The magnitude of physical exercise-induced hyperthermia is associated with changes in the intestinal permeability and expression of tight junction genes in rats.

We investigated whether the magnitude of exercise-induced hyperthermia influences intestinal permeability and tight junction gene expression. Twenty-nine male Wistar rats were divided into four groups: rest at 24 °C and exercise at 13 °C, 24 °C or 31 °C. The exercise consisted of a 90-min treadmill run at 15 m/min, and different ambient temperatures were used to produce distinct levels of exercise-induced hyperthermia. Before the experimental trials, the rats were treated by gavage with diethylenetriaminepentaacetic acid labeled with technetium-99 metastable as a radioactive probe. The rats' core body temperature (TCORE) was measured by telemetry. Immediately after the trials, the rats were euthanized, and the intestinal permeability was assessed by measuring the radioactivity of blood samples. The mRNA levels of occludin and zonula occludens-1 (ZO-1) genes were determined in duodenum samples. Exercise at 24 °C increased TCORE to values close to 39 °C, without changing permeability compared with the resting trial at the same environment. Meanwhile, rats' TCORE exceeded 40 °C during exercise at 31 °C, leading to greater permeability relative to those observed after exercise in the other ambient temperatures (e.g., 0.0037%/g at 31 °C vs. 0.0005%/g at 13 °C; data expressed as medians; p < 0.05). Likewise, the rats exercised at 31 °C exhibited higher mRNA levels of ZO-1 and occludin genes than the rats exercised at 24 °C or 13 °C. The changes in permeability and gene expression were positively and significantly associated with the magnitude of hyperthermia. We conclude that marked hyperthermia caused by exercise in the warmer environment increases intestinal permeability and mRNA levels of tight junction genes.

A Preliminary Evaluation of the Kidney Function of Sugarcane Cutters From Brazil.

OBJECTIVE: To evaluate clinical parameters, markers of kidney function, and skeletal muscle damage in a group of sugarcane cutters during harvesting season. METHODS: Seventeen volunteers were assessed for anthropometrics and cardiorespiratory fitness. Blood and urine samples were collected 48-hours after the last work session. Blood was analyzed for glucose, creatine kinase, cholesterol, and a complete hemogram. Urine and blood samples were also analyzed for markers related to kidney function. RESULTS: Volunteers were young (26 ±â€Š6 y), had low body fat (13 ±â€Š5%), and good cardiorespiratory fitness (41 ±â€Š6 mL/kg/min). Classical markers of kidney function (eGFR, creatinine, cystatin C) were within the normal range. However, ten volunteers presented elevated resting serum creatine kinase (221 ±â€Š68 U/L). CONCLUSION: Manual sugarcane harvesting is associated with sustained skeletal muscle damage which may increase the risk for kidney injury in Brazilian sugarcane cutters.

Sex-related differences in sweat gland cholinergic sensitivity exist irrespective of differences in aerobic capacity.

Mechanisms accounting for sex-related differences in the sweat response remain to be elucidated. In the present study, we focused on differences in sweat gland cholinergic sensitivity between males and females. Since, males usually possess higher aerobic capacity than females, we investigated sweating in males and females grouped according to aerobic capacity (.VO(2peak)). Forty-four subjects were assigned to four groups: males with higher (MH) and lower (ML), and females with higher (FH) and lower (FL) .VO(2peak). Forearm sweating was induced by iontophoretic administration (1.5 mA, 60 muA cm(-2), 5 min) of pure water or varying concentrations of pilocarpine hydrochloride (0.125, 0.250, 0.5, 1.0 and 2.0%). Local sweat rate (absorbent paper) and the number of activated sweat glands (iodine impregnated paper) were computed. Maximal pilocarpine-induced sweat rate (SR(max)) and the pilocarpine concentration which elicited 50% of maximal sweating response (K (m)) were calculated. Sweat rate and active gland density increased in response to greater doses of pilocarpine (p < 0.05). Inter-group differences were evident: SR(max) was greatest for MH and lowest for FL (p < 0.05), but no significant differences were observed between ML and FH (p = 0.24). Higher SR(max) were observed, within-sex, for those with greater aerobic capacity (p < 0.05). Furthermore, males' K (m) values were higher than females', indicating greater sweat gland affinity for pilocarpine even for groups having similar aerobic capacity (p < 0.05). In summary, we confirmed that the human sudomotor response is affected by aerobic capacity but, also, that sex-related differences in sweat gland cholinergic sensitivity exist and are not necessarily associated with the typical differences in .VO(2peak) observed between sexes.

Possible biphasic sweating response during short-term heat acclimation protocol for tropical natives.

The aim of the present study was to evaluate the sweat loss response during short-term heat acclimation in tropical natives. Six healthy young male subjects, inhabitants of a tropical region, were heat acclimated by means of nine days of one-hour heat-exercise treatments (40+/-0 degrees C and 32+/-1% relative humidity; 50% (.)VO(2peak) on a cycle ergometer). On days 1 to 9 of heat acclimation whole-body sweat loss was calculated by body weight variation corrected for body surface area. On days 1 and 9 rectal temperature (T(re)) and heart rate (HR) were measured continuously, and rating of perceived exertion (RPE) every 4 minutes. Heat acclimation was confirmed by reduced HR (day 1 rest: 77+/-5 b.min(-1); day 9 rest: 68+/-3 b.min(-1); day 1 final exercise: 161+/-15 b.min(-1); day 9 final exercise: 145+/-11 b.min(-1), p<0.05), RPE (13 vs. 11, p<0.05) and T(re) (day 1 rest: 37.2+/-0.2 degrees C; day 9 rest: 37.0+/-0.2 degrees C; day 1 final exercise: 38.2+/-0.2 degrees C; day 9 final exercise: 37.9+/-0.1 degrees C, p<0.05). The main finding was that whole-body sweat loss increased in days 5 and 7 (9.49+/-1.84 and 9.56+/-1.86 g.m(-2).min(-1), respectively) compared to day 1 (8.31+/-1.31 g.m(-2).min(-1), p<0.05) and was not different in day 9 (8.48+/-1.02 g.m(-2).min(-1)) compared to day 1 (p>0.05) of the protocol. These findings are consistent with the heat acclimation induced adaptations and suggest a biphasic sweat response (an increase in the sweat rate in the middle of the protocol followed by return to initial values by the end of it) during short-term heat acclimation in tropical natives.

Hidratação durante o exercício: a sede é suficiente? / Hidratación durante el ejercicio: ¿la sed es suficiente? / Exercise fluid replacement: is thirst enough?

O objetivo deste trabalho é fazer uma revisão sobre a hidratação e discutir se, durante o exercício, a reposição de líquidos de acordo com a sede é suficiente para hidratar o indivíduo. A perda hídrica pela sudorese induzida pelo exercício, especialmente realizado em ambientes quentes, pode levar à desidratação, pode alterar o equilíbrio hidroeletrolítico, dificultar a termorregulação e, assim, representar um risco para a saúde e/ou provocar uma diminuição no desempenho esportivo. Tem sido citado que os atletas não ingerem voluntariamente água suficiente para prevenir a desidratação durante uma atividade física. Em função disso, têm sido propostas recomendações internacionais sobre a hidratação. Segundo o American College of Sports Medicine (ACSM), deve-se ingerir aproximadamente 500mL de líquidos nas duas horas antecedentes ao exercício. Durante o exercício, os atletas devem começar a beber desde o início e em intervalos regulares, em volume suficiente para repor as perdas pela sudorese ou o máximo tolerado. A National Athletic Trainer's Association (NATA) faz as seguintes recomendações: ingerir 500 a 600mL de água ou outra bebida esportiva duas a três horas antes do exercício e 200 a 300mL 10 a 20 minutos antes do exercício; durante o exercício, a reposição deve aproximar as perdas pelo suor e pela urina e pelo menos manter a hidratação, com perdas máximas correspondentes a 2 por cento de perda de peso corporal; após o exercício a hidratação deve ter como objetivo corrigir quaisquer perdas líquidas acumuladas. Além disso, o ACSM e o NATA fazem referências sobre temperatura e palatabilidade do líquido, adição de carboidratos e eletrólitos de acordo com a intensidade e duração do exercício e estratégias de hidratação para facilitar a acessibilidade do atleta ao líquido. No entanto, outros autores questionam o uso da reidratação em volumes predeterminados e sugerem que a ingestão de líquidos de acordo com a sede seja capaz de manter a homeostase.

The present work proposes a review about exercise fluid replacement and a discussion whether, during exercise, the fluid ingested according to thirst is sufficient to maintain hydration. Exercise sweat loss, mainly in the heat, can cause dehydration, can alter the hidroelectrolyte balance, disturb thermoregulation, presenting a health risk and/or impairing the athletic performance. It has been asserted that athletes do not drink, spontaneously, the sufficient fluid volume to prevent dehydration during the physical activity. Thus, international recommendations to fluid replacement during physical activities have been proposed. According to the American College of Sports Medicine (ACSM), about 500 mL of fluid on the two hours before the exercise must be ingested. During exercise, they propose that athletes should start fluid replacement since the beginning in regular periods and should drink enough fluid to restore all the sweating losses or ingest the maximal volume tolerated. The National Athletic Trainer's Association (NATA) proposes the following recommendations: ingestion of 500 to 600 mL of water two or three hours before exercise or other sport drink and ingestion of 200 to 300 mL 10 to 20 minutes before exercise starting. During exercise, the fluid replacement should match the sweating and urine losses and at least should maintain hydration status reaching maximal body weight losses of 2 percent. After the exercise, fluid replacement must restore all the fluid losses accumulated. In addition, ACSM and NATA asserted about fluid temperature and palatability, beverage carbohydrate and electrolyte additions according to exercise duration and intensity and recommended hydration schedules to provide easier access to fluid ingestion. However, other authors contest the use of hydration schedules based on predetermined fluid volumes and suggest that fluid replacement according to thirst is enough to maintain body homeostasis.

El objetivo de este trabajo es hacer una revisión sobre la hidratación y discutir si, durante el ejercicio, la reposición de líquidos de acuerdo con la sed es suficiente para hidratar al individuo. La pérdida hídrica por la sudoración inducida por el ejercicio, especialmente realizado en ambientes calurosos, puede llevar a la deshidratación, puede alterar el equilibrio hidroelectrolítico, dificultar la termorregulación y, así, representar un riesgo para la salud y/o provocar una disminución en el desempeño deportivo. Ha sido citado que los atletas no ingieren voluntariamente agua suficiente para prevenir la deshidratación durante una actividad física. En función de eso, han sido propuestas recomendaciones internacionales sobre la hidratación. Según American College of Sports Medicine (ACSM), se debe ingerir aproximadamente 500 ml de líquidos durante las dos horas antecedentes al ejercicio. Durante el ejercicio, los atletas deben comenzar a beber desde el inicio y a intervalos regulares, en volumen suficiente para reponer las pérdidas por la sudoración o el máximo tolerado. La National Athletic Trainer's Association (NATA) hace las siguientes recomendaciones: ingerir 500 a 600 ml de agua u otra bebida deportiva dos a tres horas antes del ejercicio y 200 a 300 ml de 10 a 20 minutos antes del ejercicio; durante el ejercicio, la reposición debe aproximarse a las pérdidas por el sudor y por la orina y por lo menos mantener la hidratación, con pérdidas máximas correspondientes a 2 por ciento de pérdida de peso corporal; después del ejercicio la hidratación debe tener como objetivo corregir cualesquier pérdidas líquidas acumuladas. Además de esto, la ACSM y la NATA hacen referencias sobre temperatura y palatabilidad del líquido, adición de carbohidratos y electrólitos de acuerdo con la intensidad y duración del ejercicio y estrategias de hidratación para facilitar la accesibilidad del atleta al líquido. A pesar de esto, otros autores cuestionan...