Acute effect of exercise on blood glucose and insulin levels in women with gestational diabetes.

OBJECTIVE: To evaluate the effect of a single session of exercise (cycling), at rest (control condition) and at two intensity levels (low- and moderate-intensity exercise conditions), on blood glucose and insulin in pregnancy complicated by gestational diabetes mellitus (GDM).
METHODS: A one-group repeated measures design was used. Women aged 18-38 with GDM, no other complications, not on insulin, and not exercising regularly were recruited. The women rested or exercised at the two intensities for 30 min and rested for 2 h after each session. Blood was sampled for blood glucose, insulin and hematocrit at baseline and every 15 min.
RESULTS: There was no difference at baseline in blood glucose levels. The blood glucose level was significantly lower for each exercise condition compared to rest, and for moderate compared to low-intensity exercise (5.2 vs. 4.3 vs 3.9 mmol/l) at the end of exercise (30 min), and for the two exercise conditions compared to rest at 15 min after exercise (4.9 vs 4.4 vs. 4.0 mmol/l). By 45 min after exercise, the blood glucose values were nearly identical. The area under the curve for blood glucose was significantly lower for low- and moderate-intensity exercise than for rest (p = 0.01). The slope of change in insulin among the three conditions, from baseline to the 30-min session, approached significance (p = 0.065). The power for that analysis was 0.51. A sample of 23 would have been required to increase the power to 0.80.
CONCLUSIONS: Significant declines in blood glucose level were observed during low- and moderate-intensity exercise compared to rest. These differences were gone by 45 min after exercise. Continued research should examine those with high body mass index and more pronounced hyperglycemia for further evaluation of the effect of exercise on blood glucose and insulin levels in women with GDM.