Healthy aging does not impair lower extremity motor flexibility while walking across an uneven surface

Area of Science:

• Biomechanics
• Gerontology
• Neuroscience

Background:

• Age-related decline in dynamic postural control increases fall risk in older adults.
• Mediolateral gait stability, crucial for foot placement, may be compromised with aging.
• Understanding age-related changes in motor control is vital for fall prevention.

Purpose of the Study:

• To quantify the effect of age and uneven surfaces on motor equivalent control for stabilizing the mediolateral swing limb trajectory during gait.
• To analyze age-related differences in the ability to use motor flexibility to maintain gait stability.

Main Methods:

• Utilized uncontrolled manifold-analysis (UCM) to partition motor variability into stabilizing ('good') and destabilizing ('bad') components.
• Examined lower extremity segment angles as degrees of freedom (DoF) influencing the mediolateral foot trajectory.
• Compared 13 young adults (23 years) and 11 older adults (73 years) walking on even and uneven surfaces.

Main Results:

• Both age groups demonstrated motor flexibility, stabilizing foot trajectory across conditions with similar synergy indices.
• Older adults increased 'good' variability on uneven surfaces to counteract performance destabilizing variability.
• Increased variability in older adults was proportional to the challenge of the uneven surface.

Conclusions:

• Increased motor variability is an intentional compensatory strategy, not a sign of diminished motor control in older adults.
• This strategy helps compensate for age-related declines in strength and balance.
• Fall prevention programs could benefit from incorporating tasks that promote motor exploration to enhance stabilizing synergies.