Relationship between the peak time of hamstring stretch and activation during sprinting

Area of Science:

• Biomechanics
• Sports Medicine
• Exercise Physiology

Background:

• Hamstring muscle strain injuries are common in sprinters.
• Understanding the relationship between muscle mechanics and activation is crucial for injury prevention.

Purpose of the Study:

• To investigate time series relationships between peak hamstring musculotendon length and electromyography (EMG) activation during sprinting.
• To clarify the risk of muscle strain injury in specific hamstring muscles.

Main Methods:

• Recorded full-body kinematics and EMG of biceps femoris long head (BFlh) and semitendinosus (ST) in male sprinters.
• Computed hamstring musculotendon lengths using a 3D musculoskeletal model during maximal effort sprinting.
• Compared timing of peak musculotendon length with peak EMG activation across the gait cycle.

Main Results:

• Peak hamstring musculotendon length occurred during the late swing phase.
• Peak musculotendon length was synchronous with peak EMG in the BFlh.
• Peak musculotendon length occurred significantly later than peak EMG in the ST (p < 0.05).

Conclusions:

• The BFlh muscle experiences high instantaneous tensile forces during the late swing phase of sprinting.
• These findings suggest a higher risk of muscle strain injury for the BFlh compared to the ST.
• This highlights the importance of considering muscle activation timing relative to length changes for hamstring injury prevention strategies.