Metabolic response and muscle glycogen depletion pattern during prolonged electrically induced dynamic exercise in man
Kim CK, Bangsbo J, Strange S, Karpakka J, Saltin B
Department of Physiology and Pharmacology, Karolinska Institute, Stockholm, Sweden
Muscle glycogen depletion pattern and metabolic responses during voluntary (VOL) and functional electrical stimulated (FES) dynamic knee-extensor exercise with one leg were evaluated. Seven healthy men exercised 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 and FES, respectively. Heart rate reached a level around 90 beats min-1 (VOL) and up to 110 beats min-1 (FES). Muscle glycogen decreased in FES with 260 and 290 mmol kg-1 d.w. in vastus lateralis and m. rectus femoris, respectively, compared with 45 and 160 mmol kg-1 d.w. in VOL (p < 0.05). In FES the percentage of empty and almost empty fibres determined by periodic acid-Schiff staining in vastus lateralis and rectus femoris was 50 and 77% of type I, 63 and 90% of type IIa, and 59 and 84% of type IIb fibres, respectively, whereas in VOL it was 24 and 26% of type I, 7 and 19% of type IIa, and 2 and 3% of type IIb fibres. Muscle lactate reached 30 mmol kg-1 d.w. in FES and was 9 mmol kg-1 d.w. lower in VOL. The changes in blood lactate and NH3 during the exercise were slightly higher in FES than in VOL, whereas the alterations in glucose, FFA, and K+ were small in both exercise modes. The pressure in the two muscle portions at different locations (proximal-distal) and depths was always higher (approximately 50%) in FES than in VOL, reaching levels around 55 mmHg.(ABSTRACT TRUNCATED AT 250 WORDS)
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