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\"From deep ocean trenches and the geographical poles to outer space, organisms can be found living in remarkably extreme conditions. This book provides a captivating account of these systems and their extraordinary inhabitants, 'extremophiles'. A diverse, multidisciplinary group of experts discuss responses and adaptations to change; biodiversity, bioenergetic processes, and biotic and abiotic interactions; polar environments; and life and habitability, including searching for biosignatures in the extraterrestrial environment. The editors emphasize that understanding these systems is important for increasing our knowledge and utilizing their potential, but this remains an understudied area. Given the threat to these environments and their biota caused by climate change and human impact, this timely book also addresses the urgency to document these systems. It will help graduate students and researchers in conservation, marine biology, evolutionary biology, environmental change and astrobiology better understand how life exists in these environments and their susceptibility or resilience to change\"-- Provided by publisher.

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).

To determine if intermittent exercise-heat exposures (IHE) every fifth day sustain heat acclimation (HA) adaptations 25 days after initial HA. Randomized control trial. Sixteen non-heat acclimatized men heat acclimated during 10–11 days of exercise in the heat (40°C, 40% RH). A heat stress test (120min, 45% V˙O2peak) before (Pre HA) and after HA (Post HA) in similar hot conditions assessed HA status. Pair-matched participants were randomized into a control group (CON; n=7) that exercised in a temperate environment (24°C, 21%RH) or IHE group (n=9) that exercised in a hot environment (40°C, 40%RH) every fifth day for 25 days following HA (+25d) with out-of-laboratory exercise intensity and duration recorded. Both groups completed +25d in the hot condition. Both groups heat acclimated similarly (p>0.05) evidenced by lower heart rate (HR), thermoregulatory, physiological, and perceptual responses (perceived exertion, fatigue, thermal sensation) Pre HA vs. Post HA (p≤0.05). At +25d, post-exercise HR (p=0.01) and physiological strain index (p<0.05) but neither Tre (p=0.18) nor sweat rate (p=0.44) were lower in IHE vs. CON. In IHE only, post-exercise Tre and perceptual responses at Post HA and +25d were lower than Pre HA (p≤0.01). +25d post-exercise epinephrine was higher in CON vs. IHE (p=0.04). Exercise intensity during out-of-lab exercise and +25d post-exercise HR were correlated (r=−0.89, p=0.02) in IHE. Exercise-heat exposures every fifth day for 25 days and regular intense physical activity after HA sustained HR and Tre adaptations and reduced perceptual and physiological strain during exercise-heat stress ∼1 month later.

To examine the effect of pre-cooling (PreC) on cycling time-trial (CTT) performance in heat, before and after heat acclimation (HA). Randomised crossover. Ten trained/highly trained male cyclists and/or triathletes completed two 20-km CTT before (PreHA) HA training sessions (10 × 60 min intermittent-heat exposure protocol in 36 °C, 50–80 % relative humidity), and after (PostHA). No cooling (CON) or crushed-ice was ingested (i.e., PreC) 30 min prior to the CTTs. The first and final HA training sessions were matched and acted as heat stress tests for comparison. No meaningful direct relations were observed for 20-km CTT completion time between PostHA+PreC (2663 ± 307 s) and PostHA-CON (2671 ± 370 s; b = 37.81 [−109.98, 170.56]). Split times were faster in the first 12.5 km of the CTT in PostHA+PreC but slower across the rest of the CTT compared to PostHA-CON (b = −1.224 [−2.196, −0.157]). Core temperature was lower in PostHA-CON compared to PostHA+PreC (b = −0.02 [−0.04, −0.01]). No difference was observed for mean skin temperature (b = −0.16 [−0.27, −0.05]) and thermal sensation (b = −0.047 [−0.091, −0.003]) during the CTT. Insufficient evidence exists to support a meaningful performance improvement in 20-km CTT in hot-humid conditions when PreC was applied to individuals who completed an HA regime. This may be attributed to the limited effect of PreC on thermal perception, potentially leading to decreased exercise intensity in the latter stages of the CTT as a strategy to mitigate heat gain. Additionally, sub-optimal pacing strategies resulting from PreC on individuals may explain the lack of additional benefit to performance.

The training stress of heat acclimatization optimizing exercise performance in a hot environment can be demanding. This study evaluated the efficiency of different single heating protocols to elevate core temperature. Nonrandomized controlled trial. Laboratory. Ten male participants (age = 25 ± 3 years) performed 4 different 60-minute heating strategies at least 1 week apart. Sixty minutes passive heating (PAS), 30 minutes active heating using a high-intensity bike protocol (HIBP) in a hot environment with 30 minutes passive heating (EH-PAS), 60 minutes HIBP in a hot environment (EH), or 60 minutes HIBP at room temperature (EM). Body core temperature and heart rate. The highest peak gastrointestinal temperature occurred in EH-PAS (39.1 ± 0.4°C), followed by EH (38.9 ± 0.3°C), EM (38.4 ± 0.3°C), and PAS (38.1 ± 0.5°C). The average heart rate, measured as a control for intensity, was not different between exercise strategies (EH-PAS = 142 ± 12.3 beats per minute [bpm], EH = 146 ± 9.7 bpm, and EM = 142 ± 13.3 bpm; P > .05), but was different for PAS (98 ± 15.2 bpm; P < .05). Adding passive heating to a shorter exercise protocol can be just as effective in keeping core temperature elevated as exercise in the heat alone during a 60-minute session. Therefore, a single-bout combination of exercise and passive heating may result in a similar body temperature induction compared with exercise heat stress alone.

PurposeThermal perception, including thermal sensation (TS), influences exercise performance in the heat. TS is a widely used measure and we examined the impact of initial TS (iTS) on performance loss during exercise in simulated Tokyo environmental conditions among elite athletes.Methods105 Elite outdoor athletes (endurance, skill, power and mixed trained) participated in this crossover study. Participants performed a standardized exercise test in control (15.8 ± 1.2 °C, 55 ± 6% relative humidity (RH)) and simulated Tokyo (31.6 ± 1.0 °C, 74 ± 5% RH) conditions to determine performance loss. TS was assessed ± 5 min prior to exercise (iTS) and every 5 min during the incremental exercise test (TS). Based on iTS in the Tokyo condition, participants were allocated to a neutral (iTS = 0, n = 11), slightly warm (iTS = 1, n = 50), or warm-to-hot (iTS = 2/3, n = 44) subgroup.ResultsFor the whole cohort iTS was 1 [1–2] and TS increased to 3 [3–3] at the end of exercise in the Tokyo condition. Average performance loss was 26.0 ± 10.7% in the Tokyo versus control condition. The slightly warm subgroup had less performance loss (22.3 ± 11.3%) compared to the warm-to-hot subgroup (29.4 ± 8.5%, p = 0.003), whereas the neutral subgroup did not respond different (28.8 ± 11.0%, p = 0.18) from the slightly warm subgroup.ConclusioniTS impacted the magnitude of performance loss among elite athletes exercising in hot and humid conditions. Athletes with a warm-to-hot iTS had more performance loss compared to counterparts with a slightly warm iTS, indicating that pre-cooling strategies and/or heat acclimation may be of additional importance for athletes in the warm-to-hot iTS group to mitigate the impact of heat stress.

PurposeHypoxic acclimation enhances convective oxygen delivery to the muscles. Heat acclimation-elicited thermoregulatory benefits have been suggested not to be negated by adding daily exposure to hypoxia. Whether concomitant acclimation to both heat and hypoxia offers a synergistic enhancement of aerobic performance in thermoneutral or hot conditions remains unresolved.MethodsEight young males (\\[\\dot{V}{\\text{O}}_{2\\max }\\]: 51.6 ± 4.6 mL min−1 kg−1) underwent a 10-day normobaric hypoxic confinement (FiO2 = 0.14) interspersed with daily 90-min normoxic controlled hyperthermia (target rectal temperature: 38.5 °C) exercise sessions. Prior to, and following the confinement, the participants conducted a 30-min steady-state exercise followed by incremental exercise to exhaustion on a cycle ergometer in thermoneutral normoxic (NOR), thermoneutral hypoxic (FiO2 = 0.14; HYP) and hot (35 °C, 50% relative humidity; HE) conditions in a randomized and counterbalanced order. The steady-state exercise was performed at 40% NOR peak power output (Wpeak) to evaluate thermoregulatory function. Blood samples were obtained from an antecubital vein before, on days 1 and 10, and the first day post-acclimation.Results\\[\\dot{V}{\\text{O}}_{2\\max }\\] and ventilatory thresholds were not modified in any environment following acclimation. Wpeak increased by 6.3 ± 3.4% in NOR and 4.0 ± 4.9% in HE, respectively. The magnitude and gain of the forehead sweating response were augmented in HE post-acclimation. EPO increased from baseline (17.8 ± 7.0 mIU mL−1) by 10.7 ± 8.8 mIU mL−1 on day 1 but returned to baseline levels by day 10 (15.7 ± 5.9 mIU mL−1).DiscussionA 10-day combined heat and hypoxic acclimation conferred only minor benefits in aerobic performance and thermoregulation in thermoneutral or hot conditions. Thus, adoption of such a protocol does not seem warranted.

To examine the efficacy of weekly and bi-weekly heat training to maintain heat acclimatization (HAz) and heat acclimation (HA) for 8 weeks in aerobically trained athletes. Randomized, between-group. Twenty-four males (mean [m ± standard deviation [sd]; (age, 34 ± 12 y; body mass, 72.6 ± 8.8 kg, VO2peak, 57.7 ± 6.8 mL·kg−1·min−1) completed five trials (baseline, following HAz, following HA (HAz + HA), four weeks into heat training [HTWK4], and eight weeks into HT [HTWK8] that involved 60 min of steady-state exercise (59.1 ± 1.8% vVO2peak) in an environmental laboratory (wet bulb globe temperature [WBGT], 29.6 ± 1.4 °C) on a motorized treadmill. Throughout exercise, heart rate (HR) and rectal temperature (Trec) were recorded. Following HAz + HA, participants were assigned to three groups: control group (HT0), once per week heat training (HT1), and twice per week heat training (HT2). HT involved heated exercise (WBGT, 33.3 ± 1.3 °C) to achieve hyperthermia (38.5–39.75 °C) for 60 min. Repeated measures ANOVAs were used to determine differences. HAz + HA resulted in significant improvements in HR (p < 0.001) and Trec (p < 0.001). At HTWK8, HR was significantly higher in HT0 (174 ± 22 beats⋅min−1) compared to HT2 (151 ± 17 beats⋅min−1, p < 0.023), but was not different than HT1 (159 ± 17 beats⋅min−1, p = 0.112). There was no difference in % change of Trec from post-HAz + HA to HTWK4 (0.6 ± 1.3%; p = 0.218), however, HTWK8 (1.8 ± 1.4%) was significantly greater than post-HAz + HA in HT0 (p = 0.009). Bi-weekly HT provided clear evidence for the ability to maintain physiological adaptions for 8 weeks following HA.

Objectives To examine with a parallel group study design the performance and physiological responses to a 14-day off-season ‘live high-train low in the heat’ training camp in elite football players. Methods Seventeen professional Australian Rules Football players participated in outdoor football-specific skills (32±1°C, 11.5 h) and indoor strength (23±1°C, 9.3 h) sessions and slept (12 nights) and cycled indoors (4.3 h) in either normal air (NORM, n=8) or normobaric hypoxia (14±1 h/day, FiO2 15.2–14.3%, corresponding to a simulated altitude of 2500–3000 m, hypoxic (HYP), n=9). They completed the Yo-Yo Intermittent Recovery level 2 (Yo-YoIR2) in temperate conditions (23±1°C, normal air) precamp (Pre) and postcamp (Post). Plasma volume (PV) and haemoglobin mass (Hbmass) were measured at similar times and 4 weeks postcamp (4WPost). Sweat sodium concentration ((Na+)sweat) was measured Pre and Post during a heat-response test (44°C). Results Both groups showed very large improvements in Yo-YoIR2 at Post (+44%; 90% CL 38, 50), with no between-group differences in the changes (−1%; −9, 9). Postcamp, large changes in PV (+5.6%; −1.8, 5.6) and (Na+)sweat (−29%; −37, −19) were observed in both groups, while Hbmass only moderately increased in HYP (+2.6%; 0.5, 4.5). At 4WPost, there was a likely slightly greater increase in Hbmass (+4.6%; 0.0, 9.3) and PV (+6%; −5, 18, unclear) in HYP than in NORM. Conclusions The combination of heat and hypoxic exposure during sleep/training might offer a promising ‘conditioning cocktail’ in team sports.

This study investigates whether exercise as a strategy for improving physical fitness at sea level also offers comparable benefits in the unique context of high altitudes (HA), considering the physiological challenges of hypoxic conditions. Overall, 121 lowlanders who had lived on the Tibetan Plateau for >2 years and were still living at HA during the measurements were randomly classified into four groups. Each individual of the low‐intensity (LI), moderate‐intensity (MI), and high‐intensity (HI) groups performed 20 sessions of aerobic exercise at HA (3680 m) over 4 weeks, while the control group (CG) did not undergo any intervention. Physiological responses before and after the intervention were observed. The LI and MI groups experienced significant improvement in cardiopulmonary fitness (0.27 and 0.35 L/min increases in peak oxygen uptake [V˙$\\dot{\\mathrm{V}}$ O2peak], both p < 0.05) after exercise intervention, while the hematocrit (HCT) remained unchanged (p > 0.05). However, HI exercise was less efficient for cardiopulmonary fitness of lowlanders (0.02 L/min decrease in V˙$\\dot{\\mathrm{V}}$ O2peak, p > 0.05), whereas both the HCT (1.74 %, p < 0.001) and glomerular filtration rate (18.41 mL/min, p < 0.001) increased with HI intervention. Therefore, LI and MI aerobic exercise, rather than HI, can help lowlanders in Tibet become more acclimated to the HA by increasing cardiopulmonary function and counteracting erythrocytosis. Highlights Low‐ and moderate‐intensity exercise at HA can improve oxygen transport of lowlanders that may help them to become more acclimated to high altitude. High‐intensity exercise performed by lowlanders may result in erythrocytosis without improving oxygen transport. The relationship between physiological system changes induced by exercise performed at HA is modulated by exercise intensity.