A Ginástica Rítmica é praticada, em quase toda sua totalidade, por meninas, para as quais a iniciação esportiva ocorre de forma precoce. A magreza é uma característica muito prevalente nas atletas, devido às restrições calóricas realizadas, as quais podem afetar o equilíbrio hídrico. Além disso, as sessões de treino são longas (3-4 horas diárias), podendo ocasionar uma não recuperação adequada entre as sessões de treino e competições. Por conseguinte, a combinação da restrição de alimentos com a perda hídrica pela sudorese e as longas sessões de treino pode acentuar a desidratação e, de maneira adversa, prejudicar as respostas fisiológicas, o desempenho e o conforto térmico dos treinos. Objetivo: Comparar respostas fisiológicas e perceptivas de meninas atletas de ginástica rítmica entre uma sessão de treino sem hidratação, e outra com hidratação controlada. Métodos: Quatorze meninas atletas de Ginástica Rítmica que treinavam no período de aproximadamente um ano. Nenhuma tinha diagnóstico de doença crônica ou fazia uso de medicamentos. Elas foram avaliadas em duas sessões de treino (105 minutos cada), uma com hidratação controlada (CH) e outra sem hidratação (SH). A frequência cardíaca (FC), taxa de percepção de esforço (TPE), sensação térmica (ST), conforto térmico (CT) e irritabilidade (IR) foram mensuradas periodicamente. A sudorese foi avaliada, a cada sessão de treino,mediante coleta de uma amostra de suor para análise da concentração de eletrólitos (Na+, Cl- e K+). Foram realizados o teste de força máxima (dinamometria) e o teste do tempo de reação pré e pós sessão de treino. Para a revisão da literatura, foram selecionados 42 artigos nas bases de dados SciELO, Scopus e PubMed com as palavras-chave: hydration, sweating, exercise, children, RhythmicGymnastics, youngathlete. Resultados: Todas as atletas iniciaram as sessões de treino em similares condições de hidratação (hipohidratação mínima), conforme parâmetros urinários. Na sessão de treino CH,encontrou-se um percentual de desidratação de 0,07%, enquanto que na sessão de treino SH esse foi de 1,15%. A força diminuiu na sessão SH (p=0,013), enquanto que nenhuma modificação ocorreu no teste de reação em ambas as sessões. A TPE no minuto 25 foi maior na sessão de treino SH. A ST, no minuto 105, foi maior na sessão SH. O CT e a IR foram similares entre as sessões. Observou-se maior concentração de Na+ na urina na sessão de treino SH. Um grau de hipohidratação acima de 1% pode prejudicar componentes da aptidão física, do conforto térmico, assim como a motivação e a cognição, repercutindo no desempenho do atleta em treinos e competições. Conclusão: A hidratação é essencial para garantir o desempenho e a saúde dos jovens atletas. É necessário que ocorra hipohidratação antes, durante, e após os treinos e competições. Em suma, a maioria dos jovens atletas não consegue ingerir a quantidade necessária para evitar a desidratação. / The Rhythmic Gymnastics is practiced, in almost its totality, by girls, for whom the sports initiation starts early. Thinness is a prevalent characteristic in athletes, due to the caloric restrictions made, that can affect the water balance. Moreover, the training sessions are long (3-4 hours daily), which could cause a non adequate recovery between training sessions and competitions. Thus, the combination of food restriction with the water loss by sweating and the long training sessions can enhance dehydration and, adversely, impair the physiological responses, the performance and the thermal comfort from training. Aim: Compare physiological responses and perceptions of girls athletes of Rhythmic Gymnastics between one training session without hydration and other with controlled hydration. Methods: Fourteen girls athletes of Rhythmic Gymnastics who trained during a period of approximately one year. None of them had a diagnosis of chronic disease or made use of medicaments. They were evaluated in two training sessions (105 minutes each), one with controlled hydration (CH) and other without hydration (WH). The heart rate (HR), rate of perceived exertion (RPE), thermal sensation (TS), thermal comfort (TC) and irritability (IR) were measured periodically. The sweating was evaluated, in each training session, by collecting a sample of sweat to analyze the concentration of electrolytes (Na+, Cl- e K+). The maximal strength test (dynamometry) and the test of reaction time pre and post training session were performed. To literature review, were selected 42 articles in data base ScIELO, Scopus and PubMed with the keywords: hydration,sweating, exercise, children, RhythmicGymnastics, youngathlete. Results: All athletes started training sessions in similar conditions of hydration (minimal hypohydration), according to urinary parameters. In CH training session, we find a dehydration percentage of 0,07%, while in training session WH was 1,15%. The strength decreased in WS session (p=0,013), while no modification occurred in reaction test in both sessions. The RPE on minute 25 was higher than in training session WH. The TS, on minute 105, was higher in session WH. The TC and the IR were similar between sessions. Greater concentration of Na+ in urine was observed in training session WH. A hypohydration degree above 1% can harm components of physical fitness, thermal comfort, as motivation and cognition, impacting the athlete performance in training and competition. Conclusion: Hydration is essential to ensure the young athletes performance and health. In short, majority young athletes can’t ingest a necessary amount to avoid dehydration.

Estratégias de aclimatização ao calor e recomendações de segurança à saúde para crianças e jovens que se exercitam no calor são enfatizadas na literatura, devido principalmente à limitação da perda de calor pela sudorese, em comparação aos adultos; e acredita-se que, nos meninos obesos, essa resposta possa ser mais prejudicada. Aspectos relacionados à termorregulação e à sudorese, além de recomendações para a prática prolongada de exercícios no calor, em crianças e jovens, incluindo obesos, foram revisados na literatura; e um estudo experimental foi realizado. Objetivo: Comparar a temperatura retal (Tretal), a sudorese e a sensação subjetiva de calor (SSC) entre meninos púberes obesos e não-obesos que pedalam em uma similar intensidade relativa de esforço e na mesma condição ambiental. Métodos: No estudo experimental, meninos púberes fisicamente ativos foram alocados em dois grupos (obesos, n = 17; e não-obesos, n = 16). Ambos pedalaram dentro de uma câmara ambiental (35°C, 40-45% UR) por 30 min, a 50-60% do VO2pico; e, após 10 min de repouso, pedalaram até a exaustão (90% do VO2pico). A Tretal, a frequência cardíaca (FC), a sudorese, a taxa de percepção de esforço (TPE) e a SSC foram avaliadas durante os 30 min de pedalada; e a Tretal e a FC, durante a pedalada mais intensa. Resultados: O aumento da Tretal e da FC, assim como as respostas da sudorese foram similares entre os grupos, durante os 30 min de pedalada. A TPE foi maior nos obesos dos 25 aos 30 min de pedalada; e a SSC, durante os 30 min de pedalada. Obesos pedalaram intensamente (90% do VO2pico) por menos tempo que os não-obesos, e a ΔTretal foi maior nos não-obesos. Conclusão: A prescrição do exercício nas condições do protocolo seguido no presente estudo pode ser fisiologicamente segura para meninos púberes obesos fisicamente ativos e aclimatizados ao calor; mas não generalizadas a meninos obesos sedentários e/ou não-aclimatizados ao calor. O maior desconforto térmico dos meninos obesos ressalta a importância das mensurações subjetivas no auxílio à escolha da modalidade de exercício mais adequada para os meses do verão, o que pode prevenir riscos de doenças relacionadas ao calor. / Strategies of acclimatization to the heat and health safety recommendations for children and adolescents exercising in the heat are emphasized in the literature, particularly due to the limitation of heat loss through sweating as compared to adults; moreover, it is thought that this response may be impaired in obese children. Aspects relevant to thermoregulation and sweating, as well as recommendations for the prolonged practice of exercises in the heat by children and adolescents, including obese ones, were reviewed in the literature, and an experimental trial was performed. Aim: To compare the rectal temperature (Trect), sweat rate, and subjective sensation of heat (SSH) between obese and non-obese pubertal boys who cycled at a similar relative effort intensity and in the same environmental conditions. Methods: In the experimental trial, physically active pubertal boys were placed in two groups (obese, n = 17; and non-obese, n = 16). Both cycled inside an environmental chamber (35°C, 40-45% RH) for 30 min. at 50-60% VO2peak, rested for 10 min., and then cycled to exhaustion (90% VO2peak). Trect, heart rate (HR), sweat rate, rate of perceived exertion (RPE) and subjective sensation of heat (SSH) were assessed during the 30 min. of cycling; and Trect and HR during the most intense cycling. Results: The increase in Trect and HR as well as the sweating responses were similar between the groups during the 30-minute cycling. The RPE was greater in the obese at 25-30 minutes of cycling; and the SSH throughout the 30 minutes. The obese cycled intensely (90% VO2peak) for shorter than the non-obese, and Trect was greater in the non-obese. Conclusion: The prescription of exercise in the protocol conditions used in the present study may be physiologically safe for physically active, heat acclimated obese pubertal boys, but it cannot be generalized to obese boys who are sedentary and/or non-acclimated to the heat. The greatest thermal discomfort of obese boys highlights the importance of including subjective assessments in selecting the most suitable exercise modality for the summer months, which may avoid risks and prevent heat-related disorders.

A Ginástica Rítmica é praticada, em quase toda sua totalidade, por meninas, para as quais a iniciação esportiva ocorre de forma precoce. A magreza é uma característica muito prevalente nas atletas, devido às restrições calóricas realizadas, as quais podem afetar o equilíbrio hídrico. Além disso, as sessões de treino são longas (3-4 horas diárias), podendo ocasionar uma não recuperação adequada entre as sessões de treino e competições. Por conseguinte, a combinação da restrição de alimentos com a perda hídrica pela sudorese e as longas sessões de treino pode acentuar a desidratação e, de maneira adversa, prejudicar as respostas fisiológicas, o desempenho e o conforto térmico dos treinos. Objetivo: Comparar respostas fisiológicas e perceptivas de meninas atletas de ginástica rítmica entre uma sessão de treino sem hidratação, e outra com hidratação controlada. Métodos: Quatorze meninas atletas de Ginástica Rítmica que treinavam no período de aproximadamente um ano. Nenhuma tinha diagnóstico de doença crônica ou fazia uso de medicamentos. Elas foram avaliadas em duas sessões de treino (105 minutos cada), uma com hidratação controlada (CH) e outra sem hidratação (SH). A frequência cardíaca (FC), taxa de percepção de esforço (TPE), sensação térmica (ST), conforto térmico (CT) e irritabilidade (IR) foram mensuradas periodicamente. A sudorese foi avaliada, a cada sessão de treino,mediante coleta de uma amostra de suor para análise da concentração de eletrólitos (Na+, Cl- e K+). Foram realizados o teste de força máxima (dinamometria) e o teste do tempo de reação pré e pós sessão de treino. Para a revisão da literatura, foram selecionados 42 artigos nas bases de dados SciELO, Scopus e PubMed com as palavras-chave: hydration, sweating, exercise, children, RhythmicGymnastics, youngathlete. Resultados: Todas as atletas iniciaram as sessões de treino em similares condições de hidratação (hipohidratação mínima), conforme parâmetros urinários. Na sessão de treino CH,encontrou-se um percentual de desidratação de 0,07%, enquanto que na sessão de treino SH esse foi de 1,15%. A força diminuiu na sessão SH (p=0,013), enquanto que nenhuma modificação ocorreu no teste de reação em ambas as sessões. A TPE no minuto 25 foi maior na sessão de treino SH. A ST, no minuto 105, foi maior na sessão SH. O CT e a IR foram similares entre as sessões. Observou-se maior concentração de Na+ na urina na sessão de treino SH. Um grau de hipohidratação acima de 1% pode prejudicar componentes da aptidão física, do conforto térmico, assim como a motivação e a cognição, repercutindo no desempenho do atleta em treinos e competições. Conclusão: A hidratação é essencial para garantir o desempenho e a saúde dos jovens atletas. É necessário que ocorra hipohidratação antes, durante, e após os treinos e competições. Em suma, a maioria dos jovens atletas não consegue ingerir a quantidade necessária para evitar a desidratação. / The Rhythmic Gymnastics is practiced, in almost its totality, by girls, for whom the sports initiation starts early. Thinness is a prevalent characteristic in athletes, due to the caloric restrictions made, that can affect the water balance. Moreover, the training sessions are long (3-4 hours daily), which could cause a non adequate recovery between training sessions and competitions. Thus, the combination of food restriction with the water loss by sweating and the long training sessions can enhance dehydration and, adversely, impair the physiological responses, the performance and the thermal comfort from training. Aim: Compare physiological responses and perceptions of girls athletes of Rhythmic Gymnastics between one training session without hydration and other with controlled hydration. Methods: Fourteen girls athletes of Rhythmic Gymnastics who trained during a period of approximately one year. None of them had a diagnosis of chronic disease or made use of medicaments. They were evaluated in two training sessions (105 minutes each), one with controlled hydration (CH) and other without hydration (WH). The heart rate (HR), rate of perceived exertion (RPE), thermal sensation (TS), thermal comfort (TC) and irritability (IR) were measured periodically. The sweating was evaluated, in each training session, by collecting a sample of sweat to analyze the concentration of electrolytes (Na+, Cl- e K+). The maximal strength test (dynamometry) and the test of reaction time pre and post training session were performed. To literature review, were selected 42 articles in data base ScIELO, Scopus and PubMed with the keywords: hydration,sweating, exercise, children, RhythmicGymnastics, youngathlete. Results: All athletes started training sessions in similar conditions of hydration (minimal hypohydration), according to urinary parameters. In CH training session, we find a dehydration percentage of 0,07%, while in training session WH was 1,15%. The strength decreased in WS session (p=0,013), while no modification occurred in reaction test in both sessions. The RPE on minute 25 was higher than in training session WH. The TS, on minute 105, was higher in session WH. The TC and the IR were similar between sessions. Greater concentration of Na+ in urine was observed in training session WH. A hypohydration degree above 1% can harm components of physical fitness, thermal comfort, as motivation and cognition, impacting the athlete performance in training and competition. Conclusion: Hydration is essential to ensure the young athletes performance and health. In short, majority young athletes can’t ingest a necessary amount to avoid dehydration.

Estratégias de aclimatização ao calor e recomendações de segurança à saúde para crianças e jovens que se exercitam no calor são enfatizadas na literatura, devido principalmente à limitação da perda de calor pela sudorese, em comparação aos adultos; e acredita-se que, nos meninos obesos, essa resposta possa ser mais prejudicada. Aspectos relacionados à termorregulação e à sudorese, além de recomendações para a prática prolongada de exercícios no calor, em crianças e jovens, incluindo obesos, foram revisados na literatura; e um estudo experimental foi realizado. Objetivo: Comparar a temperatura retal (Tretal), a sudorese e a sensação subjetiva de calor (SSC) entre meninos púberes obesos e não-obesos que pedalam em uma similar intensidade relativa de esforço e na mesma condição ambiental. Métodos: No estudo experimental, meninos púberes fisicamente ativos foram alocados em dois grupos (obesos, n = 17; e não-obesos, n = 16). Ambos pedalaram dentro de uma câmara ambiental (35°C, 40-45% UR) por 30 min, a 50-60% do VO2pico; e, após 10 min de repouso, pedalaram até a exaustão (90% do VO2pico). A Tretal, a frequência cardíaca (FC), a sudorese, a taxa de percepção de esforço (TPE) e a SSC foram avaliadas durante os 30 min de pedalada; e a Tretal e a FC, durante a pedalada mais intensa. Resultados: O aumento da Tretal e da FC, assim como as respostas da sudorese foram similares entre os grupos, durante os 30 min de pedalada. A TPE foi maior nos obesos dos 25 aos 30 min de pedalada; e a SSC, durante os 30 min de pedalada. Obesos pedalaram intensamente (90% do VO2pico) por menos tempo que os não-obesos, e a ΔTretal foi maior nos não-obesos. Conclusão: A prescrição do exercício nas condições do protocolo seguido no presente estudo pode ser fisiologicamente segura para meninos púberes obesos fisicamente ativos e aclimatizados ao calor; mas não generalizadas a meninos obesos sedentários e/ou não-aclimatizados ao calor. O maior desconforto térmico dos meninos obesos ressalta a importância das mensurações subjetivas no auxílio à escolha da modalidade de exercício mais adequada para os meses do verão, o que pode prevenir riscos de doenças relacionadas ao calor. / Strategies of acclimatization to the heat and health safety recommendations for children and adolescents exercising in the heat are emphasized in the literature, particularly due to the limitation of heat loss through sweating as compared to adults; moreover, it is thought that this response may be impaired in obese children. Aspects relevant to thermoregulation and sweating, as well as recommendations for the prolonged practice of exercises in the heat by children and adolescents, including obese ones, were reviewed in the literature, and an experimental trial was performed. Aim: To compare the rectal temperature (Trect), sweat rate, and subjective sensation of heat (SSH) between obese and non-obese pubertal boys who cycled at a similar relative effort intensity and in the same environmental conditions. Methods: In the experimental trial, physically active pubertal boys were placed in two groups (obese, n = 17; and non-obese, n = 16). Both cycled inside an environmental chamber (35°C, 40-45% RH) for 30 min. at 50-60% VO2peak, rested for 10 min., and then cycled to exhaustion (90% VO2peak). Trect, heart rate (HR), sweat rate, rate of perceived exertion (RPE) and subjective sensation of heat (SSH) were assessed during the 30 min. of cycling; and Trect and HR during the most intense cycling. Results: The increase in Trect and HR as well as the sweating responses were similar between the groups during the 30-minute cycling. The RPE was greater in the obese at 25-30 minutes of cycling; and the SSH throughout the 30 minutes. The obese cycled intensely (90% VO2peak) for shorter than the non-obese, and Trect was greater in the non-obese. Conclusion: The prescription of exercise in the protocol conditions used in the present study may be physiologically safe for physically active, heat acclimated obese pubertal boys, but it cannot be generalized to obese boys who are sedentary and/or non-acclimated to the heat. The greatest thermal discomfort of obese boys highlights the importance of including subjective assessments in selecting the most suitable exercise modality for the summer months, which may avoid risks and prevent heat-related disorders.

A Ginástica Rítmica é praticada, em quase toda sua totalidade, por meninas, para as quais a iniciação esportiva ocorre de forma precoce. A magreza é uma característica muito prevalente nas atletas, devido às restrições calóricas realizadas, as quais podem afetar o equilíbrio hídrico. Além disso, as sessões de treino são longas (3-4 horas diárias), podendo ocasionar uma não recuperação adequada entre as sessões de treino e competições. Por conseguinte, a combinação da restrição de alimentos com a perda hídrica pela sudorese e as longas sessões de treino pode acentuar a desidratação e, de maneira adversa, prejudicar as respostas fisiológicas, o desempenho e o conforto térmico dos treinos. Objetivo: Comparar respostas fisiológicas e perceptivas de meninas atletas de ginástica rítmica entre uma sessão de treino sem hidratação, e outra com hidratação controlada. Métodos: Quatorze meninas atletas de Ginástica Rítmica que treinavam no período de aproximadamente um ano. Nenhuma tinha diagnóstico de doença crônica ou fazia uso de medicamentos. Elas foram avaliadas em duas sessões de treino (105 minutos cada), uma com hidratação controlada (CH) e outra sem hidratação (SH). A frequência cardíaca (FC), taxa de percepção de esforço (TPE), sensação térmica (ST), conforto térmico (CT) e irritabilidade (IR) foram mensuradas periodicamente. A sudorese foi avaliada, a cada sessão de treino,mediante coleta de uma amostra de suor para análise da concentração de eletrólitos (Na+, Cl- e K+). Foram realizados o teste de força máxima (dinamometria) e o teste do tempo de reação pré e pós sessão de treino. Para a revisão da literatura, foram selecionados 42 artigos nas bases de dados SciELO, Scopus e PubMed com as palavras-chave: hydration, sweating, exercise, children, RhythmicGymnastics, youngathlete. Resultados: Todas as atletas iniciaram as sessões de treino em similares condições de hidratação (hipohidratação mínima), conforme parâmetros urinários. Na sessão de treino CH,encontrou-se um percentual de desidratação de 0,07%, enquanto que na sessão de treino SH esse foi de 1,15%. A força diminuiu na sessão SH (p=0,013), enquanto que nenhuma modificação ocorreu no teste de reação em ambas as sessões. A TPE no minuto 25 foi maior na sessão de treino SH. A ST, no minuto 105, foi maior na sessão SH. O CT e a IR foram similares entre as sessões. Observou-se maior concentração de Na+ na urina na sessão de treino SH. Um grau de hipohidratação acima de 1% pode prejudicar componentes da aptidão física, do conforto térmico, assim como a motivação e a cognição, repercutindo no desempenho do atleta em treinos e competições. Conclusão: A hidratação é essencial para garantir o desempenho e a saúde dos jovens atletas. É necessário que ocorra hipohidratação antes, durante, e após os treinos e competições. Em suma, a maioria dos jovens atletas não consegue ingerir a quantidade necessária para evitar a desidratação. / The Rhythmic Gymnastics is practiced, in almost its totality, by girls, for whom the sports initiation starts early. Thinness is a prevalent characteristic in athletes, due to the caloric restrictions made, that can affect the water balance. Moreover, the training sessions are long (3-4 hours daily), which could cause a non adequate recovery between training sessions and competitions. Thus, the combination of food restriction with the water loss by sweating and the long training sessions can enhance dehydration and, adversely, impair the physiological responses, the performance and the thermal comfort from training. Aim: Compare physiological responses and perceptions of girls athletes of Rhythmic Gymnastics between one training session without hydration and other with controlled hydration. Methods: Fourteen girls athletes of Rhythmic Gymnastics who trained during a period of approximately one year. None of them had a diagnosis of chronic disease or made use of medicaments. They were evaluated in two training sessions (105 minutes each), one with controlled hydration (CH) and other without hydration (WH). The heart rate (HR), rate of perceived exertion (RPE), thermal sensation (TS), thermal comfort (TC) and irritability (IR) were measured periodically. The sweating was evaluated, in each training session, by collecting a sample of sweat to analyze the concentration of electrolytes (Na+, Cl- e K+). The maximal strength test (dynamometry) and the test of reaction time pre and post training session were performed. To literature review, were selected 42 articles in data base ScIELO, Scopus and PubMed with the keywords: hydration,sweating, exercise, children, RhythmicGymnastics, youngathlete. Results: All athletes started training sessions in similar conditions of hydration (minimal hypohydration), according to urinary parameters. In CH training session, we find a dehydration percentage of 0,07%, while in training session WH was 1,15%. The strength decreased in WS session (p=0,013), while no modification occurred in reaction test in both sessions. The RPE on minute 25 was higher than in training session WH. The TS, on minute 105, was higher in session WH. The TC and the IR were similar between sessions. Greater concentration of Na+ in urine was observed in training session WH. A hypohydration degree above 1% can harm components of physical fitness, thermal comfort, as motivation and cognition, impacting the athlete performance in training and competition. Conclusion: Hydration is essential to ensure the young athletes performance and health. In short, majority young athletes can’t ingest a necessary amount to avoid dehydration.

Abstract Parkinson's disease (PD) is known to affect both the extrapyramidal system and the autonomic nervous system even in the early phases of the disease. This study was designed to evaluate cardiovascular autonomic regulation in early PD by measuring heart rate (HR) variability from 24-hour ECG recordings. The dynamics of blood pressure (BP), HR and sweating in patients with and without wearing-off were assessed during clinical observations after a morning dose of levodopa. In patients with wearing-off the tests were repeated after selegiline withdrawal. The power spectral components of HR variability and the SD1 value of the Poincaré analysis that quantifies the short-term beat-to-beat variability were suppressed at night in the PD patients. During the daytime only the SD1 of the Poincaré was suppressed. The results indicate impairment of parasympathetic cardiovascular regulation in untreated patients with PD. The dysfunction was more pronounced at night and in patients with more severe PD. The patients with wearing-off had fluctuation of BP during the observation period, BP increasing when the motor performance worsened and vice versa (p < 0.001). The patients without wearing-off did not show fluctuation of BP. Sweating increased during the observation period, and reached its maximum level at the time of the highest UPDRS motor score phase (off-stage) in patients with wearing-off, but in the patients without wearing-off no changes in sweating were observed. Sweating of the hands was significantly higher in PD patients with motor fluctuations than in those without. Selegiline withdrawal decreased systolic BP significantly during the on-stage in a supine position as well as during the orthostatic test. The initial drop of BP in the orthostatic test was significantly smaller after selegiline withdrawal. The HR and sweating remained unaffected. The results show that the autonomic nervous system is affected in the early phases of PD. The dysfunction becomes more pronounced with the disease progression. Wearing-off type motor fluctuations are associated with fluctuation of BP and sweating and these fluctuations may represent autonomic dysfunction caused by PD, the effect of PD medication, or both. Selegiline withdrawal seems to alleviate the orthostatic reaction in patients with advanced PD.

Abstract Multiple sclerosis (MS) is one of the major causes of disability in the young, mostly affecting people between 20–45 years of age. MS is considered as an autoimmune disorder, characterized by discrete areas of central nervous system inflammation, demyelination and axonal injury. Symptoms related to alterations of the autonomic nervous system are frequent in patients with MS. Bladder dysfunction or impairment of sexual performance is highly distressing for most MS patients, whereas the clinical relevance of other autonomic symptoms is less clear. The present study was designed to clarify the involvement of cardiovascular and sudomotor dysfunctions in patients with MS, to study the sudomotor functions in patients with optic neuritis (optic neuritis being a frequent initial manifestation of MS), and to assess the extent of demyelinative lesions in the CNS by using magnetic resonance imaging and by correlating the findings thus obtained with autonomic nervous system responses. The study showed cardiovascular autonomic regulation failure in MS patients manifesting itself both in the heart rate responses to deep breathing and in the heart rate and blood pressure responses in the tilt table test. In particular, midbrain lesions were found to be associated with cardiovascular dysfunction. MS patients also showed abnormal sympathetic skin responses indicating sudomotor failure. Focal MS lesions in the temporal lobe, in the pons and in the cerebellum were also associated with abnormal sympathetic skin responses. MS patients were also found to have an impairment in thermoregulatory sweating, which seemed to be related to disease severity and to total lesion volume in the brain. Sympathetic skin responses were also abnormal in optic neuritis patients, suggesting sudomotor autonomic failure. Patients with optic neuritis showed no thermoregulatory dysfunction.

This thesis examined why NCAA Division 1 American football “linemen” experience greater heat strain than “backs” during summer training camps. In study #1, exercise at a heat production of 350 W/m2 in a hot environment (Tdb:32.4±1.0ºC; Twb:26.3±0.6ºC) resulted in greater local sweating on the upper body (head, arm, shoulder and chest; all <0.05) and a greater core temperature (P=0.033) in linemen despite a ~25% lower heat production per unit mass (L:6.0±0.5 W/kg; B:8.2±0.8 W/kg). In study #2, greater convective and evaporative heat transfer coefficients (P<0.05) were found in backs during live summer training camp drills, but these did not lead to a greater dry heat transfer or evaporative capacity. However, the maximum metabolic rate per unit mass was lower in linemen due to differences surface area-to-mass ratio. In conclusion, the greater heat strain previously reported in linemen likely arises, in part, from differences in sweating efficiency and body morphology.

Na+/K+-ATPase has been shown to regulate the sweating and cutaneous vascular responses during exercise; however, similar studies have not been conducted to assess the roles of the Na-K-2Cl cotransporter (NKCC) and K+ channels. Additionally, it remains to be determined if these mechanisms underpinning the heat loss responses differ with exercise intensity. Eleven young (24±4 years) males performed three 30-min semi-recumbent cycling bouts at low (30% VO2peak), moderate (50% VO2peak), and high (70% VO2peak) intensity exercise, respectively, each separated by 20-min recovery periods. Using intradermal microdialysis, four forearm skin sites were continuously perfused with either: 1) lactated Ringer solution (Control), 2) 6 mᴍ ouabain (Na+/K+-ATPase inhibitor), 3) 10 mᴍ bumetanide (NKCC inhibitor), or 4) 50 mᴍ BaCl2 (non-specific K+ channel inhibitor); sites at which we assessed local sweat rate (LSR) and cutaneous vascular conductance (CVC). Inhibition of Na+/K+-ATPase attenuated LSR compared to Control during the moderate and high intensity exercise bouts (both P˂0.01), whereas attenuations with NKCC and K+ channel inhibition were only apparent during the high intensity exercise bout (both P≤0.05). Na+/K+-ATPase inhibition augmented CVC during all exercise intensities (all P˂0.01), whereas CVC was greater with NKCC inhibition during the low intensity exercise only (P˂0.01) and attenuated with K+ channel inhibition during the moderate and high intensity exercise conditions (both P˂0.01). We show that Na+/K+-ATPase, NKCC and K+ channels all contribute to the regulation of sweating and cutaneous blood flow but their influence is dependent on the intensity of exercise.

Studies show that vasomotor and sudomotor activity is compromised in individuals with Type 1 Diabetes (T1DM) which could lead to altered thermoregulatory function. However, recent work suggests that the impairments may only be evidenced beyond a certain level of heat stress. We therefore examined T1DM-related differences in heat loss responses of sweating and skin blood flow (SkBF) during exercise performed at progressive increases in the requirement for heat loss. Participants were matched for age, sex, body surface area and fitness cycled at fixed rates of metabolic heat production of 200, 250, and 300 W•m-2 of body surface area, each rate being performed sequentially for 30 min. Local sweat rate (LSR), sweat gland activation (SGA), and sweat gland output (SGO) were measured on the upper back, chest and forearm while SkBF (laser-Doppler) was measured on the forearm and upper back only. We found that despite a similar requirement for heat loss, LSR was lower in T1DM on the chest and forearm only, relative to Control and only different at the end of the second and third exercise periods. Differences in chest LSR were due to reduced SGA whereas the decreased forearm LSR was the result of a decrease in SGO. SkBF did not differ between groups. The reduction in the sweating response in the T1DM group was paralleled by a greater increase in core temperature. We show that T1DM impairs heat dissipation as evidenced by reductions in LSR and not SkBF. A compromised thermoregulatory response during and following physical exertion is of considerable concern due to the associated increased risk of post-exertion heat-related injury.