Sciences of Porto Alegre. Depart- ment of Physiotherapy. Porto (original) (raw)
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Physiological Reviews, 2021
A rise in body core temperature and loss of body water via sweating are natural consequences of prolonged exercise in the heat. This review provides a comprehensive and integrative overview of how the human body responds to exercise under heat stress and the countermeasures that can be adopted to enhance aerobic performance under such environmental conditions. The fundamental concepts and physiological processes associated with thermoregulation and fluid balance are initially described, followed by a summary of methods to determine thermal strain and hydration status. An outline is provided on how exercise-heat stress disrupts these homeostatic processes, leading to hyperthermia, hypohydration, sodium disturbances, and in some cases exertional heat illness. The impact of heat stress on human performance is also examined, including the underlying physiological mechanisms that mediate the impairment of exercise performance. Similarly, the influence of hydration status on performance i...
Hyperhydration: tolerance and cardiovascular effects during uncompensable exercise-heat stress
Journal of applied physiology (Bethesda, Md. : 1985), 1998
This study examined the efficacy of glycerol and water hyperhydration (1 h before exercise) on tolerance and cardiovascular strain during uncompensable exercise-heat stress. The approach was to determine whether 1-h preexercise hyperhydration (29.1 ml H2O/kg lean body mass with or without 1.2 g/kg lean body mass of glycerol) provided a physiological advantage over euhydration. Eight heat-acclimated men completed three trials (control euhydration before exercise, and glycerol and water hyperhydrations) consisting of treadmill exercise-heat stress (ratio of evaporative heat loss required to maximal capacity of climate = 416). During exercise ( approximately 55% maximal O2 uptake), there was no difference between glycerol and water hyperhydration methods for increasing (P < 0.05) total body water. Glycerol hyperhydration endurance time (33. 8 +/- 3.0 min) was longer (P < 0.05) than for control (29.5 +/- 3.5 min), but was not different (P > 0.05) from that of water hyperhydrati...
2019
Introducción: El número de corredores ha incrementado en los últimos años. Aunque la actividad de correr implica varios beneficios para los practicantes, también puede provocar problemas de salud cuando se practica en condiciones de calor. Propósito: El objetivo de esta revisión fue evaluar cómo las altas temperaturas afectan la salud del corredor. Estrategia de búsqueda: La búsqueda de artículos para este estudio se llevó a cabo en Web of Science y Pubmed. Selección de estudios: Los criterios de inclusión fueron estudios que investigaron los efectos del ejercicio de resistencia, al menos a 27o, sobre variables de salud, determinando la intensidad y duración del ejercicio y se presentaron resultados previos y posteriores a la prueba o compararon con condiciones normales o frías. Resultados: 1336 artículos fueron identificados después del proceso de búsqueda. 333 corredores fueron evaluados en quince artículos que fueron incluidos en la síntesis cualitativa. Durante la actividad en c...
European Journal of Applied Physiology, 2001
The cumulative heat strain index (CHSI) is a new approach for assessing the total physiological strain experienced by subjects exposed to an exercise-heat stress. The index is based on inherent physiological logic that combines the thermoregulatory strain, which is described by the area under the hyperthermic curve, and the circulatory strain, which is characterized by heartbeat count. According to this model, the index re¯ects the dynamics of changes in the thermoregulatory and cardiovascular components and accounts for the complementary nature of the interaction between them. Mathematically, the index is calculated as follows:
Frontiers in physiology, 2016
Purpose: It has been suggested that dehydration is an independent stimulus for heat acclimation (HA), possibly through influencing fluid-regulation mechanisms and increasing plasma volume (PV) expansion. There is also some evidence that HA may be ergogenic in temperate conditions and that this may be linked to PV expansion. We investigated: (i) the influence of dehydration on the time-course of acquisition and decay of HA; (ii) whether dehydration augmented any ergogenic benefits in temperate conditions, particularly those related to PV expansion. Methods: Eight males [VO2max: 56.9(7.2) mL·kg(-1)·min(-1)] undertook two HA programmes (balanced cross-over design), once drinking to maintain euhydration (HAEu) and once with restricted fluid-intake (HADe). Days 1, 6, 11, and 18 were 60 min exercise-heat stress tests [HST (40°C; 50% RH)], days 2-5 and 7-10 were 90 min, isothermal-strain (Tre ~ 38.5°C), exercise-heat sessions. Performance parameters [VO2max, lactate threshold, efficiency, ...
Fluid and electrolyte supplementation for exercise heat stress
The American Journal of Clinical Nutrition
During exercise in the heat, sweat output often exceeds water intake, resulting in a body water deficit (hypohydration) and electrolyte losses. Because daily water losses can be substantial, persons need to emphasize drinking during exercise as well as at meals. For persons consuming a normal diet, electrolyte supplementation is not warranted except perhaps during the first few days of heat exposure. Aerobic exercise is likely to be adversely affected by heat stress and hypohydration; the warmer the climate the greater the potential for performance decrements. Hypohydration increases heat storage and reduces a person's ability to tolerate heat strain. The increased heat storage is mediated by a lower sweating rate (evaporative heat loss) and reduced skin blood flow (dry heat loss) for a given core temperature. Heat-acclimated persons need to pay particular attention to fluid replacement because heat acclimation increases sweat losses, and hypohydration negates the thermoregulatory advantages conferred by acclimation. It has been suggested that hyperhydration (increased total body water) may reduce physiologic strain during exercise heat stress, but data supporting that notion are not robust. Research is recommended for 3 populations with fluid and electrolyte balance problems: older adults, cystic fibrosis patients, and persons with spinal cord injuries.
Muscle-Damaging Exercise Increases Heat Strain during Subsequent Exercise Heat Stress
Medicine & Science in Sports & Exercise, 2013
Purpose It remains unclear whether exercise-induced muscle damage (EIMD) increases heat strain during subsequent exercise-heat-stress, which in-turn may increase the risk of exertional heat illness (EHI). We examined heat strain during exercise-heat-stress 30 min after EIMD to coincide with increases in circulating pyrogens (e.g. interleukin (IL)-6) and 24 h after EIMD to coincide with the delayed muscle inflammatory response when a higher rate of metabolic energy expenditure ( M ), and thus decreased economy, might also increase heat strain. Methods