FIBER AREAS AND HISTOCHEMICAL FIBER TYPES IN THE QUADRICEPS MUSCLE OFPARAPLEGIC SUBJECTS

With the advent of functional electrical stimulation (FES) there is th e possibility of paraplegic patients regaining sonic degree of locomot or activity. It is of interest to document the changes in composition histochemistry and size of muscle fibres in such patients both before and after such therapy. We have examined biopsy specimens from quadric eps muscles obtained from 7 male patients, age range 24-47 years, who had been paraplegic for times ranging from 11 months to 9 years and we report the histochemical appearance of the muscle the fibre type comp osition and the mean fibre areas. In 5 of the 7 subjects there was a m arked or complete predominance of fibres which stained as type 2 with the ATPase reaction at pH 9.4. At acid pH these fibres were seen to be predominantly 2B (fast fatiguable). The 2 subjects who had been paral ysed for the shortest periods had proportions of type 1, fibres which were relatively well preserved. The mean fibre areas of type 2 fibres were below the normal range (2500-7500 mum2) in every case as were the type 1 fibres in the 4 patients in which these were still present. Th ere was no relationship between the length of time the patient had bee n paralysed and the mean fibre areas which suggests that atrophy occur s fairly quickly following loss of voluntary control and precedes the loss of type 1 characteristics. Our findings provide an explanation fo r the rapid onset of fatigue in paraplegic patients taking part in FES programmes since muscles deficient in type 1 fibres will be unable to maintain force for any length of time.