Abstract

The effects of changes in glycogen concentrations, induced by either exercise or a combination of exercise and diet, on lactate accumulation in human skeletal muscle during a 1 min high intensity muscle fatigue test were investigated. Lactate was significantly reduced when glycogen levels were less than 40 mmol glucosyl unitskg. When acute glycogen depletion in both main groups of muscle fibres was induced by exercise, subsequent muscle strength and muscle power were impaired. Subjects with muscle rich in FT fibres demonstrated a greater impairment than those rich in ST fibres. If exercise-induced glycogen depletion was limited to the ST muscle fibre population, no significant impairment of muscle force was observed while torque decline during repeated maximal contractions was increased, i.e. the muscle was more susceptible to fatigue. Endurance exercise capacity was closely releated to the exercise intensity at which a blood lactate accumulation of 4 mmol x 1 occurred and to the ability to exercise at an intensity close to that intensity during a competition. These properties were in turn related to the percentage of slow twitch muscle fibres, capillary density, muscle enzyme activities and trainingvolume. Verf.-Referat