Effect of Different Slopes of the Lower Leg during the Nordic Hamstring Exercise on Hamstring Electromyography Activity

Abstract

The purpose of this study was to examine whether the NHE with an increased lower leg slope angle would enhance hamstring EMG activity in the final phase of the descend. The hamstring EMG activity was measured, the biceps femoris long head (BFlh) and the semitendinosus (ST). Fifteen male volunteers participated in this study. Subjects performed a prone leg curl with maximal voluntary isometric contraction to normalize the hamstring EMG activity. Subsequently, subjects performed the NHE, with the help of a certified strength and conditioning specialist, while the lower leg slope angle were randomly set at 0° (NH), 20° (N20), and 40° (N40). To compare hamstring EMG activity during the NHE variations, the knee flexion angle was set in the range from 0° to 50°, divided into five phases (0–10°, 10–20°, 20–30°, 30–40° and 40–50°), where 0° indicated that the knee was fully extended. To calculate the knee extension angular velocity, the knee flexion angle divided by time, and break point angle (BPA) was the angle at which 10°/s was exceeded. In the statistical analysis, a two-way repeated measures ANOVA was used for the hamstring EMG activity and a one-way repeated measures ANOVA was used for the BPA. The EMG activity of the BFlh and the ST in N20 and N40 was significantly higher than in NH at knee flexion angle of 0–20° (p < 0.05). For the BPA, NH (57.75° ± 13.28°), N20 (36.27° ± 9.89°) and N40 (16.26° ± 9.58°) were significantly higher in that order (p < 0.05). The results of this study revealed that the NHE with an increased lower leg slope angle shifted the BPA to the lower knee flexion angle and enhanced the hamstring EMG activity in the final phase of the descent.

Muscle Activity and Kinematics During Three Hamstring Strengthening Exercises Compared to Sprinting: A Cross-Sectional Study.

“…This reduction in range and absence of a breakpoint may alter the contribution ratio over one and may be further supported by two studies who found that ST activity is greater during the initial movement and relative BFlh activity progressively increases towards full knee extension. 37,47 This study's findings of NHE execution variation add evidence to the already stated suggestion that full ROM without loss of control could improve BFlh selectivity in NHE.…”

Hamstring Activity Before and After Break-Point Angle Calculated By Smartphone Application During the Nordic Hamstring Exercise

“…Soga et al investigated the magnitude of BF EMG activity before and after BPA calculated by motion analysis during NHE variations with different lower leg slope angles. 16 They reported that BF EMG activity peaks near the BPA during NHE variations with 20° or 40° lower leg slope, and decreases toward the shallow knee flexion position during NHE variations with 0° lower leg slope (similar to standard NHE). The results of this study support these findings, emphasizing the importance of knee flexion exercises that enhance BF EMG activity at 15-35° knee flexion to effectively prevent recurrent hamstring injuries, the BPA of the Nordic Angle should be kept within 35° to be effective in preventing recurrent hamstring injuries with standard NHE.…”

“…Given that the BPA is approximately 50° even in trained soccer players, 13 BF EMG activity at 15-35° knee flexion angle is likely diminished with standard NHE in many athletes. [14][15][16] The recent development of a smartphone application (Nordic Angle) has introduced the automatic calculation of BPA, eliminating the need to import data to a personal computer. Although it has been reported that BF EMG activity peaks near the BPA and gradually diminishes afterward, 16 the investigation of BF EMG activity before and after BPA, as calculated by the Nordic Angle, remains unexplored.…”

“…[14][15][16] The recent development of a smartphone application (Nordic Angle) has introduced the automatic calculation of BPA, eliminating the need to import data to a personal computer. Although it has been reported that BF EMG activity peaks near the BPA and gradually diminishes afterward, 16 the investigation of BF EMG activity before and after BPA, as calculated by the Nordic Angle, remains unexplored. If the BPA value obtained using the Nordic Angle determines whether BF EMG activity is enhanced at knee flexion angles of 15-35°, it could significantly benefit the field of sports medicine.…”

“…Additionally, if the angle of the lower leg slope for NHE can be adjusted based on the BPA value calculated by the Nordic Angle, it may further optimize BF EMG activity at knee flexion angles of 15-35°. 16,17 Therefore, the aim of this study was to investigate the BF EMG activity before and after BPA, as calculated using the Nordic Angle app. A secondary purpose was reassess the validity of the Nordic Angle app 18 by comparing its BPA values with those obtained through motion analysis.…”