Effects of postprandial exercise on blood glucose levels in adults with type 1 diabetes: a review.

People with type 1 diabetes experience challenges in managing blood glucose around exercise. Previous studies have examined glycaemic responses to different exercise modalities but paid little attention to participants' prandial state, although this is an important consideration and will enhance our understanding of the effects of exercise in order to improve blood glucose management around activity. This review summarises available data on the glycaemic effects of postprandial exercise (i.e. exercise within 2 h after a meal) in people with type 1 diabetes. Using a search strategy on electronic databases, literature was screened until November 2022 to identify clinical trials evaluating acute (during exercise), subacute (≤2 h after exercise) and late (>2 h to ≤24 h after exercise) effects of postprandial exercise in adults with type 1 diabetes. Studies were systematically organised and assessed by exercise modality: (1) walking exercise (WALK); (2) continuous exercise of moderate intensity (CONT MOD); (3) continuous exercise of high intensity (CONT HIGH); and (4) interval training (intermittent high-intensity exercise [IHE] or high-intensity interval training [HIIT]). Primary outcomes were blood glucose change and hypoglycaemia occurrence during and after exercise. All study details and results per outcome were listed in an evidence table. Twenty eligible articles were included: two included WALK sessions, eight included CONT MOD, seven included CONT HIGH, three included IHE and two included HIIT. All exercise modalities caused consistent acute glycaemic declines, with the largest effect size for CONT HIGH and the smallest for HIIT, depending on the duration and intensity of the exercise bout. Pre-exercise mealtime insulin reductions created higher starting blood glucose levels, thereby protecting against hypoglycaemia, in spite of similar declines in blood glucose during activity between the different insulin reduction strategies. Nocturnal hypoglycaemia occurred after higher intensity postprandial exercise, a risk that could be diminished by a post-exercise snack with concomitant bolus insulin reduction. Research on the optimal timing of postprandial exercise is inconclusive. In summary, individuals with type 1 diabetes exercising postprandially should substantially reduce insulin with the pre-exercise meal to avoid exercise-induced hypoglycaemia, with the magnitude of the reduction depending on the exercise duration and intensity. Importantly, pre-exercise blood glucose and timing of exercise should be considered to avoid hyperglycaemia around exercise. To protect against late-onset hypoglycaemia, a post-exercise meal with insulin adjustments might be advisable, especially for exercise in the evening or with a high-intensity component.

Reassessing the evidence: prandial state dictates glycaemic responses to exercise in individuals with type 1 diabetes to a greater extent than intensity.

Recent guidelines suggest that adding anaerobic (high intensity or resistance) activity to an exercise session can prevent blood glucose declines that occur during aerobic exercise in individuals with type 1 diabetes. This theory evolved from earlier study data showing that sustained, anaerobic activity (high intensity cycling) increases blood glucose levels in these participants. However, studies involving protocols where anaerobic (high intensity interval) and aerobic exercise are combined have extremely variable glycaemic outcomes, as do resistance exercise studies. Scrutinising earlier studies will reveal that, in addition to high intensity activity (intervals or weight lifting), these protocols had another common feature: participants were performing exercise after an overnight fast. Based on these findings, and data from recent exercise studies, it can be argued that participant prandial state may be a more dominant factor than exercise intensity where glycaemic changes in individuals with type 1 diabetes are concerned. As such, a reassessment of study outcomes and an update to exercise recommendations for those with type 1 diabetes may be warranted.

The competitive athlete with type 1 diabetes.

Regular exercise is important for health, fitness and longevity in people living with type 1 diabetes, and many individuals seek to train and compete while living with the condition. Muscle, liver and glycogen metabolism can be normal in athletes with diabetes with good overall glucose management, and exercise performance can be facilitated by modifications to insulin dose and nutrition. However, maintaining normal glucose levels during training, travel and competition can be a major challenge for athletes living with type 1 diabetes. Some athletes have low-to-moderate levels of carbohydrate intake during training and rest days but tend to benefit, from both a glucose and performance perspective, from high rates of carbohydrate feeding during long-distance events. This review highlights the unique metabolic responses to various types of exercise in athletes living with type 1 diabetes. Graphical abstract.

Fluid Intake Habits in Type 1 Diabetes Individuals during Typical Training Bouts.

BACKGROUND/AIMS: Hyperglycemia may influence the hydration status in diabetic individuals. During exercise, type 1 diabetes mellitus (T1DM) individuals may be challenged by a higher risk of dehydration due to a combination of fluid losses from sweat and increased urine output via glycosuria. So far, no study has characterised spontaneous fluid intake in T1DM individuals during active trainings. METHODS: A validated questionnaire was used to assess T1DM participants' diabetes therapy, sports characteristics and fluid intake during training; results were then compared to an age- and sport-matched sample of non-diabetic individuals. RESULTS: Ninety individuals completed the survey (n = 45 T1DM individuals, n = 45 matched controls). A proportion of T1DM -individuals reported blood glucose levels greater than 10.0 mmol at both the start (28.9%) and end (24.4%) of the exercise. The mean self-reported fluid intake was greater in T1DM (0.60 ± 0.47 L·h-1) compared to that of the control (0.37 ± 0.28 L·h-1, p < 0.05). In spite of drinking fluid volumes in line with international guidelines, 84.4% of those with T1DM reported that they were still feeling thirsty at the end of their training session. CONCLUSIONS: T1DM individuals self-report spontaneously consuming fluid adequate volumes suggested by sport nutrition guidelines for non-diabetic athletes. Discrepancies in the T1DM subjectively reported feelings of thirst suggest that more education on hydration during exercise is needed for this population to adequately compensate for elevated blood glucose levels. It remains to be established whether fluid volumes suggested for healthy athletes are adequate for maintaining euhydration in T1DM patients due to their altered diuresis.

Update on Management of Type 1 Diabetes and Type 2 Diabetes in Athletes.

Optimal blood glucose management still remains the biggest challenge in active individuals with diabetes, particularly in insulin users, but some newer strategies have been introduced to maintain blood glucose control. Recent studies emphasize the importance of exercise intensity on glycemic balance. In individuals with type 1 and type 2 diabetes, both resistance and high-intensity intermittent exercise have been shown to confer beneficial physiological adaptations in training studies, while also showing acute glycemic benefits from single sessions. At the same time, anyone training at higher intensities also should take into consideration potential impairments in thermoregulation in individuals with diabetes, which can increase the risk of heat stress during exercise in hot and/or humid conditions. Recent studies of medication effects on electrolyte balance and hydration give a more complete picture of potential exercise risks for athletes with diabetes. Use of the latest diabetes-related technologies also may benefit the athlete with diabetes.

Exercise strategies for hypoglycemia prevention in individuals with type 1 diabetes.

IN BRIEF Fear of hypoglycemia is one of the main barriers to physical activity for individuals with type 1 diabetes. Recent studies indicate that anaerobic forms of exercise (i.e., resistance exercise/weight lifting, sprints, and high-intensity intervals) can attenuate exercise-related declines in blood glucose both during and after exercise in young, healthy adults with type 1 diabetes. These responses might vary based on age, sex, and fitness level and in the general safety of relying on them to prevent hypoglycemia.

The blood pressure response to exercise in youth with impaired glucose tolerance and type 2 diabetes.

Type 2 diabetes is associated with hypertension and an increased risk of cardiovascular disease. In adults, blood pressure (BP) responses to exercise are predictive of these complications. To determine if the hemodynamic response to exercise is exaggerated in youth with dysglycemia (DG) compared with normoglycemic overweight/ obese (OB) and healthy weight (HW) controls a cross-sectional comparison of BP and heart rate (HR) responses to graded exercise to exhaustion in participants was performed. DG and OB youth were matched for age, BMI z-score, height and sex. Systolic (SBP) and diastolic BP (DBP) were measured every 2 min, and HR was measured every 1 min. SBP was higher in OB and DG compared with HW youth at rest (p < .001). Despite working at lower relative workloads compared with HW, the BP response was elevated during exercise in OB and DG. For similar HR and oxygen consumption rates, BP responses to exercise were slightly higher in OB and DG compared with HW. OB and DG youth both display elevated resting and exercise BP relative to HW peers. Obesity may play a greater role than dysglycemia in the exaggerated BP response to exercise in youth.

Changing Glucose Levels During the Menstrual Cycle as Observed in Adults in the Type 1 Diabetes Exercise Initiative Study.

OBJECTIVES: Evidence suggests that glucose levels in menstruating females with type 1 diabetes change throughout the menstrual cycle, reaching a peak during the luteal phase. The Type 1 Diabetes Exercise Initiative (T1DEXI) study provided the opportunity to assess glycemic metrics between early and late phases of the menstrual cycle, and whether differences could be explained by exercise, insulin, and carbohydrate intake. METHODS: One hundred seventy-nine women were included in our analysis. Glycemic metrics, carbohydrate intake, insulin requirements, and exercise habits during the early vs late phases of their menstrual cycles (i.e. 2 to 4 days after vs 2 to 4 days before reported menstruation start date) were compared. RESULTS: Mean glucose increased from 8.2±1.5 mmol/L (148±27 mg/dL) during the early follicular phase to 8.6±1.6 mmol/L (155±29 mg/dL) during the late luteal phase (p<0.001). Mean percent time-in-range (3.9 to 10.0 mmol/L [70 to 180 mg/dL]) decreased from 73±17% to 70±18% (p=0.002), and median percent time >10.0 mmol/L (>180 mg/dL) increased from 21% to 23% (p<0.001). Median total daily insulin requirements increased from 37.4 units during the early follicular phase to 38.5 units during the late luteal phase (p=0.02) and mean daily carbohydrate consumption increased slightly from 127±47 g to 133±47 g (p=0.05); however, the difference in mean glucose during early follicular vs late luteal phase was not explained by differences in exercise duration, total daily insulin units, or reported carbohydrate intake. CONCLUSIONS: Glucose levels during the late luteal phase were higher than those of the early follicular phase of the menstrual cycle. These glycemic changes suggest that glucose management for women with type 1 diabetes may need to be fine-tuned within the context of their menstrual cycles.

An Aerobic Cooldown After Morning, Fasted Resistance Exercise Has Limited Impact on Post-exercise Hyperglycemia in Adults With Type 1 Diabetes: A Randomized Crossover Study.

OBJECTIVES: Expert guidelines recommend an aerobic cooldown to lower blood glucose for the management of post-exercise hyperglycemia. This strategy has never been empirically tested. Our aim in this study was to compare the glycemic effects of performing an aerobic cooldown vs not performing a cooldown after a fasted resistance exercise session. We hypothesized that the cooldown would lower blood glucose in the 30 minutes after exercise and would result in less time in hyperglycemia in the 6 hours after exercise. METHODS: Participants completed 2 identical resistance exercise sessions. One was followed by a low-intensity (30% of peak oxygen consumption) 10-minute cycle ergometer cooldown, and the other was followed by 10 minutes of sitting. We compared the changes in capillary glucose concentration during these sessions and continuous glucose monitoring (CGM) outcomes over 24 hours post-exercise. RESULTS: Sixteen participants completed the trial. Capillary glucose was similar between conditions at the start of exercise (p=0.07). Capillary glucose concentration decreased by 0.6±1.0 mmol/L during the 10-minute cooldown, but it increased by 0.7±1.3 mmol/L during the same time in the no-cooldown condition. The resulting difference in glucose trajectory led to a significant interaction (p=0.02), with no effect from treatment (p=0.7). Capillary glucose values at the end of recovery were similar between conditions (p>0.05). There were no significant differences in CGM outcomes. CONCLUSIONS: An aerobic cooldown reduces glucose concentration in the post-exercise period, but the small and brief nature of this reduction makes this strategy unlikely to be an effective treatment for hyperglycemia occurring after fasted exercise.

The Impact of Gender on Physical Activity Preferences and Barriers in Adults With Type 1 Diabetes: A Qualitative Study.

OBJECTIVES: Current exercise recommendations for people with type 1 diabetes (T1D) are based on research involving primarily young, fit male participants. Recent studies have shown possible differences between male and female blood glucose response to exercise, but little is known about whether these differences are sex-related (due to physiological differences between male and female participants) or gender-related (behavioural differences between men and women). METHODS: To better understand gender-based behavioural differences surrounding physical activity (PA), we asked men and women (n=10 each) with T1D to participate in semistructured interviews. Topics discussed included motivation and barriers to exercise, diabetes management strategies, and PA preferences (type, frequency, duration of exercise, etc). Interview transcripts were coded by 2 analysts before being grouped into themes. RESULTS: Six themes were identified impacting participants' PA experience: motivation, fear of hypoglycemia, time lost to T1D management, medical support for PA, the role of technology in PA accessibility, and desire for more community. Gender differences were found in motivations, medical support, and desire for more community. Women were more motivated by directional weight dissatisfaction, and men were more motivated to stay in shape. Men felt less supported by their health-care providers than women. Women more often preferred to exercise in groups, and sought more community surrounding T1D and PA. CONCLUSION: Although men and women with T1D experience similar barriers around PA, there are differences in motivation, desire for community, and perceived support from medical providers.

Type 1 Diabetes and the Menstrual Cycle: Where/How Does Exercise Fit in?

Regular exercise is associated with substantial health benefits for individuals with type 1 diabetes (T1D). However, the fear of hypoglycemia (low blood glucose) due to activity-induced declines in blood glucose levels acts as a major barrier to partaking in exercise in this population. For females with T1D, hormonal fluctuations during the menstrual cycle and their effects on blood glucose levels can act as an additional barrier. The impact that these cyclic changes may have on blood glucose and insulin needs and the consequent risk of hypoglycemia during or after exercise are still unknown in this population. Therefore, in this narrative review, we gathered existing knowledge about the menstrual cycle in T1D and the effects of different cyclic phases on substrate metabolism and glucose response to exercise in females with T1D to increase knowledge and understanding around exercise in this underrepresented population. This increased knowledge in such an understudied area can help to better inform exercise guidelines for females with T1D. It can also play an important role in eliminating a significant barrier to exercise in this population, which has the potential to increase activity, improve mental health and quality of life, and decrease the risk of diabetes-related complications.

The Effect of Starting Blood Glucose Levels on Serum Electrolyte Concentrations during and after Exercise in Type 1 Diabetes.

Fear of hypoglycemia is a major exercise barrier for people with type 1 diabetes (PWT1D). Consequently, although guidelines recommend starting exercise with blood glucose (BG) concentration at 7-10 mmol/L, PWT1D often start higher, potentially affecting hydration and serum electrolyte concentrations. To test this, we examined serum and urine electrolyte concentrations during aerobic exercise (cycling 45 min at 60%VO2peak) in 12 PWT1D (10F/2M, mean ± SEM: age 29 ± 2.3 years, VO2peak 37.9 ± 2.2 mL·kg-1·min-1) with starting BG levels: 8-10 (MOD), and 12-14 (HI) mmol/L. Age, sex, and fitness-matched controls without diabetes (CON) completed one exercise session with BG in the normal physiological range. Serum glucose was significantly higher during exercise and recovery in HI versus MOD (p = 0.0002 and p < 0.0001, respectively) and in MOD versus CON (p < 0.0001). During exercise and recovery, MOD and HI were not significantly different in serum insulin (p = 0.59 and p = 0.63), sodium (p = 0.058 and p = 0.08), potassium (p = 0.17 and p = 0.16), calcium (p = 0.75 and 0.19), and magnesium p = 0.24 and p = 0.09). Our findings suggest that exercise of moderate intensity and duration with higher BG levels may not pose an immediate risk to hydration or serum electrolyte concentrations for PWT1D.

Efficacy and safety of lemborexant in subjects previously treated with placebo for 6 months in a randomized phase 3 study.

OBJECTIVE/BACKGROUND: To examine the effects of lemborexant (LEM) 5 mg (LEM5) or LEM 10 mg (LEM10) following extended placebo treatment. This post-hoc analysis used subject-reported sleep outcomes data from a phase 3 trial. PATIENTS/METHODS: The subjects in these post-hoc analyses were randomized to placebo for 6 months (Time Period [TP]1) in Study E2006-G000-303 (SUNRISE-2; NCT02952820). Following placebo exposure, subjects were re-randomized to LEM5 or LEM10 for another 6 months (TP2). Subject-reported sleep outcomes derived from sleep diaries included sleep onset latency (sSOL), wake after sleep onset (sWASO), sleep efficiency (sSE), and total sleep time (sTST). Magnitude and change rate in parameters were assessed for 7 days before/after initial randomization to placebo and 7 days before/after re-randomization to LEM (6 months later). Month 6 placebo non-responders were assessed for LEM response in TP2 using predetermined responder definitions. Safety was monitored throughout the study. RESULTS: Overall, 321 subjects received placebo; 258 re-randomized subjects received LEM5 (n = 133) and LEM10 (n = 125). Subjective sleep outcomes improved during TP1 with approximately 62 subjects (∼20%) exhibiting a sustained placebo response. Upon re-randomization to LEM, all measures showed an additional incremental benefit, most prominently in sSOL and sTST. Among Month 6 placebo non-responders, 11%-15% subsequently responded to LEM as assessed at Month 12. The safety profile was similar between treatment periods and treatment groups. CONCLUSIONS: These data suggest that even when insomnia symptoms have improved over time with placebo treatment, additional and sustained clinical gains in sleep outcomes are possible with active treatment using lemborexant.

Hyperglycemia-related anxiety during competition in an elite athlete with type 1 diabetes: A case report.

AIM: Managing blood glucose (BG) levels during intense physical activity is challenging for elite athletes with type 1 diabetes (T1D), as it can lead to unpredictable hyper- or hypoglycemia, which can affect performance. This case study presents an 18-year-old male hockey goalie with hyperglycemia-related anxiety during competition and its impact on his T1D management. METHODS: Mixed-methods approach, incorporating qualitative data from an unstructured interview and responses from the Hyperglycemia Avoidance Scale along with quantitative data retrieved from Diasend and laboratory results. RESULTS: The athlete experiences physical and cognitive symptoms during hyperglycemia, affecting his performance. Hyperglycemia-related anxiety influences insulin dosage adjustments and eating habits on game days. Glycemic variability analysis reveals lower BG levels during game time. CONCLUSION: Hyperglycemia-related anxiety leads to modified therapeutic and lifestyle regimens on competition day. Tailored treatment programs are needed for elite athletes with T1D and hyperglycemia-related anxiety.

Systematic Review and Meta-analysis of Blood Glucose Response to High-intensity Interval Exercise in Adults With Type 1 Diabetes.

OBJECTIVES: Exercise-induced hyperglycemia is recognized in type 1 diabetes (T1D) clinical guidelines, but its association with high-intensity intermittent exercise (HIIE) in acute studies is inconsistent. In this meta-analysis, we examined the available evidence of blood glucose responses to HIIE in adults with T1D. The secondary, aim was to examine predictors of blood glucose responses to HIIE. We hypothesized that there would be no consistent effect on blood glucose from HIIE, unless examined in the context of participant prandial status. METHODS: We conducted a literature search using key words related to T1D and HIIE. Studies were required to include at least 6 participants with T1D with a mean age >18 years, involve an HIIE intervention, and contain pre- and postexercise measures of blood glucose. Analyses of extracted data were performed using a general inverse variance statistical method with a random effects model and a weighted multiple regression. RESULTS: Nineteen interventions from 15 reports were included in the analysis. A mean overall blood glucose decrease of -1.3 mmol/L (95% confidence interval [CI], -2.3 to -0.2 mmol/L) was found during exercise, albeit with high heterogeneity (I2=84%). When performed after an overnight fast, exercise increased blood glucose by +1.7 mmol/L (95% CI, 0.4 to 3.0 mmol/L), whereas postprandial exercise decreased blood glucose by -2.1 mmol/L (95% CI, -2.8 to -1.4 mmol/L), with a statistically significant difference between groups (p<0.0001). No associations with fitness (p=0.4), sex (p=0.4), age (p=0.9), exercise duration (p=0.9), or interval duration (p=0.2) were found. CONCLUSION: The effect of HIIE on blood glucose is inconsistent, but partially explained by prandial status.

Efficacy and safety of lemborexant in midlife women with insomnia disorder.

OBJECTIVE: Insomnia is common in midlife women. The efficacy and safety of lemborexant (LEM), a competitive dual orexin receptor antagonist, was assessed for 12 months in a subgroup of midlife women (age, 40-58 y) from Study E2006-G000-303 (Study 303; SUNRISE-2). METHODS: This was a randomized, double-blind, placebo (PBO)-controlled (first 6 mo) study of adults with insomnia disorder ( N = 949). During treatment period 1 (TP1), participants received PBO or LEM 5 mg (LEM5) or 10 mg (LEM10). During TP2 (second 6 mo), LEM participants continued their assigned dose; PBO participants were rerandomized to LEM5 or LEM10. Assessments included patient-reported sleep- and fatigue-related measures and treatment-emergent adverse events. RESULTS: The midlife female subgroup comprised 280 of 949 participants (TP1: PBO, n = 90 of 318 [28.3%]; LEM5, n = 82 of 316 [25.9%]; LEM10, n = 108 of 315 [34.3%]). At 6 months, median changes from baseline in subjective sleep-onset latency (in minutes) were -17.9, -20.7, and - 30.4 for PBO, LEM5, and LEM10 (vs PBO: LEM5, P = not significant; LEM10, P = 0.0310). At 6 months, mean changes from baseline in subjective wake after sleep onset (in minutes) were -37.0 (59.6), -50.1 (74.5), and -54.5 (65.4) for PBO, LEM5, and LEM10 (vs PBO: LEM5 and LEM10, P = not significant), with benefits sustained through 12 months. Greater decreases from baseline (improvement) in Insomnia Severity Index total score and Fatigue Severity Scale total score were seen with LEM versus PBO at 6 months; benefits continued through 12 months. Most treatment-emergent adverse events were mild to moderate in severity. CONCLUSIONS: Consistent with the total population, subjective sleep parameters improved, and improvement was sustained over time in midlife women. LEM was well tolerated, suggesting that LEM may be a potential treatment option for midlife women with insomnia.

The Resistance Exercise in Already Active Diabetic Individuals (READI) Randomized Clinical Trial.

CONTEXT: Resistance exercise training (strength training) and aerobic exercise training are both recommended for people with type 1 diabetes, but it is unknown whether adding resistance exercise provides incremental benefits in people with this condition who already perform aerobic exercise regularly. OBJECTIVE: This work aimed to evaluate the incremental effect of resistance training on glycated hemoglobin A1c (HbA1c), fitness, body composition, and cardiometabolic risk factors in aerobically active people with type 1 diabetes. METHODS: The Resistance Exercise in Already-active Diabetic Individuals (READI) trial (NCT00410436) was a 4-center, randomized, parallel-group trial. After a 5-week run-in period with diabetes management optimization, 131 aerobically active individuals with type 1 diabetes were randomly assigned to resistance exercise (n = 71, intervention-INT) or control (n = 60, CON) for 22 additional weeks. Both groups maintained their aerobic activities and were provided dietary counseling throughout. Exercise training was 3 times per week at community-based facilities. The primary outcome was HbA1c, and secondary outcomes included fitness (peak oxygen consumption, muscle strength), body composition (anthropometrics, dual-energy x-ray absorptiometry, computed tomography), and cardiometabolic risk markers (lipids, apolipoproteins). Assessors were blinded to group allocation. RESULTS: There were no significant differences in HbA1c change between INT and CON. Declines in HbA1c (INT: 7.75 ± 0.10% [61.2 ± 1.1 mmol/mol] to 7.55 ± 0.10% [59 ± 1.1 mmol/mol]; CON: 7.70 ± 0.11% [60.7 ± 1.2 mmol/mol] to 7.57 ± 0.11% [59.6 ± 1.3 mmol/mol]; intergroup difference in change -0.07 [95% CI, -0.31 to 0.18]). Waist circumference decreased more in INT than CON after 6 months (P = .02). Muscular strength increased more in INT than in CON (P < .001). There were no intergroup differences in hypoglycemia or any other variables. CONCLUSION: Adding resistance training did not affect glycemia, but it increased strength and reduced waist circumference, in aerobically active individuals with type 1 diabetes.