Kinematic and electromyographic effects of different execution modalities during the Nordic Hamstring Exercise

The Nordic Hamstring Exercise (NHE) is widely used for eccentric hamstring strengthening and injury prevention. This study examined how three criteria-based NHE execution modalities affect break-point angle (BPA) and hamstring muscle activation. It was hypothesised that increased execution quality results in greater muscular activation and more extended BPAs. Forty-two participants completed two familiarisation sessions before performing three NHE modalities using partner fixation, rigid heel fixation, and a training device providing rigid heel fixation, controlled kneeling height and knee positioning. Kinematic data determined BPAs, while surface electromyographic (EMG) signals recorded activity of M. biceps femoris and M. semitendinosus. Friedman tests with Wilcoxon post-hoc comparisons assessed differences. Significant BPA differences occurred (p < 0.01), with the training device producing the most extended knee positions (56.0° ± 13.8), compared with partner (74.8° ± 9.4) and rigid heel fixation (74.3° ± 11.1). Root mean square and integrated EMG values were significantly higher in the training device modality than partner fixation and rigid heel fixation (p < 0.01). The more extended knee positioning was accompanied by altered thigh and shank orientation. These findings indicate that NHE execution modality substantially influences movement mechanics and neuromuscular demand. For standardised testing and training, rigid heel fixation combined with controlled kneeling height and consistent setup conditions is recommended.