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Widespread short-latency stretch reflexes and their modulation during stumbling over obstacles
A M Schillings1, B M Van Wezel, T Mulder
1Department of Medical Physics and Biophysics, University of Nijmegen, Geert Grooteplein 21, 6525 EZ, Nijmegen, Netherlands. ieke@mbfys.kun.nl
Brain Research
|January 8, 1999
Summary
Short-latency stretch reflexes occur during human stumbling reactions, with leg muscle responses appearing within 34-42 ms. These reflexes may help prepare the body for stumbling by increasing joint stiffness.
Area of Science:
- Neuroscience
- Biomechanics
- Human Motor Control
Background:
- Stumbling reactions are crucial for maintaining balance during locomotion.
- The role of short-latency stretch reflexes in human stumbling is not fully understood.
Purpose of the Study:
- To investigate the presence and characteristics of short-latency stretch reflexes during human stumbling reactions.
- To explore the underlying neural mechanisms controlling these reflexes.
Main Methods:
- Subjects walked on a treadmill and experienced unexpected foot obstruction.
- Electromyography recorded muscle activity in the leg.
- Reflex latencies and amplitudes were analyzed relative to the step cycle and perturbation.
Main Results:
- Short-latency reflex responses (34-42 ms) were observed in leg flexors and extensors of the obstructed limb.
- Response amplitudes varied with the step cycle phase, independent of background muscle activity or perturbation intensity.
- Coactivation of antagonist muscles and minimal immediate consequences suggest a role in joint stiffening.
Conclusions:
- Short-latency stretch reflexes are present and actively controlled during human stumbling.
- These reflexes likely contribute to joint stiffness as an initial protective mechanism.
- Premotoneuronal mechanisms may be involved in the phase-dependent control of stumbling reflexes.