Muscle fibers and their synapses differentially adapt to aging and endurance training

Abstract Background This project aimed to determine the adaptability of the neuromuscular system to the stimuli of exercise training, and aging. Methods Young adult, and aged male rats were randomly assigned to either exercise training, or sedentary control groups. Exercise training featured an 8 week program of treadmill running. At the end of the intervention period, neuromuscular function was quantified with ex vivo stimulation procedures on isolated soleus muscles. Morphological adaptations were determined by quantifying myofiber profiles (fiber size and type) of soleus muscles. Results Ex vivo procedures confirmed that rested (fresh) young muscles were significantly (P  Conclusions The greater strength of young muscles has a neural, rather than a muscular focal point. The loss of strength discerned over the 5 min stimulation protocol was linked to similar fatigue-related impairments in neuromuscular transmission. The two components of the neuromuscular system, i.e. nerves and muscles, do not respond in concert to the stimulus of either aging, or exercise training.