Abstract
The influence of anaerobic and aerobic exercise, promoted by computer regulated functional electrical stimulation (FES) was evaluated in four paraplegic males. Quadriceps muscle bulk was monitored by serial computerised axial tomography (CT) scanning and histology by muscle biopsies from the vastus intermedins. Anaerobic exercise consisted of 60 degree straight leg raising against increasing weights (range 1.4-11.4 kg) over a period of ten weeks. Aerobic exercise consisted of pedalling a modified Monark bicycle ergometer at 50 rpm against a fixed load ranging from 0-3/8 kilopond (0-18.75 watts) over a period of eight months. In both exercise studies the same work was not achieved by each paraplegic. FES was regulated by a closed loop system which is not presently commercially available, the frequency of the sequential muscle stimulator was 40 Hz with a pulse width of 300 us.
Quadriceps muscle area of both legs increased 62.7% (p<0.01) after anaerobic exercise; similar but less pronounced effects followed aerobic exercise. Histologically two distinct patterns were noted from the outset, one had normal fibre type distribution the remainder had marked Type 1 loss. Both exercise regimens failed to change these although the number of internal nuclei per 100 fibres steadily increased (from 7.0% to 13.8% to 26.0%) as did the % of fibres with internal nuclei (5.4% to 10.5% to 25.7%) throughout the exercise periods. The significance of these observations is not immediately apparent but may signify continuing damage which may be due to the eccentric rather than the concentric nature of FES promoted muscular contraction.