The effect of an exercise intervention on peripheral sensorimotor function in neuropathic diabetics

Abstract

Peripheral neuropathy is the first and most common microvascular complication of diabetes mellitus, and involves the distal-to-proximal necrosis of peripheral nerves. Loss of peripheral sensory function, combined with confounding autonomic and neuromuscular complications, leads to an increase in the risk of plantar ulceration due to traumatic or repetitive loading. The evidence for the effectiveness of an exercise intervention in improving sensorimotor function in this population is building, but care is needed when implementing these interventions due to the risk of exacerbating associated neuropathic complications. Therefore the purpose of the current thesis was to investigate the effect of a low-impact balance and lower limb strength training intervention on the sensorimotor complications of peripheral diabetic neuropathy. Ten diabetics with peripheral neuropathy (age 61 ± 9 yrs, BMI 32 ± 5) underwent a twice-weekly supervised low-impact exercise intervention for 12 weeks, which comprised of balance board, isolated ankle strength and passive strength training components. Two pre-intervention (0-weeks and 4-weeks), and two post-intervention (16-weeks and 28-weeks) biomechanical assessments were performed to assess the effectiveness of the intervention. During these assessments six experimental components were investigated, each of which addressed a different aspect of sensorimotor function. These components included sensory threshold, postural stability, gait, foot morphology and plantar loading, muscle strength and quality of life. Despite the observation of low group homogeneity in terms of sensory function, significant improvements in this measure were observed following the intervention; however it was observed that those participants with the most severe sensory loss exhibited no change. It was theorised that these findings were best explained by an improvement in the function of pre-existing sensory nerves, most probably due to improved vascular flow. Due to a low sample size, the current study lacks the statistical power to make any definitive statements regarding the efficacy of the intervention in improving sensory function in a wider neuropathic population. No significant group improvements in the multiple measures of motor function were observed as a result of the intervention. It was theorised that these findings were best explained by a combination of an absence of severe motor pathology in most instances and the inability of the current low-intensity exercise intervention to cause motor adaptation in the instances where dysfunction was found. No significant group improvements in quality of life were observed following the intervention, possibly due to relatively high quality of life levels in the current participants prior to the intervention. This is the first study to exhibit quantifiable changes in sensory function as a result of a low-impact balance and strength training intervention in a neuropathic diabetic population. This is also the first study to investigate the effect of an exercise intervention on the kinematic and kinetic qualities of neuropathic gait, as well as the first study to investigate the effect of an exercise intervention on foot morphology and plantar loading in this population. Future research should incorporate advanced peripheral and cortical neural imaging techniques, as well as measures of peripheral vascular flow, in order to further understand the observed changes in sensory function.