High Intensity Interval Training reduces hypoglycemic events compared with continuous aerobic training in individuals with type 1 diabetes: HIIT and hypoglycemia in type 1 diabetes

Impact of Time of Day on Glycemia in Response to Postprandial Supramaximal Sprints in Adults With Type 1 Diabetes

OBJECTIVES

In this study we explore the impact of postprandial exercise timing (morning vs evening) on glycemia in individuals with type 1 diabetes (T1D) during short all-out sprints on a cycle ergometer.

METHODS

Ten healthy physically sedentary male (n=7) and female (n=3) volunteers with type 1 diabetes, 22.8±2.8 years of age, and with a diabetes duration of 9.7±5.5 years and glycated hemoglobin level of 8.6±1.2%, underwent comprehensive screening and assessment of their physical health and fitness status before study participation, under the guidance of a physician. Each participant underwent 2 postprandial exercise sessions on separate days: the first in the morning at 8:00 AM and second in the evening at 8:00 PM, both conducted 60 minutes after a standardized meal.

RESULTS

Morning exercise showed a less pronounced reduction in plasma glucose (PG) levels compared with evening exercise (-2.01±1.24 vs -3.56±1.6 mmol/L, p=0.03). In addition, higher cortisol levels were observed in the morning vs evening (128.59±34 vs 67.79±26 ng/mL, p<0.001).

CONCLUSIONS

Morning repeated sprint exercise conducted in the postprandial state consistent with the protective effect of higher cortisol levels resulted in a smaller reduction in PG levels compared with evening exercise. This highlights the potential influence of exercise timing on glycemic responses and cortisol secretion in the management of T1D.

Optimal exercise intensity for improving executive function in patients with attention deficit hyperactivity disorder: systematic review and network meta-analysis

This study aimed to compare and rank the effectiveness of optimal exercise intensity in improving executive function in patients with ADHD (Attention deficit hyperactivity disorder, ADHD) through a comprehensive comparison of direct and indirect evidence. A systematic search was performed in five electronic databases to explore the optimal exercise intensity for improving executive function in patients with ADHD by directly and indirectly comparing a variety of exercise intervention intensities. In addition, the isolated effects of exercise on improving executive function in patients with ADHD were explored through classical meta-analysis of paired direct comparisons. Twenty-nine studies were retrieved and included in this study. Classical paired meta-analysis showed that for the patients with ADHD in the age group of 7-17 years, statistical difference was observed for all the parameters of exercise interventions (intensity, frequency, period, and training method), the three dimensions of executive function, the use of medication or not, the high and low quality of the methodological approach. Network meta-analysis showed that high-intensity exercise training was optimal for improving working memory (97.4%) and inhibitory function (85.7%) in patients with ADHD. Meanwhile, moderate-intensity exercise training was optimal for improving cognitive flexibility (77.3%) in patients with ADHD. Moderate to high intensity exercise training shows potential for improving executive function in these patients. Therefore, we recommend applying high-intensity exercise intervention to improve executive function in patients with ADHD to achieve substantial improvement.

Effects of HIIT Interventions on Cardiorespiratory Fitness and Glycemic Parameters in Adults with Type 1 Diabetes: A Systematic Review and Meta-Analysis

BACKGROUND

Individuals with type 1 diabetes mellitus (T1DM) face impaired cardiorespiratory fitness and glycemic control, increasing the risk of cardiovascular complications. High-intensity interval training (HIIT) has emerged as a promising exercise modality with potential benefits for both aspects in this population.

OBJECTIVES

The primary aim was to investigate the effects of HIIT on cardiorespiratory fitness and glycemic parameters in patients with T1DM. The secondary aim was to examine the most effective HIIT protocol for cardiorespiratory fitness and glycemic parameters in patients with T1DM.

DESIGN

Systematic review and meta-analysis.

DATA SOURCES

Two major electronic databases (Web of Science and PubMed) were searched up to February 2024.

ELIGIBILITY CRITERIA FOR SELECTING STUDIES

Randomized and non-randomized trials involving adult patients with T1DM, free of complications and other diseases examining the effects of HIIT (HIIT pre vs. post; HIIT vs. control group or HIIT vs. moderate-intensity continuous training (MICT)) on cardiorespiratory fitness and glycemic parameters were included.

RESULTS

A total of ten studies met the inclusion criteria. The meta-analysis revealed a significant improvement in cardiorespiratory fitness following HIIT interventions (pre vs. post) in patients with T1DM (standardized mean difference (SMD) = 0.59, 95% confidence interval (CI) = 0.16 to 1, p = 0.01). Furthermore, HIIT (pre vs. post) was associated with significant improvements in 24-h mean glucose control (SMD = - 0.44, 95% CI = - 0.81 to - 0.06, p = 0.02), but the results (pre vs. post) failed to identify significant improvements in fasting glucose (SMD = - 0.26, 95% CI = - 0.78 to 0.24, p = 0.3) and glycated hemoglobin (HbA1C) values (SMD = - 0.28, 95% CI = - 0.61 to 0.05, p = 0.1). However, in comparison with a control group, HIIT showed significantly favorable effects on HbA1C (SMD = - 0.74, 95% CI = - 1.35 to - 0.14, p = 0.02). Finally, the meta-regression analysis did not find any moderating effect of any HIIT characteristics (i.e., intervention duration, session duration, work time, rest time, number of bouts, and intensity) on cardiorespiratory fitness and glycemic parameters.

CONCLUSION

Our systematic review and meta-analysis show that T1DM patients who performed a HIIT intervention significantly improved cardiorespiratory fitness and reduced their 24-h mean glucose levels, but not their HbA1C and fasting glucose. These findings support the application of HIIT interventions in T1DM patients. However, the guidelines for the most effective protocol remain unclear; hence, future studies are needed.

Accuracy of Two Continuous Glucose Monitoring Devices During Aerobic and High-Intensity Interval Training in Individuals with Type 1 Diabetes

Background: This study aimed to evaluate the accuracy of Dexcom G6 (DG6) and FreeStyle Libre-2 (FSL2) during aerobic training and high-intensity interval training (HIIT) in individuals with type 1 diabetes. Methods: Twenty-six males (mean age 29.3 ± 6.3 years and mean duration of diabetes 14.9 ± 6.1 years) participated in this study. Interstitial glucose levels were measured using DG6 and FSL2, while plasma glucose levels were measured every 10 min using YSI 2500 as the reference for glucose measurements in this study. The measurements began 20 min before the start of exercise and continued for 20 min after exercise. Seven measurements were taken for each subject and exercise. Results: Both DG6 and FSL2 devices showed significant differences compared to YSI glucose data for both aerobic and HIIT exercises. Continuous glucose monitoring (CGM) devices exhibited superior performance during HIIT than aerobic training, with DG6 showing a mean absolute relative difference of 14.03% versus 31.98%, respectively. In the comparison between the two devices, FSL2 demonstrated significantly higher effectiveness in aerobic training, yet its performance was inferior to DG6 during HIIT. According to the 40/40 criteria, both sensors performed similarly, with marks over 93% for all ranges and both exercises, and above 99% for HIIT and in the >180 mg/dL range, which is in accordance with FDA guidelines. Conclusions: The findings suggest that the accuracy of DG6 and FSL2 deteriorates during and immediately after exercise but remains acceptable for both devices during HIIT. However, accuracy is compromised with DG6 during aerobic exercise. This study is the first to compare the accuracy of two CGMs, DG6, and FSL2, during two exercise modalities, using plasma glucose YSI measurements as the gold standard for comparisons. It was registered at clinicaltrials.gov (NCT06080542).

People with type 1 diabetes exhibit lower exercise capacity compared to a control population with similar physical activity levels

AIMS

We aimed to assess physical activity (PA) levels, adherence to PA guidelines, and fitness capacity in individuals with type 1 diabetes (T1D) and control population.

METHODS

This cross-sectional study included 232 T1D and 248 controls. PA levels (IPAQ-SF questionnaire), adherence to guidelines (>150 min/week of moderate-to-vigorous PA), fitness capacity (VO2max, maximal incremental test on a cycle ergometer and 1RM test) were assessed, along with other clinical variables.

RESULTS

Total PA levels (T1D 2202 ± 1839 vs. controls 2357 ± 2189 METs/min/week), adherence (T1D 53.1 % vs controls 53.2 %), and sedentariness (T1D 27.3 % vs. controls 25.1 %) were similar between groups. However, participants with T1D exhibited significantly lower levels of VO2max (29.1 ± 10.5 vs. 32.5 ± 11.5 mlO2/kg/min, p < 0.001), work capacity (2.73 ± 1.03 vs. 3 ± 10 W/kg of body weight, p = 0.004) and strength capacity (2.29 ± 0.53 vs. 2.41 ± 0.79 kg/kg body weight in 1RM, p = 0.01) than controls, after adjusting for sex and age.

CONCLUSIONS

Individuals with T1D exhibit lower fitness capacity compared to a control population, regardless of age and sex, even when presenting similar levels of total physical activity and adherence to guidelines.

Continuous moderate and intermittent high-intensity exercise in youth with type 1 diabetes: Which protection for dysglycemia?

AIM

From an early age, exercise is key to managing type 1 diabetes (T1D). However, hypoglycemia around aerobic exercise is a major barrier to physical activity in children. We explore whether intermittent high-intensity aerobic exercise (IHE), designed to mimic spontaneous childhood physical activity patterns, offers better protection against glycemic drop than continuous moderate-intensity exercise (CME).

METHODS

Five boys and 7 girls with T1D (9.8 ± 1.4y) performed ergo cycle-based randomized CME and IHE of identical duration and total mechanical load [50 %PWC170vs. 15sec(150 %PWC170)/30 sec passive recovery; both during two 10-min sets, 5 min in-between]. Capillary glycemia during exercise and interstitial glucose during recovery were compared between exercises and an inactive condition, controlling for baseline glycemia, carbohydrate and insulin.

RESULTS

The exercise-induced decrease in capillary glycemia was attenuated by 1.47 mmol·L-1 for IHE vs. CME (P < 0.05). No symptomatic hypoglycemic episodes occurred during exercises. Post-exercise time in hypoglycemia did not differ between conditions. During early recovery, CME reduced time spent > 16.7 mmol·L-1 compared with inactive days (P < 0.05; CME: 0 %; IHE: 16,7 %; INACTIVE: 41,7 %).

CONCLUSION

IHE appeared to limit the glycemic drop compared to CME. Performing 20-min CME or IHE was not associated with increased hypoglycemic risk compared to being inactive. CME appeared even transiently protective against serious hyperglycemia.

Single Exercise for Core Symptoms and Executive Functions in ADHD: A Systematic Review and Meta-Analysis

OBJECTIVES

A systematic review and meta-analysis of studies of single exercise on core symptoms and executive function in adolescents with ADHD.

METHODS

Four databases were searched for studies of the effects of single exercise on core symptoms and executive functioning in adolescents with ADHD.

RESULTS

Thirteen studies were included, and a single session of exercise had small effect-size improvements in core symptoms and executive function in adolescents with ADHD: 10 to 13 year olds in the early adolescent-elementary school years and 18 to 24 year olds in the late adolescent-college years. Moderate-intensity continuous training, high-intensity interval training, single sessions of less than 30 minutes, and single sessions of 30 minutes and more significantly improved cycling training, attention, inhibition, substance use, and pre-study abstinence.

CONCLUSIONS

A single session of exercise had an overall ameliorative effect on core symptoms and executive function in adolescents with ADHD.

High-intensity interval training ameliorates chronic unpredictable mild stress-induced depressive behaviors via HDAC2-BDNF signaling in the ventral hippocampus

Major depressive disorder (MDD) is a devastating psychiatric disease, and current therapies could not well meet the demand for MDD treatment. Exercise benefits mental illness, and notably, exercise has been recommended as an alternative option for MDD treatment in some countries. However, the paradigm and intensity of exercise for MDD treatment has yet to be determined. High-intensity interval training (HIIT) is a potent and time-efficient type of exercise training and has gained popularity in recent years. In this study, we exposed the mice to chronic unpredictable mild stress (CUMS) and found HIIT exerted substantial antidepressant effect. Moreover, HIIT further enhanced the antidepressant effect of fluoxetine, a classic antidepressant in the clinic, confirming the antidepressant role of HIIT. HIIT significantly reversed the CUMS-induced upregulations in HDAC2 mRNA and protein level in the ventral hippocampus. We also found HIIT rescued the CUMS-induced downregulation in the expression of brain-derived neurotrophic factor (BDNF) and HDAC2 overexpression counteracted the HIIT-induced increase in BDNF level. More importantly, both virus-mediated HDAC2 overexpression and microinfusion of TrkB-Fc, a BDNF scavenger, in the ventral hippocampus abolished the antidepressant effect of HIIT. Together, our results strongly demonstrate that HIIT attenuates depressive behaviors, probably via HDAC2-BDNF signaling pathway and reveal that HIIT may serve as an alternative option for MDD treatment.