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Postural muscle activity patterns during standing at rest and on an oscillating floor
Katsuo Fujiwara1, Hiroshi Toyama, Takeo Kiyota
1Department of Human Movement and Health, Graduate School of Medical Science, Kanazawa University, 13-1 Takara-machi, Kanazawa 920-8640, Japan. fujikatu@med.kanazawa-u.ac.jp
Summary
Postural muscle activity shifts between anterior and posterior dominance in the thigh during oscillating balance tasks. Thigh muscle activity becomes less periodic in anterior-dominant individuals as oscillation frequency increases.
Area of Science:
- Biomedical Engineering
- Neuroscience
- Biomechanics
Background:
- Postural control relies on coordinated muscle activity.
- Understanding muscle response to external perturbations is crucial for balance.
- Previous research has explored postural sway but less on specific muscle group dominance patterns.
Purpose of the Study:
- To investigate postural muscle activity patterns in the eyes-closed state during anteroposterior floor oscillations.
- To determine how muscle dominance (anterior vs. posterior) in the trunk and thigh is affected by oscillation frequency.
- To analyze the periodicity of muscle activity in relation to oscillation frequency and muscle group dominance.
Main Methods:
- Twenty-three subjects were assessed for postural muscle dominance in the trunk and thigh during quiet stance.
- Subjects then underwent anteroposterior floor oscillations at varying frequencies (0.1-1.5 Hz) with eyes closed.
- Electromyography (EMG) amplitude spectrum was used to evaluate muscle activity periodicity.
Main Results:
- Posterior muscle dominance was generally maintained in the trunk and thigh.
- Anterior-dominant subjects showed a shift to posterior dominance at higher oscillation frequencies (1.0-1.5 Hz).
- Thigh muscle activity periodicity decreased in anterior-dominant individuals at higher frequencies, attributed to alternating muscle activation.
Conclusions:
- Postural muscle activity patterns adapt to oscillating conditions, with frequency-dependent shifts in dominance observed.
- Thigh muscle control during balance perturbations is influenced by the interplay between anterior and posterior muscle groups.
- Lower leg muscles (soleus, gastrocnemius) exhibit increased periodicity with higher oscillation frequencies, with gastrocnemius showing greater periodicity.