The Effect of Variations in Knee and Hip Angles on Electromyographic Activity of the Hamstrings and Related Muscles During the Nordic Hamstring Exercise

Background The benefit of performing the Nordic Hamstring Exercise (NHE) on an inclined board has been described, however, isometric hamstring activation in different knee and hip angles has not yet been thoroughly explored. Purpose This study investigated the effect of variations in knee and hip angles during the isometric performance of the NHE on electromyographic activity of the hamstring muscles. Study design Crossover study Methods Thirteen male volunteers performed isometric contractions during the NHE with the knee (30°, 50°, 60°) and the hip (0°, 30°, and 45°) in various angles of flexion on a leg support platform which was inclined at 30°. An electrical goniometer was used to monitor the knee and hip joint angles during 5-s isometric contractions. A multivariate analysis of variance with repeated measures was used to compare normalized electromyographic values of each muscle across different knee and hip angles, followed by pairwise comparisons. Results The electromyographic activity of the biceps femoris, semitendinosus, and semimembranosus at a knee angle of 30° and hip angle of 0° were significantly higher than those observed with a knee angle of 50° and hip angle of 0°, or a knee angle of 60° and hip angle of 0° (p<0.05). The electromyographic activity of the semimembranosus at a knee angle of 60° and hip angle of 45° was significantly higher than values obtained with knee and hip angles of 60° and 0°, respectively (p<0.05). Conclusions The results indicate that using a knee flexion of 30° and a hip flexion of 0°, while isometrically performing the NHE on a platform inclined at 30°, may optimize electromyographic activity of the hamstrings.