Glucose Turnover During Recovery from Intensive Exercise

Abstract

This study was undertaken to examine glucose turnover during a 30-min recovery period following an acute bout of intensive exercise (85% VO2 max) performed to exhaustion (11.7 ± 1.4 min). Plasma glucose (basal 85 ± 2 mg/dl) rose by 10 mg/dl at exhaustion and increased further during the initial phase of recovery, reaching a peak value of 35 mg/dl above basal at 5 min of recovery. Thereafter, there was a gradual decline, but the values remained 15–20 mg/dl above basal at 30 min. The early rise in plasma glucose during recovery was due to an imbalance between glucose production and utilization caused by a more rapid decline in utilization than production. At 5 min of recovery, glucose production was fivefold greater than in the basal state and comparable to peak values observed at exhaustion, while glucose utilization was 33% lower than observed at exhaustion and only 75% higher than in the basal state. Beyond 5 min of recovery glucose utilization and production again differed in the direction of response. Glucose production fell to basal values while glucose utilization remained 70–80% above baseline. The maintenance of basal rates of glucose production and increased rates of glucose utilization occurred in a setting in which plasma insulin levels were increased by 25–50%. Plasma catechol-amines, which rose 5–10-fold during exercise, fell rapidly during the initial 3 min of recovery. We conclude that recovery from exhaustive exercise is characterized by a biphasic imbalance between glucose production and utilization in which production exceeds utilization for the initial 5 min and utilization exceeds production at 10–30 min. The hormone-substrate milieu (modest increments in plasma insulin and glucose) accompanying the changes in glucose kinetics observed beyond 5 min suggests that the recovery period from acute exercise may be characterized by an increase in peripheral sensitivity to insulin, which could provide a mechanism for facilitating muscle glycogen repletion during recovery from intensive exercise.