Effects of aerobic exercise and weight reduction on carbohydrate metabolism during submaximal exercise in sedentary, overweight women

Hormonal and metabolic responses to submaximal exercise were studied in 11 sedentary, overweight women who participated in an 8 week aerobic exercise program (80% VO2 max) while consuming a hypocaloric diet. A maximal and submaximal treadmill exercise test were performed before and after the program. During the submaximal exercise test, a graded portion (mean time 6.4 min) preceded the submaximal phase during which subjects worked at 80% VO2 max until exhaustion (mean time l2 min). Blood was sampled before and after the work via venipuncture. Whole blood was immediately analyzed for lactate accumulation. The remaining blood was centrifuged, separated, and frozen for subsequent serum glucose, cortisol, and insulin measurement. There was a significant increase in oxygen uptake (ml/kg/min), and a decrease in body weight, ( 6.7%), and body fat (14%). Resting heart rate was significantly lower post-training (5.4%), as were exercise RQ (VCO2/VO2) ratios. Pretraining serum glucose and blood lactate significantly increased while nonsignificant decreases were noted in insulin and cortisol as a result of the submaximal exercise bout. The significant increases in glucose and lactate during exercise were blunted after the training program. However, only the post-training response of lactate was significantly different from the pretraining response. The insulin and cortisol response was not significantly different from that during the pretraining exercise test. A correlation was observed between RPE and lactate at the end of exercise both pretraining and post-training. In summary, the combined exercise and weight loss program resulted in exercise being less stressful, both metabolically and subjectively. This improvement enables greater exercise intensity to be performed prior to the significant accumulation of lactate and perception of fatigue which may inspire the sedentary, overweight female to establish and/or continue a regular exercise program.