Effect of hip joint angle on concentric knee extension torque

Area of Science:

• Biomechanics
• Human Movement Science
• Kinesiology

Background:

• The relationship between hip and knee joint angles is crucial for understanding lower limb biomechanics.
• Previous research has not fully elucidated how hip joint positioning affects knee extension torque across various knee angles.

Purpose of the Study:

• To investigate the influence of hip joint angle on concentric knee extension torque.
• To determine if this effect is dependent on the knee joint angle during a single knee extension task.

Main Methods:

• Twelve healthy men performed maximal concentric knee extensions in both extended and 80° flexed hip positions.
• Experiments were conducted at two angular velocities (30°/s and 180°/s).
• Peak torque and torques at specific knee joint angles were measured, alongside muscle activation via electromyography.

Main Results:

• Peak knee extension torque was significantly greater with the hip flexed compared to the hip extended, regardless of angular velocity.
• Greater torques were observed at 70° and 90° knee flexion (and 50° at 180°/s) with a flexed hip.
• No significant differences in muscle activation were found between hip positions.

Conclusions:

• The study supports the hypothesis that hip joint angle modulates knee extension torque, with the effect varying by knee joint angle.
• These findings suggest that the rectus femoris's force-length and force-velocity properties may explain the observed torque differences.
• Understanding these inter-joint dynamics is important for optimizing movement and performance.