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Compensations for increased rotational inertia during human cutting turns
Mu Qiao1, Brian Brown, Devin L Jindrich
1Kinesiology Program, School of Nutrition and Health Promotion, Arizona State University, Phoenix, AZ 85004-0698, USA.
The Journal of Experimental Biology
|October 12, 2013
Summary
Human runners use anticipatory adjustments to maintain stability during sidestep cutting turns, not braking forces, even when body rotational inertia changes significantly. This suggests robust control strategies in legged locomotion.
Area of Science:
- Biomechanics
- Human Locomotion
- Motor Control
Background:
- Unsteady locomotion, crucial for complex environments, involves stability and maneuverability, which are not fully understood.
- Previous research suggested 'braking' forces prevent over-rotation during turns due to low human yaw rotational inertia.
Purpose of the Study:
- To investigate human strategies for sidestep cutting turns during running.
- To test the hypothesis that braking forces decrease with increased body rotational inertia.
Main Methods:
- Seven participants performed 45-degree sidestep cutting turns and straight running.
- Body rotational inertia was increased up to fourfold while recording ground reaction forces and body kinematics.
Main Results:
- Contrary to predictions, braking forces remained consistent across different rotational inertias.
- Anticipatory changes in body rotational speed compensated for increased inertia.
- Legged systems demonstrated robustness, compensating for fourfold inertia changes with <50% velocity adjustments.
Conclusions:
- Human runners employ anticipatory adjustments rather than solely relying on braking forces for turn stability.
- Legged locomotion systems exhibit resilience to morphological changes during submaximal turning.
- Compensatory strategies involve minor, inter-step adjustments to initial stance conditions.
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