Electrically evoked knee flexion torque increases with increased pelvifemoral angles.

Area of Science:

• Biomechanics
• Human Physiology
• Neuromuscular Function

Background:

• Knee flexion torque is crucial for various physical activities.
• Understanding factors influencing hamstring muscle torque is important for rehabilitation and performance.
• Previous research has explored maximal voluntary contractions, but less is known about electrically evoked contractions under varying joint angles.

Purpose of the Study:

• To investigate the impact of different pelvifemoral angles on electrically evoked knee flexion torques generated by hamstring muscles.
• To quantify the torque differences across various body positions (supine, upright, leaning forward).

Main Methods:

• Nineteen healthy subjects received submaximal electrical stimulation of hamstring muscles.
• Subjects were positioned supine, sitting upright, and sitting leaning forward.
• Pelvifemoral angles were measured, and knee flexion torque was calculated based on force and lever arm measurements.

Main Results:

• Significant differences in pelvifemoral angles and knee flexion torques were observed across positions (P < 0.001).
• Mean torques in upright and leaning forward positions were 2.2 and 3.7 times greater than in the supine position, respectively.
• The torque increase from supine to leaning forward surpassed previously reported increases during maximal voluntary contractions.

Conclusions:

• Body positioning, specifically altering the pelvifemoral angle, significantly influences hamstring muscle-generated knee flexion torque during electrical stimulation.
• The findings suggest that the angle of the pelvis relative to the femur plays a critical role in modulating muscle force production, even with submaximal stimulation.
• This has implications for understanding muscle mechanics and optimizing therapeutic or training interventions involving the hamstring muscles.