METABOLIC RESPONSE AND MUSCLE GLYCOGEN DEPLETION PATTERN DURING PROLONGED ELECTRICALLY-INDUCED DYNAMIC EXERCISE IN MAN

Muscle glycogen depletion pattern and metabolic responses during volun tary (VOL) and functional electrical stimulated (FES) dynamic knee-ext ensor exercise with one leg were evaluated. Seven healthy men exercise d for 60 minutes at 30 W with an pulmonary oxygen uptake of 0.8 and 1. 01 min(-1), and respiratory exchange ratios of 0.90 and 0.95 in VOL an d FES, respectively. Heart rate reached a level around 90 beats min(-1 ) (VOL) and up to 110 beats min(-1) (FES). Muscle glycogen decreased i n FES with 260 and 290 mmol kg(-1) d.w. in vastus lateralis and m. rec tus femoris, respectively, compared with 45 and 160 mmol kg(-1) d.w. i n VOL (p < 0.05). In FES the percentage of empty and almost empty fibr es determined by periodic acid-Schiff staining in vastus lateralis and rectus femoris was 50 and 77% of type I, 63 and 90% of type Ha, and 5 9 and 84% of type IIb, fibres, respectively, whereas in VOL it was 24 and 26% of type I, 7 and 19% of type Ha, and 2 and 3% of type IIb fibr es. Muscle lactate reached 30 mmol kg(-1) d.w. in FES and was 9 mmol k g(-1) d.w. lower in VOL. The changes in blood lactate and NH3 during t he exercise were slightly higher in FES than in VOL, whereas the alter ations in glucose, FFA, and K+ were small in both exercise modes. The pressure in the two muscle portions at different locations (proximal-d istal) and depths was always higher (similar to 50%) in FES than in VO L, reaching levels around 55 mmHg. It is concluded that with FES the e ntire quadriceps muscle was engaged and all fibre types were recruited , resulting in a quite significant energy turnover and a more pronounc ed metabolic response compared to VOL. Furthermore, FES can be used fo r prolonged dynamic exercise.