The human preference for symmetric walking often disappears when one leg is constrained

Area of Science:

• Biomechanics
• Human locomotion
• Energetics

Background:

• Healthy human walking is typically bilateral and symmetric.
• Clinical conditions affecting one leg often lead to asymmetric gait.
• It is unclear if asymmetry is an inevitable consequence or an energy-saving strategy.

Purpose of the Study:

• To test the hypothesis that minimizing metabolic power drives asymmetric walking when one leg is constrained.
• To investigate if healthy adults adopt asymmetric gaits to reduce energy expenditure under unilateral constraints.

Main Methods:

• Two experiments were conducted on healthy adults using a treadmill with visual feedback.
• Experiment 1: One step length was constrained to be markedly shorter or longer than preferred.
• Experiment 2: Milder constraints mimicking clinical asymmetry magnitudes were applied.

Main Results:

• Constraining one step length significantly reduced metabolic power with asymmetric (one constrained, one preferred step) vs. symmetric (both constrained steps) gaits.
• Participants naturally adopted less effortful asymmetric gaits when one step was constrained.
• Most participants adopted asymmetric gaits even with milder constraints.

Conclusions:

• Bilateral symmetry is not always energetically optimal during constrained walking.
• Individuals may prefer asymmetric gaits to minimize metabolic cost when one leg's function is limited.
• Findings suggest a potential mechanism for gait asymmetry in clinical populations.