An Evidence-Based Framework for Strengthening Exercises to Prevent Hamstring Injury

Abstract

Strength training is a valuable component of hamstring strain injury prevention programmes; however, in recent years a significant body of work has emerged to suggest that the acute responses and chronic adaptations to training with different exercises are heterogeneous. Unfortunately, these research findings do not appear to have uniformly influenced clinical guidelines for exercise selection in hamstring injury prevention or rehabilitation programmes. The purpose of this review was to provide the practitioner with an evidence-base from which to prescribe strengthening exercises to mitigate the risk of hamstring injury. Several studies have established that eccentric knee flexor conditioning reduces the risk of hamstring strain injury when compliance is adequate. The benefits of this type of training are likely to be at least partly mediated by increases in biceps femoris long head fascicle length and improvements in eccentric knee flexor strength. Therefore, selecting exercises with a proven benefit on these variables should form the basis of effective injury prevention protocols. In addition, a growing body of work suggests that the patterns of hamstring muscle activation diverge significantly between different exercises. Typically, relatively higher levels of biceps femoris long head and semimembranosus activity have been observed during hip extension-oriented movements, whereas preferential semitendinosus and biceps femoris short head activation have been reported during knee flexion-oriented movements. These findings may have implications for targeting specific muscles in injury prevention programmes. An evidence-based approach to strength training for the prevention of hamstring strain injury should consider the impact of exercise selection on muscle activation, and the effect of training interventions on hamstring muscle architecture, morphology and function. Most importantly, practitioners should consider the effect of a strength training programme on known or proposed risk factors for hamstring injury.

High‐density electromyography activity in various hamstring exercises

“…Thus, balanced strengthening of these muscles should be a training goal. Although conventional EMG studies are not in agreement, previous mfMRI studies suggest that BFlh is relatively more active in hip‐dominant exercises, while ST is relatively more active in knee‐dominant exercises . Based on the current study, it seems rather challenging to preferentially activate BFlh.…”

“…Although conventional EMG studies are not in agreement, previous mfMRI studies suggest that BFlh is relatively more active in hip-dominant exercises, while ST is relatively more active in knee-dominant exercises. 20 Based on the current study, it seems rather challenging to preferentially activate BFlh. Previously, mfMRI showed relatively high activity in BFlh compared to ST in 45HE, 17 which is confirmed by our results.…”

“…For example, non-uniform adaptations to exercise interventions 11,15,16 may be associated with nonuniform hamstring activity patterns across exercises. 11,[17][18][19] Moreover, study results are inconsistent concerning which hamstring muscles are activated in different exercises, as well as the extent of activation, 20 and it is questionable whether these differences are real or at least partly reflect the (in)accuracy with which different methods can define muscle activity.…”

“…Electromyography (EMG) is the most commonly used method to examine hamstring muscle activity. 20 In conventional EMG studies, electrodes are placed over the mid-belly of hamstring muscles, ignoring possible proximal-distal differences in muscle activity. Studies have shown non-uniform proximal-distal metabolic activity patterns within hamstring muscles.…”

Late swing or early stance? A narrative review of hamstring injury mechanisms during high‐speed running

“…For example, there is growing support for the importance of injury prevention exercises that result in lengthening of muscle fascicles. [67][68][69] Understanding the relative contribution of muscle fascicles to overall strain of the musculotendon complex would serve to validate and inform this training principle. Finally, there is a distinct lack of prospective studies examining the relationship between running mechanics and hamstring injury occurrence.…”