Effect of combining pre‐exercise carbohydrate intake and repeated short sprints on the blood glucose response to moderate‐intensity exercise in young individuals with Type 1 diabetes

Abstract

AimsTo determine whether pre-exercise ingestion of carbohydrates to maintain stable glycaemia during moderateintensity exercise results in excessive hyperglycaemia if combined with repeated sprints in individuals with Type 1 diabetes.Methods Eight overnight-fasted people with Type 1 diabetes completed the following four 40-min exercise sessions on separate days in a randomized counterbalanced order under basal insulinaemic conditions: continuous moderateintensity exercise at 50% _ VO 2 peak; intermittent high-intensity exercise (moderate-intensity exercise interspersed with 4s sprints every 2 min and a final 10-s sprint); continuous moderate-intensity exercise with prior carbohydrate intake (~10 g per person); and intermittent high-intensity exercise with prior carbohydrate intake. Venous blood was sampled during and 2 h after exercise to measure glucose and lactate levels. ResultsThe difference in marginal mean time-averaged area under the blood glucose curve between continuous moderateintensity exercise + prior carbohydrate and intermittent high-intensity exercise + prior carbohydrate during exercise and recovery was not significant [0.2 mmol/l (95% CI -0.7, 1.1); P = 0.635], nor was the difference in peak blood glucose level after adjusting for baseline level [0.2 mmol/l (95% CI -0.7, 1.1); P = 0.695]. The difference in marginal mean time-averaged area under the blood glucose curve between continuous moderate-intensity and intermittent high-intensity exercise during exercise and recovery was also not significant [-0.2 mmol/l (95% CI -1.2, 0.8); P = 0.651].Conclusions When carbohydrates are ingested prior to moderate-intensity exercise, adding repeated sprints is not significantly detrimental to glycaemic management in overnight fasted people with Type 1 diabetes under basal insulin conditions.

Reproducibility of plasma glucose responses to moderate‐intensity exercise in individuals with type 1 diabetes

“…During the 1 h recovery period, plasma glucose levels fell modestly (0.6 mmoL/L on average), a finding consistent with those of other studies reporting minimal disruptions to glycaemia during recovery from exercise performed after an overnight fast and under basal insulin conditions 14,16 . The stability of plasma glucose levels during recovery may be explained by a rapid fall in muscle glucose uptake at the end of exercise which results from the cessation of muscle contraction, an effect which can occur within minutes 26,27 .…”

“…14,23 During the 1 h recovery period, plasma glucose levels fell modestly (0.6 mmoL/L on average), a finding consistent with of other studies reporting minimal disruptions to glycaemia during recovery from exercise performed after an overnight fast and under basal insulin conditions. 14,16 The stability of plasma glucose levels during recovery may be explained by a rapid fall in muscle glucose uptake at the end of exercise which results from the cessation of muscle contraction, an effect which can occur within minutes. 26,27 While exercise does increase insulin sensitivity, the basal insulin conditions that exercise was performed under in this study may have limited the insulin-mediated uptake of glucose as post-exercise glucose levels have been found to continue to fall under higher insulin conditions.…”

“…Exercise after an overnight fast and under basal insulin conditions was chosen as this reduces the risk of acute hypoglycaemia given that circulating insulin levels are typically low, 17 and 30-40 min of moderate-intensity exercise has been shown to have relatively little impact on average on blood glucose levels under similar conditions. 15,16,[18][19][20] We hypothesised that the plasma glucose level response to moderate-intensity exercise is reproducible under these conditions.…”

“…Therefore the primary aim of the present study was to assess the within‐person variability of plasma glucose responses during 40 min of continuous moderate‐intensity exercise after an overnight fast and under basal insulin conditions, without any prior plasma glucose or insulin level adjustments, in young individuals with type 1 diabetes. The 40‐min duration of exercise was selected as it is a duration that has been achieved by a similar cohort in the past 16 . Given that the rate of fall in the level of blood glucose during exercise is affected by the level of glucose pre‐exercise and considering the challenge of matching those levels without the use of an insulin clamp, we chose to test the participants on three separate days and examined the within‐person variability of plasma glucose responses during exercise and recovery using only the two closest matched visits per participant by plasma glucose level prior to exercise.…”

“…Given that the rate of fall in the level of blood glucose during exercise is affected by the level of glucose pre‐exercise and considering the challenge of matching those levels without the use of an insulin clamp, we chose to test the participants on three separate days and examined the within‐person variability of plasma glucose responses during exercise and recovery using only the two closest matched visits per participant by plasma glucose level prior to exercise. Exercise after an overnight fast and under basal insulin conditions was chosen as this reduces the risk of acute hypoglycaemia given that circulating insulin levels are typically low, 17 and 30–40 min of moderate‐intensity exercise has been shown to have relatively little impact on average on blood glucose levels under similar conditions 15,16,18–20 . We hypothesised that the plasma glucose level response to moderate‐intensity exercise is reproducible under these conditions.…”