Does body stability depend on postural chain mobility or stability area?

Area of Science:

• Biomechanics
• Human Physiology
• Postural Control

Background:

• Postural stability is crucial for maintaining balance.
• Previous research has primarily focused on the support base area's role in stability.
• The influence of respiratory movements on postural control remains less understood.

Purpose of the Study:

• To investigate if postural stability is solely determined by the support base perimeter.
• To examine the impact of respiratory variations (quiet breathing, deep breathing, apnea) on postural stability.
• To assess the role of postural chain mobility, specifically pelvis and lumbar spine, in maintaining balance during respiratory challenges.

Main Methods:

• Seven healthy subjects maintained standing and two sitting postures with varying stability areas and pelvis mobility.
• Measurements included thoracic perimeter, center of pressure (CP) displacement, and iliac crest acceleration (as an index of pelvis mobility).
• Subjects performed quiet breathing, deep breathing, and breath-holding (apnea).

Main Results:

• Sway path (SP) was significantly longer in seated postures compared to standing, and in the Sit100 posture versus Sit30.
• The distance between extreme CP positions (Delta Xp) showed an inverse relationship with SP.
• Iliac crest and thoracic displacements were synchronized in sitting postures but lacked a clear pattern when standing.

Conclusions:

• Postural steadiness is dependent on both the stability area and the mobility of the postural chain.
• Pelvic and lumbar spine mobility contribute significantly to the overall postural chain mobility.
• These factors are essential for compensating for perturbations caused by respiratory movements.