Abstract
AIMS/HYPOTHESIS: The aim of this study was to test the hypothesis that exercise in cool water results in a greater decrease in blood glucose concentration than in thermoneutral water or on land in individuals with type 1 diabetes. METHODS: Eight overnight-fasted individuals (aged 18-40 years) with type 1 diabetes completed 3 × 60 min cycling sessions on an ergometer at 40% of their on-land V˙O2peak under the following conditions: while immersed in cool water (22°C) or in thermoneutral water (32°C) or on land at thermoneutrality (22°C). At time intervals, the following variables were measured: concentration of blood glucose and plasma insulin, skin blood flow, skin temperature and rate of carbohydrate and fat oxidation. RESULTS: Blood glucose concentration did not change in response to cycling while immersed in cool or thermoneutral water (p>0.05) but decreased during cycling on land (p<0.05). The concentration of plasma insulin decreased during and early after cycling in cool water (p<0.05). During 60 min of on-land recovery (at 24°C) after cycling in cool water, blood glucose concentration increased significantly (~2 mmol/l, p<0.05), but not after cycling in thermoneutral water or on-land. CONCLUSIONS/INTERPRETATION: Exercise at 40% V˙O2peak performed in a basal insulinaemic state in cool water in people with type 1 diabetes does not cause a greater decrease in blood glucose concentration than in thermoneutral water or on land, but blood glucose increases early during on-land recovery, probably as a result of a transient fall in plasma insulin.