Effects of exercise on hypoglycaemic responses in insulin-dependent diabetes mellitus

This study sought to determine whether moderate exercise influences hypoglycaemic responses in insulin-dependent diabetes mellitus (IDDM). Ten patients with IDDM and no history of hypoglycaemia unawareness or autonomic neuropathy were included. The patients were studied in random order on 4 occasions: twice during euglycaemia (once at rest and once on a treadmill) and twice during a gradual drop in blood glucose from 5 to 2 mmol/l (once at rest and once on a treadmill). Blood samples for hormones and glucose were drawn, and a symptom questionnaire was filled out every 5 min. Cognitive tests were performed at the start and end of each study. Glucose thresholds for hormones and symptoms are reported as the plasma glucose level at which responses were more than two standard deviations above basal level and continued to increase. The thresholds for adrenaline and noradrenaline release came at a significantly higher blood glucose level during exercise than at rest: 2.7 +/- 0.2 vs 2.1 +/- 0.2 mmol/l (p < 0.05) for adrenaline and 2.7 +/- 0.2 vs 2.0 +/- 0.1 mmol/l (p < 0.01) for noradrenaline. Thresholds for neuroglycopenic symptoms were also at a significantly higher blood glucose level during exercise: 2.6 +/- 0.2 vs 2.0 +/- 0.2 mmol/l (p < 0.05). During hypoglycaemia, patients showed a non-significant trend towards a lower score on cognitive tests during exercise than at rest. It is concluded that moderate exercise during a gradual drop in blood glucose does not mask hypoglycaemic responses in patients with IDDM.