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Cross‐adaptation occurs when exposure to one environmental stressor (e.g., heat) induces protective responses to another (e.g., hypoxia). Although post‐exercise hot‐water immersion (HWI) induces heat acclimation, its potential to elicit cross‐adaptation remains unclear. This study evaluated the effectiveness of a 6‐week post‐exercise HWI intervention on exercise performance in hypoxia (O2 = 13%). Twenty healthy volunteers (28 ± 5 years; V̇O2peak ${\\dot V_{{{\\mathrm{O}}_2}{\\mathrm{peak}}}$47.4 ± 8.9 mL kg−1 min−1; 12 males, 8 females) completed interval cycling (4×4 min at 90 ± 5% maximal heart rate, 3×/week) followed by water immersion at either 34.5°C (control) or 42°C (HWI) for 40–50 min, five times per week. Following the 6‐week intervention, the post‐exercise HWI group exhibited lower resting heart rate (P < 0.01, q = 0.02; d = −1.32) and core temperature (P < 0.01, q = 0.001; d = −1.88) and elevated haemoglobin concentration (P < 0.01, q = 0.02; d = 1.38). Compared to the control group, the HWI group also showed greater improvements in time‐to‐exhaustion (TTE) trial (P and q < 0.01; d = 1.2) under hypoxia, but not in aerobic peak power (P = 0.03, q = 0.08; d = 0.86) or peak oxygen consumption (V̇O2peak ${\\dot V_{{{\\mathrm{O}}_2}{\\mathrm{peak}}}$ ) (P = 0.04, q = 0.10; d = 0.82). Throughout the TTE, lower core temperature and tidal volume, with increased oxygen saturation and V̇O2 ${\\dot V_{{{\\mathrm{O}}_2}}}$were observed (P and q < 0.05). During hypoxic steady‐state exercise at 60% of V̇O2peak ${\\dot V_{{{\\mathrm{O}}_2}{\\mathrm{peak}}}$ , the HWI group exhibited lower core temperature and higher peripheral oxygen saturation in hypoxia. No between‐group differences were observed in mean V̇O2 ${\\dot V_{{{\\mathrm{O}}_2}}}$ , respiratory exchange ratio, heart rate or rate of perceived exertion, nor in V̇O2peak ${\\dot V_{{{\\mathrm{O}}_2}{\\mathrm{peak}}}$and aerobic peak power under normoxia (P and q > 0.05). In conclusion, post‐exercise HWI enhances maximal exercise performance under acute hypoxia, likely due to increased haemoglobin concentration, lower core temperature and improved respiratory efficiency. What is the central question of this study? Can post‐exercise hot‐water immersion (HWI) induce a cross‐adaptation effect enhancing exercise performance in acute hypoxia? What is the main finding and its importance? Six weeks of daily post‐exercise HWI at 42°C (chest level, 40–50 min) elicits a cross‐adaptation effect in healthy, active cyclists. Post‐exercise HWI intervention improves exercise performance in acute hypoxia (13% O₂, simulating ∼4300 m altitude), as demonstrated by increased time‐to‐exhaustion at 80% of V̇O2peak ${\\dot V_{{{\\mathrm{O}}_2}{\\mathrm{peak}}}$ . This improvement may be attributed to increased haemoglobin concentration, lower core temperature and enhanced respiratory efficiency (i.e., lower tidal volume, reduced V̇E ${\\dot V_{\\mathrm{E}}}$and increased absolute V̇O2 ${\\dot V_{{{\\mathrm{O}}_2}}}$and oxygen saturation).

Marathon open‐water swimming presents extreme thermophysiological challenges, particularly in cold environments. This case report describes continuous core temperature data from a solo crossing of New Zealand's Foveaux Strait, an infamously cold (13°C –14°C), turbulent open‐water swim. A 52‐year‐old male swimmer (body mass index, 27.9 kg m−2; body fat, 18%) completed the 37 km swim in 9 h 52 min under standard marathon swimming rules (no wetsuit). Core temperature (measured via an ingestible thermometer pill) decreased rapidly after immersion, falling from 37.9°C to <35.0°C within 50 min. The swimmer reached a nadir of 33.88°C at 2 h 42 min and remained hypothermic for more than half of the swim (total, 369 min). Despite this, he displayed no overt cognitive or motor impairment, completed the swim unaided and did not experience an after‐drop post‐immersion. This case highlights the remarkable thermoregulatory tolerance of a cold‐adapted endurance swimmer. What is the main observation in this case? A cold‐adapted marathon swimmer tolerated prolonged moderate hypothermia (core temperature <35°C for >6 h; nadir 33.88°C) during an open‐water swim in 13–14°C water. What insights does it reveal? This case demonstrates that in a trained and cold‐adapted marathon swimmer, prolonged immersion in cold water can be tolerated at core temperatures traditionally classified as clinically hypothermic, without functional compromise or adverse outcomes.

A previous study (Meng et al. in Water 12(9):2388, 2020. https://doi.org/10.3390/w12092388) analysed and studied the law of water infiltration in loess. As a continuation of prior research, this paper will further study the collapsible settlement characteristics of loess. The collapsibility of loess means that after water infiltrates into the pores between the loess particles, it destroys the original pore structure of loess and causes the strength of loess to rapidly decrease. Under the action of its own gravity loads and the gravity loads of water, the phenomenon of overall settlement and collapse appears. This paper monitored the settlement law of loess over time through shallow and deep punctuations buried in loess, which results in daily settlement and 65 d cumulative settlement. Then, the gravity load of the water in the infiltrated loess was calculated and compared with the gravity load of the loess. Finally, based on the test data, the sensitivities of the loess collapsibility coefficient and self-weight collapsibility coefficient to loess parameters were analysed. The research in this paper provides the experimental basis for related studies.

There are an increasing number of cases wherein the soil around a tunnel is immersed in water, which adversely affects the tunnel. To study the influence mechanism of local immersion of loess stratum on metro shield tunnel in detail, a similarity model test and numerical simulation were used in this study. These were used to investigate the stress and deformation of tunnel lining and stratum and surface settlement after a local soil collapse in the tunnel, and the mechanical mechanism that causes this effect. Further, the influences of different methods of water immersion on the tunnel lining were studied using numerical simulation. The results showed that the larger the collapsing area, the larger the bending moment and the axial force increment of the tunnel lining and the surface settlement; the bending moment and axial force near the side of the collapsing area were larger than those of the non-wet side. Vertical stress in the collapsible area was reduced, while the vertical stress of the non-collapsible soil on both sides of the collapsible area was increased due to the transmission of stress. When the water immersion area was the same, different water immersion methods also made the internal force of the tunnel lining slightly different; however, the difference was not obvious.

Envenomation by marine animals poses a significant health concern globally, affecting both local residents and tourists in coastal regions. The primary objective of this review is to critically evaluate the existing scientific literature to determine the most effective first-aid treatment for envenomations caused by marine animals, specifically whether hot-water immersion (HWI) or ice-pack treatment (IPT) provides the best immediate care. This comprehensive review covers a wide range of marine envenomations, from jellyfish stings to stingray injuries. While our focus is primarily on the efficacy of HWI and IPT, we also explore the role of cold-water treatment as a result of its relevance and similarity to ice-pack applications. In addition, we examine other treatments mentioned in the literature, such as medications or vinegar, and highlight their findings where applicable. To provide a clear and structured overview, we summarised the articles in separate tables. These tables categorise the type of research conducted, the marine species studied, the region of origin of the marine species, and the key findings of each study. Our analysis of the available evidence indicates a general consensus in the scientific community on the effectiveness of HWI or IPT for envenomation by marine animals. However, when treating those injuries, it is crucial to consider all factors since there is no universally superior treatment due to the diverse nature of marine habitats.

Background This systematic review and network meta-analysis assessed via direct and indirect comparisons the recovery effects of hydrotherapy and cold therapy at different temperatures on exercise induced muscle damage. Methods Five databases were searched in English and Chinese. The included studies included exercise interventions such as resistance training, high-intensity interval training, and ball games, which the authors were able to define as activities that induce the appearance of EIMD. The included RCTs were analyzed using the Cochrane Risk of Bias tool. Eligible studies were included and and two independent review authors extracted data. Frequentist network meta-analytical approaches were calculated based on standardized mean difference (SMD) using random effects models. The effectiveness of each intervention was ranked and the optimal intervention was determined using the surface under the cumulative ranking curve (SUCRA) indicator. Results 57 studies with 1220 healthy participants were included, and four interventions were examined: Cold Water Immersion (CWI), Contrast Water Therapy (CWT), Thermoneutral or Hot Water Immersion (TWI/HWI), and Cryotherapy(CRYO). According to network meta-analysis, Contrast Water Immersion (SUCRA: 79.9% )is most effective in recovering the biochemical marker Creatine Kinase. Cryotherapy (SUCRA: 88.3%) works best to relieve Delayed Onset Muscle Soreness. In the recovery of Jump Ability, cryotherapy (SUCRA: 83.7%) still ranks the highest. Conclusion We found that CWT was the best for recovering biochemical markers CK, and CRYO was best for muscle soreness and neuromuscular recovery. In clinical practice, we recommend the use of CWI and CRYO for reducing EIMD. Systematic Review Registration [PROSPERO], identifier [CRD42023396067].

As cold‐water immersion becomes more popular and accessible, it is important to explore potential risks. This study examines the cardiac autonomic response and arrhythmia occurrence in healthy adolescents during face and body immersion. Healthy ninth‐grade students, aged 15–16 years, were recruited to perform face immersion (FI) in 10°C water and body immersion in 2°C water (IWI). Electrocardiograms (ECGs) were continuously recorded, and the heart rate (HR) response and occurrence of arrhythmias were assessed. Among the 54 individuals performing FI, six had supraventricular extrasystoles, and two had ventricular bigeminy. Among the 20 performing IWI, four had supraventricular extrasystoles. The HR response was more pronounced during FI compared to IWI (p < 0.001). During both FI and IWI, girls showed initially higher HR and more pronounced HR reduction than boys, but there were no significant sex differences (p = 0.26). During the first 30 seconds of IWI, boys maintained a steady HR (p = 0.176), while girls experienced a near‐linear reduction (p = 0.009). This study indicates a low risk of severe arrhythmias when briefly immersing the body in ice‐cold water in healthy adolescents. However, the risk could increase if combined with face submersion and apnea.

The effect of long-term water immersion on the mechanical properties of porphyritic gypsum rock containing coarse-grained gypsum minerals and a variety of fine-grained minerals was explored using uniaxial and triaxial compression tests. XRD, SEM, and EDS analyses were utilized to discuss the water-softening mechanism in relation to the rock fabric. The results show that the elastic modulus decreases while Poisson’s ratio increases for rocks without lateral confinement after long-term immersion, which exerts a weak effect on the internal friction angle of rocks but greatly weakens the cohesion. The softening effect of water on rocks attenuates nonlinearly with increasing immersion time, and the compressive strength changes as a logarithmic function of immersion time. As the confining pressure increases, the sensitivity of the compressive strength to immersion time tends to weaken. The increase in the confining pressure causes the transition from brittleness to ductility of rocks, and long-term water immersion leads to a decrease in the transitional confining pressure. The softening of rocks is attributed to structural damage caused by the dissolution of gypsum minerals and the disintegration of material zones composed of fine-grained minerals under immersion conditions. Water infiltration is facilitated by intergranular pores within the fine-grained mineral zone as microcracks are distributed along the gypsum cleavages and contact boundaries between coarse- and fine-grained mineral zones. During prolonged water immersion, the water activity shifts from a predominance of infiltration to that of dissolution and disintegration, resulting in a transient increase followed by a gradual decrease in the mass of gypsum rock.

Abstract Context It is unclear whether immersion in cool water, typical of many beaches, increases the concentration of blood glucose in individuals with type 1 diabetes mellitus (T1DM). Objective To test the hypothesis in individuals with T1DM that immersion neck-deep in cool water (COOL) causes an increase in blood glucose concentration, but not exposure to thermoneutral water (THERMO) or thermoneutral air. Methods Eight overnight-fasted participants with T1DM were exposed for 60 minutes on separate days to 3 experimental conditions: cool water (COOL, 23 °C); thermoneutral water (THERMO, 33.5 °C); or thermoneutral air (24 °C). They then recovered for 60 minutes on land at 24 °C. At time intervals, we measured: blood glucose and plasma insulin concentration, rate of carbohydrate and fat oxidation, skin and core temperature, subcutaneous blood flow, and shivering via electromyography. Results There was no change in blood glucose concentration during the 3 experimental conditions (P > .05). During recovery after COOL, blood glucose increased (P < .05) but did not change in the other 2 conditions. The rate of carbohydrate oxidation during and early after COOL was higher than in the other 2 conditions (P < .05), and COOL led to a decrease in subcutaneous blood flow and the concentration of plasma insulin (P < .05). Conclusion Cool or thermoneutral neck-deep immersion in water does not cause a change in the concentration of blood glucose in people with T1DM, but on-land recovery from COOL causes an increase in blood glucose that may be due, at least in part, to the accompanying decrease in plasma insulin.

This study quantifies how pressurized water immersion alters the reciprocating sliding behavior of glass and Kevlar woven fabric-reinforced polymer hybrid composite laminates. Specimens were immersed in deionized water at 10 bar and 25 °C for 0, 7, 14, and 21 days, then tested against a 6 mm 100Cr6 steel ball at 20 N under four regimes that combine 1 or 2 Hz with 10 m or 20 m total sliding. Water uptake rose from 0 to 8.54% by day 21 and followed a short-time Fickian square root of time trend, indicating diffusion-controlled sorption. The coefficient of friction exhibited a robust nonmonotonic response with a pronounced minimum at 14 days that was typically 20 to 40% lower than the unaged reference across frequencies and distances, while 7 days produced a partial decrease and 21 days trended upward. Three-dimensional profilometry showed progressive widening and deepening of wear tracks with immersion, for example, at 1 Hz and 10 m width increased from about 1596 to about 2050 to 2101 μm and depth from about 128 to about 184 to 185 μm, with a transient narrowing at 2 Hz after 7 days. Scanning electron microscopy corroborated a transition from mild plowing to matrix plasticization with fiber–matrix debonding and debris compaction. Beyond geometric wear metrics, this study re-processed the existing profilometry and COF records to derive a moisture-dependent mechanistic approach. Moisture uptake up to 8.54% reorganizes the third body at the interface so that friction drops markedly at 14 days (typically 20–40% below the unaged state), while concurrent matrix plasticization and interface weakening enlarge the wear cross-section extracted from the same 3D maps, decoupling friction from damage width/depth under wet conditioning. Factorial analysis ranked immersion time as the dominant driver of damage for width and depth with frequency as a secondary factor and sliding distance as a minor factor, highlighting immersion-controlled tribological design windows for marine and humid service.