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.

Standardised Exercise Prescription for Patients with Chronic Coronary Syndrome and/or Heart Failure: A Consensus Statement from the EXPERT Working Group.

Whereas exercise training, as part of multidisciplinary rehabilitation, is a key component in the management of patients with chronic coronary syndrome (CCS) and/or congestive heart failure (CHF), physicians and exercise professionals disagree among themselves on the type and characteristics of the exercise to be prescribed to these patients, and the exercise prescriptions are not consistent with the international guidelines. This impacts the efficacy and quality of the intervention of rehabilitation. To overcome these barriers, a digital training and decision support system [i.e. EXercise Prescription in Everyday practice & Rehabilitative Training (EXPERT) tool], i.e. a stepwise aid to exercise prescription in patients with CCS and/or CHF, affected by concomitant risk factors and comorbidities, in the setting of multidisciplinary rehabilitation, was developed. The EXPERT working group members reviewed the literature and formulated exercise recommendations (exercise training intensity, frequency, volume, type, session and programme duration) and safety precautions for CCS and/or CHF (including heart transplantation). Also, highly prevalent comorbidities (e.g. peripheral arterial disease) or cardiac devices (e.g. pacemaker, implanted cardioverter defibrillator, left-ventricular assist device) were considered, as well as indications for the in-hospital phase (e.g. after coronary revascularisation or hospitalisation for CHF). The contributions of physical fitness, medications and adverse events during exercise testing were also considered. The EXPERT tool was developed on the basis of this evidence. In this paper, the exercise prescriptions for patients with CCS and/or CHF formulated for the EXPERT tool are presented. Finally, to demonstrate how the EXPERT tool proposes exercise prescriptions in patients with CCS and/or CHF with different combinations of CVD risk factors, three patient cases with solutions are presented.

Barriers to Physical Activity in Children and Adults Living With Type 1 Diabetes: A Complex Link With Real-life Glycemic Excursions.

OBJECTIVES: Ever since the first research on barriers to physical activity (PA) highlighting fear of hypoglycemia as a major barrier, many studies have attempted to understand their demographic and behavioural determinants. However, no research has been conducted on whether these perceived barriers toward PA are based on real-life-experienced adverse glycemic effects of exercise. METHODS: Sixty-two adults and 53 children/adolescents living with type 1 diabetes, along with their parents, completed the Barriers to Physical Activity in Type 1 Diabetes-1 (BAPAD-1) questionnaire on barriers to PA. Continuous glucose-monitoring data were collected during 1 week of everyday life for 26 adults and 33 children/adolescents. Multiple linear regressions were used to explore links between BAPAD-1 scores and glycemic excursions experienced during and after everyday-life self-reported PA sessions, controlling for behavioural (accelerometry) and demographic confounders. RESULTS: In children/adolescents, the more time spent in hypoglycemia on nights after PA sessions, the more they reported hypoglycemic risk as a barrier (ß=+0.365, p=0.034). Conversely, in adults, the higher the proportion of PA sessions accompanied by a drop in blood glucose, the less hypoglycemia was a barrier (ß=-0.046, p=0.004). In parents, BAPAD-1 scores were unrelated to children/adolescents' everyday-life exercise-induced hypo/hyperglycemia. CONCLUSIONS: In children/adolescents, fear of hypoglycemia was predominant in those exposed to nocturnal hypoglycemia associated with PA sessions. In adults, fewer barriers may mean they accept a bigger drop in their glycemia during PA. This shows the importance of finding and promoting age-specific solutions to prevent exercise-induced hypoglycemia.

Thirty days of combined consumption of a high-fat diet and fructose-rich beverages promotes insulin resistance and modulates inflammatory response and histomorphometry parameters of liver, pancreas, and adipose tissue in Wistar rats.

OBJECTIVE: The aim of this study was to verify the effects of consumption of a high-fat diet (HFD) combined with fructose-rich beverages (FRT) in promoting metabolic and physiologic changes associated with insulin resistance. METHODS: Thirty-two male Wistar rats (250 ± 10 g) were randomly allocated into four groups (n = 8) that received either a standard diet (CON), HFD, FRT, or HFD + FRT for 30 d. Insulin sensitivity and glucose tolerance were evaluated using the insulin tolerance test (ITT) and oral glucose tolerance test (OGTT). Serum samples were used to analyze the metabolic parameters and hormone levels. Interleukin (IL)-6, IL-10, IL-1ß, and tumor necrosis factor-α assays were performed in the liver, pancreas, gastrocnemius muscle, and epididymal adipose tissue by enzyme-linked immunosorbent assay. Histologic and morphometric analyses were performed on the liver, pancreas, and adipose tissues. RESULTS: Consumption of HFD + FRT promoted a significant increase (P < 0.05) in body weight, index adiposity, and in the area under the curve of ITT (P < 0.001) and OGTT (P < 0.001) when compared with the CON group. Consumption of FRT alone increased fasting glucose (P = 0.015), insulin (P = 0.035), and homeostasis model assessment index (P = 0.018), and these changes were of greater magnitude when FRT was combined with HFD. Moreover, the rats fed an HFD + FRT demonstrated a significant increase in lipid droplets in the liver (P < 0.001), an increase in adipocyte area, and an increase in inflammatory cytokines in the liver, pancreas, skeletal muscle, and adipose tissue. CONCLUSION: Consumption of an HFD + FRT promotes insulin resistance, increases inflammatory cytokines, and modulates histomorphometric parameters of the liver, pancreas, and adipose tissue, typical of insulin resistance in humans.

The effect of acute cocoa flavanol intake on the BOLD response and cognitive function in type 1 diabetes: a randomized, placebo-controlled, double-blinded cross-over pilot study.

RATIONALE: Type 1 diabetes (T1D), a chronic autoimmune disease, can result in cognitive dysfunction and is associated with vascular dysfunction. Cocoa flavanols (CFs) can stimulate nitric oxide-dependent vasodilation, resulting in enhanced hemodynamic responses and better cognitive function. OBJECTIVES: To investigate whether acute CF supplementation can improve cognitive function and hemodynamic responses in T1D. METHODS: In this randomized, double-blinded, cross-over pilot study, 11 patients with T1D and their healthy matched controls consumed CF (900 mg CF) and placebo (15 mg CF) 2 h before a flanker test. fMRI was used to measure blood oxygen level-dependent (BOLD) response during the cognitive test. Repeated measure ANOVAs were used to test the effects of CF and T1D on BOLD response and cognitive performance. RESULTS: CF improved reaction time on the flanker test and increased the BOLD response in the supramarginal gyrus parietal lobe and inferior frontal gyrus, compared to placebo, in both groups. In patients with T1D, cognitive performance was not deteriorated while the BOLD response was smaller in T1D compared to healthy controls in the subgyral temporal lobe and the cerebellum. CONCLUSIONS: Acute CF intake improved reaction time on the flanker test and increased the BOLD response in the activated brain areas in patients with T1D and their matched controls.

High intensity interval training is associated with greater impact on physical fitness, insulin sensitivity and muscle mitochondrial content in males with overweight/obesity, as opposed to continuous endurance training: a randomized controlled trial.

OBJECTIVES: To evaluate the effect of high intensity training (HIT) on physical fitness, basal respiratory exchange ratio (bRER), insulin sensitivity and muscle histology in overweight/obese men compared to continuous aerobic training (CAT). MATERIAL AND METHODS: 16 male participants with overweight/obesity (age: 42-57 years, body mass index: 28-36 kg/m2) were randomized to HIT (n=8) or CAT (n=8) for 10 weeks, twice a week. HIT was composed of 10 minutes high intensity, 10 minutes continuous aerobic, 10 minutes high intensity exercises. CAT was composed of three times 10 minutes continuous exercising. Changes in anthropometry, physical and metabolic fitness were evaluated. Muscle histology (mitochondria and lipid content) was evaluated by transmission electron microscopy (TEM). RESULTS: HIT showed a significant increase for peak VO2 (P=0.01), for insulin sensitivity (AUC glucose (P<0,001), AUC insulin (P<0,001), OGTT composite score (P=0.007)) and a significant decrease of bRER (P<0.001) compared to CAT. Muscle mitochondrial content was significantly increased after HIT at the subsarcolemmal (P=0.004 number and P=0.001 surface) as well as the intermyofibrillar site (P<0.001 number and P=0.001 surface). CONCLUSION: High intensity training elicits stronger beneficial effects on physical fitness, basal RER, insulin sensitivity, and muscle mitochondrial content, as compared to continuous aerobic training.

Exercise Prescription in Patients with Different Combinations of Cardiovascular Disease Risk Factors: A Consensus Statement from the EXPERT Working Group.

Whereas exercise training is key in the management of patients with cardiovascular disease (CVD) risk (obesity, diabetes, dyslipidaemia, hypertension), clinicians experience difficulties in how to optimally prescribe exercise in patients with different CVD risk factors. Therefore, a consensus statement for state-of-the-art exercise prescription in patients with combinations of CVD risk factors as integrated into a digital training and decision support system (the EXercise Prescription in Everyday practice & Rehabilitative Training (EXPERT) tool) needed to be established. EXPERT working group members systematically reviewed the literature for meta-analyses, systematic reviews and/or clinical studies addressing exercise prescriptions in specific CVD risk factors and formulated exercise recommendations (exercise training intensity, frequency, volume and type, session and programme duration) and exercise safety precautions, for obesity, arterial hypertension, type 1 and 2 diabetes, and dyslipidaemia. The impact of physical fitness, CVD risk altering medications and adverse events during exercise testing was further taken into account to fine-tune this exercise prescription. An algorithm, supported by the interactive EXPERT tool, was developed by Hasselt University based on these data. Specific exercise recommendations were formulated with the aim to decrease adipose tissue mass, improve glycaemic control and blood lipid profile, and lower blood pressure. The impact of medications to improve CVD risk, adverse events during exercise testing and physical fitness was also taken into account. Simulations were made of how the EXPERT tool provides exercise prescriptions according to the variables provided. In this paper, state-of-the-art exercise prescription to patients with combinations of CVD risk factors is formulated, and it is shown how the EXPERT tool may assist clinicians. This contributes to an appropriately tailored exercise regimen for every CVD risk patient.

One-week cocoa flavanol intake increases prefrontal cortex oxygenation at rest and during moderate-intensity exercise in normoxia and hypoxia.

During exercise in hypoxia, O2 delivery to brain and muscle is compromised, and oxidative stress is elicited. Cocoa flavanols (CF) have antioxidant capacities and can increase blood flow by stimulating endothelial function. We aimed to examine the effects of 7-day CF intake on oxidative stress, nitric oxide production, and tissue oxygenation in response to exercise in normobaric hypoxia (14.3% O2). In a randomized, double-blind, cross-over study, 14 well-trained male cyclists completed four trials: exercise in normoxia or hypoxia, after 7-day CF or placebo intake. Flow-mediated dilation (FMD) was measured before intake of the last dose CF or placebo. One hundred minutes later, 20-min steady-state (SS; 45% V̇o2max) and 20-min time trial (TT) (cycling) were performed. Blood samples were taken. Prefrontal and muscular oxygenation was assessed by near-infrared spectroscopy. At baseline, FMD was increased by CF. Hypoxia increased exercise-induced elevations in lipid peroxidation and antioxidant capacity. CF suppressed exercise-induced lipid peroxidation but did not influence antioxidant capacity. At rest and during SS, prefrontal and muscular oxygenation was decreased by hypoxia. CF elevated prefrontal oxygenation but did not impact muscular oxygenation. During TT, hypoxia accelerated the exercise-induced decrease in prefrontal oxygenation, but not in muscular oxygenation. During TT, CF did not alter prefrontal and muscular oxygenation. CF did not change plasma nitrite, nitrate, and arginine:citrulline. During high-intensity exercise, CF improved neither tissue oxygenation nor performance in well-trained athletes. At rest and during moderate-intensity exercise, CF reduced exercise-induced lipid peroxidation and partially restored the hypoxia-induced decline in prefrontal oxygenation. NEW & NOTEWORTHY For the first time, we showed that CF had beneficial effects on endothelial function at rest, as well as on prefrontal oxygenation at rest and during moderate-intensity exercise, both in normoxia and hypoxia. Moreover, we showed that CF intake inhibited oxidative stress during exhaustive exercise in hypoxia.

Cocoa Flavanol Supplementation and Exercise: A Systematic Review.

BACKGROUND: Cocoa flavanols (CFs) have antioxidant and anti-inflammatory capacities and can improve vascular function. It has recently been suggested that CF intake may improve exercise performance and recovery. This systematic review aimed to evaluate the literature on the effects of CF intake on exercise performance and recovery and exercise-induced changes in vascular function, cognitive function, oxidative stress, inflammation, and metabolic parameters. METHODS: Two electronic databases (Pubmed and Web of Science) were searched for studies examining the combination of CF intake and exercise in humans (up to 28 March 2017). Articles were included if the exact amount of CFs was mentioned. The methodological quality and level of bias of the 13 included studies was assessed according to the checklist for randomized controlled trials from the Dutch Cochrane center. RESULTS: Acute, sub-chronic (2 weeks) and chronic (3 months) CF intake reduced exercise-induced oxidative stress. Evidence on the effect of CF on exercise-induced inflammation and platelet activation was scarce. Acute CF intake reduced and tempered the exercise-induced increase in blood pressure in obese participants. Acute and sub-chronic CF intake altered fat and carbohydrate metabolism during exercise. Acute and sub-chronic CF intake did not have ergogenic effects in athletes, while chronic CF intake improved mitochondrial efficiency in untrained participants. While combining sub-chronic CF intake and exercise training improved cardiovascular risk factors and vascular function, evidence on the synergistic effects of CF and exercise training on oxidative stress, inflammation, and fat and glucose metabolism was lacking. CONCLUSION: CF intake may improve vascular function, reduce exercise-induced oxidative stress, and alter fat and carbohydrate utilization during exercise, but without affecting exercise performance. There is a strong need for future studies examining the synergetic effect of chronic CF intake and exercise training.

Acute cocoa Flavanols intake has minimal effects on exercise-induced oxidative stress and nitric oxide production in healthy cyclists: a randomized controlled trial.

BACKGROUND: Cocoa flavanols (CF) can stimulate vasodilation by improved nitric oxide (NO) synthesis and have antioxidant and anti-inflammatory capacities. This study aimed to examine whether acute CF intake can affect exercise-induced changes in antioxidant capacity, oxidative stress, inflammation and NO production, as well as exercise performance and recovery in well-trained cyclists. METHODS: Twelve well-trained male cyclists (mean ± SD age, VO2max: 30 ± 3 years, 63.0 ± 3.5 ml/kg/min) participated in this randomized, double-blind, cross over study. On 2 separate occasions, subjects performed two 30-min time trials 1.5 (TT1) and 3 (TT2) hours after CF (900 mg CF) or placebo (PL, 13 mg CF) intake, interposed by passive rest. Lactate, glucose, heartrate, rating of perceived exertion (RPE) and power output were measured during the TTs. Blood was drawn at baseline, before and after each TT and analyzed for epicatechin serum concentrations, trolox equivalent antioxidative capacity (TEAC), uric acid (UA), malonaldehyde (MDA), L-arginine/ADMA, citrulline, interleukin (IL)-1, IL-6 and tumor necrosis factor (TNF)-α plasma concentrations. Relative changes in blood markers and pacing strategy during TT were analysed by repeated measured ANOVA. TT performance was compared between PL and CF by paired t-test. RESULTS: Epicatechin concentrations were increased by CF intake. Exercise-induced increase in TEAC/UA was improved by CF intake (F(1) = 5.57; p = .038) (post-TT1: PL: 113.34 ± 3.9%, CF: 117.64 ± 3.96%, post-TT2: PL: 108.59 ± 3.95%, CF: 123.72 ± 7.4% to baseline), while exercise-induced increases in MDA, IL-1 and IL-6 were not affected by CF intake. TNF-α was unaltered by exercise and by CF. Exercise-induced decreases in L-arginine/ADMA and increases in citrulline were not affected by CF intake. TT1 and TT2 performance and exercise-induced physiological changes were unaffected by CF intake. CONCLUSION: Acute CF intake increased total antioxidant capacity in rest and during exercise, but did not affect exercise-induced lipid peroxidation, inflammation, nor NO production in healthy athletes. Acute CF intake did not improve TT performance and recovery. TRIAL REGISTRATION: ISRCTN32875, 21-11-2016, retrospectively registered.

The European Association of Preventive Cardiology Exercise Prescription in Everyday Practice and Rehabilitative Training (EXPERT) tool: A digital training and decision support system for optimized exercise prescription in cardiovascular disease. Concept, definitions and construction methodology.

Background Exercise rehabilitation is highly recommended by current guidelines on prevention of cardiovascular disease, but its implementation is still poor. Many clinicians experience difficulties in prescribing exercise in the presence of different concomitant cardiovascular diseases and risk factors within the same patient. It was aimed to develop a digital training and decision support system for exercise prescription in cardiovascular disease patients in clinical practice: the European Association of Preventive Cardiology Exercise Prescription in Everyday Practice and Rehabilitative Training (EXPERT) tool. Methods EXPERT working group members were requested to define (a) diagnostic criteria for specific cardiovascular diseases, cardiovascular disease risk factors, and other chronic non-cardiovascular conditions, (b) primary goals of exercise intervention, (c) disease-specific prescription of exercise training (intensity, frequency, volume, type, session and programme duration), and (d) exercise training safety advices. The impact of exercise tolerance, common cardiovascular medications and adverse events during exercise testing were further taken into account for optimized exercise prescription. Results Exercise training recommendations and safety advices were formulated for 10 cardiovascular diseases, five cardiovascular disease risk factors (type 1 and 2 diabetes, obesity, hypertension, hypercholesterolaemia), and three common chronic non-cardiovascular conditions (lung and renal failure and sarcopaenia), but also accounted for baseline exercise tolerance, common cardiovascular medications and occurrence of adverse events during exercise testing. An algorithm, supported by an interactive tool, was constructed based on these data. This training and decision support system automatically provides an exercise prescription according to the variables provided. Conclusion This digital training and decision support system may contribute in overcoming barriers in exercise implementation in common cardiovascular diseases.

Association Between Exercise-Induced Hyperthermia and Intestinal Permeability: A Systematic Review.

BACKGROUND: Prolonged and strenuous physical exercise increases intestinal permeability, allowing luminal endotoxins to translocate through the intestinal barrier and reach the bloodstream. When recognized by the immune system, these endotoxins trigger a systemic inflammatory response that may affect physical performance and, in severe cases, induce heat stroke. However, it remains to be elucidated whether there is a relationship between the magnitude of exercise-induced hyperthermia and changes in intestinal permeability. OBJECTIVE: In this systematic review, we evaluated whether an exercise-induced increase in core body temperature (T Core) is associated with an exercise-induced increase in intestinal permeability. METHODS: The present systematic review screened the MEDLINE/PubMed and Web of Science databases in September 2016, without any date restrictions. Sixteen studies that were performed in healthy participants, presented original data, and measured both the exercise-induced changes in T Core and intestinal permeability were selected. These studies assessed intestinal permeability through the measurement of sugar levels in the urine and measurement of intestinal fatty acid binding protein or lipopolysaccharide levels in the blood. RESULTS: Exercise increased both T Core and intestinal permeability in most of the 16 studies. In addition, a positive and strong correlation was observed between the two parameters (r = 0.793; p < 0.001), and a T Core exceeding 39 °C was always associated with augmented permeability. CONCLUSION: The magnitude of exercise-induced hyperthermia is directly associated with the increase in intestinal permeability.

Acute cocoa flavanol improves cerebral oxygenation without enhancing executive function at rest or after exercise.

Acute exercise-induced improvements in cognitive function are accompanied by increased (cerebral) blood flow and increased brain-derived neurotrophic factor (BDNF) levels. Acute cocoa flavanol (CF) intake may improve cognitive function, cerebral blood flow (in humans), and BNDF levels (in animals). This study investigated (i) the effect of CF intake in combination with exercise on cognitive function and (ii) cerebral hemodynamics and BDNF in response to CF intake and exercise. Twelve healthy men participated in this randomized, double-blind, crossover study. Participants performed a cognitive task (CT) at 100 min after acute 903-mg CF or placebo (PL) intake, followed by a 30-min time-trial. Immediately after this exercise, the same CT was performed. Prefrontal near-infrared spectroscopy was applied during CT and exercise to measure changes in oxygenated (ΔHbO2), deoxygenated (ΔHHb), and total haemoglobin (ΔHbtot) and blood samples were drawn and analyzed for BDNF. Reaction time was faster postexercise, but was not influenced by CF. ΔHbO2 during the resting CT was increased by CF, compared with PL. ΔHbO2, ΔHHb, and ΔHbtot increased in response to exercise without any effect of CF. During the postexercise cognitive task, there were no hemodynamic differences between CF or PL. Serum BDNF was increased by exercise, but was not influenced by CF. In conclusion, at rest, CF intake increased cerebral oxygenation, but not BDNF concentrations, and no impact on executive function was detected. This beneficial effect of CF on cerebral oxygenation at rest was overruled by the strong exercise-induced increases in cerebral perfusion and oxygenation.

Effect of Intensive Training on Mood With No Effect on Brain-Derived Neurotrophic Factor.

CONTEXT: Monitoring mood state is a useful tool for avoiding nonfunctional overreaching. Brain-derived neurotrophic factor (BDNF) is implicated in stress-related mood disorders. PURPOSE: To investigate the impact of intensified training-induced mood disturbance on plasma BDNF concentrations at rest and in response to exercise. METHODS: Eight cyclists performed 1 wk of normal (NT), 1 wk of intensified (INT), and 1 wk of recovery (REC) training. Fasted blood samples were collected before and after exercise on day 7 of each training week and analyzed for plasma BDNF and cortisol concentrations. A 24-item Profile of Mood State questionnaire was administered on day 7 of each training week, and global mood score (GMS) was calculated. RESULTS: Time-trial performance was impaired during INT (P = .01) and REC (P = .02) compared with NT. Basal plasma cortisol (NT = 153 ± 16 ng/mL, INT = 130 ± 11 ng/mL, REC = 150 ± 14 ng/ml) and BDNF (NT = 484 ± 122 pg/mL, INT = 488 ± 122 pg/mL, REC = 383 ± 56 pg/mL) concentrations were similar between training conditions. Likewise, similar exercise-induced increases in cortisol and BDNF concentrations were observed between training conditions. GMS was 32% greater during INT vs NT (P < .001). CONCLUSIONS: Consistent with a state of functional overreaching (FOR), impairments in performance and mood state with INT were restored after 1 wk of REC. These results support evidence for mood changes before plasma BDNF concentrations as a biochemical marker of FOR and that cortisol is not a useful marker for predicting FOR.

The influence of a mild thermal challenge and severe hypoxia on exercise performance and serum BDNF.

AIM: To examine the isolated and combined effects of severe hypoxia and a mild thermal challenge on performance, physiological measures, cognition, and serum brain-derived neurotrophic factor (BDNF). METHODS: Nine trained male athletes (age: 23 ± 3 years; W max: 333 ± 45 W) completed four experimental trials (CON: 15 °C/0 m, ALT: 15 °C/3800 m, TEMP: 25 °C/0 m, ALT + TEMP: 25 °C/3800 m) in a double blind, randomized, cross-over design. Subjects cycled for 30 min in a self-paced test starting at 75% W max, their goal was to 'perform as much work as possible in 30 min.' Power output, heart rate, blood lactate, pulse oximetry, core and skin temperature, thermal sensation, ratings of perceived exertion, reaction time (RT), and BDNF were assessed. RESULTS: The amount of work produced in 30 min was reduced by temperature (F(1,8) = 7.1; p = 0.029; 360 ± 19 kJ in 15 °C; 344 ± 18 kJ in 25 °C) and altitude (F(1,8) = 94.2; p < 0.001; 427 ± 24 kJ at sea level; 277 ± 15 kJ at altitude), yet there was no interaction effect. Altitude increased mean RT (F(1,8) = 8.0; p = 0.022; 281.9 ± 9.4 ms at sea level; 289.3 ± 10.0 ms at altitude) and RT variability (F(1,8) = 8.5; p = 0.020; 44 ± 3 ms at sea level: 50 ± 4 ms at altitude). Exercise increased BDNF (F(1,8) = 15.2; p = 0.005; PRE: 21.8 ± 1.3 ng/mL; POST: 26.5 ± 2.1 ng/mL). CONCLUSION: Exercise capacity was significantly reduced due to an increase in altitude (3800 m; -34.3%) or a 10 °C increase in ambient temperature (-3.2%). The combination of both stressors showed to be additive (-38.0 %). Altitude induced an increase in RT and RT variability presenting a deterioration in cognitive functioning during acute hypoxia. Exercise significantly increased BDNF, but no effect of altitude on the BDNF concentration was observed.

Neurotrophins and cognitive functions in T1D compared with healthy controls: effects of a high-intensity exercise.

Exercise is known to have beneficial effects on cognitive function. This effect is greatly favored by an exercise-induced increase in neurotrophic factors, such as brain-derived neurotrophic factor (BDNF) and insulin-like growth factor-1 (IGF-1), especially with high-intensity exercises (HIE). As a complication of type 1 diabetes (T1D), a cognitive decline may occur, mostly ascribed to hypoglycaemia and chronic hyperglycaemia. Therefore, the purpose of this study was to examine the effects of acute HIE on cognitive function and neurotrophins in T1D and matched controls. Ten trained T1D (8 males, 2 females) participants and their matched (by age, sex, fitness level) controls were evaluated on 2 occasions after familiarization: a maximal test to exhaustion and an HIE bout (10 intervals of 60 s at 90% of their maximal wattage followed by 60 s at 50 W). Cognitive tests and analyses of serum BDNF, IGF-1, and free insulin were performed before and after HIE and following 30 min of recovery. At baseline, cognitive performance was better in the controls compared with the T1D participants (p < 0.05). After exercise, no significant differences in cognitive performance were detected. BDNF levels were significantly higher and IGF-1 levels were significantly lower in T1D compared with the control group (p < 0.05) at all time points. Exercise increased BDNF and IGF-1 levels in a comparable percentage in both groups (p < 0.05). In conclusion, although resting levels of serum BDNF and IGF-1 were altered by T1D, comparable increasing effects on BDNF and IGF-1 in T1D and healthy participants were found. Therefore, regularly repeating acute HIE could be a promising strategy for brain health in T1D.

Type 1 diabetes-associated cognitive decline: a meta-analysis and update of the current literature.

BACKGROUND: Type 1 diabetes (T1D) can have a significant impact on brain structure and function, which is referred to as T1D-associated cognitive decline (T1DACD). Diabetes duration, early onset disease, and diabetes-associated complications are all proposed as factors contributing to T1DACD. However, there have been no comparisons in T1DACD between children and adults with T1D. To obtain a better insight into the occurrence and effects of T1DACD in T1D, the aim of the present meta-analysis was to investigate differences between children and adults and to analyse factors contributing T1DACD. METHODS: Two electronic databases were consulted: PubMed and ISI Web of Knowledge. Literature published up until the end of 2013 was included in the analysis. Effect sizes (Cohen's d), which are standardized differences between experimental and control groups, were calculated. RESULTS: There was a small to modest decrease in cognitive performance in T1D patients compared with non-diabetic controls. Children with T1D performed worse while testing for executive function, full intelligence quotient (IQ), and motor speed, whereas adults with T1D performed worse while testing the full, verbal and performance IQ, part of the executive function, memory, spatial memory, and motor speed. Episodes of severe hypoglycemia, chronic hyperglycemia, and age of onset can be significant factors influencing cognitive function in T1D. CONCLUSIONS: The findings in the literature suggest that T1DACD is more severe in adults than children, indicating that age and diabetes duration contribute to this T1DACD.

Effects of different types of acute and chronic (training) exercise on glycaemic control in type 1 diabetes mellitus: a meta-analysis.

OBJECTIVE: Exercise has been accepted and generally recommended for the management of type 1 diabetes mellitus (T1D) and for improving the overall quality of life in affected individuals. This meta-analysis was conducted to determine the overall effects of exercise (acute bouts of exercise and chronic exercise [or training]) on acute and chronic glycaemic control in patients with T1D, the effects of different types of exercise on glycaemic control and which conditions are required to obtain these positive effects. METHODS: PubMed, ISI Web of Knowledge and SPORTDiscus™ were consulted to identify studies on T1D and exercise. Cohen's d statistics were used for calculating mean effect sizes (ES) as follows: small d = 0.3, medium d = 0.5 and large d = 0.8. Ninety-five percent confidence intervals (95% CIs) were used to establish the significance of our findings. RESULTS: From a total of 937 studies, 33 that met the inclusion criteria were selected. Nine studies were used to calculate the ES of a single bout of aerobic exercise; 13 studies to calculate the ES of aerobic training; 2 studies to calculate the ES of strength training; 4 studies to calculate the ES of combined (aerobic and strength) training and 6 studies to calculate the ES of high-intensity exercise (HIE) and training. ES for exercise on acute glycaemic control were large, while they were small for chronic glycaemic control. Aerobic exercise, resistance exercise, mixed exercise (aerobic combined with resistance training) and HIE acutely decreased blood glucose levels. To prevent late-onset hypoglycaemic episodes, the use of single bouts of sprints into an aerobic exercise can be recommended. This meta-analysis also showed that a regular exercise training programme has a significant effect on acute and chronic glycaemic control, although not all exercise forms showed significant results. Specifically, aerobic training is a favourable tool for decreasing chronic glycaemic control, while resistance training, mixed and HIE did not significantly improve chronic glycaemic control. Although, this meta-analysis showed there was a tendency for improvement in glycaemic control due to resistance training or resistance training combined with endurance training, there were not enough studies and/or subjects to confirm this statistically. CONCLUSIONS: Based on this meta-analysis, we can conclude that the addition of brief bouts of high-intensity, sprint-type exercise to aerobic exercise can minimize the risk of sustaining a hypoglycaemic episode. We can also conclude that only regular aerobic training will improve the glycated haemoglobin level of a patient with T1D.