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PURPOSE: Impaired insulin sensitivity is central in the etiology of type 2 diabetes in people with obesity. The effectiveness of resistance training (RE) alone in improving insulin sensitivity in people with obesity is undetermined. This study aimed to determine the influence of obesity on insulin sensitivity responses to RE. METHODS: Nineteen sedentary men were allocated to Lean (BMI 22.7 ± 2.5 kg m-2; n = 10) or Obese group (BMI 33.2 ± 3.2 kg m-2; n = 9). Participants were evaluated before and after a 10-week supervised progressive RE (3 sets of 10 repetition maximum (RM), 3 d/wk) for insulin sensitivity indexes using an oral glucose tolerance test, body composition using anthropometrics, and strength using 1RM. RESULTS: Groups were matched at baseline for all variables except for body composition and absolute strength. Body fat was not changed in both groups. Matsuda insulin sensitivity index, hepatic insulin resistance, and insulin area under the curve improved by 64.3 ± 61.9 unit, - 58.2 ± 102.9 unit, 2.3 ± 4.1 unit, and - 721.6 ± 858.2 µU/ml, respectively, only in the Lean group. The increased 1RM% for leg press was greater in the Lean (49.5 ± 18.7%) than in the Obese (31.5 ± 13.9), but not different for bench press (18.0 ± 9.1% vs. 16.4 ± 6.0%, respectively). CONCLUSION: Sustained obesity precludes insulin sensitivity improvements and attenuates strength gains in response to progressive RE. Additional strategies such as caloric restriction might be necessary for RE to improve insulin sensitivity, particularly at high levels of obesity.
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Resistência à Insulina , Obesidade , Treinamento Resistido , Humanos , Masculino , Resistência à Insulina/fisiologia , Treinamento Resistido/métodos , Obesidade/fisiopatologia , Obesidade/terapia , Adulto , Força Muscular/fisiologia , Composição Corporal/fisiologiaRESUMO
The rise of artificial intelligence (AI) applications in healthcare provides new possibilities for personalized health management. AI-based fitness applications are becoming more common, facilitating the opportunity for individualised exercise prescription. However, the use of AI carries the risk of inadequate expert supervision, and the efficacy and validity of such applications have not been thoroughly investigated, particularly in the context of diverse health conditions. The aim of the study was to critically assess the efficacy of exercise prescriptions generated by OpenAI's Generative Pre-Trained Transformer 4 (GPT-4) model for five example patient profiles with diverse health conditions and fitness goals. Our focus was to assess the model's ability to generate exercise prescriptions based on a singular, initial interaction, akin to a typical user experience. The evaluation was conducted by leading experts in the field of exercise prescription. Five distinct scenarios were formulated, each representing a hypothetical individual with a specific health condition and fitness objective. Upon receiving details of each individual, the GPT-4 model was tasked with generating a 30-day exercise program. These AI-derived exercise programs were subsequently subjected to a thorough evaluation by experts in exercise prescription. The evaluation encompassed adherence to established principles of frequency, intensity, time, and exercise type; integration of perceived exertion levels; consideration for medication intake and the respective medical condition; and the extent of program individualization tailored to each hypothetical profile. The AI model could create general safety-conscious exercise programs for various scenarios. However, the AI-generated exercise prescriptions lacked precision in addressing individual health conditions and goals, often prioritizing excessive safety over the effectiveness of training. The AI-based approach aimed to ensure patient improvement through gradual increases in training load and intensity, but the model's potential to fine-tune its recommendations through ongoing interaction was not fully satisfying. AI technologies, in their current state, can serve as supplemental tools in exercise prescription, particularly in enhancing accessibility for individuals unable to access, often costly, professional advice. However, AI technologies are not yet recommended as a substitute for personalized, progressive, and health condition-specific prescriptions provided by healthcare and fitness professionals. Further research is needed to explore more interactive use of AI models and integration of real-time physiological feedback.
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Introduction: Despite decades of research, obesity and its related medical complications remain a major health concern globally. Therefore, novel therapeutic strategies are needed to combat obesity and its numerous debilitating complications. Resveratrol (RES) has a potential therapeutic effect in obesity and diabetes by improving oxidative metabolism and insulin signaling. Background and Objectives: The aim of this study was to investigate the effect of RES treatment on weight loss and glucose and fatty acid metabolism. Methods: Obesity was induced in 24 mice by exposure to a high-fat diet (HFD) for 8 weeks. Mice were randomly assigned to one group of either: group 1: control, non-treated low-fat diet (LFD) for 12 weeks (n = 8), group 2: non-treated high-fat diet (HFD) for 12 weeks (n = 8), group 3: RES-treated HFD (HFD + RES) (n = 8), or group 4: RES-treated and switched to LFD (HFD-LFD + RES) (n = 8). HFD + RES mice were first fed an HFD for 8 weeks followed by 4 weeks of RES. The HFD-LFD + RES group was first fed an HFD for 8 weeks and then treated with RES and switched to an LFD for 4 weeks. Results: After 12 weeks, group 2 mice had significantly higher body weights compared to group 1 (23.71 ± 1.95 vs. 47.83 ± 2.27; p < 0.05). Group 4 had a significant decrease in body weight and improvement in glucose tolerance compared to mice in group 2 (71.3 ± 1.17 vs. 46.1 ± 1.82 and 40.9 ± 1.75, respectively; p < 0.05). Skeletal muscles expression of SIRT1, SIRT3, and PGC1α were induced in group 3 and 4 mice compared to group 2 (p < 0.01), with no changes in AMP-activated protein kinase expression levels. Furthermore, combination of RES and diet ameliorated skeletal muscle intermediate lipid accumulation and significantly improved insulin sensitivity and secretion. Conclusions: The results of this study suggest a synergistic beneficial effect of LFD and RES to lower body weight and enhance glucose and fatty acid metabolism.
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Dieta Hiperlipídica , Sirtuína 3 , Proteínas Quinases Ativadas por AMP/metabolismo , Animais , Peso Corporal , Dieta Hiperlipídica/efeitos adversos , Ácidos Graxos/metabolismo , Glucose , Insulina/metabolismo , Lipídeos , Camundongos , Obesidade/tratamento farmacológico , Obesidade/metabolismo , Coativador 1-alfa do Receptor gama Ativado por Proliferador de Peroxissomo/metabolismo , Resveratrol/farmacologia , Resveratrol/uso terapêutico , Sirtuína 1/metabolismo , Sirtuína 3/metabolismoRESUMO
This study investigated the changes in myocardial myosin heavy chain (MHC) isoforms, MHC-α and MHC-ß composition in young healthy rodents following endurance training, with and without post-exercise cold-water immersion (CWI). Male rats were either trained on a treadmill for 10 weeks with (CWI) or without (Ex) regular CWI after each running session, or left sedentary (CON). Left ventricular mRNA of MHC-α, MHC-ß, thyroid receptor α1 (TR-α1) and ß (TR-ß) were analyzed using rt-PCR and semiquantitative PCR analysis. MHC isoform protein composition was determined using SDS-PAGE electrophoresis. MHC-α isoform protein was predominant in all groups. The relative expression of MHC-ß (%MHC-ß) protein was not different between groups (CWI 34.7 ± 6.9%; Ex 32 ± 5.3%; CON 35.5 ± 10%; P = 0.7). MHC-ß mRNA was reduced in Ex (0.7 ± 0.3-fold) compared to CWI (1.3 ± 0.2-fold; P < 0.001) and CON (1.01 ± 0.2-fold; P = 0.03). TRα1 mRNA was lower in CWI (0.4 ± 0.05-fold) than Ex (1.02 ± 0.3-fold) and CON (1.01 ± 0.2-fold) (P < 0.001 for both). CWI exhibited greater %MHC-ß mRNA (56.8 ± 4.1%) than Ex (44.4 ± 7.7%; P = 0.001) and CON (48.5 ± 7.8%; P = 0.03). Neither exercise nor post-exercise CWI demonstrated a distinct effect on myocardial MHC protein isoform composition. However, CWI increased the relative expression of MHC-ß mRNA compared with Ex and CON. Although this implicates a potential negative long-term impact of post-exercise CWI, future studies should include measures of cardiac function to better understand the effect of such isoform mRNA shifts following regular use of CWI.
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Imersão , Cadeias Pesadas de Miosina , Animais , Masculino , Miocárdio , Cadeias Pesadas de Miosina/genética , Isoformas de Proteínas/genética , Ratos , ÁguaRESUMO
This study investigated the noradrenergic contribution during the cutaneous vasoconstrictor response to local cooling in the leg and forearm. On each limb, one site was perfused with Yoh/Prop to block the postsynaptic adrenoceptors and another with Lactated Ringer's (control) using microdialysis. Blood flow was measured by Laser-Doppler flowmetry (LDF). Cutaneous vascular conductance (CVC) was calculated as LDF units divided by the mean arterial pressure. After baseline measures, skin was locally cooled to 24°C. Basal CVC was similar at all sites in the leg and forearm (all p > 0.1). During the first 10 min of local cooling, CVC was reduced in the leg (p < 0.005) and unchanged in the forearm control sites (p = 0.2). Yoh/Prop induced an increased CVC in the leg and forearm to a similar level (39.2 ± 11.5, and 41.3 ± 3.3%CVC, respectively; p < 0.35). Late during local cooling, the vasoconstriction was attenuated in the leg and forearm at Yoh/Prop (-38.2 ± 5.3 -37.1 ± 5.3%CVC, respectively; p = 0.5) compared to control sites (-69.1 ± 5.8 vs. -54.5 ± 6.4%CVC, respectively; p < 0.005). Noradrenergic contribution was greater in the leg than the forearm during the late vasoconstrictor response (p = 0.006). These data indicate that the leg skin can induce greater vasoconstriction than forearm during local cooling, possibly via higher noradrenergic sensitivity in the leg skin.
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Neurônios Adrenérgicos/fisiologia , Velocidade do Fluxo Sanguíneo/fisiologia , Regulação da Temperatura Corporal/fisiologia , Temperatura Baixa , Temperatura Cutânea/fisiologia , Vasoconstrição/fisiologia , Adulto , Sistema Nervoso Autônomo/fisiologia , Feminino , Antebraço/inervação , Antebraço/fisiologia , Humanos , Perna (Membro)/inervação , Perna (Membro)/fisiologia , MasculinoRESUMO
Background Cisplatin, a widely used chemotherapeutic agent, offers therapeutic benefits for cancer treatment but often leads to adverse effects on neurogenesis and oxidative stress, causing cognitive impairment. Concurrent physical activity has been proposed as a potential strategy to counteract these side effects. This study aimed to investigate the impact of physical exercise on cisplatin-induced cognitive impairment in a mouse model. Methods Adult male mice (n=45) were divided into three groups: control, cisplatin-treated (2.3 mg/kg), and exercise/cisplatin. Cisplatin was administered intraperitoneally over one month, while the exercise/cisplatin group underwent moderate-intensity exercise alongside cisplatin treatment. Spatial memory was evaluated using the novel object recognition (NOR) task, and hippocampal proliferation and oxidative stress were examined using Ki-67 and glutathione peroxidase (GPx) immunohistochemistry (IHC) staining, respectively. Statistical analyses were performed using the GraphPad Prism 4.0 software (GraphPad Software, San Diego, CA). Results The cisplatin-treated mice exhibited significantly lower preference index (PI) scores in the NOR task compared to the control (p<0.001) and exercise/cisplatin (p<0.001) groups. IHC staining revealed impaired hippocampal proliferation and increased oxidative stress in the cisplatin-treated group relative to the control and exercise/cisplatin groups. The introduction of a moderate-intensity exercise protocol appeared to mitigate the decline in hippocampal proliferation and oxidative damage induced by cisplatin. Additionally, cisplatin-treated mice experienced weight loss, while exercise attenuated this effect. Conclusion Cisplatin treatment resulted in decreased memory, hippocampal proliferation, and weight loss in mice. Concurrent moderate-intensity exercise seemed to alleviate these effects, suggesting a potential role for physical activity in ameliorating cisplatin-induced cognitive decline. This study underscores the importance of incorporating exercise as a complementary strategy to enhance cognitive outcomes in cancer patients undergoing cisplatin treatment.
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Objective: We assessed the direct and indirect relationships between sleep quality, mental health, and physical activity with quality of life (QOL) in college and university students. Methods: In a cross-sectional design, 3,380 college students (60% females; age = 22.7 ± 5.4) from four continents (Africa: 32%; America: 5%; Asia: 46%; and Europe: 15%; others: 2%) completed the Pittsburgh Sleep Quality Index (PSQI); Insomnia Severity Index (ISI); Epworth Sleepiness Scale (ESS); the Depression, Anxiety, and Stress Scale 21 (DASS); the International Physical Activity Questionnaire short-form (IPAQ); and the World Health Organization Quality of Life-BREF (WHOQOL-Brief). Results: We showed that sleep quality, insomnia, and depression had direct negative effects on the physical domain of QOL (ß = -0.22, -0.19, -0.31, respectively, p < 0.001). There was a strong negative direct association between depression and the psychological domain of QOL (ß = -0.60, z = -22.21, p < 0.001). Both stress and PSQI had direct effects on social relationships QOL (ß = 0.11; z = 4.09; and ß = -0.13; z = -7.40, respectively, p < 0.001). However, depression had the strongest direct impact on social relationships QOL (ß = -0.41, z = -15.79, p < 0.001). Conclusion: The overall QOL of university students is associated with their sleep quality, mental health, and physical activity warranting further interventional studies aiming at improving students' quality of life.
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Exercício Físico , Saúde Mental , Qualidade de Vida , Qualidade do Sono , Estudantes , Humanos , Feminino , Masculino , Estudantes/psicologia , Estudantes/estatística & dados numéricos , Estudos Transversais , Universidades , Adulto Jovem , Saúde Mental/estatística & dados numéricos , Exercício Físico/psicologia , Inquéritos e Questionários , Adulto , Análise de Classes Latentes , Depressão/epidemiologia , Depressão/psicologia , AdolescenteRESUMO
PURPOSE: To investigate differences in athletes' knowledge, beliefs, and training practices during COVID-19 lockdowns with reference to sport classification and sex. This work extends an initial descriptive evaluation focusing on athlete classification. METHODS: Athletes (12,526; 66% male; 142 countries) completed an online survey (May-July 2020) assessing knowledge, beliefs, and practices toward training. Sports were classified as team sports (45%), endurance (20%), power/technical (10%), combat (9%), aquatic (6%), recreational (4%), racquet (3%), precision (2%), parasports (1%), and others (1%). Further analysis by sex was performed. RESULTS: During lockdown, athletes practiced body-weight-based exercises routinely (67% females and 64% males), ranging from 50% (precision) to 78% (parasports). More sport-specific technical skills were performed in combat, parasports, and precision (â¼50%) than other sports (â¼35%). Most athletes (range: 50% [parasports] to 75% [endurance]) performed cardiorespiratory training (trivial sex differences). Compared to prelockdown, perceived training intensity was reduced by 29% to 41%, depending on sport (largest decline: â¼38% in team sports, unaffected by sex). Some athletes (range: 7%-49%) maintained their training intensity for strength, endurance, speed, plyometric, change-of-direction, and technical training. Athletes who previously trained ≥5 sessions per week reduced their volume (range: 18%-28%) during lockdown. The proportion of athletes (81%) training ≥60 min/session reduced by 31% to 43% during lockdown. Males and females had comparable moderate levels of training knowledge (56% vs 58%) and beliefs/attitudes (54% vs 56%). CONCLUSIONS: Changes in athletes' training practices were sport-specific, with few or no sex differences. Team-based sports were generally more susceptible to changes than individual sports. Policy makers should provide athletes with specific training arrangements and educational resources to facilitate remote and/or home-based training during lockdown-type events.
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COVID-19 , Esportes , Atletas , COVID-19/epidemiologia , COVID-19/prevenção & controle , Controle de Doenças Transmissíveis , Feminino , Humanos , Masculino , Inquéritos e QuestionáriosRESUMO
OBJECTIVE: Our objective was to explore the training-related knowledge, beliefs, and practices of athletes and the influence of lockdowns in response to the coronavirus disease 2019 (COVID-19) pandemic caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). METHODS: Athletes (n = 12,526, comprising 13% world class, 21% international, 36% national, 24% state, and 6% recreational) completed an online survey that was available from 17 May to 5 July 2020 and explored their training behaviors (training knowledge, beliefs/attitudes, and practices), including specific questions on their training intensity, frequency, and session duration before and during lockdown (March-June 2020). RESULTS: Overall, 85% of athletes wanted to "maintain training," and 79% disagreed with the statement that it is "okay to not train during lockdown," with a greater prevalence for both in higher-level athletes. In total, 60% of athletes considered "coaching by correspondence (remote coaching)" to be sufficient (highest amongst world-class athletes). During lockdown, < 40% were able to maintain sport-specific training (e.g., long endurance [39%], interval training [35%], weightlifting [33%], plyometric exercise [30%]) at pre-lockdown levels (higher among world-class, international, and national athletes), with most (83%) training for "general fitness and health maintenance" during lockdown. Athletes trained alone (80%) and focused on bodyweight (65%) and cardiovascular (59%) exercise/training during lockdown. Compared with before lockdown, most athletes reported reduced training frequency (from between five and seven sessions per week to four or fewer), shorter training sessions (from ≥ 60 to < 60 min), and lower sport-specific intensity (~ 38% reduction), irrespective of athlete classification. CONCLUSIONS: COVID-19-related lockdowns saw marked reductions in athletic training specificity, intensity, frequency, and duration, with notable within-sample differences (by athlete classification). Higher classification athletes had the strongest desire to "maintain" training and the greatest opposition to "not training" during lockdowns. These higher classification athletes retained training specificity to a greater degree than others, probably because of preferential access to limited training resources. More higher classification athletes considered "coaching by correspondence" as sufficient than did lower classification athletes. These lockdown-mediated changes in training were not conducive to maintenance or progression of athletes' physical capacities and were also likely detrimental to athletes' mental health. These data can be used by policy makers, athletes, and their multidisciplinary teams to modulate their practice, with a degree of individualization, in the current and continued pandemic-related scenario. Furthermore, the data may drive training-related educational resources for athletes and their multidisciplinary teams. Such upskilling would provide athletes with evidence to inform their training modifications in response to germane situations (e.g., COVID related, injury, and illness).
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COVID-19 , Atletas/psicologia , Controle de Doenças Transmissíveis , Humanos , Pandemias , SARS-CoV-2RESUMO
Objective: Disrupted sleep and training behaviors in athletes have been reported during the COVID-19 pandemic. We aimed at investigating the combined effects of Ramadan observance and COVID-19 related lockdown in Muslim athletes. Methods: From an international sample of athletes (n = 3,911), 1,681 Muslim athletes (from 44 countries; 25.1 ± 8.7 years, 38% females, 41% elite, 51% team sport athletes) answered a retrospective, cross-sectional questionnaire relating to their behavioral habits pre- and during- COVID-19 lockdown, including: (i) Pittsburgh sleep quality index (PSQI); (ii) insomnia severity index (ISI); (iii) bespoke questions about training, napping, and eating behaviors, and (iv) questions related to training and sleep behaviors during-lockdown and Ramadan compared to lockdown outside of Ramadan. The survey was disseminated predominately through social media, opening 8 July and closing 30 September 2020. Results: The lockdown reduced sleep quality and increased insomnia severity (both p < 0.001). Compared to non-Muslim (n = 2,230), Muslim athletes reported higher PSQI and ISI scores during-lockdown (both p < 0.001), but not pre-lockdown (p > 0.05). Muslim athletes reported longer (p < 0.001; d = 0.29) and later (p < 0.001; d = 0.14) daytime naps, and an increase in late-night meals (p < 0.001; d = 0.49) during- compared to pre-lockdown, associated with lower sleep quality (all p < 0.001). Both sleep quality (χ2 = 222.6; p < 0.001) and training volume (χ2 = 342.4; p < 0.001) were lower during-lockdown and Ramadan compared to lockdown outside of Ramadan in the Muslims athletes. Conclusion: Muslim athletes reported lower sleep quality and higher insomnia severity during- compared to pre-lockdown, and this was exacerbated by Ramadan observance. Therefore, further attention to Muslim athletes is warranted when a circadian disrupter (e.g., lockdown) occurs during Ramadan.
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Objective: To investigate the effect of 1) lockdown duration and 2) training intensity on sleep quality and insomnia symptoms in elite athletes. Methods: 1,454 elite athletes (24.1 ± 6.7 years; 42% female; 41% individual sports) from 40 countries answered a retrospective, cross-sectional, web-based questionnaire relating to their behavioral habits pre- and during- COVID-19 lockdown, including: 1) Pittsburgh sleep quality index (PSQI); 2) Insomnia severity index (ISI); bespoke questions about 3) napping; and 4) training behaviors. The association between dependent (PSQI and ISI) and independent variables (sleep, napping and training behaviors) was determined with multiple regression and is reported as semi-partial correlation coefficient squared (in percentage). Results: 15% of the sample spent < 1 month, 27% spent 1-2 months and 58% spent > 2 months in lockdown. 29% self-reported maintaining the same training intensity during-lockdown whilst 71% reduced training intensity. PSQI (4.1 ± 2.4 to 5.8 ± 3.1; mean difference (MD): 1.7; 95% confidence interval of the difference (95% CI): 1.6-1.9) and ISI (5.1 ± 4.7 to 7.7 ± 6.4; MD: 2.6; 95% CI: 2.3-2.9) scores were higher during-compared to pre-lockdown, associated (all p < 0.001) with longer sleep onset latency (PSQI: 28%; ISI: 23%), later bedtime (PSQI: 13%; ISI: 14%) and later preferred time of day to train (PSQI: 9%; ISI: 5%) during-lockdown. Those who reduced training intensity during-lockdown showed higher PSQI (p < 0.001; MD: 1.25; 95% CI: 0.87-1.63) and ISI (p < 0.001; MD: 2.5; 95% CI: 1.72-3.27) scores compared to those who maintained training intensity. Although PSQI score was not affected by the lockdown duration, ISI score was higher in athletes who spent > 2 months confined compared to those who spent < 1 month (p < 0.001; MD: 1.28; 95% CI: 0.26-2.3). Conclusion: Reducing training intensity during the COVID-19-induced lockdown was associated with lower sleep quality and higher insomnia severity in elite athletes. Lockdown duration had further disrupting effects on elite athletes' sleep behavior. These findings could be of relevance in future lockdown or lockdown-like situations (e.g., prolonged illness, injury, and quarantine after international travel).
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Myocardial mitochondrial biogenesis and vascular angiogenesis biomarker responses to postexercise cold-water immersion (CWI) have not been reported. Therefore, to determine those cardiac adaptations, adult male Sprague-Dawley rats were divided into three groups: postexercise CWI (CWI; n = 13), exercise only (Ex; n = 12), and untreated control (CON; n = 10). CWI and Ex were trained for 10 wk, 5 sessions/wk, 30-60 min/session. CWI rats were immersed after each session in cold water (15 min at ~12°C). CON remained sedentary. Left ventricle tissue was obtained 48 h after the last exercise session and analyzed for peroxisome proliferator-activated receptor γ coactivator-1α (PGC-1α), vascular endothelial growth factor (VEGF), and heat shock protein 70 kDa (Hsp70) protein content and mRNA expression levels. In addition, superoxide dismutase activity and mRNA and malondialdehyde levels were evaluated. Ex and CWI induced higher PGC-1α protein content compared with CON (1.8 ± 0.6-fold, P < 0.001), which was significantly higher in CWI than Ex rats (P = 0.01). VEGF protein (4.3 ± 3.7-fold) and mRNA (10.1 ± 1.1-fold) were markedly increased only in CWI (P < 0.001) relative to CON. CWI and Ex augmented cardiac Hsp70 protein to a similar level relative to CON (P < 0.05); however, Hsp70 mRNA increased only in Ex (P = 0.002). No further differences were observed between groups. These results suggest that postexercise CWI may further enhance cardiac oxidative capacity by increasing the angiogenic and mitochondrial biogenic factors. In addition, CWI does not seem to worsen exercise-induced cardioprotection and oxidative stress. NEW & NOTEWORTHY A regular postexercise cold-water immersion for 10 wk of endurance training augmented the myocardial mitochondrial biogenesis and vascular angiogenesis coactivators peroxisome proliferator-activated receptor γ coactivator-1α and vascular endothelial growth factor, respectively. In addition, postexercise cold-water immersion did not attenuate the exercise-induced increase in the cardioprotective biomarker heat shock protein 70 kDa or increase exercise-induced oxidative stress.
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Imersão/fisiopatologia , Coativador 1-alfa do Receptor gama Ativado por Proliferador de Peroxissomo/metabolismo , Condicionamento Físico Animal/fisiologia , Fator A de Crescimento do Endotélio Vascular/metabolismo , Água/fisiologia , Adaptação Fisiológica/fisiologia , Animais , Temperatura Corporal/fisiologia , Temperatura Baixa , Coração/fisiologia , Masculino , Músculo Esquelético/metabolismo , Músculo Esquelético/fisiologia , RNA Mensageiro/metabolismo , Ratos , Ratos Sprague-DawleyRESUMO
BACKGROUND: Heat stress limits endurance exercise performance. Combining precooling and warm-up prior to endurance exercise in the heat may exploit the benefits of both strategies while avoiding the potential negative consequences of each. This study tested the hypothesis that precooling combined with warm-up improves time trial cycling performance in the heat relative to either treatment alone. METHODS: Nine healthy men completed three 16.1-km time trials in 33°C after: 1) precooling (ice slurry and ice vest) alone (PREC); 2) warm-up alone (WU); or 3) PREC plus WU (COMBO). RESULTS: Tre was lower after PREC compared to WU throughout exercise and lower than COMBO for the first 12 km; COMBO was lower than WU for the first 4 km. Tsk during PREC was lower than COMBO and WU for the first 8 km, and lower in COMBO than WU for the first 4 km. PREC lowered pre-exercise heart rate relative to COMBO and WU (68 ± 10, 106 ± 12, 101 ± 13 bpm, respectively), but it increased similarly during exercise. Local sweat rate (SR) was lower in PREC (0.1 ± 0.1 mg · cm-2 · min-1) than COMBO (0.5 ± 0.2 mg · cm-2 · min-1) and WU (0.6 ± 0.2 mg · cm-2 · min-1) for the first 4 km. Treatments did not differentially affect performance (PREC = 31.9 ± 1.9 min, COMBO = 32.6 ± 2.7 min, WU = 33.1 ± 2.9 min). DISCUSSION: We conclude precooling alone or with warm-up mitigated thermal strain during exercise, but did not significantly improve 16.1-km cycling time trial performance.Al-horani RA, Wingo JE, Ng J, Bishop P, Richardson M. Precooling and warm-up effects on time trial cycling during heat stress. Aerosp Med Hum Perform. 2018; 89(2):87-93.