Temperature最新文献

Aging is associated with impairments in thermoregulatory function, which may augment the neuroendocrine and immune response in older relative to young adults during physical activity in the heat. This study was therefore aimed at examining changes in circulating endocrine hormones as cortisol (COR), prolactin (PRL), human growth hormone (hGH) and interleukin-6 (IL-6) in young and older men prior to and following an incremental, exercise-heat stress protocol (40°C and ~15% relative humidity). Accordingly, ten habitually active young (mean±SD; 21 ± 1 years) and ten older (65 ± 3 years) men performed three 30-min bouts of cycling at increasing metabolic heat productions (300, 400 and 500 W, equal to light, moderate and vigorous exercise), each separated by a 15-min recovery. Consistent with our hypothesis, we observed augmented IL-6 in older (3.55 ± 1.62 pg/mL) compared to young men (1.59 ± 0.88 pg/mL) following the protocol (p < 0.001). However, no significant between-group differences were observed for COR and hGH (all p > 0.050). We show that when assessed following incremental exercise in the heat, older men display augmented interleukin-6, but similar levels of stress hormones relative to young men.

As most fish are ectotherms, their physiology is strongly affected by temperature. Temperature affects their metabolic rate and thus their energy balance and behavior, including locomotor and feeding behavior. Temperature influences the ability/desire of the fish to obtain food, and how they process food through digestion, absorb nutrients within the gastrointestinal tract, and store excess energy. As fish display a large variability in habitats, feeding habits, and anatomical and physiological features, the effects of temperature are complex and species-specific. The effects of temperature depend on the timing, intensity, and duration of exposure as well as the speed at which temperature changes occur. Whereas acute short-term variations of temperature might have drastic, often detrimental, effects on fish physiology, long-term gradual variations might lead to acclimation, e.g. variations in metabolic and digestive enzyme profiles. The goal of this review is to summarize our current knowledge on the effects of temperature on energy homeostasis, with specific focus on metabolism, feeding, digestion, and how fish are often able to "adapt" to changing environments through phenotypic and physiological changes.

Athletes exercising in heat stress experience increased perceived fatigue acutely, however it is unknown whether heat acclimation (HA) reduces the magnitude of this perceptual response and whether different HA protocols influence the response. This study investigated sensations of fatigue following; acute exercise-heat stress; short- (5-sessions) and medium-term (10-sessions) HA; and between once- (ODHA) and twice-daily HA (TDHA) protocols. Twenty male participants (peak oxygen uptake: 3.75 ± 0.47 L·min-1) completed 10 sessions (60-min cycling at ~2 W·kg-1, 45°C/20% relative humidity) of ODHA (n = 10) or non-consecutive TDHA (n = 10). Sensations of fatigue (General, Physical, Emotional, Mental, Vigor and Total Fatigue) were assessed using the multi-dimensional fatigue scale inventory-short form pre and post session 1, 5 and 10. Heat adaptation was induced following ODHA and TDHA, with reductions in resting rectal temperature and heart rate, and increased plasma volume and sweat rate (P < 0.05). General, Physical and Total Fatigue increased from pre-to-post for session 1 within both groups (P < 0.05). Increases in General, Physical and Total Fatigue were attenuated in session 5 and 10 vs. session 1 of ODHA (P < 0.05). This change only occurred at session 10 of TDHA (P < 0.05). Whilst comparative heat adaptations followed ODHA and TDHA, perceived fatigue is prolonged within TDHA.

Abbreviations: ∆: Change; ANOVA: Analysis of variance; HA: Heat acclimation; HR: Heart rate; IL-6: Interleukin-6; MFS-SF: Multi-dimensional fatigue symptom inventory-short form (MFSI-SF); MTHA: Medium-term heat acclimation; Na⁺: Sodium; ODHA: Once daily heat acclimation; PV: Plasma volume; RH: Relative humidity; RPE: Rating of perceived exertion; SD: Standard deviation; SE: Standard error of the slope coefficient or intercept; SE_E : Standard error of the estimate for the regression equation; STHA: Short-term heat acclimation; TDHA: Twice daily heat acclimation; TC: Thermal Comfort; T_re: Rectal temperature; TSS: Thermal sensation; V̇O_2peak: Peak oxygen uptake; WBSL: whole-body sweat loss.

The purpose of this study was to compare the separate and combined effects of two practical cooling methods (hand and torso) used prior to exercise on subsequent high-intensity cycling performance in heat. Ten trained male cyclists (V̇O₂peak: 65.7 ± 10.7 ml.kg^-1.min^-1) performed four experimental trials (randomised within-subjects design) involving 30-min of pre-cooling (20-min seated; PRE-COOL, 10 min warm-up; PRE-COOL+WUP), while using a: (1) hand-cooling glove (CG); (2) cooling jacket (CJ); (3) both CG and CJ (CG+J); or (4) no-cooling (NC) control, followed by a cycling race simulation protocol (all performed in 35.0 ± 0.6°C and 56.6 ± 4.5% RH). During the 30-min of pre-cooling, no reductions in core (Tc) or mean skin temperature (Tsk) occurred; however, Tsk remained lower in the CJ and CG+J trials compared to NC and CG (p = 0.002-0.040, d= 0.55-1.01). Thermal sensation ratings also indicated that participants felt "hotter" during NC compared to all other trials during both PRE-COOL and PRE-COOL+WUP (p = 0.001-0.015, d= 1.0-2.19), plus the early stages of exercise (sets 1-2; p = 0.005-0.050, d= 0.56-1.22). Following cooling, no differences were found for absolute Tc and Tsk responses between trials over the entire exercise protocol (p > 0.05). Exercise and cognitive (working memory) performance also did not differ between trials (p = 0.843); however, cognitive performance improved over time in all trials (p < 0.001). In summary, pre-cooling (20-min seated and 10-min warm-up) in heat did not improve subsequent high-intensity cycling performance, cognitive responses and associated thermoregulatory strain (Tc and Tsk) compared to control.