Effects of prior exercise on glycemic responses following carbohydrate inges on in individuals with type 2 diabetes

Exercise is effective in reducing glycemia, especially when it is performed in the postprandial period. However, no consensus exists in the literature about the effect of exercise on postprandial glucose control when it is performed before carbohydrate consumption.

The main aim was to determine whether 20 min of exercise performed prior to carbohydrate consumption reduces postprandial glycemic and insulinemic responses. A secondary aim was to analyze the effectiveness of short-term (10 min) exercise bout with respect to postprandial glycemia reduction.

Nine individuals with type 2 diabetes (54.9 ± 1.7 years; 30.7 ± 1.8 kg/m²; glycemia level of 167.0 ±10.6 mg/dL) participated in the study and underwent the following procedures: (a) an incremental test to determine the lactate threshold; (b) an exercise session for 20 minutes at moderate intensity (90% of the lactate threshold); and c) a control session. The last two sessions were randomized, and the participants were monitored during 135 minutes of post-exercise recovery. A standard meal was consumed two hours before the experimental procedures started. A dextrose solution was administered at 45 minutes of post-exercise recovery while monitoring glucose and insulin concentrations. At 135 min of post-exercise recovery, eight of the participants performed an additional 10-min exercise bout following induced hyperglycemia.

Exercise reduced glycemia (-46.6 ± 7.9 mg/dL) and the insulin/glucose ratio (from 1.73 ± 0.59 to 0.93 ± 0.22 µU/mL/mmol/L) during the first 45 minutes of post-exercise recovery. Glycemia was significantly increased after carbohydrate consumption, reaching its peak value at 105 minutes of post-exercise recovery (261.8 ± 15.8 mg/dL) or control (281.3 ± 13.4 mg/dL). There was no effect of the previous exercise in attenuating glycemia or reducing the area under the curve for glucose and insulin after carbohydrate consumption. However, the effectiveness of exercise in reducing glycemia was shown again when it was performed at the end of the experimental session, even in case of only a 10-min exercise (reduction of -44.5 ± 4.9 mg/dL).

Twenty minutes of moderate exercise does not alter the kinetics or the area under the curve in terms of glycemia and insulinemia after subsequent carbohydrate consumption. However, moderate exercise, even if performed for only 10-20 minutes, is effective in reducing postprandial glycemia in individuals with type 2 diabetes.

Moderate-intensity exercise, even of short duration, may benefit individuals with type 2 diabetes on blood glucose control. A fast reduction in postprandial glycemia can be obtained with only ten minutes of exercise that, in turn, may ameliorate some of complications associated with the disease.