Steady-state fluctuations of human walking.

Area of Science:

• Biomechanics
• Human locomotion
• Gait analysis

Background:

• Steady-state walking exhibits inherent fluctuations in spatio-temporal gait parameters.
• Understanding these intrinsic fluctuations is crucial for analyzing gait stability and control.

Purpose of the Study:

• To analyze intrinsic gait fluctuations on a subject-driven treadmill with adjustable inertial forces.
• To compare these fluctuations with those during overground locomotion, which includes optical flow.
• To investigate the role of optical flow in modulating gait dynamics.

Main Methods:

• Four adult subjects walked on a subject-driven treadmill and during overground locomotion.
• Gait fluctuations in leg movement and speed were measured in both conditions.
• Comparison of instantaneous and low-frequency fluctuations with and without optical flow.

Main Results:

• Instantaneous fluctuations in leg movement and speed showed similar frequency and amplitude with or without optical flow.
• A low-frequency fluctuation in walking speed emerged without optical flow, resulting from accumulated leg-movement fluctuations.
• Optical flow appears to mitigate this low-frequency speed fluctuation by providing displacement information.

Conclusions:

• Optical flow plays a role in maintaining steady leg movement by preventing the accumulation of fluctuations.
• Low-frequency speed fluctuations in gait may stem from underlying fluctuations in stiffness, as suggested by theoretical models.