HEAT ACCLIMATIZATION - Sportsci

Physical exercise - Wikipedia

An apple a day keeps the doctor away -- ScienceDaily

Conservation of sodium chloride (NaCl) also occurs during heatacclimatization. The NaCl losses in sweat and urine decrease duringdays 3-9 of heat acclimatization, resulting in an expandedextracellular fluid volume. Subsequently, NaCl losses in sweat andurine increase toward pre-acclimatization levels, once physiologicstrain (i.e., cardiovascular, thermal) moderates. Francesconi andcolleagues (1993) recently demonstrated that NaCl losses, during astrenuous 10-day heat acclimatization protocol, were related toplasma renin (PR) and plasma aldosterone (A) concentrations. Whensubjects consumed a low salt diet (4g NaCl per day) and a moderatesalt diet (8g NaCl per day), both PR and A increased during the firstfour days of heat acclimatization, but decreased during the remaining6 days of heat acclimatization. The improved cardiovascularstability, which occurred on days 1-4 of heat acclimatization,allowed equivalent exercise performance with both diets andapparently reduced the stimulation and need for large elevations ofPR and A. No change in plasma levels of arginine vasopressin (AVP)were observed across time, in either dietary group, possibly becausehourly water intake matched the fluid lost in sweat. Usually, AVPsynthesis is stimulated by an increase in plasma osmolarity oralterations in blood pressure, plasma volume, and renal or hepaticblood blow. Therefore, it is unlikely that the ability tosuccessfully sustain exercise, during the latter days of the heatacclimatization process, is specifically related to the action ofhormones that regulate fluid-electrolyte balance. This isparticularly true when salt balance has been achieved.

N Akazawa, Y Choi, A Miyaki, Y Tanabe, J Sugawara, R Ajisaka, S Maeda

Plasma cortisol concentration generally indicates the strainexperienced by the body. Heat-acclimated, well-hydrated humansexhibit no change in plasma cortisol when exercise in a hotenvironment is mild. Under the same conditions, the lack of heatacclimatization and dehydration can result in large plasma cortisolincreases. When exercise is intense and core body temperature risesmarkedly, the plasma cortisol concentration increases during theinitial days of heat acclimatization, but returns to control levelsafter 8 days of heat acclimatization, reflecting the reduction intotal body strain.

02/10/2011 · Does elevating your heart rate during exercise have the same effect on you as a fight or flight response? - asks Anh Nguyen from San Jose, California

Physical training in a cool environment may or may not improveexercise economy. Metabolism can be affected by heat acclimatization,in that oxygen uptake during submaximal exercise is reduced. Largeeffects have been reported for stair stepping; treadmill andcycle-ergometer exercise produce smaller, but statisticallysignificant, changes. The physiologic mechanism has not been definedexactly, but three theories exist: (a) blood flow to the skinincreases, thus reducing central blood volume, venous return to theheart, and cardiac output; (b) the portion of cardiac outputperfusing muscle decreases; and (c) the recruitment of muscle fibersshifts from predominantly oxidative to glycolytic fibers. Heatacclimatization reduces muscle glycogen utilization and post-exercisemuscle lactate concentration.

Heart Rate Questions including "Why is it dangerous to just 'stop' exercising to take your heart rate" and "What is the normal pulse rate for an adult"

The phrase "heat intolerance" has been used in a wide variety ofcontexts. Interestingly, heat intolerance has been defined by someexperts as an inability to develop normal physiologic adaptations,during repeated days of exercise in a hot environment. Some humans donot show the classic decreases in heart rate and rectal temperaturethat exemplify successful heat acclimatization. This has been ofparticular concern among persons with cardiovascular disease andprior heat stroke patients. One recent publication (Armstrong et al.,1990), however, reported that 9 out of 10 prior heat stroke patientsexhibited normal heat acclimatization responses (90 minutes treadmillwalking per day, 7 days, 40°C air temperature), 61 days afterexperiencing heatstroke.

Background Controlled clinical trials have shown that beta-blockers can produce hemodynamic and symptomatic improvement in chronic heart failure, but the effect …

The physiologic adaptations to exercise training in a coolenvironment are lost after several weeks or months of inactivity. Incontrast, heat acclimatization adaptations may vanish after only afew days or weeks of inactivity (i.e., 18-28 days). The firstadaptations to decay are those that develop first: heart rate andother cardiovascular variables. The rate of decay of adaptations isaffected by the number of heat exposures per week, the number andformat of training sessions, and the degree to which core bodytemperature is elevated. Athletes with high VO usually will lose heat acclimatizationadaptations slower than individuals with low VO.

Jun 11, 2007 · Does elevating your heart rate during exercise have the same effect on you as a fight or flight response? - asks Anh Nguyen from San Jose, California

Milrinone, a phosphodiesterase inhibitor, enhances cardiac contractility by increasing intracellular levels of cyclic AMP, but the long-term effect of this type of positive inotropic agent on the survival of patients with chronic heart failure has not been determined.