Temperature最新文献

The optimal Whole-body cryostimulation (WBC) exposure duration to reach the target skin temperature may vary depending on individual factors such as age, sex, and body mass index (BMI). Maintaining skin temperatures below 13.6°C is necessary to trigger significant cold-induced analgesia. The aim of our study is to investigate how these variables influence the duration required to reach the analgesic threshold temperature of 13.6°C during WBC. A randomized cross-over controlled trial was conducted with 90 healthy participants, categorized by age, sex, and BMI. Each participant underwent two sessions: a 4 min WBC exposure at -50°C and a control session. Skin temperature was measured using a thermal imaging camera before, during and after cold exposure. Significant differences in skin temperature were observed between groups. Among young participants, normal-weight men required 4 minutes of exposure to reach the analgesic threshold (p < 0.05), while normal-weight women reached it in 3 minutes (p < 0.01). Overweight young men needed 3 minutes and 30 seconds (p < 0.001), whereas overweight young women reached the threshold earlier, at 2 min and 30 s (p < 0.01). For senior participants, both normal-weight men and women reached the analgesic threshold at 3 minutes of exposure (p < 0.001). In contrast, overweight senior men and women needed only 2 minutes and 30 seconds to reach the target skin temperature (p < 0.01). The optimal WBC exposure duration for achieving analgesic effects varies significantly depending on individual characteristics, suggesting that WBC protocols should be tailored to maximize therapeutic benefits.

Swimming in cold water is intrinsically unsafe. One of the threats is a fall in deep-body temperature, which adversely affects all body systems and increases the risk of death. Wetsuits mitigate, but do not negate this threat. Environmental conditions may confound findings from laboratory studies or mathematical models. The study aimed to elucidate associations and patterns of deep-body temperature change in open water wetsuited swimmers, thus facilitating risk assessment and improving swimmer safety. In this exploratory cohort study, following collection of anthropomorphic data including a Dual-energy X-ray Absorptiometry scan, deep-body temperature was continuously measured in 76 open water swims by 31 wetsuited swimmers in water temperatures ranging from 8.4°C to 24.5°C. The temperature trajectories were analyzed by piece-wise and linear mixed model regression. Registered with clinicaltrials.gov NCT06685627. Following immersion, there was a tri-phasic deep-body temperature trajectory, although not all phases were present in all swims: an initial rise, then a plateau phase and then thermal decompensation. Water temperature was correlated with the duration of these phases, as was body habitus for the initial rise. Minimum deep-body temperature was correlated with pre-swim temperature. Despite environmental and individual variations, this paper identified a tri-phasic deep-body temperature trajectory for wetsuited swimmers and proposed physiological mechanisms that may account for them. The tri-phasic pattern of an initial rise, a plateau phase and then thermal decompensation, may be useful in assessing the risks of open water swimming and may facilitate development and validation of deep-body temperature models for wetsuited swimmers.

 The objective of this study was to characterize the 24-h blood pressure response following an acute hot-water immersion exposure, specifically examining the effect of immersion duration and water temperature, in people with hypertension. Sixteen participants (11 females; 62 ± 7 y; 31.7 ± 7.5 kg.m^-2) with hypertension (taking at least one anti-hypertensive medication) completed four randomized sessions: 1) 20-min and 2) 40-min hot-water immersion (40°C), 3) 40-min thermoneutral immersion (36.5°C), and 4) control (seated, no immersion). Blood pressure, heart rate, perceptual and affective responses were recorded throughout exposure. Immediately after exposure, participants were fitted with an ambulatory blood pressure monitor for the following 24 h. Twenty-four-hour SBP was 7 mm Hg lower (95% CI: -11, -2; p = 0.001) after the 40-min hot-water immersion and 6 mm Hg lower after both the 20-min hot-water immersion (-10, -1; p = 0.006) and 40-min thermoneutral immersion (-9, -3; p = 0.002) compared to control; these effects were similar across nighttime (i.e. 10 pm-6 am) and daytime periods. Twenty-four-hour DBP was not statistically different across any exposure (p = 0.093). The percentage of 24 h in target range for SBP (110-130 mm Hg) more than doubled (39% vs. 18%) following the 40-min hot-water immersion, compared to control. Clinically meaningful decreases in systolic blood pressure were evident with hot-water immersion in people with hypertension; these effects were present irrespective of immersion duration (i.e. 20 min vs. 40 min) or water temperature (36.5°C vs 40°C).

This study investigated the effect of mixed pre-cooling (cooling vest and ice-slurry) on thermal and cardiovascular strain and performance in unacclimatized females exercising in the heat during menstrual cycle (MC) Phase-1 (low estrogen and progesterone) and Phase-4 (moderate estrogen and high progesterone). In a randomized crossover design, 11 runners completed two trials in each MC Phase: mixed pre-cooling (wearing a cooling vest around the torso for 30 min and ingesting 7.5 g.kg^-1 of body mass of ice slurry), and control (equivalent slurry volume at ~20°C without a cooling vest), prior to a 10-km running time trial (TT) in 34°C and 60% relative humidity. Rectal temperature (T_re), heart rate (HR), and perceptual responses were measured throughout the TT. Linear mixed models were fitted to estimate intervention and MC phase effects. Mixed pre-cooling had no effect on HR (1.06 [-0.83, 2.95] beats.min^-1; p = 0.272) or TT completion time (-0.23 [-1.32, 0.86] min; p = 0.677) versus control. T_re (-0.21 [-0.34, -0.07] °C; p = 0.003) and thermal sensation (-0.61 [-0.78, -0.44] au; p < 0.001) were significantly lower with mixed pre-cooling compared to control. Rise in T_re (-0.1 [-0.3, 0.0] °C) and thermal sensation were attenuated in MC phase-4 (-0.57 [-0.81, -0.34] au; all p < 0.05). Mixed pre-cooling was effective at attenuating the rise in T_re for a similar work rate, particularly in MC phase-4, where females may experience greater heat thermosensation. However, the magnitude of attenuated T_re does not improve 10-km running performance in the heat, suggesting additional cooling and/or heat mitigation strategies may be required to improve performance.

Cardiovascular disease is more prevalent in individuals of Black-African (BA) and South-Asian (SA) descent than White-European (WE) counterparts, with vascular dysfunction identified as contributing to this disparity. Chronic heat therapy can elicit positive vascular adaptations, potentially underpinned by the repeated cardiovascular strain experienced during acute heat exposures. This study examined the cutaneous peripheral microvascular responses following acute hot (HWI) and thermoneutral (CON) water immersion between males of WE, BA, and SA descent. Thirty-one young, healthy WE (n = 10), BA (n = 10), SA (n = 11) males completed 60 minutes of HWI (39°C) and CON (36°C) with thermoregulatory, cardiovascular, and perceptual responses measured throughout. Following 60 minutes of thermoneutral rest, forearm and Great toe cutaneous vascular conductance (CVC) were recorded during cutaneous post-occlusive reactive hyperemia (PORH) and local heating (LH). Baseline CVC was similar between groups (p ≥ 0.08). During PORH, BA had lower peak forearm and Great toe CVC than WE and SA, and a reduced CVC area under the curve compared to WE (p ≤ 0.01). Furthermore, BA Great toe CVC was blunted compared to WE and SA during both 42°C (p ≤ 0.033) and 44°C (p ≤ 0.02) LH, respectively. Great toe CVC was acutely increased following HWI in responses to 44°C LH compared to CON (p ≤ 0.039), with no race × condition interaction effects. In conclusion, despite blunted microvascular responses in BA, acute HWI did not elicit distinct effects between males of WE, BA, and SA descent, although microvascular responses to LH were greater following HWI.