The magnitude of exercise-induced hyperthermia is directly associated with the increase in intestinal permeability.

Heat acclimation (HA) results in whole body adaptations that increase heat tolerance, and in addition, HA may also result in protective cellular adaptations. We hypothesized that, after HA, basal intracellular heat shock protein (HSP) 72 and extracellular IL-10 levels would increase, while extracellular HSP72 levels decrease. Ten male and two female subjects completed a 10-day exercise/HA protocol (100-min exercise bout at 56% of maximum O(2) uptake in a 42.5 degrees C DB, 27.9% RH environment); subjects exhibited classic adaptations that accompany HA. Peripheral blood mononuclear cells (PBMCs) were isolated before and after each acclimation session on days 1, 6, and 10; plasma and serum were collected before and after exercise on the 1st and 10th day of HA. SDS-PAGE was used to determine PBMC HSP72 levels during HA, and ELISA was used to measure plasma IL-10 and serum HSP72 concentrations. The increase in PBMC HSP72 from pre- to postexercise on the 1st day of HA was not significant (mean +/- SD, 1.0 +/- 0 vs. 1.6 +/- 0.6 density units). Preexercise HSP72 levels on day 1 were significantly lower compared with the pre- and postexercise samples on days 6 and 10 (mean +/- SD, day 6: 2.1 +/- 1.0 and 2.2 +/- 1.0, day 10: 2.0 +/- 1.3 and 2.2 +/- 1.0 density units, respectively, P < 0.05). There were no differences in plasma IL-10 and serum HSP72 postexercise or after 10 days of HA. The sustained elevation of HSP72 from days 6 to 10 may be evidence of a cellular adaptation to HA that contributes to improved heat tolerance and reduced heat illness risk.

Resumo As ondas de calor impactam setores socioeconômicos em diversas regiões do mundo. Dentro deste tema, o efeito do calor à saúde pública é um dos mais estudados, especialmente no que tange ao aumento da taxa de mortalidade humana. Procurando dar subsídios para possíveis ações mitigadoras no Brasil, o presente estudo propõe apresentar as características de frequência, duração, abrangência espacial e intensidade das ondas de calor. Utilizou-se dados de temperatura máxima diária (Tmax) da série histórica (1961-2014) de 265 estações meteorológicas do Instituto Nacional de Meteorologia (INMET), separadas em três áreas do Brasil. Primeiramente, selecionou-se os eventos que, durante três ou mais dias, pelo menos a metade das observações na área apresentaram Tmax superando a média de Tmax mais um desvio padrão. Posteriormente, a média espacial e temporal da Tmax foi definida como intensidade, Int. Por fim, os eventos com valores superiores ao terceiro quartil de Int foram definidos como ondas de calor. Foram encontradas 11 ondas de calor na área 1, 23 na área 2 e 31 na área 3, a maioria na primavera e/ou verão. Nosso principal achado mostra que o número de ondas de calor tem aumentado ao longo das últimas cinco décadas, sendo a maioria das ocorrências concentradas após os anos 2000, na atual fase fria da Oscilação Decadal do Pacífico (ODP). Também nesse período, foram verificadas as ondas de calor mais duradouras e intensas. As conclusões deste trabalho sobre frequência, duração e intensidade das ondas de calor aparecem como forte indicativo de que as mudanças climáticas globais têm influenciado o campo de temperatura no Brasil.

In order to verify the effects of heat and exercise acclimation (HA) on resting and exercise-induced expression of plasma and leukocyte heat shock protein 72 (Hsp72) in humans, nine healthy young male volunteers (25.0± 0.7 years; 80.5±2.0 kg; 180±2 cm, mean ± SE) exercised for 60 min in a hot, dry environment (40±0°C and 45±0% relative humidity) for 11 days. The protocol consisted of running on a treadmill using a controlled hyperthermia technique in which the work rate was adjusted to elevate the rectal temperature by 1°C in 30 min and maintain it elevated for another 30 min. Before and after the HA, the volunteers performed a heat stress test (HST) at 50% of their individual maximal power output for 90 min in the same environment. Blood was drawn before (REST), immediately after (POST) and 1 h after (1 h POST) HST, and plasma and leukocytes were separated and stored.