Abstract

Previous research has shown that the rate of muscle glycogen utilization is related to exercise intensity expressed as VO2max. The purpose of this study was to compare the relationship between glycogen utilization and VO2max to that between glycogen utilization and intensity expressed relative to the onset of blood lactate accumulation (OBLA) during cycle exercise. It was hypothesized that the rate of glycogen utilization would be related more closely to intensity expressed as OBLA than to intensity expressed as VO2max. Nineteen subjects performed tests to determine VO2max and OBLA during continuous incremental exercise. Biopsies were taken from the m. vastus lateralis before and after 30 min of exercise at randomly assigned intensities ranging from 50-80 VO2max, corresponding to 67-117 OBLA. There was a large inter-subject variation in aerobic fitness with VO2max ranging from 34 to 66 mL/kg/min and OBLA ranging from 64-84 VO2max. Absolute VO2max and the VO2 at OBLA were correlated strongly (r=0.90). The change in glycogen concentration during the 30-min exercise bout ranged from an increase of 58 to a depletion of 200 mmol glucose units/kg dry muscle weight. Neither absolute nor relative glycogen utilization was significantly related to the exercise intensity expressed as either VO2max or OBLA. VO2max (ml/kg/min) was the only variable which accounted for a significant amount of the intersubject variation in glycogen depletion (r=-0.56).The hypothesis was not accepted. Verf.-Referat (gekuerzt)