OBJECTIVE -To investigate whether a short maximal sprint can provide another means to counter the rapid fall in glycemia associated with moderate-intensity exercise in individuals with type 1 diabetes and therefore decrease the risk of early postexercise hypoglycemia.RESEARCH DESIGN AND METHODS -In the study, seven male subjects with type 1 diabetes injected their normal insulin dose and ate their usual breakfast. When their postprandial glycemia fell to ϳ11 mmol/l, they pedaled at 40%VO 2peak for 20 min on a cycle ergometer then immediately engaged in a maximal 10-s cycling sprint (sprint trial) or rested (control trial); the sprint and rest trials were administered in a counterbalanced order.RESULTS -Moderate-intensity exercise resulted in a significant fall (P Ͻ 0.05) in glycemia in both trials (means Ϯ SE: 3.6 Ϯ 0.5 vs. 3.1 Ϯ 0.5 mmol/l for sprint and control, respectively). The subsequent short cycling sprint opposed a further fall in glycemia for 120 min, whereas in the absence of a sprint, glycemia decreased further (3.6 Ϯ 1.22 mmol/l; P Ͻ 0.05) after exercise. The stabilization of glycemia in the sprint trial was associated with elevated levels of catecholamines, growth hormone, and cortisol. In contrast, these hormones remained at stable or near-stable levels in the control trial. Changes in insulin and free fatty acid levels were similar in the sprint and control trials.CONCLUSIONS -These results suggest that after moderate-intensity exercise, it is preferable for young individuals with insulin-treated, complication-free type 1 diabetes to engage in a 10-s maximal sprint to acutely oppose a further fall in glycemia than to only rest. The addition of the sprint after moderate-intensity exercise provides another means to reduce the risk of hypoglycemia in active individuals with type 1 diabetes. Diabetes Care 29:601-606, 2006I t is well established that exercise of moderate intensity increases the risk of hypoglycemia during and after exercise in type 1 diabetic individuals (1,2) due, in part, to a contraction-mediated activation of glucose utilization in skeletal muscle (3) and an increase in insulin sensitivity (4). In contrast, 10 -15 min of highintensity exercise (Ͼ80% of maximal rate of oxygen consumption [VO 2peak ]) causes an increase in postexercise blood glucose levels in insulin-treated individuals with type 1 diabetes, irrespective of their level of glycemic control (5-10). This hyperglycemic effect of prolonged, highintensity exercise raises the intriguing possibility that this type of exercise might provide a means other than carbohydrate intake to counter a fall in postexercise glycemia in individuals with complicationfree type 1 diabetes and thus acutely reduce their risk of hypoglycemia. However, 10 -15 min of high-intensity exercise is unlikely to be well tolerated by most type 1 diabetic individuals due to the very intense nature of such exercise combined with its impractical duration.A more practical way of using intense exercise as a means to prevent glycemia from falling might be to...

It is generally acknowledged that even without a glycogen-depleting period of exercise, trained athletes can store maximal amounts of muscle glycogen if fed a carbohydrate-rich diet for 3 days. What has never been examined is whether under these conditions this many days are necessary for the content of muscle glycogen to attain these high levels. To examine this issue, eight endurance-trained male athletes were asked to eat 10 g.day(-1).kg(-1) body mass of high-carbohydrate foods having a high glycaemic index over 3 days, while remaining physically inactive. Muscle biopsies were taken prior to carbohydrate loading and after 1 and 3 days of eating the carbohydrate-rich diet. Muscle glycogen content increased significantly ( P<0.05) from pre-loading levels of [mean (SE)] 95 (5) to 180 (15) mmol.kg(-1) wet mass after only 1 day, and remained stable afterwards despite another 2 days of carbohydrate-rich diet. Densitometric analyses of muscle sections stained with periodic acid-Schiff not only supported these findings, but also indicated that only 1 day of high carbohydrate intake was required for glycogen stores to reach maximal levels in types I, IIa, and IIb muscle fibres. In conclusion, these findings showed that combining physical inactivity with a high intake of carbohydrate enables trained athletes to attain maximal muscle glycogen contents within only 24 h.

Aims/hypothesis We investigated whether a 10-s maximal sprint effort performed immediately prior to moderateintensity exercise provides another means to counter the rapid fall in glycaemia associated with moderate-intensity exercise in individuals with type 1 diabetes. Materials and methods Seven complication-free type 1 diabetic males (21.6±3.6 years; mean±SD) with HbA 1c levels of 7.4±0.7% injected their normal morning insulin dose and ate their usual breakfast. When post-meal glycaemia fell to ∼11 mmol/l, participants were asked to perform a 10-s all-out sprint (sprint trial) or to rest (control trial) immediately before cycling at 40% of peak rate of oxygen consumption for 20 min, with both trials conducted in a random counterbalanced order. Results Sprinting did not affect the rapid fall in glycaemia during the subsequent bout of moderate-intensity exercise (2.9±0.4 mmol/l in 20 min; p=0.00; mean±SE). However, during the following 45 min of recovery, glycaemia in the control trial decreased by 1.23±0.60 mmol/l (p=0.04) while remaining stable in the sprint trial, subsequently decreasing in this latter trial at a rate similar to that in the control trial. The large increase in noradrenaline (norepinephrine) (p=0.005) and lactate levels (p=0.0005) may have contributed to the early post-exercise stabilisation of glycaemia in the sprint trial. During recovery, adrenaline (epinephrine) and NEFA levels increased marginally in the sprint trial, but other counter-regulatory hormones did not change significantly (p<0.05). Conclusions/interpretation A 10-s sprint performed immediately prior to moderate-intensity exercise prevents glycaemia from falling during early recovery from moderateintensity exercise in individuals with type 1 diabetes.

OBJECTIVETo determine whether performing a 10-s sprint after moderate-intensity exercise increases the amount of carbohydrate required to maintain euglycemia and prevent late-onset postexercise hypoglycemia relative to moderate-intensity exercise alone.RESEARCH DESIGN AND METHODSSeven individuals with type 1 diabetes underwent a hyperinsulinemic-euglycemic clamp and performed 30 min of moderate-intensity exercise on two separate occasions followed by either a 10-s maximal sprint effort or no sprint. During the following 8 h, glucose infusion rate to maintain euglycemia and rates of glucose appearance and disappearance were measured continuously.RESULTSIn response to exercise and throughout the 8-h recovery period, there were no differences in glucose infusion rate, blood glucose levels, plasma insulin concentrations, and rates of glucose appearance and disappearance between the two experimental conditions (P > 0.05).CONCLUSIONSA 10-s sprint performed after 30 min of moderate-intensity exercise does not affect the amount of carbohydrate required to maintain euglycemia postexercise in individuals with type 1 diabetes.