The role of neuromuscular electrical stimulation in reversing age-related and pathological muscle atrophy

Abstract

An ageing population increases the number of frail, elderly individuals. Physiotherapists are increasingly treating frail individuals due to the associated rate of rapid muscle atrophy. A rapid loss of muscle strength can result in difficulty performing activities of daily living, making individuals more susceptible to other age-related pathologies. Some frail individuals are unable to contract their muscle sufficiently to complete a rehabilitation programme. This can be exacerbated in a
neurological population such as stroke. The aim of this thesis was to prevent muscle atrophy associated with age to allow rehabilitation to commence with a quicker onset.

Neuromuscular electrical stimulation (NMES) is a treatment modality capable of producing muscle
contraction. Its use is poorly understood, with little guidance surrounding optimal parameters or muscular response to treatment. This thesis has identified optimal stimulation parameters for strength training with NMES, and tested them on a healthy population of varying ages, and in a stroke population. A muscle measurement device was designed and tested to allow accurate measurements of moments about joints.

Results indicate that the protocol is effective in inducing hypertrophy, as indicated by advances in pennation angle and maximal isometric force production. The protocol was effective at producing a
small decline in force associated with a hypertrophic stimulus. Results indicate that treatment should be administered with the highest available stimulation amplitude to achieve optimal results. NMES appears to be able to advance internal muscle architecture, despite lack of volitional muscle control post stroke. Variability of response was investigated through blood biomarkers (Creatine Kinase) which was demonstrated to increase in line with volitional strength training literature. The exercise status of the individual appears to be correlated with muscle response.

It is recommended that NMES could be administered in the acute period of a physiotherapy protocol to prevent muscle atrophy associated with ageing. Further work should focus on developing the strength measurement device used throughout this thesis, and investigating a protocol suitable for other applications to allow a smooth transition into clinical settings.