Temperature最新文献

Thermoregulatory processes are closely linked to sleep initiation and maintenance throughout the circadian cycle, and may contribute to the increased tendency to nap in older adults. This cross-sectional study examined whether habitual napping in healthy older individuals is associated with altered skin temperature-derived heat-loss dynamics and their relationship with sleep onset. Thirty self-reported habitual nappers and 28 non-nappers (59-82 y) completed a 40-hour multiple-nap protocol under controlled laboratory conditions, with continuous polysomnography and distal-proximal skin temperature gradients (DPG) recordings. DPG was analyzed across scheduled wake episodes and at lights-off preceding each nap opportunity. Habitual nappers exhibited distinct changes in thermoregulatory dynamics compared to non-nappers. Overall, they had a lower DPG during scheduled wakefulness, particularly during the afternoon nap window (14:45-17:30). Their circadian organization of the DPG also differed markedly: they had a higher 24-hour DPG amplitude, a more pronounced 12-hour component, and an earlier DPG phase than the non-nappers. During nap opportunities, shorter sleep onset latency (SOL) was associated with a faster increase in DPG after lights-off in both groups. However, in habitual nappers, sleep onset occurred more rapidly despite a reduced dependence on pre-sleep DPG increase. Together, these findings indicate that habitual napping in older adults is accompanied by altered heat-loss rhythms across the circadian cycle and a reduced coupling between pre-sleep thermoregulatory dynamics and sleep initiation. Circadian-driven thermoregulatory changes may underlie the greater propensity to nap in older adults and differentiate habitual nappers from non-nappers. However, the causal direction of this relationship requires further investigation.

The 2025 FIFA Club World Cup was held primarily during the summer season in the Northern Hemisphere, with reports of athletes exposed to significant environmental heat stress. We investigated whether environmental conditions, along with other factors (e.g., time of day, players' age and field position, and club geographic origin), influenced physical performance in this tournament. Information about the performance during 57 matches (n = 1070 observations) was extracted from FIFA technical reports, whereas environmental conditions were obtained through mathematical modeling (ERA5 reanalysis). Linear mixed models were used to identify factors that explained variance in total distance covered and in distances covered at high, moderate, and low speeds. Mean wet-bulb globe temperature (WBGT) exceeded 28°C in 31 of the 57 matches analyzed, confirming that players were exposed to conditions of extreme heat illness risk. WBGT and air temperature explained total distance and distances at different speeds, while relative humidity explained distance only at high speeds (p < 0.001). More specifically, high WBGT, air temperature, and relative humidity values reduced the distances covered. Other factors also influenced players' performance, including their position and age, time of day, and club geographic origin: longer distances were observed in midfielders/forwards, younger players, in the evening, and in clubs from cold climates (p < 0.05). In conclusion, the findings from this tournament, which featured many matches under extreme heat, highlight the multifaceted regulation of physical performance in soccer and emphasize the prominent role of environmental conditions in determining the distance players cover at different speeds.

Turbulent airflow is a fundamental characteristic of real-world outdoor and mechanically ventilated environments, yet most thermoregulation models rely on heat transfer coefficients derived from steady indoor airflows with low turbulence intensity. Using an updated Stolwijk thermoregulation model and a turbulence-informed heat transfer correlation, we evaluated the impact of turbulence intensity and integral length scale on human thermophysiological responses. Simulations were conducted across three environmental conditions (hot-dry, hot-humid, temperate), two clothing levels (0 and 0.6 clo), two activity levels (1.2 and 4.0 MET), and air speeds ranging from 0.4 to 5 m/s. Results show that turbulence significantly enhances convective and evaporative heat loss in temperate and hot-dry environments when unclothed. Compared to baseline simulations that neglect turbulence characteristics at equivalent air speed, core temperature differed by up to 0.3°C, and skin temperature by up to 1.8°C, highlighting the potential physiological relevance of turbulence. In contrast, the influence of turbulence is minimal in hot-humid environments and when clothed. These findings demonstrate that turbulence should not be viewed as inherently beneficial or detrimental, but rather as a mechanistic modifier of heat and mass transfer whose physiological impact depends on context, including ambient temperature, metabolic rate, clothing, and the skin-air temperature difference. This work advances the field by introducing a turbulence-resolved approach to support the improved assessment of heat exposure across vulnerable populations, including outdoor workers and athletes, and to guide the design of more effective cooling strategies and ventilation systems, such as fans, based on different climate and personal contexts.

Cold-induced metabolic responses across human organs and tissues vary markedly and do not regulate metabolism uniformly. The magnitude and nature of these responses differ depending on the type of cold exposure, ranging from mild surface cooling and beta-adrenergic stimulation to deep tissue cooling impacting intracellular biophysical and metabolic properties. Upregulating brown adipose tissue (BAT) activity has been proposed to improve whole-body metabolism. Despite its high metabolic activity, BAT mass is typically only 50-100 g and may contribute less than 1% of total heat production during thermogenesis. In contrast, skeletal muscles and white adipocytes may play greater roles in thermogenic and metabolic regulation. Cold exposure triggers a cascade of metabolic responses across tissues, extending beyond fuel partitioning and the regulation of uncoupling proteins. It also alters gene expression, protein synthesis, and metabolic pathways. In response to cold, the body increases sympathetic nervous system activity, leading to peripheral vasoconstriction and energy substrate mobilization. Brown adipocytes increase mitochondrial uncoupling to produce heat, while skeletal muscle contributes through shivering and non-shivering thermogenesis. The liver adjusts glucose production and lipid metabolism, the heart and circulatory system adapt to altered hemodynamic demands, and the kidneys modify fluid balance. Endocrine systems, including the thyroid, amplify thermogenic capacity, and the brain integrates thermal sensing with behavioral responses. Cold exposure also modulates immune function, cytokine profiles and inflammatory pathways across tissues, and shifts in gut microbiome composition influence nutrient absorption, bile acid metabolism and energy homeostasis. These coordinated tissue-specific adaptations enable the maintenance of core temperature during cold stress.

Adequate post-exercise protein intake supports muscle recovery. Studies showed that hot drinks accelerate gastric emptying and enhance nutrient absorption. However, the effect of drink temperature on muscle strength and mass remains unclear. Therefore, this study conducted a 4-week intervention study and an acute study focusing on digestion rate. In Study 1, a 4-week parallel-group trial was conducted in 38 healthy adults without exercise habits, assigned to either a Cold ( < 10°C) or Hot (60°C) group. Participants consumed a 250 mL of protein drink daily at the designated temperature and performed 30 minutes of leg strength training three times per week. Knee extensor strength and leg muscle mass were assessed before and after the intervention. In Study 2, the effect of 200 mL of a protein drink temperature (4 or 60°C) on gastric emptying rate was investigated using ¹³C stable isotope breath test. In Study 1, an analysis of covariance, with pre-intervention values as covariates, revealed a significant group effect on post-intervention knee extensor strength in the right leg, with the Hot group showing 12% higher strength (35.7 ± 1.3 kgf, mean±standard error) compared to the Cold group (31.4 ± 1.2 kgf) (p = 0.017). There was no significant difference in muscle mass between the groups. In Study 2, the initial ¹³CO₂ excretion rate was higher in the Hot group (p < 0.001). The findings of this study suggest that the temperature of protein drinks may modestly influence early-phase digestion and may have a limited impact on muscle strength in individuals without regular exercise habits.

NFL teams may have an advantage over their opposition when players are more familiar with game-day temperatures; however, relationships between game-day air temperature and team performance had not been examined using official at-stadia air temperatures. Game data from 2017 to 25 were collected from NFL "Gamebooks." Data were extracted for games contested by a team based in a cool climate >39° N (North teams, n = 17) against a team based in a warm climate <39° N (South teams, n = 15). Data extracted included game-day temperature (°C), game location (North, South), game outcome (win, no-win [relative to North team]), and point differential (points [relative to North team]). Mixed effects logistic regressions examined whether game-day temperature associated with game outcome, while mixed effects models examined whether temperature associated with point differential. Models were run for all games combined, and for games contested in North and South locations, respectively. North team win probability declined as game-day temperature increased (OR = 0.974, 95% CI [0.951, 0.997], p = .026), and North team point differential was negatively associated with temperature (β = -0.175, 95% CI [-0.286, -0.063], p = .002). Models run according to game location revealed that North team point differential was associated with game-day temperature for games played South (β = -0.152, 95% CI [-0.242, -0.063], p = .001). In NFL games contested by North (>39° N) versus South (<39° N) teams, North teams are less likely to win and have worse point differentials, as game-day temperatures increase. Research should explore whether behavioral or psychological adaptations to familiar game-day temperatures explain these findings.

This study examined the impact of cold-induced stress on cognitive and motor performance. Thirteen males (19.7 ± 0.23 yr) trained on a computer-based visuomotor task once daily for six consecutive days. The task (19 min per trial; joystick-controlled falling blocks) included brief rest/training intervals. After the first three trials, participants were allocated to control (CON, n = 5) or cold stress (CS, n = 8). On days 4-6, CS completed a 60-min head-out cold-water immersion immediately before the task, producing a ~ 0.5°C drop in core temperature, whereas CON remained stable. Heart rate, ventilation, respiratory frequency (R _f), inspiratory drive (I _d), oxygen consumption, epinephrine, norepinephrine (NEP), cortisol, and subjective measures (thermal comfort, TC; temporal judgment, TJ) were recorded pre-, during, and end-of-trial. CON improved performance by 84%, whereas CS performance was attenuated;(p < 0.01). CON showed no significant physiological or subjective changes. In CS, performance correlated inversely with R _f (r =  -0.56, p = 0.004), and regression indicated I _d, NEP, Rf, TC, and TJ predicted performance;(p < 0.0001; R² = 0.87). Thus, repeated pre-task cold exposure impaired performance, consistent with a complex interaction between physiological and subjective responses.

Occupational heat stress and hydration recommendations aim to prevent core temperatures from exceeding 38.0°C and dehydration in unacclimated workers. These guidelines do not consider individual differences in body composition. We hypothesized that core temperatures would be higher in adults with obesity during simulated occupational heat stress compared to adults without obesity when adhering to the current heat stress recommendations. Twenty-two unacclimated adults with [n = 10; 6 women; body fat % (37 ± 5%)] or without [n = 12; 7 women; body fat % (22 ± 6%)] obesity completed a 4-hour (half workday) exposure to a fixed wet-bulb globe temperature (WBGT) and work intensity. Work-rest ratio was 30 minutes of walking and 30 minutes of seated rest each hour. Work intensity [i.e. metabolic heat production (H_prod)] was prescribed as a function of WBGT (27.6 ± 0.5°C) and normalized to body mass (5.0 ± 0.4 W•kg^-1). All subjects were provided 237 mL of Gatorade every 15 min and drank ad libitum. Peak core temperature was higher in the obese (38.4 ± 0.3°C) compared to the non-obese (37.7 ± 0.4°C; p < 0.01) group. Mean core temperature was higher in the obese (37.9 ± 0.2°C) compared to the non-obese (37.4 ± 0.3°C; p < 0.01) group. Ad libitum drinking was not different between the obese (1.8 ± 0.8 L) and non-obese (1.8 ± 0.7 L; p = 0.94) groups. Percent change in body mass did not differ between the obese (-0.6 ± 0.6%) and non-obese (-0.4 ± 0.9%; p = 0.63) groups. Adherence to the heat stress recommendations during a 4-hour exposure resulted in elevated core temperature responses in adults with obesity compared to adults without obesity.