Strength, not flexibility is responsive to match-play in Australian Football athletes

Abstract

Introduction: Hamstring strain injury remains the most common injury in Australian Football (AF) despite a large body of research dedicated to understanding the associated risk factors. Modifiable risk factors such as hamstring strength deficits and lower limb flexibility measures have previously been identified with respect to increased risk of hamstring strain injury. The aim of this study was to evaluate the variability of clinically feasible lower limb strength and flexibility tests pre- and post-AF match-play to determine their usefulness as injury prevention measures within a secondary prevention program (with the goal of early detection and intervention). Methods: This repeated measures design involved male (n = 10 (20 limbs); height, 186.1 ± 6.3 cm; weight 83.5 ± 8.6 kg; age, 21.3 ± 2.2 years) semi-professional AF athletes who completed maximal voluntary isometric hamstring strength (HSIS) and lower limb flexibility measures of the hip, knee and ankle prior to and at three time points (<1 h, 26 h, 50 h and 74 h) following competitive match-play. Linear mixed-effect models were used to determine differences across time points with fixed effects for the test score and random effects for participant to account for within subject variation. Clinically worthwhile changes were set a priori to ensure any observed effect is of clinical utility (HSIS, >14% of group baseline; flexibility: hip, 10°, knee 10°, ankle, 2 cm). Statistical significance was determined when the 95%CI did not include 0 (representing no change from baseline). Results: Maximal isometric hamstring strength was significantly reduced at a group level compared to baseline measurements immediately (−122.8 N, 95%CI: −156.2–89.4, p < 0.001) and at 26 h (−89.6 N, 95%CI: −122.9–56.2, p < 0.001) following match-play. No significant differences from baseline were observed at 50 and 74 h. These observed reductions in force exceeded minimal clinically meaningful changes. Hip, knee and ankle flexibility tests did not reach clinically meaningful changes at any time point. Discussion: Clinically meaningful and statistically significant reductions in maximal isometric hamstring strength are evident for up to 26 h following competitive match-play. This information may have implications for planning recovery timeframes following competition and implementation of routine monitoring. At a group level, isometric strength should return to baseline levels within 50 h and failure to achieve this recovery level may warrant further investigation. Lower limb flexibility measures were not changed from baseline values in a clinically meaningful way and therefore are not recommended for use as routine monitoring in injury prevention.