The effects of aerobic exercise on glucose and counterregulatory hormone concentrations in children with type 1 diabetes

Abstract

Objective: To examine the acute glucose-lowering effects of aerobic exercise in children and adolescents with type 1 diabetes.

Research design and methods: Fifty children and adolescents with type 1 diabetes (ages 10 to <18 years) were studied during exercise. The 75-min exercise session consisted of four 15-min periods of walking on a treadmill to a target heart rate of 140 bpm and three 5-min rest periods. Blood glucose and plasma glucagon, cortisol, growth hormone, and norepinephrine concentrations were measured before, during, and after exercise.

Results: In most subjects (83%), plasma glucose concentration dropped at least 25% from baseline, and 15 (30%) subjects became hypoglycemic (< or = 60 mg/dl) or were treated for low glucose either during or immediately following the exercise session. The incidence of hypoglycemia and/or treatment for low glucose varied significantly by baseline glucose, occurring in 86 vs. 13 vs. 6% of subjects with baseline values <120, 120-180, and >180 mg/dl, respectively (P < 0.001). Exercise-induced increases in growth hormone and norepinephrine concentrations were marginally higher in subjects whose glucose dropped < or = 70 mg/dl. Treatment of hypoglycemia with 15 g of oral glucose resulted in only about a 20-mg/dl rise in glucose concentrations.

Conclusions: In youth with type 1 diabetes, prolonged moderate aerobic exercise results in a consistent reduction in plasma glucose and the frequent occurrence of hypoglycemia when preexercise glucose concentrations are <120 mg/dl. Moreover, treatment with 15 g of oral glucose is often insufficient to reliably treat hypoglycemia during exercise in these youngsters.

Figure 1. Change in Glucose Concentrations during Exercise (N=48)

Two subjects excluded because baseline glucose was unavailable (see Methods). Black dots denote mean values and boxes denote median, 25^th and 75^th percentiles.

Figure 2. Nadir Glucose during Exercise vs. Baseline Concentration (N=48)

Two subjects excluded because baseline glucose was unavailable (see Methods). Diagonal represents the line of identity.

Figure 3. Hormone Concentrations during Exercise

Distributions given for growth hormone (A), norepinephrine (B), cortisol (C) and glucagon (D). Black dots denote mean values and boxes denote median, 25^th and 75^th percentiles. Hormone data available for N=45 subjects (N=23 whose glucose fell ≤70 mg/dL during exercise vs. N=22 whose glucose stayed >70 mg/dL). Norepinephrine data available for N=30 subjects (16 of whom had their glucose fall ≤70 mg/dL).