Title

Lower limb fatigue asymmetry after a repeated-sprint test in Australian Rules Football (ARF) players with and without previous unilateral hamstring injury

Date of Award

2020

Degree Type

Thesis

Degree Name

Master of Science (Sports Science)

School

School of Medical and Health Sciences

First Advisor

Associate Professor Anthony Blazevich

Second Advisor

Dr Fadi Ma’ayah

Abstract

Australian Rules Football (ARF) is the most widely played sport in Australia, with hamstring injuries (HSIs) remaining the most common type of injury. The ability to detect differences in strength and fatigability between injured and non-injured limbs might help identify ARF players at risk of HSI, reducing injury rates. A previous investigation revealed that data obtained from an Isokinetic Endurance Test (IET; a fatiguing knee extension/flexion test), performed before and after a repeated-sprint test (RST) could be used to correctly identify previous unilateral HSIs with 100% accuracy in soccer players. However, it remains unknown whether these results can be replicated in other football cohorts, such as ARF, despite the sports sharing similarities in physical demands and movement patterns. It also remains unknown whether simpler tests such as the Nordic Hamstring Test (NHT) can be used with similar success. The purpose of the present study was to (1) determine whether changes in force production capacity resulting from fatiguing exercise (RST) differed between previously injured and non-injured limbs in ARF players; (2) investigate whether a more practical and cost effective test (NHT or RST) can accurately identify previous HSI in ARF players; and (3) attempt to replicate the findings of previous research in a different population of footballers (i.e. ARF vs. soccer). 30 semi-professional ARF players (15 with and without previous unilateral HSI history) performed an IET and NHT before and after a RST. Significant differences between injured and non-injured limbs were observed during the IET when performed after the RST, in previously injured participants, with peak knee flexor torque (PKFT) being greater in non-injured (131.6 ± 16.3 Nm) than injured (120.9 ± 14.5 Nm) limbs (p < 0.001). Hamstring:quadriceps (H:Q) ratio was also greater in non-injured (0.77 ± 0.06) than injured (0.69 ± 0.07) limbs (p = 0.001), and percent decreases in PKFT and H:Q ratio from pre- to post-RST were greater in injured (-14% and -12% respectively) than non-injured (-7% and -5% respectively) limbs (p ≤ 0.003). The percent decreases in PKFT and H:Q ratio from pre- to post-RST identified 80% of injured and non-injured limbs in previously injured participants, showing outstanding discrimination of previous HSI (AUC = 0.911). No statistical differences between injured and noninjured limbs were observed in eccentric knee flexor torque during the NHT, or in ground reaction forces measured during the RST, in previously injured participants. In addition, the NHT and RST were poor discriminators of previous HSI (AUC = 0.622 and 0.556, respectively). The results suggest that previous HSI is associated with reduced concentric knee flexor torque capacity and enhanced fatigue responses after a RST. It also suggests that functional deficits, indicating a player is not back to full function and with potentially greater risk of future HSI, may only be visible when tested after sport-specific fatiguing exercise. While data obtained from the IET might now be examined prospectively for its ability to predict future HSI, a test that can be performed on lessexpensive and readily-available equipment is still required for many ARF clubs.

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