Thermoregulatory, cardiovascular, and muscular factors related to exercise after precooling

Abstract

The effect of slightly lowered body temperature on endurance time and possibly related physiological factors was studied in seven male volunteers exercising on a cycle ergometer at an ambient temperature (Ta) of 18 degrees C. Work load was increased to 40% in a stepwise manner (phase I, min 0-16) followed by a period at 80% of peak oxygen consumption (VO2) sustained to exhaustion. On one day, exercise was preceded by a double cold exposure (precooling test, PRET), resulting in a 204-kJ/m2 negative heat storage and a 4 and 0.2 degrees C lower mean skin and core temperature at the start of exercise compared with the control test (CONT). Core temperature dropped further during exercise in PRET. Endurance time at 80% of peak VO2 was increased by 12% (P less than 0.05) in PRET. Heart rate (HR) was decreased throughout PRET (P less than 0.05); oxygen pulse and arteriovenous O2 difference were significantly increased in phase I of PRET, whereas the PRET-CONT differences in stroke volume and cardiac output were not significant. In phase II of PRET (min 16-28, heavy exercise) sweat rate (SR) and heat conductivity, indicating forearm blood flow, were lower (-39%, P less than 0.001; -37%). Pedal rate (PR) was 9% lower (P less than 0.01) in phase II of PRET. At the termination of exercise, PRET-CONT differences in HR, SR, and PR had disappeared.

Precooling and Warm-up Effects on Time Trial Cycling Performance During Heat Stress

“…Cold exposure induced a lower initial T c and lower T c throughout exercise, and as a result heat storage was greater (Lee & Haymes, 1995). Exposure to cooler air (0 °C) also increased the work rate and cycling time to exhaustion at a cooler ambient temperature (18 °C), and like the previous study this was accompanied with lower T c at the beginning and during exercise compared to that of the control group (Schmidt & Brück, 1981;Olschewski & Brück, 1988). Taken together, these studies indicate that precooling with various methods can improve exercise time to exhaustion, most likely through reduced initial body temperature.…”

“…The decrease in the initial T c after precooling may explain the mechanism underlying enhanced performance in hyperthermia, through widening the capacity for heat storage and, consequently, increasing the time to reach a critical T c (Marino, 2002). sk after precooling facilitates a greater thermal gradient between core and skin such that heat storage capacity is increased, thereby attenuating cardiovascular and thermoregulatory strain (Olschewski & Brück, 1988;Lee & Haymes, 1995;Booth et al, 1997).…”

Self-Paced Exercise Performance in the Heat After Pre-Exercise Cold-Fluid Ingestion

“…[11][12][13][14][15][16][17][18][19][20][21] Direct comparisons with the magnitude of ergogenic effect observed in previous studies are limited because authors of only 2 studies 3,4 used the same protocol as we did, and only Kay et al 4 used the same mode of exercise. Kay et al 4 observed a 6.0% (900 m) improvement in performance when using an identical exercise protocol after 60 minutes of coolwater immersion, and Booth et al 3 observed a 4.2% improvement in distance run in 30 minutes after 60 minutes of coolwater immersion.…”

The effects of creatine supplementation on thermoregulation and physical (cognitive) performance: a review and future prospects

“…Numerous strategies have therefore been designed to reduce the detrimental effects of dehydration on thermoregulation during exercise including precooling, fluid ingestion and plasma volume expansion (Olschewski and Bruck 1988;Lee 9 and Haymes 1995; Galloway and Maughan 2000;Watt et al 2000). The increased body mass associated with Cr loading has been attributed to osmotic effects resulting in cell swelling and increased protein synthesis (Haussinger et al 1993).…”