SKELETAL-MUSCLE CHANGES AFTER SHORT-TERM VIBRATION

Six female Wistar rats were anaesthetised and attached to a vibrating table, (80 Hz/32 m/s(2)) five hours daily for two days. Histological, enzyme and immunohistochemical, and morphometric analyses of the direc tly exposed and opposite control plantar muscles were made. Neither fi bre necrosis nor regenerative activity were seen. The mean (SD) area ( mu m(2)) of vibration-exposed muscle fibres was significantly increase d compared with controls (682 (274) and 642 (230), p < 0.05). Both typ e 1 and 2C fibres were significantly larger after vibration (773 (293) and 650 (223) compared with 683 (209) and 579 (149), p < 0.05) while type 2A and 2AB fibres were not significantly enlarged. The percentage of centrally located nuclei was significantly increased after vibrati on. This study shows that short term vibration can induce changes in s ize in muscle fibres. We postulate that this is the first indication o f a vibration-induced muscle injury that may develop into chronic impa irment of muscle function if the exposure continues for an extended pe riod of time.