Temperature最新文献

Sunscreens may affect thermoregulation and sweating during exercise in warm climates. In this study, we compared the effects of three sunscreens on local sweating rate (LSR) during exercise under controlled conditions (32°C, relative humidity 55%). Fifteen subjects (8 men, 7 women) underwent 20-min cycles in four randomized conditions: control (CON), sunscreen A (SSA), sunscreen B (SSB) and sunscreen C (SSC). LSR was measured by a patch on the scapular region (p < .001). CON showed higher LSR (182.21 μL/min·dm², CI95% 168 to 195 μL/min·dm²) compared to SSA (142.10 μL/min·dm², CI95% 128 to 155 μL/min·dm²), SSB (158.06 μL/min·dm², CI95% 144 to 171 μL/min·dm²), and SSC (159.00 μL/min·dm², CI95% 145 to 172 μL/min·dm²). In men, SSA showed lower LSR compared to CON, SSB, and SSC (p < .05). On the other hand, no statistically significant differences were found in LSR between SSB, SSC, and CON conditions. In women, CON was superior to all sunscreens in LSR (p < .001), and there was no difference between them (SSA, SSB, SSC, p > .05). Sunscreen reduced LSR during moderate exercise in a hot and moderate humidity environment compared to CON, especially SSA in men and all sunscreens in women.

Wet bulb globe temperature (WBGT) is a commonly used measure to predict heat strain in workers. Different combinations of environmental conditions can create equivalent WBGT, yet it remains unknown whether biophysical, physiological, and perceptual responses vary when working in different but equivalent hot conditions. The purpose of the study was to compare body heat storage and physiological and perceptual strain during walking in hot-dry and warm-wet conditions of the same WBGT. Twelve subjects (age: 22 ± 2 y) walked for 90 min at 60% maximum heart rate in a 27.8°C WBGT environment of hot-dry (HD: 40°C, 19% relative humidity) or warm-wet (WW: 30°C, 77% relative humidity) conditions. Partitional calorimetry was used to estimate heat storage. Core temperature at 90 min (HD: 38.5 ± 0.5°C; WW: 38.4 ± 0.3°C, p = 0.244) and cumulative heat storage (HD: 115 ± 531 Kj; WW: 333 ± 269 Kj, p = 0.242) were not different. At 90 min, heart rate was not different (HD: 160 ± 19 bpm; WW: 154 ± 15 bpm, p = 0.149) but skin temperature (HD: 36.6 ± 0.9°C; WW: 34.7 ± 0.6°C, p < 0.001), thirst (HD: 6.8 a.u.; WW: 5.3 a.u. p = 0.043), and sweat rate (HD: 15.1 ± 4.4 g·min^-1; WW: 10.0 ± 4.1 g·min^-1, p < 0.001) were greater in HD compared to WW. Hot environments of equivalent 27.8°C WBGT created equivalent core temperature despite differences in physiological strain during exercise, including earlier onset of cardiovascular strain, greater sweat rate, and higher skin temperature compared to a WW environment. ClinicalTrials.gov ID NCT04624919.

The International Olympic Committee recently introduced a consensus statement on recommendations for outdoor sports in the heat. However, indoor sports such as fencing whereby athletes are required to wear full body protective clothing when competing have received no recommendations. Such scenarios could cause high thermoregulatory demands particularly as competition progresses into latter rounds (direct elimination; DE). Therefore, the aim of this study was to determine the thermoregulatory responses of épée fencing across different phases of competition (Poule and DE). Seven well-trained fencers competed in a simulated competition comprising of seven Poule and seven DE fights. Gastrointestinal temperature (T_gast), skin temperature (T_skin), mask temperature (T_mask), heart rate (HR), thermal sensation, differentiated ratings of perceived exertion (RPE), and movement characteristics were collected for all fights. There was a moderate thermoregulatory demand during Poule rounds shown by post-fight T_gast (38.1 ± 0.4°C), T_skin (34.4 ± 0.7°C), and thermal sensation ratings (6 ± 1). A greater thermoregulatory and perceptual demand observed during DE rounds evidenced by T_gast (38.7 ± 0.3°C post fight), T_skin (35.1 ± 0.7°C), thermal sensation (7 ± 1), increases in T_mask across DE rounds (~1.1°C), and RPE (~15). Furthermore, a significant (p < 0.05) reduction in distance covered from DE 1 to DE 7 suggests a thermoregulatory based impact on performance. This is the first study demonstrating the thermoregulatory demands of épée fencing, highlighting the need to develop heat exertion guidelines within fencing.

Impaired thermoregulatory function is a clinical feature of many health conditions that affect triathletes using wheelchairs and consequently, individual athlete performances may fluctuate according to environmental temperature. We aimed to determine the effect of 1) water temperature on wheelchair triathlon swim time and 2) air temperature on handcycle and wheelchair run (push) time. Published race records from 2017 to 2023 (n = 49 events) were extracted from the World Triathlon website. Bayesian negative binomial regression was used to separately model the nonlinear relationships between water temperature and swim time, and air temperature and handcycle and push time. Age, sex, sport class, whether wetsuits were worn (swim model), and swim time (handcycle and push model) were included as fixed effects. Over the observed water temperature range of 15.7-30.5°C, male swim time (mm:ss) improved from 14:13 (95% credible interval [CrI] = 12:27, 16:09) to 12:35 (95% CrI = 11:00, 14:19). Female swim time improved from 15:33 (95% CrI = 13:24, 17:55) to 12:46 (95% CrI = 11:03, 14:38). It was unclear whether handcycle and push time slowed over the observed air temperature range of 14-33°C. Warmer water temperatures, up to 30.5°C, were associated with faster swim times. It was unclear whether combined handcycle and push time slowed with increases in air temperature, up to 33°C. The integration of information on athlete impairment type and severity with performance data is needed to better understand the extent to which individual athlete performances fluctuate across environmental conditions.

Short-term heat acclimation (HA) appears adequate for maximizing sudomotor adaptations and enhancing thermal resilience in trained athletes. However, for enhanced erythropoiesis and transfer effects to exercise capacity in cooler environments, prolonged HA appears necessary. To establish the time-course for physiological adaptations and performance effects, 20 male elite cyclists were divided into an intervention group (HEAT; n = 10) completing 5 weeks of HA (six one-hour HA-training sessions per week) and control (n = 10) tested pre and post in hot (40°C) and cool conditions (20°C). HEAT completed tests at 40°C every week during HA with measures of sweat rate and [Na⁺] and a decay test 2 weeks after termination of HA. HEAT improved time for exhaustion by 15 min (p < 0.001) in the 40°C test, increased sweat rate by 0.44 L/hour (p < 0.001), and lowered sweat sodium concentration [Na⁺] by 14.1 mmol/L (p = 0.006) from pre- to post-HA, with performance returning to pre-HA levels in the 2-week decay test. Total hemoglobin mass (tHb_mass) was increased by 30 grams (+3%, p = 0.048) after 3 weeks and 40 grams (+4%, p = 0.038) after 5 weeks in HEAT but returned to pre-HA levels at the 2-week decay test. HEAT improved incremental peak power output (+12 W, p = 0.001) without significant changes in maximal oxygen uptake (p = 0.094). In conclusion, improvements in heat exercise tolerance and sudomotor adaptations materialized during the first ~3 weeks and the entire 5 weeks of HA augmented both cool exercise capacity and tHb_mass. However, the 2-week post-HA evaluation demonstrated a rapid decay of physiological adaptations and exercise capacity in the heat.

Blood lactate concentration during exercise is a reliable indicator of energy metabolism and endurance performance. Lactate is also present in sweat, and sweating plays an important role in thermoregulation, especially in hot conditions. Recently, wearable sensors have enabled the real-time and noninvasive measurement of sweat lactate concentration, potentially serving as an alternative indicator of blood lactate response. However, the evidence regarding the relationship between sweat and blood lactate responses during incremental exercise in hot conditions is lacking. In a randomized cross-over design, six highly trained male runners completed two incremental treadmill tests under normal (20°C/50%RH) or hot (30°C/50%RH) conditions. The tests include 3-min running stages and 1-min recovery, starting at 12 km/h and increasing by 1 km/h at each stage. Blood and sweat lactate concentrations were measured at each stage to determine blood and sweat lactate thresholds (LT). Blood lactate concentrations were higher under hot conditions (p < 0.01), but there was no difference in the response pattern or velocity at blood LT between conditions. Significant early increase (p < 0.01) in sweat lactate and low velocity at sweat LT (p < 0.05) were observed under hot conditions. A significant correlation between blood and sweat lactate concentrations was found under normal conditions (p < 0.001) but not under hot conditions, and no significant correlations were observed between the velocity at blood and sweat LT. In conclusion, sweat lactate concentration does not consistently reflect blood lactate concentration during incremental exercise.