Decreased isometric muscle strength after acute hyperglycaemia in Type 1 diabetic patients

Aims Fatigue is a common complaint in diabetic patients during periods of hyperglycaemia. To test whether muscle performance is reduced during acute hyperglycaemia, diabetic patients were studied whilst performing maximal isokinetic and isometric contractions. Methods In this double-blind placebo controlled study, maximal isometric and isokinetic muscle strength was determined in seven Type 1 diabetic patients during normo- and hyperglycaemia using a hyperglycaemic clamp technique. On two separate days, maximal muscle strength of the knee extensors was determined quantitatively using a dynamometer. On both days, muscle strength was determined before a constant blood glucose level was obtained and after the blood glucose level had been kept constant at either 5 or 16 mmol/l for 3 h. Percentage of change from baseline at the two glycaemic levels were calculated and compared. In addition, the changes from baseline at these glycaemic levels were related to glucose turnover. Results Following hyperglycaemia, a significant decrease in maximal isometric muscle strength was found as compared with normoglycaemia (86 vs. 104% of the initial level) (P = 0.018). In contrast, no alteration of maximal isokinetic muscle strength was found comparing normo- and hyperglycaemia (96 and 95%) (P = 0.74). Changes in muscle strength were not significantly related to either basal or hyperglycaemic glucose turnover. Conclusions A few hours of hyperglycaemia in Type 1 diabetic patients leads to a reduction of isometric muscle performance, whereas isokinetic muscle strength is unchanged. The reduction in muscle strength could play a role in the development of fatigue and is related more closely to ambient glucose concentrations than to systemic glucose availability.