Investigating fatigue, balance and mobility in people with Multiple Sclerosis

Abstract

Fatigue and difficulty with mobility are major problems for people with Multiple Sclerosis (MS). The aim of this thesis was to investigate the adverse effects of walking on a number of key motor functions, and test a targeted intervention designed to minimize these effects. Thirty-four people with moderately disabling MS were assessed with the Expanded Disability Status Scale (EDSS) and then participated in three laboratory-based sessions conducted on separate days. Each session involved one of three 6-minute conditions: (1) seated rest, (2) 6 minute walk test (6MWT) and (3) 6MWT with a Dorsiflexion Assist Orthosis (DAO). Standing postural sway, lower limb strength, simple hand and foot reaction time, choice stepping reaction time and gait were assessed before and after each 6-minute condition. A matched sample of 10 healthy controls also completed the 6MWT protocol. Increased sway correlated with total EDSS neurological disability levels and cerebellar dysfunction in people with MS. The 6MWT led to number of significant changes in people with MS, including increased perceived fatigue, slower simple hand and foot reaction time and choice stepping reaction time, increased postural sway and reduced knee extensor and ankle dorsiflexor strength. Changes in gait parameters included: decreased ankle dorsiflexion at heel contact, increased knee and hip flexor moments and increased hip 9 power absorption on the more affected side. On the less affected side, ankle and knee power absorption and hip extensor moment all increased. In contrast, healthy controls demonstrated gait changes that reflect increased gait speed, with no change in postural sway or strength following the 6MWT. Wearing the DAO was effective in reducing the physiological cost of walking and mitigating the fatigue effects on knee extensor strength and standing postural sway in people with MS. These studies have identified a number of motor functions adversely affected by walking which can be measured in the clinic. These signs of motor fatigue have implications for safe mobility in people with moderately disabling MS. The DAO showed promise in mitigating some of these motor-fatigue effects and improving walking efficiency. Future research should investigate any training benefits of wearing the DAO over prolonged periods.