Lower Leg Muscle Function: A Contributory Risk Factor of Gait and Balance Impairment after Six Minutes Walk among People with Multiple Sclerosis

Background/Purpose: Multiple sclerosis (MS) is a progressive neurological disease that results in increased fatigue, decreased muscle function, and impaired gait and balance. The purpose of this study was to evaluate the relationship between lower leg muscle function and changes in gait and balance immediately and 20 minutes after 6mins walk-induced fatigue. Methods: Six persons with MS (Patient-Determined Disease Steps 3-5) participated in the study. Perceived fatigue and demographic information were taken at baseline. Muscle fatigability and mitochondria capacity was measured in the lower leg muscles before walking. Reported fatigue (VAFS, 0-10), gait variability, gait asymmetry, and static balance were measured before and immediately after a self-paced 6 minutes treadmill walk with slight elevation, and after 20 minutes of rest. Results: Participant’s baseline MFIS score ranged from 14 - 71. There was a 173% increase in reported fatigue scores after walking. Gait was impaired with a ~26% increase in gait variability and ~40% increase in gait asymmetry immediately after walking (Cohen’s D = 0.4, 0.3 respectively). There was also ~69% increase in balance postural sway with eyes opened and a ~20% increase with eyes closed (Cohen’s D = 0.5, 0.2 respectively). Gait and balance remained impaired after 20 minutes of rest. The decline in gait parameters after walking had a negative correlation with muscle endurance (r=-0.80, p=0.03), and mitochondrial capacity (r=-0.92, p<0.01). The changes in gait and balance were more evident in participants with a higher disability. Conclusions: Six minutes of self-paced walking with slight elevation worsened gait and balance among people with MS (PwMS), which did not completely recover after 20 minutes of rest. The changes in gait after walking were associated with lower leg muscle function. Lower leg muscle function might be an important intervention target to improve gait and balance fall risk among PwMS.