Effects of resistance training on neuromuscular junction morphology

The aim of this study was to determine the impact of resistance exercise on neuromuscular junction (NMJ) architecture. Eighteen Sprague-Dawley rats ei ther participated in a 7-week resistance training program or served as untr ained controls. Following the experimental period, the NMJs of soleus muscl es were visualized with immunofluorescent techniques, and muscle fibers wer e stained histochemically. Results indicate that resistance training signif icantly (P < 0.05) increased endplate perimeter length (15%) and area (16%) , and significantly enhanced the dispersion of acetylcholine receptors with in the endplate region. Pre- and post-synaptic modifications to resistance exercise were well-coupled. No significant alterations in muscle fiber size or fiber type were detected. The data presented here indicate that the sti mulus of resistance training was sufficiently potent to remodel NMJ structu re, and that this effect cannot be attributed to muscle fiber hypertrophy o r fiber type conversion. (C) 2000 John Wiley & Sons, Inc.