Background The Nordic hamstring exercise (NHE) reduces the risk of hamstring strain injury (HSI). It is unknown if measuring eccentric hamstring strength during the NHE can predict risk of future HSI in elite Australian footballers.

Objective To determine if measures of eccentric hamstring strength during the NHE identify athletes at risk of future HSI.

Design Prospective cohort study.

Setting Single competitive season in elite Australian football.

Participants Elite Australian footballers able to perform the NHE maximally at the time of testing. 210 athletes from 5 teams had their eccentric hamstring strength assessed.

Risk factor assessment Eccentric hamstring strength was determined using a custom made device at the start and end of pre-season training. Reports of previous history of hamstring, quadriceps, groin and calf injury in the prior 12 months and any history of anterior cruciate ligament injury for all athletes were ascertained.

Main Outcome Measurements Prospective occurrence of HSI. The hypotheses (a priori), were that athletes with lower levels of eccentric hamstring strength and greater between limb imbalances in strength would be at greater risk of HSI.

Results Low levels of eccentric hamstring strength at the start and end of preseason training increased the risk of future HSI by 3.3 (P=.002) and 2.8 fold (P=.027) respectively. Prior HSI increased the risk of future HSI by 3.1 fold (P=.018). No measure of between limb imbalance or any other prior injury data increased the risk of future HSI. Multivariate logistic regression revealed an interaction between increasing age and eccentric hamstring weakness leading to an increased risk of HSI.

Conclusions Low levels of eccentric hamstring strength during the NHE increases the risk of future HSI in elite Australian footballers and this effect is magnified in older athletes.