Force control during submaximal isometric contractions is associated with walking performance in persons with...

Area of Science:

• Neurology
• Movement Science
• Rehabilitation Medicine

Background:

• Multiple sclerosis (MS) causes progressive motor impairments, notably affecting walking.
• Understanding the relationship between lower limb muscle function and walking deficits is crucial for rehabilitation.

Purpose of the Study:

• To compare how lower leg muscle functional capabilities explain walking performance variations in individuals with MS versus healthy controls.
• To investigate the association between muscle strength, force steadiness, and motor unit control with walking performance.

Main Methods:

• Participants with MS and matched controls underwent walking tests (6-min walk, 25-ft walk).
• Lower leg muscle strength (plantar flexors, dorsiflexors) and force steadiness during isometric contractions were assessed.
• High-density electromyography (EMG) recorded motor unit activity during contractions.

Main Results:

• Individuals with MS showed significant differences in force steadiness, muscle strength, and motor unit discharge characteristics compared to controls.
• Poorer walking performance in the MS group was moderately associated with reduced force steadiness of plantar and dorsiflexor muscles.
• Control group performance correlated with muscle strength and dorsiflexor force steadiness.

Conclusions:

• Reduced ability to maintain steady submaximal muscle force is moderately linked to walking performance deficits in multiple sclerosis.
• Walking impairments in MS appear more related to force control issues than solely to decreased muscle strength.