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Does postural chain muscular stiffness reduce postural steadiness in a sitting posture?
Alain Hamaoui1, Serge Le Bozec, Laurent Poupard
1Laboratoire Contrôle Moteur et Perception, UPRES EA 4042, Université Paris Sud, 91405 Orsay Cedex, France. alain.hamaoui@wanadoo.fr
Gait & Posture
|May 16, 2006
Summary
Increased postural muscle stiffness, measured by electromyography (iEMG), reduces body steadiness during rhythmic breathing. This suggests stiffer muscles may impair the body's ability to compensate for respiratory disturbances.
Area of Science:
- Biomechanics
- Human Physiology
- Motor Control
Background:
- Postural steadiness is crucial for maintaining balance.
- Respiratory movements can perturb postural control.
- The role of muscular stiffness in adapting to these perturbations is not fully understood.
Purpose of the Study:
- To investigate how postural chain muscular stiffening affects postural steadiness.
- To examine the influence of respiratory rhythm on this effect.
- To analyze center of pressure (CP) displacements under varying conditions.
Main Methods:
- Participants performed sub-maximum pushing efforts (20% and 40% MVC) in a sitting posture.
- Muscular stiffness was assessed using surface electromyography (iEMG).
- Lumbo-pelvic mobility was altered via different seat support areas (100% BP and 30% BP).
- Respiratory disturbance was manipulated using quiet breathing (QB) and fast breathing (FB).
Main Results:
- Increased pushing effort correlated with higher iEMG levels.
- Higher muscular stiffness led to greater mean deviation (X (p)) and sway path (SP) in antero-posterior CP displacements.
- Postural steadiness was reduced with increased muscular stiffness.
Conclusions:
- Postural muscle stiffness significantly impairs postural steadiness.
- This impairment may be linked to a reduced capacity to compensate for respiratory disturbances.
- Findings suggest implications for understanding balance control and potential interventions.