Differences in the electromyographic activity of the hamstring muscles during maximal eccentric knee flexion

Area of Science:

• Biomechanics
• Human Movement Science
• Neuroscience

Background:

• Hamstring muscle activation is crucial for knee flexion control.
• Understanding muscle response to varying velocities and joint angles is key for injury prevention and performance enhancement.

Purpose of the Study:

• To investigate the influence of knee joint angle and angular velocity on hamstring muscle activation during maximal eccentric knee flexion.
• To explore potential neural mechanisms underlying force and activation changes.

Main Methods:

• Ten healthy males performed maximal eccentric knee flexion at 10, 60, 180, and 300 deg/s.
• Measured eccentric knee flexion torque and surface electromyography (EMG) of biceps femoris (BF), semitendinosus (ST), and semimembranosus (SM).

Main Results:

• Eccentric torque was lower at 10 deg/s compared to faster velocities.
• No significant changes in torque or EMG amplitude were observed across faster velocities (60-300 deg/s), though a decreasing tendency was noted towards knee extension.
• Biceps femoris (BF) EMG significantly decreased towards knee extension, while semitendinosus (ST) and semimembranosus (SM) remained constant.

Conclusions:

• Neural inhibitory mechanisms may reduce maximal voluntary force and hamstring activation towards knee extension during high-velocity eccentric contractions.
• Difficulty in maintaining high eccentric force throughout the motion is suggested.
• Architectural differences between hamstring muscles might explain the reduced BF activation near knee extension.