Visual control of step length during running over irregular terrain

Area of Science:

• Biomechanics
• Motor Control
• Visual Perception

Background:

• Running on uneven terrain necessitates precise control of step length for stability.
• Visual feedback is crucial for regulating gait parameters during locomotion.

Purpose of the Study:

• To investigate the mechanisms by which runners adjust step length to meet irregularly spaced targets.
• To determine the relative contributions of different motor control strategies in regulating step length.

Main Methods:

• Subjects ran on a treadmill with irregularly spaced targets.
• Lower limb and coccyx movements were tracked using an opto-electronic Selspot system.
• Analysis focused on impulse components (vertical and horizontal) and foot placement.

Main Results:

• Step length was primarily adjusted by modulating the vertical component of ground impulse during the stance phase.
• Horizontal impulse and forward reach of the foot showed minimal variation.
• Changes in vertical impulse directly influenced step time proportionally.

Conclusions:

• Running step length regulation is achieved by adjusting vertical impulse, consistent with a time-based model.
• The optic variable delta tau likely modulates vertical impulse to bridge time gaps between targets.
• This suggests a visually guided, time-dependent control strategy for running on challenging surfaces.