Differences in activation properties of the hamstring muscles during overground sprinting

- We examined the muscle activity of hamstring muscles during overground sprinting.
- The biceps femoris was highly activated before and after foot contact.
- The medial hamstring was highly activated in the late stance and middle-swing phases.
- The activation characteristics of each hamstring muscle differ during sprinting.

The purpose of this study was to quantify activation of the biceps femoris (BF) and medial hamstring (MH) during overground sprinting. Lower-extremity kinematics and electromyography (EMG) of the BF and MH were recorded in 13 male sprinters performing overground sprinting at maximum effort. Mean EMG activity was calculated in the early stance, late stance, mid-swing, and late-swing phases. Activation of the BF was significantly greater during the early stance phase than the late stance phase (p < 0.01). Activation of the BF muscle was significantly lower during the first half of the mid-swing phase than the other phases (p < 0.05). The MH had significantly greater EMG activation relative to its recorded maximum values compared to that for the BF during the late stance (p < 0.05) and mid-swing (p < 0.01) phases. These results indicate that the BF shows high activation before and after foot contact, while the MH shows high activation during the late stance and mid-swing phases. We concluded that the activation properties of the BF and MH muscles differ within the sprinting gait cycle.