Voluntarily changing step length or step width affects dynamic stability of human walking.

Area of Science:

• Biomechanics
• Gait Analysis
• Human Movement Science

Background:

• Step width (SW) and step length (SL) variability are linked to fall risk.
• The direct effects of voluntary SW and SL alterations on gait variability and dynamic stability remain unclear.

Purpose of the Study:

• To quantify how voluntary changes in SW and SL affect gait variability and dynamic stability.
• To investigate the relationship between manipulated gait parameters and trunk (C7 vertebra) motion stability.

Main Methods:

• 14 healthy young adults walked on a treadmill under various conditions: preferred gait, metronome-guided, and manipulated SW/SL (narrower, wider, shorter, longer).
• Quantified gait variability (SW, SL, stride time) and dynamic stability of C7 marker movements (local and orbital stability in anterior-posterior and mediolateral directions).

Main Results:

• Narrower steps increased SL variability and altered trunk stability (ML more stable, AP less stable).
• Wider steps increased SW and SL variability, reducing ML trunk stability.
• Altering SL increased variability in SW, SL, and stride time.
• Shorter steps increased ML trunk instability and decreased AP trunk instability.
• Longer steps increased long-term instability in AP, ML, and vertical trunk movements.

Conclusions:

• Voluntary, short-term changes in SW and SL significantly alter the local and orbital stability of trunk motions.
• While mean SW and SL showed weak correlations with stability, specific manipulations demonstrably impacted dynamic stability, providing mechanistic insights into gait control and fall risk.