Effects of low-intensity exercise on contractile property of skeletal muscle and the number of motor neurons in diabetic rats

The mode of diabetes-induced muscle and motor neuron damage depends on the type of muscle and motor neuron. One of the purposes of exercise therapy for diabetes is to improve blood glucose levels; however, information on the effects of low-intensity exercise on muscle and motor neuron disorders remain unknown. Therefore, this study aimed to examine the effects of low-intensity exercise on diabetes-induced muscle and motor neuron damage in a rat model of type 1 diabetes mellitus. We subjected adult male Wistar rats treated with streptozotocin to develop type 1 diabetes and age-matched rats to low-intensity treadmill exercise for 12 weeks. We recorded electrically evoked maximum twitch tension in leg muscles, and examined the number of motor neurons and cell body sizes. Low-intensity exercise ameliorated the prolonged half-relaxation time and the decreased numbers of the retrograde-labeled motor neurons observed in the soleus muscle of type 1 diabetic rats. However, no effect was observed in the diabetic group, as atrophy was not improved and the twitch force in the medial gastrocnemius muscle was decreased in the diabetic group. In addition, there was no improvement in the blood glucose levels after exercise. These data indicate that low-intensity exercise may relieve the onset of muscle and motor neuron damage in the soleus muscle of type 1 diabetic rats.