During exercise in the heat, sweat output often exceeds water intake, resulting in hypohydration, which is defined as a body fluid deficit. This fluid deficit is comprised of water loss from both the intracellular and extracellular fluid compartments. Hypohydration during exercise causes a greater heat storage and reduces endurance in comparison with euhydration levels. The greater heat storage...

Participants in prolonged, physically demanding cold-weather activities are at risk for a condition called "thermoregulatory fatigue". During cold exposure, the increased gradient favoring body heat loss to the environment is opposed by physiological responses and clothing and behavioral strategies that conserve body heat stores to defend body temperature. The primary human physiological respon...

In resting man, deep body temperature is maintained at about 37-380C. The existence of such a steady temperature indicates that the rates of metabolic heat production is balanced -by the rate of heat loss to the environment. At rest the main challenge to the regulation of body temperature comes from changes in environmental conditions. At low ambient temperatures, especially if this is coupled ...

In the heat, a positive body heat storage and the associated increase in core body temperature elicit the reflex physiological thermoregulatory mechanisms of sweating and cutaneous vasodilation in order to enhance heat dissipation. However under circumstances where these mechanisms cannot facilitate a sufficiently high rate of heat loss, core body temperature continually rises, and if left unch...

Flying animals generate large amounts of heat, which must be dissipated to avoid overheating. In birds, heat dissipation is complicated by feathers, which cover most body surfaces and retard heat loss. To understand how birds manage heat budgets during flight, it is critical to know how heat moves from the skin to the external environment. Hummingbirds are instructive because they fly at speeds...

We examined whether older individuals experience greater levels of hyperthermia and cardiovascular strain during an extreme heat exposure compared to young adults. During a 3-hour extreme heat exposure (44°C, 30% relative humidity), we compared body heat storage, core temperature (rectal, visceral) and cardiovascular (heart rate, cardiac output, mean arterial pressure, limb blood flow) response...

purpose weight loss in wrestling has been found to be an interesting issue for researchers. in this regard, complications of weight loss in wrestlers before the competitions and their weight gain in course of competitions have been debated in previous studies. the objective of this study was to investigate the extent of weight gain and to estimate the percentage of body fat in participants in t...

Endothermy (the metabolic production and retention of heat to warm body temperature above ambient) enhances physiological function, and whole-body endothermy generally sets mammals and birds apart from other animals. Here, we describe a whole-body form of endothermy in a fish, the opah (Lampris guttatus), that produces heat through the constant "flapping" of wing-like pectoral fins and minimize...