Glucose Supplement Needed Before Exercise in Type 1 Diabetes

Forty grams of glucose supplement is required for patients with type 1 diabetes who are engaging in 60 minutes of moderate exercise without changing insulin regimen.

"Two strategies have been suggested to counter the risk of hypoglycemia either during or postexercise: reduce insulin doses before the meal preceding the planned exercise or add a glucose supplement before a spontaneous exercise session," write Marie-Christine Dube, MD, from Laval University in Quebec, Canada, and colleagues. "There are some guidelines for premeal insulin dose reduction when postprandial exercise is planned in Type 1 DM subjects treated with different intensive insulin regimen. However, to our knowledge, no preexercise glucose supplements have been evaluated in Type 1 DM patients treated with an insulin regimen of Humulin N ([human insulin NPH;] N) and the newer insulin analog Humalog ([insulin lispro] Lispro, LI), which is often used in these patients."

Three hours after a standard breakfast, nine subjects taking human insulin NPH and analog insulin lispro performed 60 minutes of ergocycle exercise (50% maximum volume of oxygen) in three different conditions. Before exercise, the subjects were randomized to receive a liquid supplement containing 0 g of glucose (0G), 15 g of glucose (15G), or 30 g of glucose (30G). Blood glucose (BG) level was measured before, during, and after exercise. When BG level decreased below 90mg/dl (5 mmol)·of insulin lispro, dextrose infusion was given.

The magnitude of the decrease in BG level induced by exercise was similar in the three experimental conditions. However, the quantity of dextrose infused was significantly higher in the 0G condition (10.5 ± 3.2 g) than in the 15G (3.5 ± 1.8 g) or the 30G conditions (1.6 ± 1.0 g). Adding glucose to the supplement significantly increased the time before dextrose infusion was needed (31.7 ± 7.5 minutes for 0G, 51.3 ± 4.2 minutes for 15G, and 55.6 ± 2.6 minutes for 30G).

By plotting the quantity of dextrose infusion vs the glucose dosage in the preexercise supplements, the investigators obtained a regression equation. Solving this equation indicated that a glucose supplement of 40 g would maintain normal BG levels during and after exercise.

"For 60 minutes of late postprandial exercise followed by 60 minutes of recovery, an estimated 40 g of a liquid glucose supplement, ingested 15 minutes prior [to] exercise, would seem likely to help maintain safe BG levels in subjects using N-Lispro [insulin lispro]," the authors write. "The quantity estimated (40 g of glucose) can be easily obtained from unsweetened fruit juice (375 mL of orange juice) or sport liquid preparations and should resolve the problem of consuming excessive glucose to prevent hypoglycemia."
Med Sci Sports Exer. 2005;37:1276-1282

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