Afternoon aerobic and resistance exercise have limited impact on 24-h CGM outcomes in adults with type 1 diabetes: A secondary analysis.

AIMS: This study examined post-exercise glycemic variability in individuals with type 1 diabetes after acute bouts of resistance (RE) and aerobic exercise (AE) compared to a no-exercise day (CON). We hypothesized that exercise days would have greater glucose variability (standard deviation - SD, coefficient of variation - CV), and less time in range (TIR), compared to CON. METHODS: A secondary analysis was conducted on previously collected data. Twelve active participants with type 1 diabetes performed three testing sessions in random order with at least 48 h in between: AE (45-min treadmill run at 60%VO2max), RE (three sets of eight repetitions, seven weight-lifting exercises), and CON (45-min no-exercise control). Interstitial glucose levels were monitored by blinded continuous glucose monitoring (CGM). Glycemic variability was evaluated for 0-6 h, overnight (00:00-06:00) and 24 h after exercise. RESULTS: Mean CGM glucose, TIR, and time above/below range were similar among conditions (P > 0.05). Lower SD (0.8 [0.5-1.1], 1.4 [0.9-2.4]mmol/L, p = 0.009) and CV (11.4 [8.6-15.3], 23.4 [13.7-31.6]%, p = 0.007) were found overnight after AE versus CON. Otherwise, AE and RE had limited impact on post-exercise glycemia. CONCLUSIONS: Acute RE and AE bouts may have limited impact on post-exercise glycemic variability compared to rest in habitually active individuals with type 1 diabetes.

Sex-Related Differences in Blood Glucose Responses to Resistance Exercise in Adults With Type 1 Diabetes: A Secondary Data Analysis.

OBJECTIVES: In adults with type 1 diabetes, resistance exercise (RE) is associated with more stable blood glucose (BG) levels than aerobic exercise, both during and after exercise. In individuals without diabetes, growth hormone and epinephrine responses to RE differ between the sexes. These hormones are known to affect BG levels in individuals with type 1 diabetes. In this study, we explored whether sex-related differences may exist in BG responses to RE in individuals with type 1 diabetes. METHODS: A secondary data analysis was conducted on pooled data from 2 studies with identical RE protocols for individuals with type 1 diabetes (13 males, age range 16 to 63 years; 10 females, age range 19 to 45 years). The RE session consisted of 7 resistance-based exercises performed at 5 pm. Plasma glucose samples were collected before, immediately after and 1 h after exercise. Interstitial glucose levels were recorded through blinded continuous glucose monitoring 24 h before, during and 24 h after exercise. RESULTS: There was a significant sex-by-time interaction (p<0.001) in plasma glucose responses to RE. Plasma glucose decreased significantly in males from 8.6±2.5 to 6.3±2.1 mmol/L (p<0.001) during exercise, whereas females experienced no significant change (7.2±1.3 to 7.3±1.3 mmol/L, p=0.999). In the 6 h after RE, males developed significantly more hypoglycemia, as measured by continuous glucose monitoring (p=0.048). CONCLUSIONS: Males may have a greater risk of hypoglycemia with an acute bout of RE than females. Further research is needed to examine this phenomenon more closely, as sex-specific recommendations for preventing hypoglycemia around RE may be necessary in type 1 diabetes.

Could Age, Sex and Physical Fitness Affect Blood Glucose Responses to Exercise in Type 1 Diabetes?

Closed-loop systems for patients with type 1 diabetes are progressing rapidly. Despite these advances, current systems may struggle in dealing with the acute stress of exercise. Algorithms to predict exercise-induced blood glucose changes in current systems are mostly derived from data involving relatively young, fit males. Little is known about the magnitude of confounding variables such as sex, age, and fitness level-underlying, uncontrollable factors that might influence blood glucose control during exercise. Sex-related differences in hormonal responses to physical exercise exist in studies involving individuals without diabetes, and result in altered fuel metabolism during exercise. Increasing age is associated with attenuated catecholamine responses and lower carbohydrate oxidation during activity. Furthermore, higher fitness levels can alter hormonal and fuel selection responses to exercise. Compounding the limited research on these factors in the metabolic response to exercise in type 1 diabetes is a limited understanding of how these variables affect blood glucose levels during different types, timing and intensities of activity in individuals with type 1 diabetes (T1D). Thus, there is currently insufficient information to model a closed-loop system that can predict them accurately and consistently prevent hypoglycemia. Further, studies involving both sexes, along with a range of ages and fitness levels, are needed to create a closed-loop system that will be more precise in regulating blood glucose during exercise in a wide variety of individuals with T1D.

Sex-related differences in fuel utilization and hormonal response to exercise: implications for individuals with type 1 diabetes.

Sex-related differences in metabolic and neuroendocrine response to exercise in individuals without diabetes have been well established. Men and women differ in fuel selection during exercise, in which women rely to a greater extent on fat oxidation, whereas males rely mostly on carbohydrate oxidation for energy production. The difference in fuel selection appears to be mediated by sex-related differences in hormonal (including catecholamines, growth hormone, and estrogen) response to different types and intensities of exercise. In general, men exhibit an amplified counter-regulatory response to exercise, with elevated levels of catecholamines compared with women. However, women exhibit greater sensitivity to the lipolytic action of the catecholamines and deplete less of their glycogen stores than men during exercise, which suggests that women may experience a greater defense in blood glucose control after exercise than men. Conversely, little is known about sex-related differences in response to exercise in individuals with type 1 diabetes (T1D). A single study investigating sex-related differences in response to moderate aerobic exercise in individuals with T1D found sex-related differences in catecholamine response and fuel selection, but changes in blood glucose were not measured. To our knowledge, there are no studies investigating sex-related differences in blood glucose responses to different types and intensities of exercise in individuals with T1D. This review summarizes sex-related differences in exercise responses that could potentially impact blood glucose levels during exercise in individuals with T1D and highlights the need for further research.