Competitive sport and the insulin-dependent diabetic patient

Many insulin dependent diabetic patients have competed, against the odds, at national or international level in strenuous sports. The increase in psychological wellbeing'-3 and in insulin sensitivity in both Type I4-6 and Type II diabetic subjects5'7'8 with moderate exercise have been well documented, as has the improvement in lipid profile6'8'9 and mild to moderate hypertension.'0 But earlier theories that exercise improves metabolic control in Type I diabetes" have now been challenged,'2'13 and strenuous exercise is not without its risks. Proliferative retinopathy may progress to retinal haemorrhage,4'15 and proteinuria increases with exercise'6 (though this may not be of pathological significance'5). Even mild peripheral neuropathy greatly increases the risk of soft tissue injury, particularly to the feet.'5 Autonomic neuropathy, as well as reducing the cardiovascular response to exercise,5'17 impairs the response to overheating and dehydration.15 However, the most immediate risks to the diabetic athlete are metabolic. Exercise increases both the risk of hypoglycaemia in the hyperinsulinaemic subject15'58 and that of ketosis in the insulin deficient subject.19'20 In order to give sensible advice on diet and insulin regimens to the diabetic athlete, an understanding of the metabolic basis of physical exercise is necessary.