Safety and magnitude of changes in blood glucose levels following exercise performed in the fasted and the postprandial state in men with type 2 diabetes.

BACKGROUND: Information on the extent to which acute exercise reduces blood glucose levels (BGL) in type 2 diabetes is lacking. For this reason, the effects of exercise initiated at different preexercise BGL were assessed in men with type 2 diabetes both in the fasted (FS) and the postprandial states (PS). DESIGN AND METHODS: Forty-three men with type 2 diabetes, 12 on diet alone and 31 on hypoglycaemic agents, completed a total of 1555 exercise sessions performed in the FS and 0-1, 1-2, 2-3, 3-4, 4-5, and 5-8 h in the PS. Capillary BGL were measured before and immediately after a 1h standardized aerobic exercise session on an ergocycle at 60% of VO2 peak.
RESULTS: In the FS, there was an increase in postexercise BGL of 27+/-21% (mean+/-SD; P<0.001) when preexercise BGL was < or =6 mmol/l, no change when preexercise BGL were between 6 and 8 mmol/l, and a significant decrease of 12+/-13% when preexercise BGL were >8 mmol/l (P<0.001). In the PS, most exercise sessions were associated with significant decreases in BGL ranging between 18+/-17 and 50+/-12% (P<0.001), depending on the time interval between meals and the onset of exercise. Regarding the metabolic PS, the decline in BGL was most pronounced with high preexercise BGL.
CONCLUSIONS: Our observations not only demonstrate that it was safe for middle-aged obese men with type 2 diabetes to exercise in the FS, but also show that the decrease in BGL during aerobic exercise was largely dependent on preexercise BGL.