Heat Acclimation Training Research Articles

Constructing A Makeshift Heat Chamber Suitable For Thermoregulatory Research And Heat Acclimation Training

Constructing A Makeshift Heat Chamber Suitable For Thermoregulatory Research And Heat Acclimation Training

Time-course for onset and decay of physiological adaptations in endurance trained athletes undertaking prolonged heat acclimation training

ABSTRACT 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 (tHbmass) 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 tHbmass. However, the 2-week post-HA evaluation demonstrated a rapid decay of physiological adaptations and exercise capacity in the heat.

Long-term heat acclimation training in mice: Similar metabolic and running performance adaptations despite a lower absolute intensity than training at temperate conditions

This study investigated the impact of long-term heat acclimation (HA) training on mouse thermoregulation, metabolism, and running performance in temperate (T) and hot (H) environments. Male Swiss mice were divided into 1) Sedentary (SED) mice kept in T (22 °C; SED/T), 2) Endurance Trained mice (ET, 1 h/day, 5 days/week, 8 weeks, 60 % of maximum speed) in T (ET/T), 3) SED kept in H (32 °C; SED/H), and 4) ET in H (ET/H). All groups performed incremental load tests (ILT) in both environments before (pre-ET) and after four and eight weeks of ET. In the pre-ET period, H impaired (∼30 %) performance variables (maximum speed and external work) and increased (1.3 °C) maximum abdominal body temperature compared with T. In T, after four weeks, although ET/H exercised at a lower (∼30 %) absolute intensity than ET/T, performance variables and aerobic power (peak oxygen uptake, VO2peak) were similarly increased in both ET groups compared with SED/T. After eight weeks, the external work was higher in both ET groups compared with SED/T. Only ET/T significantly increased VO2peak (∼11 %) relative to its pre-ET period. In H, only after eight weeks, both ET groups improved (∼19 %) maximum speed and reduced (∼46 %) post-ILT blood lactate concentrations compared with their respective pre-ET values. Liver glycogen content increased (34 %) in both ET groups and SED/H compared with SED/T. Thus, ET/H was performed at a lower absolute intensity but promoted similar effects to ET/T on metabolism, aerobic power, and running performance. Our findings open perspectives for applying HA training as part of a training program or orthopedic and metabolic rehabilitation programs in injured or even obese animals, reducing mechanical load with equivalent or higher physiological demand.

Comprehensive preparation strategies for a world-class endurance athlete competing in major international competitions in hot environmental conditions: A case study

Purpose To document a world-class race walking athlete's preparation for the 2019 International Association of Athletics Federations (IAAF) World Championships (Doha, Qatar), including periodized training, physiological data, cooling strategies and nutritional practices. Methods Physiological data (VO2max, mL·kg−1·min−1; submaximal economy, mL·kg−1·min−1; and %VO2max), training volume (km) and intensity (min·km−1) were recorded (January–May 2019). Additional training strategies and interventions (altitude training, heat acclimation/acclimatization, cooling methods and pre- and during-race nutrition) were described (February–October 2019). Performances in IAAF-sanctioned 20 km races were also reported. Results The athlete's highest VO2max result was 74.6 mL·kg−1·min−1, and his highest 4 mmol·L−1 walking speed was 15.7 km·h−1. The best submaximal economy measures (the lowest proportional oxygen use at 13 km·h−1) were 48.4 mL·kg−1·min−1 (65.2% VO2max). The best performance outcome was a bronze medal-winning performance at the 2019 IAAF World Championships (32°C; 77% RH). Six blocks of altitude training were performed (119 days). Five blocks of heat acclimatization training (127 days), one block of heat acclimation training (8 days) and two blocks of post-training passive heat sessions (16 days) were completed. Internal and external cooling strategies were used, and the athlete's nutritional intake focused on carbohydrate and fluid intake prior to and during races, pre-race supplementation with sodium bicarbonate using chronic and acute protocols, caffeine supplementation during races and pre-race hyperhydration. Conclusion The strategies used by this elite athlete included repeated heat acclimation, heat acclimatization, passive heat exposure, hypoxic training and heat mitigation strategies. Similar strategies may provide benefit to elite athletes preparing for major international competitions in hot conditions.

Alteration of gut microbiota after heat acclimation may reduce organ damage by regulating immune factors during heat stress.

Heat-related illnesses can lead to morbidity, which are anticipated to increase frequency with predictions of increased global surface temperatures and extreme weather events. Although heat acclimation training (HAT) could prevent heat-related diseases, the mechanisms underlying HAT-promoting beneficial changes in organ function, immunity, and gut microbes remain unclear. In the current study, we recruited 32 healthy young soldiers and randomly divided them into 4 teams to conduct HATs for 10 days: the equipment-assisted training team at high temperature (HE); the equipment-assisted training team under normal hot weather (NE); the high-intensity interval training team at high temperature (HIIT), and the control team without training. A standard heat tolerance test (HTT) was conducted before (HTT-1st) and after (HTT-2nd) the training to judge whether the participants met the heat acclimation (HA) criteria. We found that the participants in both HE and NE teams had significantly higher acclimation rates (HA/total population) than whom in the HIIT team. The effects of HAT on the participants of the HE team outperformed that of the NE team. In the HA group, the differences of physiological indicators and plasma organ damage biomarkers (ALT, ALP, creatinine, LDH, α-HBDH and cholinesterase) before and after HTT-2nd were significantly reduced to those during HTT-1st, but the differences of immune factors (IL-10, IL-6, CXCL2, CCL4, CCL5, and CCL11) elevated. The composition, metabolism, and pathogenicity of gut microbes changed significantly, with a decreased proportion of potentially pathogenic bacteria (Escherichia-Shigella and Lactococcus) and increased probiotics (Dorea, Blautia, and Lactobacillus) in the HA group. Training for a longer time in a high temperature and humidity showed beneficial effects for intestinal probiotics. These findings revealed that pathogenic gut bacteria decrease while probiotics increase following HA, with elevated immune factors and reduced organ damage during heat stress, thereby improving the body's heat adaption.

High or hot-Perspectives on altitude camps and heat-acclimation training as preparation for prolonged stage races.

Adaptation to heat stress and hypoxia are relevant for athletes participating in Tour de France or similar cycling races taking place during the summertime in landscapes with varying altitude. Both to minimize detrimental performance effects associated with arterial desaturation occurring at moderate altitudes in elite athletes, respectively, reduce the risk of hyperthermia on hot days, but also as a pre-competition acclimatization strategy to boost blood volume in already highly adapted athletes. The hematological adaptations require weeks of exposure to manifest, but are attractive as an augmented hemoglobin mass may improve arterial oxygen delivery and hence benefit prolonged performances. Altitude training camps have in this context a long history in exercise physiology and are still common practice in elite cycling. However, heat-acclimation training provides an attractive alternative for some athletes either as a stand-alone approach or in combination with altitude. The present paper provides an update and practical perspectives on the potential to utilize hypoxia and heat exposure to optimize hematological adaptations. Furthermore, we will consider temporal aspects both in terms of onset and decay of the adaptations relevant for improved thermoregulatory capacity and respiratory adaptations to abate arterial desaturation during altitude exposure. From focus on involved physiological mechanisms, time course, and responsiveness in elite athletes, we will provide guidance based on our experience from practical implementation in cyclists preparing for prolonged stage races such as the Tour de France.

Evidence that heat acclimation training may alter sleep and incidental activity

ABSTRACT This randomized cross-over study tested the hypothesis that heat acclimation training would detrimentally affect sleep variables and alter incidental physical activity compared to a thermoneutral training control condition. Eight recreationally trained males (V̇O2peak 49±4.9 mL.kg-1.min-1) completed two separate interventions separated by at least 31 days: 5 consecutive day training blocks of moderate-intensity cycling (60 min·day-1 at 50% peak power output) in a hot (34.9±0.7 °C and 53±4 % relative humidity) and a temperate (22.2±2.6 °C; 65±8 % relative humidity) environment. Wrist-mounted accelerometers were worn continuously for the length of the training blocks and recorded physical activity, sleep quality and quantity. Data were analysed in a Bayesian framework, with the results presented as the posterior probability that a coefficient was greater or less than zero. Compared to the temperate training environment, heat acclimation impaired sleep efficiency (Pr β<0 = .979) and wake on sleep onset (Pr β>0 = .917). Daily sedentary time was, on average, 35 min longer (Pr β>0 = .973) and light physical activity time 18 min shorter (Pr β>0 = .960) during the heat acclimation period. No differences were observed between conditions in sleep duration, subjective sleep quality, or moderate or vigorous physical activity. These findings may suggest that athletes and coaches need to be cognisant that heat acclimation training may alter sleep quality and increase sedentary behaviour. Highlights Five consecutive days of heat training negatively affected some objective measures of sleep quality and incidental physical activity in recreationally trained athletes. Athletes and coaches need to be aware of the potential unintended consequences of using heat acclimation on sleep behaviours.

Can ten days of heat acclimation training improve temperate-condition rowing performance in national-level rowers?

This study investigated whether heat acclimation (HA) could improve rowing performance in temperate conditions in national-level rowers. Using a parallel-group design, eleven rowers (3 female, 8 male, age: 21±3 years, height: 182.3±6.8cm, mass: 79.2±9.0kg, [Formula: see text]: 61.4±5.1ml·kg·min-1) completed either a HA intervention (HEAT, n = 5) or acted as controls (CON, n = 6). The intervention replaced usual cross-training sessions and consisted of an hour of submaximal cycling or rowing ergometry in either 34±0°C for HEAT or 14±1°C for CON daily over two five-day blocks (10 sessions total), separated by 72h. Participants performed the '10+4' test that consists of 10-min submaximal rowing and a 4-min time-trial (TT) in temperate conditions (20±0°C) before and after the intervention. Heat acclimation following the 10-session intervention was evidenced by large significant (p<0.05) decreases in maximum tympanic temperature (d = -1.68) and rate of perceived exertion (RPE) (d = -2.26), and a large significant increase in sweat loss (d = 0.91). Large non-significant (p>0.05) decreases were seen in average tympanic temperature (d = -3.08) and average heart rate (d = -1.53) in HEAT from session 2 to session 10 of the intervention. Furthermore, a large significant increase was seen in plasma volume (d = 3.74), with large significant decreases in haemoglobin concentration (d = -1.78) and hematocrit (d = -12.9). Following the intervention, large non-significant increases in respiratory exchange ratio (d = 0.87) and blood lactate (d = 1.40) as well as a large non-significant decrease in RPE (d = -1.23) were seen in HEAT during the 10-min submaximal rowing. A large significant decrease in peak heart rate (d = -2.27), as well as a large non-significant decrease in relative [Formula: see text] (d = -0.90) and large non-significant increases in respiratory exchange ratio (d = 1.18), blood lactate concentration (d = 1.25) and power output (d = 0.96) were seen in HEAT during the 4-min TT. This study suggests that a 10-session HA intervention may elicit HA in national-level rowers, with potential to improve 4-min TT performance in temperate conditions.

Competing in Hot Conditions at the Tokyo Olympic Games: Preparation Strategies Used by Australian Race Walkers.

IntroductionThe Tokyo 2021 Olympic Games was anticipated to expose athletes to the most challenging climatic conditions experienced in the history of the modern Olympic Games. This study documents strategies executed by Australian endurance athletes during the team holding camp and Olympic Games experiences, including (1) baseline physiological data, training data, and heat acclimation/acclimatization practices; (2) pre- and in-race cooling and nutritional strategies, and (3) Olympic Games race performance data.MethodsSix athletes (three males, three females; age 24 ± 4 years; VO2max 63.2 ± 8.7 mL⋅kg–1⋅min–1; sum of 7 skinfolds 53.1 ± 23.4 mm) were observed prior to and during the team holding camp held in Cairns, QLD, Australia. Athletes completed 6–7 weeks of intermittent heat acclimation training, utilizing a combination of 2–4 passive and active acclimation sessions per week. Active acclimation was systematically increased via exposure time, exercise intensity, temperature, and humidity. In the team holding camp, athletes undertook a further 23 heat acclimatization training sessions over 18 days in a continuous fashion. Hyperhydration (using sodium and glycerol osmolytes), and internal and external pre-and in-race cooling methods were also utilized. A low energy availability intervention was implemented with two athletes, as a strategy to periodize ideal race body composition. Race performance data and environmental conditions from the 2021 Olympic Games were also documented.ResultsThe highest values for aerobic capacity were 63.6 mL⋅kg–1⋅min–1 for female race walkers and 73.7 mL⋅kg–1⋅min–1 for males. Training volume for the six athletes was the highest in the second week of the team holding camp, and training intensity was lowest in the first week of the team holding camp. Performance outcomes included 6th place in the women’s 20 km event (1:30:39), which was within 2% of her 20 km personal best time, and 8th place in the men’s 50 km event (3:52:01), which was a personal best performance time.ConclusionPeriodized training, heat acclimation/acclimatization, cooling and nutritional strategies study may have contributed to the race outcomes in Olympic Games held hot, humid conditions, for the race walkers within this observational study.

Heat acclimation training support in consideration of infection control

Heat acclimation training support in consideration of infection control

Short-term heat acclimation preserves knee extensor torque but does not improve 20\xa0km self-paced cycling performance in the heat

PurposeThis study investigated the effect of 5 days of heat acclimation training on neuromuscular function, intestinal damage, and 20 km cycling (20TT) performance in the heat.MethodsEight recreationally trained males completed two 5-day training blocks (cycling 60 min day−1 at 50% peak power output) in a counter-balanced, cross-over design, with a 20TT completed before and after each block. Training was conducted in hot (HA: 34.9 ± 0.7 °C, 53 ± 4% relative humidity) or temperate (CON: 22.2 ± 2.6 °C, 65 ± 8% relative humidity) environment. All 20TTs were completed in the heat (35.1 ± 0.5 °C, 51 ± 4% relative humidity). Neuromuscular assessment of knee extensors (5 × 5 s maximum voluntary contraction; MVC) was completed before and after each 20TT and on the first and last days of each training block.ResultsMVC torque was statistically higher after 5 days of HA training compared to CON (mean difference = 14 N m [95% confidence interval; 6, 23]; p < 0.001; d = 0.77). However, 20TT performance after 5 days of HA training was not statistically different to CON, with a between-conditions mean difference in the completion time of 68 s [95% confidence interval; − 9, 145] (p = 0.076; d = 0.35).ConclusionShort-term heat acclimation training may increase knee extensor strength without changes in central fatigue or intestinal damage. Nevertheless, it is insufficient to improve 20 km self-paced cycling performance in the heat compared to workload-matched training in a temperate environment. These data suggest that recreationally trained athletes gain no worthwhile performance advantage from short-term heat-training before competing in the heat.

Heat acclimation training with intermittent and self-regulated intensity may be used as an alternative to traditional steady state and power-regulated intensity in endurance cyclists.

The study aimed to determine the effects of self-regulated and variable intensities sustained during short-term heat acclimation training on cycling performance. Seventeen competitive-level male athletes performed a 20-km cycling time trial before (TT-PRE), immediately after (TT-POST1) and one week after (TT-POST2) a 5-day acclimation training program, including either RPE-regulated intermittent (HA-HIT, N=9) or fixed and low-intensity (HA-LOW, N=8) training sessions in the heat (39°C; 40% relative humidity). Total training volume was 23% lower in HA-HIT compared to HA-LOW. Physiological responses were evaluated during a 40-min fixed-RPE cycling exercise performed before (HST-PRE) and immediately after (HST-POST) heat acclimation. All participants in HA-LOW group tended to improve mean power output from TT-PRE to TT-POST1 (+8.1±5.2%; ES=0.55±0.23), as well as eight of the nine athletes in HA-HIT group (+4.3±2.0%; ES=0.29±0.31) without difference between groups, but TT-POST2 results showed that improvements were dissipated one week after. Similar improvements in thermal sensation and lower elevations of core temperature in HST-POST following HA-LOW and HA-HIT training protocols suggest that high intensity and RPE regulated bouts could be an efficient strategy for short term heat acclimation protocols, for example prior to the competition. Furthermore, the modest impact of lowered thermal sensation on cycling performance confirms that perceptual responses of acclimated athletes are dissociated from physiological stress when exercising in the heat.

Post-exercise hot water immersion elicites heat acclimation responses in endurance and recreational athletes. A systematic review and meta-analysis

Aims This meta-analysis aims to evaluate the effectiveness of heat acclimation (HA) via hot water immersion protocols and their effect on time trial (TT) performance, heart rate (HRE, HRM and HRTT), rectal temperature (Tre), Rate of perceived exertion (RPE), psychological stress index (PhSI), thermal comfort (Tcomf), thermal sensation (Tsen) and maximum oxygen uptake (Vo2max). Methods Pubmed, Scopus, Sportdiscus and Web of Science databases were used alongside the grey matter sites Google Scholar and Researchgate. The databases were then searched for randomised control trials and mixed-method design studies. Two RTCs, six repeated measure design studies and one randomised crossover design study were included after screening a total of 50 titles and 28 full-text articles. Sample sizes range from 1 - 13 with all participants having not participated in any form of heat training 6 months before their inclusion in the study. Results The mean difference (MD) for Heart rate (HR) was -9.1125 BPM (95% CI p = 0.026) and was considered to be statistically significant. The MD for Rectal temperature (Tre) effect size was -0.3814 Tre (°C) (95% CI; p = 0.05). The MD for sweat rate was 0.085; (96% CI; p = 0.0179) The changes in RPE, PhSI, Tcomf and Tsen were too small to be considered statistically significant. There was no significant difference between pre and post HA for Vo2max and PV. This meta-analysis implies that HA via HWI may improve tolerance to discomfort during heat exposure and thus subsequently improve physical performance during exercise in hot conditions. Conclusion The primary finding of this meta-analysis is that athletic performance is improved with post-exercise hot water immersion heat acclimation training. HWI HA protocols should focus on the following guidelines: 40-50 minutes of submaximal exercise (&gt;65% of Vo2max) should be followed directly (within 10 minutes) by 40 minutes of hot water immersion at 40°C with the individual immersed up to their neck. The HA protocol should last between 6-9 days with a single bout of HWI every day for this period.

Effectiveness of skin-heating using a water-perfused suit as passive and post-exercise heat acclimation strategies.

The purpose of the present study was to evaluate the effectiveness of passive and post-exercise heat acclimation strategies through directly heating the skin with a water-perfused suit. Nineteen young males participated in the heat acclimation (HA) protocols for 10 days, which were conducted at an air temperature of 33oC with 60%RH. The exercise-only condition (N=6) conducted 1-h treadmill walking (6km·h-1) followed by 1-h rest. The post-exercise passive-heating condition (N=6) wore the suit (inflow water temperature 44.2oC) for 1-h after 1-h walking. The passive-heating condition (N=7) donned the suit for 2h. Heat tolerance tests (leg immersion in 42oC water for 60min) were conducted before and after the training to evaluate changes due to the 10-day intervention. Reflecting that suit-wearing for 10 days as both passive and post-exercise HA strategies can effectively induce adaptive changes, significant interaction effects appeared in: increase or decrease in mean skin temperature (P<0.05) and elevation in whole-body sweat rate (P<0.05). Reduction in rectal temperature (P<0.05) and blood pressure (P<0.05) were found most prominently in the passive-heating condition. These results indicate that this new method of heat acclimation training, donning a skin-heating water-perfused suit, can generate thermoregulatory benefits. The passive HA intervention could be applied to individuals for whom doing exercise regularly are not feasible.

Adaptive changes in physiological and perceptual responses during 10-day heat acclimation training using a water-perfused suit

BackgroundWhile active heat acclimation strategies have been robustly explored, not many studies highlighted passive heat acclimation strategies. Particularly, little evidence demonstrated advantages of utilizing a water-perfused suit as a passive heating strategy. This study aimed to explore heat adaptive changes in physiological and perceptual responses during 10-day heat acclimation training using a water-perfused suit.MethodsNineteen young males were divided into three experimental groups: exercise condition (N = 6, HAEXE, 1-h exercise at 6 km h−1 followed by 1-h rest in a sitting position), exercise and passive heating condition (N = 6, HAEXE+SUIT, 1-h exercise at 6 km h−1 followed 1-h passive heating in a sitting position), and passive heating condition (N = 7, HASUIT, 2-h passive heating in a sitting position). All heating programs were conducted for 10 consecutive days in a climatic chamber maintained at 33 °C with 60% relative humidity. The passive heating was conducted using a newly developed water-perfused suit with 44 °C water.ResultsGreater whole-body sweat rate and alleviated perceptual strain were found in HASUIT and HAEXE+SUIT after 5 and/or 10 days (P < 0.05) but not in the exercise-only condition (HAEXE). Lower rectal temperature and heart rate were found in all conditions after the training (P < 0.05). Heat adaptive changes appeared earlier in HASUIT except for sweat responses.ConclusionsFor heat acclimation in hot humid environments, passive and post-exercise heat acclimation training using the suit (water inflow temperature 44 °C) were more effective than the mild exercise (1-h walking at 6 km h−1). This form of passive heating (HASUIT) may be an especially effective strategy for the elderly and the disabled who are not able to exercise in hot environments.

Short-term heat acclimation training improves cycling performance in the heat and enhances knee extensor strength

Short-term heat acclimation training improves cycling performance in the heat and enhances knee extensor strength

Precooling With Crushed Ice: As Effective as Heat Acclimation at Improving Cycling Time-Trial Performance in the Heat.

This study compared the effects of precooling (ice ingestion) and heat-acclimation training on cycling time-trial (CTT) performance in the heat. Fifteen male cyclists/triathletes completed two 800-kJ CTTs in the heat, with a 12-d training program in between. Initially, all participants consumed 7g/kg of water (22°C) in 30min before completing an 800-kJ CTT in hot, humid conditions (pre-CTT) (35°C, 50% relative humidity [RH]). Participants were then split into 2 groups, with the precooling group (n = 7) training in thermoneutral conditions and then undergoing precooling with ice ingestion (7g/kg, 1°C) prior to the final CTT (post-CTT) and the heat-acclimation group (n = 8) training in hot conditions (35°C, 50% RH) and consuming water (7g/kg) prior to post-CTT. After training in both conditions, improvement in CTT time was deemed a likely positive benefit (precooling -166 ± 133s, heat acclimation -105 ± 62s), with this result being similar between conditions (d = 0.22, -0.68-1.08 90% confidence interval [CI]). Core temperature for post-CTT was lower in precooling than in heat acclimation from 20min into the precooling period until the 100-kJ mark of the CTT (d > 0.98). Sweat onset occurred later in precooling (250 ± 100s) than in heat acclimation (180 ± 80s) for post-CTT (d = 0.65, -0.30-1.50 90% CI). Thermal sensation was lower at the end of the precooling period prior to post-CTT for the precooling trial than with heat acclimation (d = 1.24, 0.90-1.58 90% CI). Precooling with ice ingestion offers an alternative method of improving endurance-cycling performance in hot conditions if heat acclimation cannot be attained.

Managing heat and immune stress in athletes with evidence-based strategies.

Heat and immune stress can affect athletes in a wide range of sports and environmental conditions. The classical thermoregulatory model of heat stress has been well characterized, as has a wide range of practical strategies largely centered on cooling and heat-acclimation training. In the last decade evidence has emerged of an inflammatory pathway that can also contribute to heat stress. Studies are now addressing the complex and dynamic interplay between hyperthermia, the coagulation cascade, and a systemic inflammatory response occurring after transient damage to the gastrointestinal tract. Damage to the intestinal mucosal membrane increases permeability, resulting in leakage of endotoxins into the circulation. Practical strategies that target both thermoregulatory and inflammatory causes of heat stress include precooling; short-term heat-acclimation training; nutritional countermeasures including hydration, energy replacement, and probiotic supplementation; pacing strategies during events; and postevent cooling measures. Cooperation between international, national, and local sporting organizations is required to ensure that heat-management policies and strategies are implemented effectively to promote athletes' well-being and performance.

Short-term heat acclimation training improves physical performance: a systematic review, and exploration of physiological adaptations and application for team sports.

Studies have demonstrated that longer-term heat acclimation training (≥8 heat exposures) improves physical performance. The physiological adaptations gained through short-term heat acclimation (STHA) training suggest that physical performance can be enhanced within a brief timeframe. The aim of this systematic review was to determine if STHA training (≤7 heat exposures) can improve physical performance in healthy adults. MEDLINE, PubMed, and SPORTDiscus™ databases were searched for available literature. Studies were included if they met the following criteria: STHA intervention, performance measure outcome, apparently healthy participants, adult participants (≥18 years of age), primary data, and human participants. A modified McMaster critical appraisal tool determined the level of bias in each included study. Eight papers met the inclusion criteria. Studies varied from having a low to a high risk of bias. The review identified aerobic-based tests of performance benefit from STHA training. Peak anaerobic power efforts have not been demonstrated to improve. At the review level, this systematic review did not include tolerance time exercise tests; however, certain professions may be interested in this type of exercise (e.g. fire-fighters). At the outcome level, the review was limited by the moderate level of bias that exists in the field. Only two randomized controlled trials were included. Furthermore, a limited number of studies could be identified (eight), and only one of these articles focused on women participants. The review identified that aerobic-based tests of performance benefit from STHA training. This is possibly through a number of cardiovascular, thermoregulatory, and metabolic adaptations improving the perception of effort and fatigue through a reduction in anaerobic energy release and elevation of the anaerobic threshold. These results should be viewed with caution due to the level of available evidence, and the limited number of papers that met the inclusion criteria of the review. STHA training can be applied in the team-sport environment during a range of instances within the competitive season. A mixed high-intensity protocol may only require five sessions with a duration of 60 min to potentially improve aerobic-based performance in trained athletes.

Short-term Heat Acclimation Training Does Not Improve Kinetics Of Lactate Removal Following Maximal Exercise

Short-term Heat Acclimation Training Does Not Improve Kinetics Of Lactate Removal Following Maximal Exercise