Effect of intensity and energy expenditure on postexercise insulin responses in women

The purposes of the study were to compare insulin responses after rest and exercise of two different intensities and equal total energy expenditure and to examine these responses in normoglycemic women. Twenty-four untrained women (age 23.4 +/- 0.9 yr) completed three randomly assigned treatments over the course of a 3- to 4-wk period: rest, 40% maximal oxygen consumption x 87 min (Low), and 70% maximal oxygen consumption x 50 min (High). Total energy expenditure was 1,821 +/- 61 and 1,692 +/- 59 kJ, heart rate was 119 +/- 2 and 163 +/- 2 beats/min, and oxygen consumption was 17.1 and 27.2 ml.kg-1.min-1 for Low and High, respectively. Fifteen to 17 h posttreatment and 12 h postprandial, each subject drank a 75-g glucose solution (oral glucose tolerance test). Blood samples were drawn before and at 30, 60, 90, 120, and 150 min after ingestion and were analyzed for glucose and insulin. Glucose areas and responses at the same time points across treatments were similar. Area under the insulin curve was significantly lower (P < 0.05) after High (51,864 +/- 3,780 pM x min) compared with rest (61,009 +/- 4,425 pM x min), but Low (59,191 +/- 5,307 pM x min) was not different from either rest or High. The insulin level at the 120-min time point was significantly (P < 0.01) lower after High (290.8 pM) compared with rest (391.7 pM). On the basis of these results, exercise-related changes in insulin responses are more dependent on exercise intensity than on energy expenditure in untrained women.