Target-Seeking Behavior of Plasma Glucose With Exercise in Type 1 Diabetes

Abstract

OBJECTIVE -To investigate the reproducibility of the plasma glucose (PG) response to exercise in subjects with type 1 diabetes on a nonintensive insulin regimen.RESEARCH DESIGN AND METHODS -Subjects cycled for 45 min at 50% VO 2max on two occasions (studies 1 and 2) either 1 h after lunch and usual insulin (protocol A) or after overnight fasting without morning insulin (protocol B). Identical diet, activity, and insulin (twice daily neutral and intermediate) were maintained before and during each study day. A total of 13 type 1 diabetic subjects (6 men and 7 women, BMI 24.0 Ϯ 0.9 kg/m 2 [means Ϯ SE], age 42.6 Ϯ 2.7 years, diabetes duration 14.1 Ϯ 2.8 years) completed protocol A, and 7 (3 men and 4 women, BMI 25.8 Ϯ 1.3 kg/m 2 , age 39.7 Ϯ 1.3 years, diabetes duration 14 Ϯ 4.4 years) completed protocol B.RESULTS -In protocol A (fed), the fall in PG during exercise was 4.5 Ϯ 1.0 and 5.0 Ϯ 0.8 mmol/l in studies 1 and 2, respectively, whereas in protocol B (fasted), it was 0.6 Ϯ 0.8 and 3.4 Ϯ 1.6 mmol/l. Regression analysis of the change in PG in protocol A in study 1 versus study 2 showed poor reproducibility (r 2 ϭ 0.12, P ϭ 0.25) despite uniform conditions. In protocol B, the fall in PG was more reproducible (r 2 ϭ 0.81, P ϭ 0.006). In fed subjects, there was better (P ϭ 0.01) and clinically useful reproducibility of the PG at exercise completion (r 2 ϭ 0.77, P ϭ 0.0001) compared with preexercise.CONCLUSIONS -These results indicate poor reproducibility of the change in PG during exercise after feeding in type 1 diabetes on nonintensive insulin regimens but reasonable reproducibility when fasting. Exercise apparently decreases the glycemic variability after feeding, so that PG concentrations after exercise seek a reproducible "target." Thus, the absolute PG level after a typical bout of exercise in the fed state should be a good guide to carbohydrate or insulin adjustment on subsequent occasions.

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

“…Another unexpected finding is that without prior carbohydrate intake, moderate-intensity exercise with or without repeated sprints did not significantly affect blood glucose levels. These different experimental conditions may explain the absence of an exercise-mediated fall in blood glucose reported here, as others have shown similar findings when exercise is performed after a prolonged fast [15][16][17][18]. Our findings contrast with those of Guelfi et al [9], where moderate-intensity exercise, with and without repeated sprints, was shown to result in a significant fall in blood glucose level, albeit to a lesser extent with the latter.…”

Impact of Exercise on Overnight Glycemic Control in Children with Type 1 Diabetes Mellitus

“…These findings extend those of MacDonald et al, 3 who reported in a prospective (though uncontrolled) outpatient case series that 48 of 300 (16%) patients with T1DM (age 4 to 24 years) self-reported at least 1 episode of moderate or severe hypoglycemia occurring 4 or more hours after exercise during a 2-year period. Although a number of studies have evaluated the incidence of hypoglycemia during or immediately after exercise, [13][14][15][16][17] we are not aware of a previous study that has systematically evaluated the occurrence of overnight hypoglycemia after exercise in children or in adults.…”

Individual glucose responses to prolonged moderate intensity aerobic exercise in adolescents with type 1 diabetes: The higher they start, the harder they fall

“…One of the most discussed topics with patients around exercise management is the notion that there is unexplainable inter‐patient variability in the glucose responses to exercise . According to a limited number of small studies, a higher pre‐exercise blood glucose concentration tends to be associated with a greater absolute drop in glycemia during prolonged aerobic exercise .…”