Desempenho e termorregulação de corredores jovens e de meia-idade com VO2 máx similar em corridas de intensidades fixa e autorregulada em ambientes quente e termoneutro
Jacqueline de Paula Viveiros
DATA DE PUBLICAÇÃO
In order to compare the heat exercise performance between middle-aged and young runners with similar VO2peak using self-paced and fixed workload intensity, 26 endurance runners; seven men (MA_M: 54 ± 2 years; 58 ± 4 ml.kg-1.min-1) and six middle-aged women (MA_W: 54 ± 4 years; 48 ± 3 ml.kg-1.min-1); seven men (YO_M: 28 ± 1 years; 61 ± 5 ml.kg-1.min-1) and six young women (YO_W: 24 ± 3 years; 49 ± 3 ml.kg-1.min-1), underwent to 10 km of self-paced, as fast as possible, and fixed work load run until fatigue on a treadmill in hot (SP40 and FX40; 40 0C and 30% RH) and in moderate (SP20 and FX20; 20 0C and 50% RH) environments on sessions separated for a week . Fixed intensity was 90% speed run in an official 10-km race of each individual. Total time (TT), average speed, physiological strain index, rectal temperature, heat storage rate, sweat rate, number of heat-activated sweat glands (HASG) and sweat rate per sweat activated gland (SR/SG) were measured or calculated. Anthropometric characteristics, VO2peak, TT, average speed and thermoregulatory responses, besides HASG and SR/SG, were similar between the age groups. In MA_M, SR/SG (SP40: 0.19±0.1 and SP20: 0.19±0.1; FX40: 0.26±0,1 and FX20: 0.21±0.1 g.m-2.min-1.cm-2) were smaller than in younger runners (SP40: 0.48±0.1 and SP20: 0.46±0.2; FX40: 0.59±0,1 and FX20: 0.48±0.1 g.m-2.min-1.cm-2) and HASG (SP40: 88±1 and SP20: 80±2; FX40: 90±2 and FX20: 66±1 cm-1) were higher than in younger (SP40: 43±1 and SP20: 32±1; FX40: 37±1 and FX20: 31±1 cm-2). FX40 total time (MA_M: 27±2 and YO_M: 27±2; MA_W: 29±3 and YO_W: 28±2 min) were smaller than in SP40 (MA_M: 59±3 and YO_M: 60±2; MA_W: 70±7 and YO_W: 64±7 min). SP40 average speeds (MA_M: 10±1 and YO_M: 10±0,3; MA_W: 9±1 and YO_W: 9±1 km.h-1) were smaller than in SP20 (MA_M: 12±1 and YO_M: 12±1; MA_W: 10±1 and YO_W: 10±1 min) and were smaller than in run with fixed work load (MA_M: 13±1 and YO_M: 13±1; MA_W: 10±1 and YO_W: 11±0.3 min). Sweat rate, heat storage rate and HASG were higher in hot, compared with moderate environment. MA_M sweat rates and YO_M sweat rates were higher than MA_W and YO_W. It is concluded 1. Fixed and self-paced run performance are not different between middle-aged and young runners of similar VO2peak. 2. Self-paced run performance and thermoregulatory responses are different from those in fixed run only in hot environment. These differences were attributed to the lower speed used in SP40. 3. The heat affects run performance, independent of their modality and age group. 4. Compared with men, women present lower self-paced and fixed run performance and sweat rates, independent of the age group.