Eccentric training for hamstring injury, and its relationship to strength and flexibility: A case-series

BACKGROUND: Reduced strength and flexibility are commonly hypothesised risk factors for the development of hamstring injury, and both are improved with eccentric training in non-injured populations. However, there is a lack of studies investigating the effect of eccentric training on strength and flexibility among previously injured athletes. This study examined the effects of a modified eccentric hamstring strength program on strength and flexibility in previously injured athletes. METHODS: Ten participants (8 Male, 2 Female) ranging from 18-36 years of age were recruited from the local community to participate in the study. All participants demonstrated a previous history of hamstring injury but had since returned to their chosen sport of Gaelic football, hurling, soccer or rugby. A single group repeated measures intervention study was carried out. Two strength parameters; peak torque (PT) and angle of peak torque (AngPT), as well as two flexibility parameters; stretch tolerance (ST) and extensibility were assessed before and after a six week eccentric hamstring strength program. Muscle soreness was recorded using a likert scale. Paired samples t-tests and Wilcoxon signed-ranks tests compared strength and flexibility before and after the eccentric program. RESULTS: There was a significant increase in eccentric hamstring PT (p < 0.001) and eccentric hamstring AngPT (p = 0.001) following the intervention. The results also indicated a significant increase in ST (p ≤ 0.001), but not extensibility (p = 0.892), following the eccentric intervention. Mean(±SD) muscle soreness with the exercise programme was minimal (1.85 ± 0.84) with 100% compliance during the eccentric programme. CONCLUSIONS: Significant changes in PT, AngPT and ST were observed after the eccentric training programme, consistent with previous research among uninjured populations. Extensibility was unchanged after the intervention. Eccentric training programmes similar to that performed in the current study have been associated with reduced injury rates when progressed gradually throughout a season. This study adds support to the hypothesis that eccentric training can improve both strength and flexibility parameters. However further well designed randomised control trials (RCTs) and field-based studies, which include injury outcomes, are needed.