Impulsive ankle push-off powers leg swing in human walking.

Area of Science:

• Biomechanics
• Human locomotion
• Kinetics and kinematics

Background:

• High ankle joint power output during push-off is observed in human walking.
• Previous models suggest push-off redirects the body's center of mass or provides kinetic energy for swing initiation.
• The exact biomechanical process behind high ankle extensor power output remains unclear.

Purpose of the Study:

• To comprehensively analyze human walking push-off mechanics.
• To identify and describe distinct phases within the push-off process.
• To investigate the energy transfer and joint actions during push-off.

Main Methods:

• Analysis of kinematic and dynamic data from human walking.
• Data collected at walking speeds ranging from 0.5 to 2.5 m/s.
• Identification and characterization of push-off phases.

Main Results:

• Push-off was divided into an alleviation phase (positive ankle power) and a launching phase (stored energy release).
• Only a small portion of stored ankle energy was released during alleviation.
• The launching phase showed greater impulse for the trailing leg, with knee buckling limiting power transfer to the body.

Conclusions:

• Human walking push-off consists of distinct alleviation and launching phases.
• Ankle push-off generates impulse for the trailing leg, but knee buckling restricts body-wide power transfer.
• Swing initiation appears to benefit from the impulsive ankle push-off, potentially via a 'catapult without escapement' mechanism.