Effect of Hip Joint Position on Electromyographic Activity of the Individual Hamstring Muscles During Stiff-Leg Deadlift.

Kawama, R, Takahashi, K, and Wakahara, T. Effect of hip joint position on electromyographic activity of the individual hamstring muscles during stiff-leg deadlift. J Strength Cond Res 35(2S): S38-S43, 2021-This study investigated the effect of hip joint position on the activity level of individual hamstring muscles during stiff-leg deadlift. Fourteen male collegiate sprinters performed stiff-leg deadlift in the adducted (ADD), neutral (NT), abducted (ABD), internally rotated by 20° (IN20), and externally rotated positions by 20° (EX20) and by 40° (EX40) of the hip joint. Surface electromyogram (EMG) was recorded from the proximal and distal regions of the biceps femoris long head (BFlh), semitendinosus (ST), and semimembranosus (SM). Root mean square value of EMG (RMS-EMG) data were calculated for the concentric and eccentric phases of deadlift and was normalized by RMS-EMG during maximal voluntary contraction of isometric knee flexion as an activity level. Results revealed that the activity level of BFlh during the concentric phase was higher in EX20 (p = 0.008, difference = 6.3%) and EX40 (p = 0.001, difference = 9.4%) than in NT. Semimembranosus showed a higher activity level in IN20 than in EX40 during the concentric (p = 0.004, difference = 4.3%) and eccentric phases (p = 0.023, difference = 4.1%). In addition, the activity level was higher in ABD than in NT for BFlh (p = 0.015, difference = 4.6%), ST (p = 0.047, difference = 3.8%), and SM (p = 0.005, difference = 3.9%) during the concentric phase of deadlift. In conclusion, the deadlift in the hip-abducted position requires high activation of the individual hamstrings and that in the hip externally and internally rotated positions needs high activation of BFlh and SM, respectively.