AN 8 YEAR LONGITUDINAL-STUDY OF MUSCLE STRENGTH, MUSCLE-FIBER SIZE, AND DYNAMIC ELECTROMYOGRAM IN INDIVIDUAL WITH LATE POLIO

Twenty-one subjects with polio 24 to 51 years prior to the first exami nation were studied on three occasions, each 4 years apart with measur ements of muscle strength and endurance for knee extension, macro EMG, and muscle biopsy from vastus lateralis. On average the muscle streng th decreased during the 8-year follow-up by 9-15%. Endurance decreased during the observation period. The muscle fiber area was markedly inc reased in most subjects. There was a decrease in the capillarization d uring the follow-up. Macro EMG was increased in all subjects (range 3- 42 times control) and increased in 20 legs during the 8-year follow-up , but showed a decrease in 8 of 9 legs with an approximative breakpoin t when macro MUPs were around 20 times the normal size. Thus, evidence of on-going denervation/reinnervation as well as of failing capacity to maintain large motor units was demonstrated. SFEMG showed a moderat e degree of disturbed neuromuscular transmission. (C) 1998 John Wiley & Sons, Inc, Muscle Nerve 21: 1428-1437, 1998.