Muscle Dysfunction and Walking Impairment in Women with Multiple Sclerosis

Abstract

Background: Recent evidence suggests that skeletal muscle dysfunction is involved in disability progression in people with multiple sclerosis (MS). However, the relationship between muscle dysfunction and walking impairments in MS remains unclear. Thus, the cross-sectional relationships between muscle-specific oxidative capacity and walking endurance in women with MS were evaluated. Methods: Twenty women with MS (11 African American, 9 white) were tested. Muscle oxidative capacity of the medial gastrocnemius was measured using near-infrared spectroscopy after electrical stimulation. Muscle endurance was evaluated using accelerometer-based mechanomyography during electrical stimulation. Muscle strength was measured during maximal voluntary plantarflexion using handheld dynamometry. Walking function was measured using the Timed 25-Foot Walk test and the 6-Minute Walk Test (6MWT). Results: Reduced muscle oxidative capacity (R2 = 0.68–0.71, P < .01) and muscle endurance (R2 = 0.59–0.78, P < .01) were associated with lower Timed 25-Foot Walk time and 6MWT distance. Muscle strength was weakly correlated to 6MWT distance (R2 = 0.21, P = .02). No differences in muscle function or clinical outcome measures were found between African American and white subgroups. Women with moderate-to-severe disability (Expanded Disability Status Scale [EDSS] score, 5.0–6.5) had significantly reduced muscle oxidative capacity, muscle endurance, and walking ability compared with women with mild disability (EDSS score, 2.5–4.5). Conclusions: Reductions in muscle function in people with MS are related to declines in walking function across all levels of disability. Muscle dysfunction is not differentially related to walking impairment in African American and white women with MS.

The Case for Measuring Long Bone Hemodynamics With Near-Infrared Spectroscopy

“…The application of NIRS to assess bone hemodynamics and oxygenation might be expected to be based on the rather extensive literature on the use of NIRS to study skeletal muscle in both healthy (van Beekvelt et al, 2001a,b;Ryan et al, 2013a,b;Southern et al, 2014;Zhang et al, 2020) as well as in clinical populations (Abozguia et al, 2008;Sjogaard et al, 2010;Bossie et al, 2017;Willingham et al, 2019). NIRS measurements of skeletal muscle can mainly be divided into three categories: (1) measuring levels of oxygen at rest and during exercise (Hesford et al, 2013;Niemeijer et al, 2017), (2) measuring the rate of re-oxygenation after ischemia or exercise (Willingham et al, 2016;Willingham and McCully, 2017;Lucero et al, 2018), and finally (3) using short periods of repeated ischemia to measure oxidative metabolism or mitochondrial capacity (Ryan et al, 2013b;Bossie et al, 2017;Sumner et al, 2020).…”

Endurance of the Dorsal and Ventral Muscles in the Neck

“…Previous studies have used accelerometry to study muscle contractile function [ 22 , 23 ]. In addition, an accelerometer has been used to evaluate muscle endurance as changes in twitch contraction speeds [ 10 , 11 , 12 , 14 , 15 ]. These studies have shown a good relationship between muscle accelerometry and muscle mitochondrial capacity in clinical populations [ 14 ].…”

“…In addition, an accelerometer has been used to evaluate muscle endurance as changes in twitch contraction speeds [ 10 , 11 , 12 , 14 , 15 ]. These studies have shown a good relationship between muscle accelerometry and muscle mitochondrial capacity in clinical populations [ 14 ]. Other approaches to measure muscle contractile function have used task failure in response to an applied load [ 16 , 18 ].…”

“…Muscle endurance was measured using a 5 min stimulation protocol, similar to a previously published nine-minute endurance protocol [ 10 , 11 , 12 , 14 , 15 ]. Custom-made foil electrodes were placed on the neck and ultrasound gel was placed underneath the electrodes.…”

Regional Differences in Mitochondrial Capacity in the Finger Flexors of Piano Players

“…NIRS-measured mitochondrial capacity measures the transition rate of oxidative metabolism from exercise to rest, similar to methods using magnetic resonance spectroscopy to measure the rate of phosphocreatine resynthesis after exercise [ 4 , 5 ]. Mitochondrial capacity has been associated with increased muscle endurance [ 6 ].…”