral isometric knee flexion strength returns to pre-competition levels by 50 h following match-play in AF athletes is valuable for planning recovery time frames and may inform implementation of secondary prevention strategies.

Introduction

A large body of literature has been dedicated to understanding potential risk factors associated with hamstring strain. A number of non-modifiable risk factors have been identified including increased player age, indigenous race and a past history of both hamstring and other injuries (Verrall, Slavotinek, Barnes et al., 2001). Other known risk factors, such as hip, knee and ankle flexibility have been reported (Bradley and Portas, 2007, Gabbe et al., 2006, Witvrouw et al., 2003). Hamstring strength deficits have also been consistently identified (Orchard, Marsden, Lord et al., 1997), and are modifiable. However, despite this, high rates of hamstring strain have been stable and hamstring strain remains the most common and prevalent injury reported since the inception of injury surveillance in the Australian Football League (Orchard, Seward, & Orchard, 2013). One reason for this might be that identified strength deficits have been reported as single measures usually conducted in the pre-season (Opar et al., 2014, Orchard et al., 1997) and are unable to reflect weekly fluctuations that might occur due a variety of reasons such as the accumulation of fatigue. It has been reported that high-intensity activities are significantly reduced in the final stages of competitive match-play, across several matches for intermittent team sports (Bradley et al., 2009, Sykes et al., 2011), possibly associated with match-induced fatigue (Black, Gabbett, Naughton et al., 2016).

Knowledge of weekly fluctuations of hamstring strength and lower limb flexibility profile changes throughout the in-season period, particularly in response to match-play, may contribute to a better understanding of the aetiology of hamstring injuries. It is currently uncertain as to whether potential variations may elucidate athletes at risk of injury or maladaptation to the completed workloads. In this context, routine monitoring of strength and lower limb flexibility may present an opportunity for secondary prevention (Jacobsson & Timpka, 2015). Secondary prevention is one of three sub-categories (primary, secondary and tertiary) of preventative measures aimed at preventing a specific pathology. Secondary prevention measures are implemented before pathology has caused long-term disability where sub-clinical signs of pathology may exist (Jacobsson & Timpka, 2015), in practice this refers to early detection and interventions addressing clinical signs which may result in injury.

Recently, a simple and inexpensive method of measuring isometric knee flexion strength, namely externally fixed dynamometry, has been evaluated in response to competitive match-play in junior elite soccer athletes (Wollin, Thorborg, & Pizzari, 2016b). Results demonstrated significant reductions in strength compared with pre-match measures immediately and at 24 h following match-play. This is yet to be investigated in AF, where, similarly to soccer, match running volumes are large and the rate of hamstring strain is high (Bradley and Noakes, 2013, Woods et al., 2004). Information on recovery of strength and flexibility measures following Australian Football match-play would be able to inform sports specific injury prevention practices.

The aim of this study was to evaluate the effect of competitive match-play on measures of isometric knee flexion strength and lower limb flexibility in semi-professional AF athletes. Knowledge of timeframes of recovery of knee flexion strength and ankle, hip and knee flexibility using clinically feasible tools could assist planning of training and inform implementation of in-season monitoring strategies in high-risk cohorts as a component of secondary prevention.