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ObjectivesTo adapt key components of exertional heat stroke (EHS) prehospital management proposed by the Intenational Olympic Committee Adverse Weather Impact Expert Working Group for the Olympic Games Tokyo 2020 so that it is applicable for the Paralympic athletes.MethodsAn expert working group representing members with research, clinical and lived sports experience from a Para sports perspective reviewed and revised the IOC consensus document of current best practice regarding the prehospital management of EHS.ResultsSimilar to Olympic competitions, Paralympic competitions are also scheduled under high environmental heat stress; thus, policies and procedures for EHS prehospital management should also be established and followed. For Olympic athletes, the basic principles of EHS prehospital care are: early recognition, early diagnosis, rapid, on-site cooling and advanced clinical care. Although these principles also apply for Paralympic athletes, slight differences related to athlete physiology (eg, autonomic dysfunction) and mechanisms for hands-on management (eg, transferring the collapsed athlete or techniques for whole-body cooling) may require adaptation for care of the Paralympic athlete.ConclusionsPrehospital management of EHS in the Paralympic setting employs the same procedures as for Olympic athletes with some important alterations.

This study examined the effect of graded hypoxia during exhaustive intermittent cycling on subsequent exercise performance and neuromuscular fatigue characteristics in normoxia. Fifteen well-trained cyclists performed an exhaustive intermittent cycling exercise (EICE 1; 15 s at 30% of anaerobic power reserve interspersed with 45 s of passive recovery) at sea level (SL; FiO2 ~ 0.21), moderate (MH; FiO2 ~ 0.16) and severe hypoxia (SH; FiO2 ~ 0.12). This was followed, after 30 min of passive recovery in normoxia, by an identical exercise bout in normoxia (EICE 2). Neuromuscular function of the knee extensors was assessed at baseline, after EICE 1 (post-EICE 1), and EICE 2 (post-EICE 2). The number of efforts completed decreased with increasing hypoxic severity during EICE 1 (SL: 39 ± 30, MH: 22 ± 13, SH: 13 ± 6; p ≤ 0.02), whereas there was no difference between conditions during EICE 2 (SL: 16 ± 9, MH: 20 ± 14, SH: 24 ± 17; p ≥ 0.09). Maximal torque (p = 0.007), peripheral (p = 0.02) and cortical voluntary activation (p

We investigate the effects of seasonal heat stress on cognitive function in outdoor workers. Thirty-nine workers from an oil and gas industry in the Middle-East volunteered for cognitive testing before (5.30 to 7.00 am) and after (3.30 to 5.00 pm) their daily work-shift in hot (August – average daily temperature: ~41°C) and temperate (January – average daily temperature: ~22°C) seasons. While physical activity was reduced in hot compared to temperate season (average normalized acceleration: 96 ± 33 vs. 112 ± 31 × 10(−3) g; −12.5 ± 4.7%; P = 0.010), the average core temperature during the work-shift was higher in the hot season (37.4 ± 0.2 vs. 37.2 ± 0.2°C; P = 0.002). Peak core temperature was 38.0 ± 0.1°C and 37.8 ± 0.1°C in hot and temperate seasons, respectively. Cognitive performance did not differ between seasons for tests of recognition memory (P = 0.169), working memory (P = 0.797) and executive function (P = 0.145), independent of testing time. Whereas there was no significant main effect of testing time for tests of recognition memory (P = 0.503) and working memory (P = 0.849), the number of problems solved on the first choice for the executive function test was lower in the afternoon than the morning (−9.2 ± 5.3%; P = 0.039). There was no season × testing time interaction for any cognitive tests (P ≥ 0.145). In the absence of hyperthermia, living and working in a hot environment does not alter cognitive function in oil and gas industry workers tested in a quiet and temperature-controlled room, with reduced clothing encumbrance (relative to work). Conclusions should not be extrapolated to more stressful situations (i.e., thermal stressor present, pronounced dehydration, noise).

ObjectivesThis document aimed to summarise the key components of exertional heat stroke (EHS) prehospital management.MethodsMembers of the International Olympic Committee Adverse Weather Impact Expert Working Group for the Olympic Games Tokyo 2020 summarised the current best practice regarding the EHS prehospital management.ResultsSports competitions that are scheduled under high environmental heat stress or those that include events with high metabolic demands should implement and adopt policy and procedures for EHS prehospital management. The basic principles of EHS prehospital care are: early recognition, early diagnosis, rapid, on-site cooling and advanced clinical care. In order to achieve these principles, medical organisers must establish an area called the heat deck within or adjacent to the main medical tent that is optimised for EHS diagnosis, treatment and monitoring. Once admitted to the heat deck, the rectal temperature of the athlete with suspected EHS is assessed to confirm an elevated core body temperature. After EHS is diagnosed, the athlete must be cooled on-site until the rectal temperature is below 39°C. While cooling the athlete, medical providers are recommended to conduct a blood analysis to rule out exercise-associated hyponatraemia or hypoglycaemia, provided that this can be safely performed without interrupting cooling. The athlete is transported to advanced care for a full medical evaluation only after the treatment has been provided on-site.ConclusionsA coordination of care among all medical stakeholders at the sports venue, during transport, and at the hospital is warranted to ensure effective management is provided to the EHS athlete.

PurposeTo characterise hydration, cooling, body mass loss, and core (Tcore) and skin (Tsk) temperatures during World Athletics Championships in hot-humid conditions.MethodsMarathon and race-walk (20 km and 50 km) athletes (n=83, 36 women) completed a pre-race questionnaire. Pre-race and post-race body weight (n=74), Tcore (n=56) and Tsk (n=49; thermography) were measured.ResultsMost athletes (93%) had a pre-planned drinking strategy (electrolytes (83%), carbohydrates (81%)) while ice slurry was less common (11%; pcore was lower in athletes using ice vests (37.5°C±0.4°C vs 37.8°C±0.3°C, p=0.024). Tcore (pre-race 37.7°C±0.3°C, post-race 39.6°C±0.6°C) was independent of event, ranking or performance (p≥0.225). Pre-race Tsk was correlated with faster race completion (r=0.32, p=0.046) and was higher in non-finishers (did not finish (DNF); 33.8°C±0.9°C vs 32.6°C±1.4°C, p=0.017). Body mass loss was higher in men than women (−2.8±1.5% vs −1.3±1.6%, pConclusionMost athletes’ hydration strategies were pre-planned based on personal experience. Ice vests were the most adopted pre-cooling strategy and the only one minimising Tcore, suggesting that event organisers should be cognisant of logistics (ie, freezers). Dehydration was moderate and unrelated to performance. Pre-race Tsk was related to performance and DNF, suggesting that Tsk modulation should be incorporated into pre-race strategies.

This study aimed to determine if sleep quality and psychological factors were associated with time to meet the discharge criteria to return to sport (RTS) following anterior cruciate ligament reconstruction (ACL-R) among athletes. A cohort-study design included 89 athletes following ACL-R. Each participant completed a battery of questionnaires at 6 different time points: within 3 days of injury occurrence and at post-surgery (1.5 m, 3 m, 4.5 m, 6 m and when discharge criteria were met). Assessment included sleep quality and quantity, symptoms of depression, anxiety, stress, psychological readiness to RTS and fear of re-injury. The primary outcome was the time needed to meet all discharge criteria to RTS. Sleep parameters and psychological factors were not associated with time to meet the discharge criteria to RTS. However, athletes that had lower scores of anxiety (OR 1.2 (95% CI 1.0, 1.3) and insomnia (OR 1.2 (95% CI 1.0, 1.3) at baseline were more likely to meet the RTS discharge criteria. Athletes with better sleep quality at 3m, 4.5m and 6m were more likely to meet the RTS discharge criteria OR 1.3 (95% CI 1.1, 1.7), 2.0 (95% CI 1.1–3.4) and 1.4 (95% CI 1.0, 1.9) respectively. Sleep quality and psychological factors were not associated with time to meet the discharge criteria to RTS but impacted whether athletes adhered and completed their rehabilitation program or not. Monitoring sleep quality and psychological factors of athletes before and following ACL-R surgery is important to identify athletes who could have difficulties in adhering to and completing their rehabilitation program to RTS.

Animal and human studies have shown that repeated heating may induce skeletal muscle adaptations, increasing muscle strength. The aim of this study is to investigate the effect of 6 weeks of localized heating on skeletal muscle strength, volume and contractile properties in healthy humans. Fifteen active participants (8 males/7 females, 35 ± 6 years, 70 ± 14 kg, 173 ± 7 cm, average training of 87 min per week) were subjected to 6 weeks of single-leg heat therapy. Heat pads were applied for 8 h/day, 5 days/week, on one randomly selected calf of each participant, while the contralateral leg acted as control. The heat pads increased muscle temperature by 4.6 ± 1.2 °C (p

Rapid advances in wearable technologies and real-time monitoring have resulted in major inroads in the world of recreational and elite sport. One such innovation is the application of real-time monitoring, which comprises a smartwatch application and ecosystem, designed to collect, process and transmit a wide range of physiological, biomechanical, bioenergetic and environmental data using cloud-based services. We plan to assess the impact of this wireless technology during Tokyo 2020, where this technology could help characterize the physiological and thermal strain experienced by an athlete, as well as determine future management of athletes during a medical emergency as a result of a more timely and accurate diagnosis. Here we describe some of the innovative technologies developed for numerous sports at Tokyo 2020 ranging from race walking (20 km and 50 km events), marathon, triathlon, road cycling (including the time trial event), mountain biking, to potentially team sports played outdoors. A more symbiotic relationship between sport, health and technology needs to be encouraged that harnesses the unique demands of elite sport (e.g., the need for unobtrusive devices that provide real-time feedback) and serves as medical and preventive support for the athlete's care. The implementation of such applications would be particularly welcome in the field of medicine (i.e., telemedicine applications) and the workplace (with particular relevance to emergency services, the military and generally workers under extreme environmental conditions). Laboratory and field-based studies are required in simulated scenarios to validate such emerging technologies, with the field of sport serving as an excellent model to understand and impact disease.

Background Heat-related illness, including heat exhaustion and heat stroke, is seen as a major risk for athletes with a physical impairment. Objective Primary: To survey the illness statistics during the 2015 Para Athletics World Championships and report on any cases of significant heat-related illnesses. Secondary: To document the heat countermeasures taken on behalf of the organizing committee. Design Retrospective audit. Setting Medical records collected at medical centers during the 2015 Para Athletics World Championships. Participants Athletes participating in the 2015 Para Athletics World Championships. Methods Illness statistics and records of hospitalizations of athletes participating in the championships were recorded by the medical officials during the precompetition (3 days) and competition (10 days) periods. Furthermore, wet-bulb globe temperatures (WBGTs) were measured at the competition venues. Main outcome measurements Incidence rates of illness during the precompetition and competition periods. Results WBGTs ranged from 24.6°C to 36.0°C, regularly exceeding the American College of Sports Medicine (ACSM) and International Association of Athletics Federations (IAAF) guidelines for cancelation in the morning both during the competition (ACSM, 52%; IAAF, 97%) and precompetition periods (ACSM, 75%; IAAF, 100%). These guidelines were not exceeded as regularly during the evening and noon for both the precompetition and competition periods (ACSM, 0%-5%; IAAF, 0%-58%). The illness incidence rate was 2.89 per 1000 athlete-days (incidence proportion = 3.76%; confidence interval = 2.69%-4.83%). Only seven cases of heat-related illness were recorded, of which three required hospitalization. Conclusion This study indicates low rates of illness, including hospitalization and intravenous administration for heat-related illness among athletes participating in the 2015 Para Athletics World Championships. Level of evidence III.

Objective. To investigate the use of infrared thermography (IRT) for skin temperature measurement of moving athletes during competition and its sensitivity to factors that are traditionally standardised. Approach. Thermograms were collected for 18 female athletes during the 20 km racewalk at the 2019 World Athletics Championships, with a medium-wave, cooled indium antimonide medium wave infrared band (MWIR) and a long-wave, uncooled microbolometer longwave infrared band (LWIR) infrared camera. Main results. The MWIR provided greater clarity images of motion due to a shorter exposure and response time and produced a higher percentage of acceptable images. Analysing acceptable images only, the LWIR and WMIR produced good levels of agreement, with a bias of −0.1 ± 0.6 °C in mean skin temperature for the LWIR. As the surface area of an ROI was reduced, the measured temperature became less representative of the whole ROI. Compared to measuring the whole area ROI, a single central pixel produced a bias of 0.3 ± 0.3 °C (MWIR) and 0.1 ± 0.4 °C (LWIR) whilst using the maximum and minimum temperature pixels resulted in deviations of 1.3 ± 0.4 °C and −1.1 ± 0.3 °C (MWIR) and 1.2 ± 0.3 °C and −1.3 ± 0.4 °C (LWIR). The sensitivity to air and reflected temperatures was lower for the LWIR camera, due to the higher emissivity of skin in its wavelength. Significance. IRT provides an appropriate tool for the measurement of skin temperature during real-world competition and critically during athlete motion. The cheaper LWIR camera provides a feasible alternative to the MWIR in low rate of motion scenarios, with comparable precision and sensitivity to analysis. However, the LWIR is limited when higher speeds prevent the accurate measurement and ability to capture motion.

Objective To provide best-practice recommendations for developing and implementing heat-acclimatization strategies in secondary school athletics. Data Sources An extensive literature review on topics related to heat acclimatization and heat acclimation was conducted by a group of content experts. Using the Delphi method, action-oriented recommendations were developed. Conclusions A period of heat acclimatization consisting of ≥14 consecutive days should be implemented at the start of fall preseason training or practices for all secondary school athletes to mitigate the risk of exertional heat illness. The heat-acclimatization guidelines should outline specific actions for secondary school athletics personnel to use, including the duration of training, the number of training sessions permitted per day, and adequate rest periods in a cool environment. Further, these guidelines should include sport-specific and athlete-specific recommendations, such as phasing in protective equipment and reintroducing heat acclimatization after periods of inactivity. Heat-acclimatization guidelines should be clearly detailed in the secondary school's policy and procedures manual and disseminated to all stakeholders. Heat-acclimatization guidelines, when used in conjunction with current best practices surrounding the prevention, management, and care of secondary school student-athletes with exertional heat stroke, will optimize their health and safety.

The aim of this study was to assess the history of exertional heat illness (EHI), heat preparation, cooling strategies, heat related symptoms, and hydration during an ultra-endurance running event in a warm and humid environment. This survey-based study was open to all people who participated in one of the three ultra-endurance races of the Grand Raid de la Réunion. Ambient temperature and relative humidity were 18.6 ± 5.7 °C (max = 29.7 °C) and 74 ± 17%, respectively. A total of 3317 runners (56% of the total eligible population) participated in the study. Overall, 78% of the runners declared a history of heat-related symptoms while training or competing, and 1.9% reported a previous diagnosis of EHI. Only 24.3% of study participants living in temperate climates declared having trained in the heat before the races, and 45.1% of all respondents reported a cooling strategy during the races. Three quarter of all participants declared a hydration strategy. The planned hydration volume was 663 ± 240 mL/h. Fifty-nine percent of the runners had enriched their food or drink with sodium during the race. The present study shows that ultra-endurance runners have a wide variability of hydration and heat preparation strategies. Understandings of heat stress repercussions in ultra-endurance running need to be improved by specific field research.

International outdoor athletics championships are typically hosted during the summer season, frequently in hot and humid climatic conditions. Therefore, we analyzed the association between apparent temperature and heat-related illnesses occurrence during international outdoor athletics championships and compared its incidence rates between athletics disciplines. Heat-related illnesses were selected from illness data prospectively collected at seven international outdoor athletics championships between 2009 and 2018 using a standardized methodology. The Universal Thermal Climate Index (UTCI) was calculated as a measure of the apparent temperature based on weather data for each day of the championships. Heat-related illness numbers and (daily) incidence rates were calculated and analyzed in relation to the daily maximum UTCI temperature and between disciplines. During 50 championships days with UTCI temperatures between 15celcius and 37celcius, 132 heat-related illnesses were recorded. Average incidence rate of heat-related illnesses was 11.7 (95%CI 9.7 to 13.7) per 1000 registered athletes. The expected daily incidence rate of heat-related illnesses increased significantly with UTCI temperature (0.12 more illnesses per 1000 registered athletes/degrees C; 95%CI 0.08-0.16) and was found to double from 25 to 35 degrees C UTCI. Race walkers (RR = 45.5, 95%CI 21.6-96.0) and marathon runners (RR = 47.7, 95%CI 23.0-98.8) had higher heat-related illness rates than athletes competing in short-duration disciplines. Higher UTCI temperatures were associated with more heat-related illnesses, with marathon and race walking athletes having higher risk than athletes competing in short-duration disciplines. Heat-related illness prevention strategies should predominantly focus on marathon and race walking events of outdoor athletics championships when high temperatures are forecast.

To compare the effects of different hypoxia severities on exercise capacity, cardio-respiratory, tissue oxygenation and neuromuscular fatigue characteristics in response to exhaustive intermittent cycling. Eleven well-trained cyclists, repeated supra-maximal cycling efforts of 15 s (30% of anaerobic power reserve, 609 ± 23 W), interspersed with 45 s of passive rest until task failure. The exercise was performed on separate days in normoxia (SL; simulated altitude/end-exercise arterial oxygen saturation = 0 m/~ 96%), moderate (MH; 2200 m/~ 90%) and severe (SH; 4200 m/~ 79%) hypoxia in a cross-over design. Neuromuscular tests, including brief (5 s) and sustained (30 s) maximal isometric voluntary contractions of the knee extensors, were performed at baseline and exhaustion. Exercise capacity decreased with hypoxia severity (23 ± 9, 16 ± 6 and 9 ± 3 cycle efforts in SL, MH and SH, respectively; P

The COVID-19 pandemic has created many challenges to ensure a safe environment for competitive sport. While modern medicine has already developed effective protocols for the treatment and prevention of the disease, there are serious concerns about hosting a sporting event of the scale of the Olympic Games, where more than 11 000 athletes from over 200 nations are expected to participate. Accordingly, there have been many calls to cancel the Tokyo Olympic Games, also known as Tokyo 2020, in both the international press and the scientific literature. A recent perspective published in the New England Journal of Medicine (NEJM)1 highlights the complexity and risks of convening the Tokyo Olympic Games during the COVID-19 pandemic. Despite the many uncertainties,1 much has been learnt over the past 18 months and many policies trialled and tested to protect athletes during sports participation. To develop a rapid understanding of the perspectives from the international sports and exercise medicine community, an informal survey of the International Federation of Sports Medicine (FIMS) Executive Committee, Commissions, and Collaborating Centres of Sports Medicine agreed that the Tokyo Olympic Games could go ahead safely based on the plans addressing the pandemic developed by the IOC (figure 1). This international network of 26 research laboratories and clinics has a mission to promote best practice …

Purpose: To measure core temperature (Tcore) in open-water (OW) swimmers during a 25-km competition and identify the predictors of Tcore drop and hypothermia-related dropouts. Methods: Twenty-four national- and international-level OW swimmers participated in the study. Participants completed a personal questionnaire and a body fat/muscle mass assessment before the race. The average speed was calculated on each lap over a 2500-m course. Tcore was continuously recorded via an ingestible temperature sensor (e-Celsius, BodyCap). Hypothermia-related dropouts (H group) were compared with finishers (nH group). Results: Average prerace Tcore was 37.5°C (0.3°C) (N = 21). 7 participants dropped out due to hypothermia (H, n = 7) with a mean Tcore at dropout of 35.3°C (1.5°C). Multiple logistic regression analysis found that body fat percentage and initial Tcore were associated with hypothermia (G2 = 17.26, P < .001). Early Tcore drop ≤37.1°C at 2500 m was associated with a greater rate of hypothermia-related dropouts (71.4% vs 14.3%, P = .017). Multiple linear regression found that body fat percentage and previous participation were associated with Tcore drop (F = 4.95, P = .019). There was a positive correlation between the decrease in speed and Tcore drop (r = .462, P < .001). Conclusions: During an OW 25-km competition at 20°C to 21°C, lower initial Tcore and lower body fat, as well as premature Tcore drop, were associated with an increased risk of hypothermia-related dropout. Lower body fat and no previous participation, as well as decrease in swimming speed, were associated with Tcore drop.

All sport events have inherent injury and illness risks for participants. Healthcare services for sport events should be planned and delivered to mitigate these risks which is the ethical responsibility of all sport event organisers. The objective of this paper was to develop consensus-driven guidelines describing the basic standards of services necessary to protect athlete health and safety during large sporting events. By using the Knowledge Translation Scheme Framework, a gap in International Federation healthcare programming for sport events was identified. Event healthcare content areas were determined through a narrative review of the scientific literature. Content experts were systematically identified. Following a literature search, an iterative consensus process was undertaken. The outcome document was written by the knowledge translation expert writing group, with the assistance of a focus group consisting of a cohort of International Federation Medical Chairpersons. Athletes were recruited to review and provide comment. The Healthcare Guidelines for International Federation Events document was developed including content-related to (i) pre-event planning (eg, sport medical risk assessment, public health requirements, environmental considerations), (ii) event safety (eg, venue medical services, emergency action plan, emergency transport, safety and security) and (iii) additional considerations (eg, event health research, spectator medical services). We developed a generic standardised template guide to facilitate the planning and delivery of medical services at international sport events. The organisers of medical services should adapt, evaluate and modify this guide to meet the sport-specific local context.

The games of the XXXII Olympiad have been announced from 23 July to 8 August 2021, coinciding with the height of the Japanese summer. Heat acclimation/acclimatisation (HA) is the most important countermeasure athletes can adopt to safeguard their health and performance when competing in the heat. However, it is important for practitioners to recognise that repeated daily exposures to heat stress is a physiologically demanding endeavour. Prolonged heat exposure is characterised by increased thermal and cardiovascular strain, augmented glycogen utilisation and fluid losses, increased hormonal responses (ie, increased cortisol and catecholamine secretion), cytokinaemia and endotoxaemia, which may result in sleep and gastrointestinal disturbances, augmented lethargy and delayed physical recovery.1–3 For instance, consecutive days of training in the heat, particularly at high exercise intensities, can result in a state of over-reaching, despite signs of successful heat adaptation.4 It is therefore imperative to manage recovery when training in the heat, as accumulated fatigue may impact on the overall success of the HA programme, as well as interfere with the quality of other training sessions. This editorial aims to provide practitioners and coaches with an up-to-date synopsis of recovery strategies during HA (figure 1). Figure 1 Schematic illustration on the responses to repeated training in the heat and recovery strategies. Pre-exercise nutritional strategies are crucial in limiting fluid and electrolyte imbalance during exertional heat stress, such that HA sessions can be optimally …

As presented in the first editorial from this series, the Tokyo Olympics are expected to be the hottest in modern history.1 While the postponing from 2020 to 2021 will not change the period of the year, it will allow more time for athletes to plan for multiple heat acclimation camps. Indeed, heat acclimation is the most important countermeasure athletes can adopt to protect their health and enhance performance.2 Heat acclimation develops following repeated training in hot conditions in response to marked increases in core and skin temperature, skin blood flow and sweat rate.2 It is commonly accepted that daily training in the heat for 60–90 min for 2 weeks allows for adaptations to occur, including plasma volume expansion and enhanced heat dissipation.3 These adaptations contribute to lower the cardiovascular response associated with exercising in the heat and thus improve performance.3 The time course of these adaptations is relatively rapid with a large fraction of adaptations occurring during …

PurposeAssess the health status and heat preparation strategies of athletes competing in a World Cycling Championships held in hot ambient conditions (37°C, 25% relative humidity, wet-bulb-globe-temperature 27°C) and monitor the medical events arising during competition.Methods69 cyclists (~9% of the world championships participants) completed a pre-competition questionnaire. Illnesses and injuries encountered by the Athlete Medical Centre (AMC) were extracted from the race reports.Results22% of respondents reported illness symptoms in the 10 days preceding the Championships. 57% of respondents had previously experienced heat-related symptoms (cramping most commonly) while 17% had previously been diagnosed with exertional heat illness. 61% of the respondents had undergone some form of heat exposure prior to the Championships, with 38% acclimating for 5 to 30 days. In addition, several respondents declared to live in warm countries and all arrived in Qatar ~5 days prior to their event. 96% of the respondents used a pre-cooling strategy for the time trials and 74% did so before the road race (pConclusionsThe prevalence of previous heat illness in elite cyclists calls for team and event organisation doctors to be trained on heat illness management, including early diagnosis and rapid on-site cooling. Some cyclists had been exposed to the heat prior to the Championships, but few had a dedicated plan, calling for additional education on the importance of heat acclimation. Pre-cooling was widely adopted.

We tested the hypothesis that backward downhill walking (eccentric component) impairs both voluntary activation and muscle contractile properties in the plantar flexors and delays recovery as compared to a gradient and distance-matched uphill walk. Fourteen males performed two 30-min walking exercises (velocity: 1 m/ s; grade: 25%; load: 12% of body weight), one downhill (DW) and one uphill (UP), in a counterbalanced order, separated by 6 weeks. Neuromuscular test sessions were performed before, after, 24-, 48- and 72-h post-exercise, including motor nerve stimulations during brief (5 s) and sustained (1 min) maximal isometric voluntary contractions of the plantar flexors. DW (-18.1 ± 11.1%, P .001), but not UP (-6.0 ± 7.7%, P =.15), decreased torque production during brief contractions for at least three days post-exercise (P .05). Voluntary activation during brief contractions decreased after DW (P .05), but not UP, and recovered by 24 h. Both UP (-9.3 ± 9.0%, P = .024) and DW (-25.6 ± 10.3%, P .001) decreased torque production during sustained contractions but voluntary activation (P = .001) was lower in DW than UP. Peak twitch torque and maximum rates of torque development and relaxation were equally reduced after UP and DW (P .05), and recovered by 24 h. DW induced an increase in muscle soreness with peak values observed 48 h post-walking (P .001), whereas post-UP exercise changes were non-significant (all P .05). Using a direct comparison, the capacity to drive the plantar flexors during sustained contractions remains sub-optimal during the three-day recovery period in response to non-exhaustive, downhill backward walking in reference to an uphill exercise matched for distance covered.

The environmental conditions during Tokyo Summer Olympics are expected to be comparable to previous years1 with air temperatures and relative humidity in excess of 30°C and >70%, respectively.2 A previous consensus statement highlighted the main considerations for prevention, recognition and treatment of exertional heat illnesses,3 while the impact of extreme heat on athletic performance is examined elsewhere.4 Cooling strategies applied before and during the exercise in the heat have been shown to help athletes better maintain their performances5 by lowering body heat storage and core body temperature.6 The Tokyo Games have also encouraged the development of wearable technologies that could also be used for prevention, diagnosis and real-time monitoring of skin and core temperature and will be trialled during competition in Tokyo 2020. Here, we aim to highlight the potential application of current novel technologies and the associated ethical dilemmas regarding their effectiveness, the use of athlete biodata and predictive algorithms. Recently, manufacturers have developed new cooling wearables that have the potential to reduce exertional heatstroke (EHS) risk and to reduce the decline in athletic performance in hot environments, with the most novel summarised in table 1. Here, the focus is not on cooling …

The hot-humid environmental conditions (27°C–31°C, 60%–80% relative humidity) expected for the 2021 Tokyo Olympics will pose a considerable thermoregulatory challenge for athletes, which will impair performance and potentially compromise safety. Perhaps due to the conventional belief that women are at a thermoregulatory disadvantage compared with men, many coaches have questioned whether training and competing in such conditions will be particularly challenging for female athletes. As an extension of this editorial series,1 we therefore provide a physiologist’s perspective on three of the common questions raised. Numerous investigators have documented sex differences in exercise thermoregulation; however, until recently, it remained uncertain whether those differences were related to sex per se or simply due to secondary differences in body size and aerobic fitness between the men and women studied. Such secondary differences influence exercise thermoregulation primarily by modulating metabolic heat production and the heat loss required to prevent continued rises in core temperature. For example, due to their smaller size, heat production per unit body mass or surface area and the resultant rise in core temperature would be greater in women during weight-supported exercise at a fixed work rate (eg, cycling at 200 W). While determining the potential, magnitude of these effects during training or competition is complex, they pose no more of a …

Endurance and team-sport athletes competing at the 2021 Tokyo Olympics Games can expect hot and humid conditions. Ensuring euhydration prior to an event and minimising dehydration during competition will be important, to ensure an optimal physiological state and competitive advantage.1 Contention exists, however, regarding a primary recommendation provided to athletes: drink to thirst or plan to drink. The debate is centred on the level of dehydration that can be incurred prior to its effects influencing physiological responses and performance.2 Whole-body sweat rate during exercise ranges from 0.5 to 2.0 L hour−1 with some athletes (~2%) sweating substantially more (>3.0 L hour−1).3 Gradual reductions in body mass of 2%–5% can occur if body water losses are not replenished, resulting in marked decrements in plasma (≥10%) and blood (≥6%) volume.4 Such levels of dehydration lead to a state of hyperosmotic hypovolaemia that is proportional to the decrement in total body water.5 Hyperosmolality during exercise reduces sweat rate, and thus evaporative heat loss, for any given core temperature.6 As a result, the magnitude of hyperthermia experienced during endurance exercise under heat stress is exacerbated. Progressive dehydration and hyperthermia also intensify tachycardia and compromise the ability to maintain cardiac output, leading to …

Elite athletes competing at high-intensity in the hot and humid ambient conditions of the upcoming Games of the XXXII Olympiad (Tokyo 2020) are likely to reach elevated core temperature (≈41.5°C) as previously reported in elite competitions in the heat and the risk of exertional heat stroke (EHS) is heightened.1 EHS is a medical condition defined as an internal body temperature exceeding 40.5°C with central nervous system dysfunction (eg, disorientation, aggressiveness, hysteria, delirium, altered consciousness, irrational behaviour).2 3 Survival and sequela from EHS depend on the duration of hyperthermia.4 In 2020, evidence-based consensus suggests whole-body cooling until 39°C within the first 30 min of collapse as the critical requirement to maximise patient outcome.2 3 5 Whole-body cold water immersion (CWI) was associated with 100% survival rate in 274 runners diagnosed with EHS over the 18 years of patients treated at the New Balance Falmouth Road Race, with average cooling rate of 0.22°C min–1.5 In a different study, CWI using circulated water controlled at 2°C demonstrated an average cooling rate of 0.35°C min–1.6 To achieve the clinical target, medical providers at Tokyo 2020 must: 1. provide on-site assessment of …

The 2020 Tokyo Olympics will be held from 24 July to 9 August, in hot and humid environments, in the world’s largest metropolitan area. Two years to the day before the 2020 Olympics, temperatures surpassed 41°C with over 65 heat-related deaths recorded in a single week. Protecting the health and performance of the athlete under these conditions is a shared responsibility among the International Olympic Committee (IOC), the local organiser (LOC), the International Federations (IFs), the National Olympic Committees (NOCs), the national federation medical staff, the coaching staff and the athletes themselves. Unfortunately, these various stake holders do not always have the appropriate information to adopt the necessary preventive countermeasures. Following the motto ‘By failing to prepare you are preparing to fail’ (Benjamin Franklin, 1706–1790), a series of editorials will be published between now and the Olympics with clear information for practitioners on how to prepare. First of all, endurance and team sports athletes should be aware that heat stress dramatically decreases performance. Fortunately, the acute effects of heat stress can be progressively attenuated by repeated training in …

International audience; Hot and humid ambient conditions may play a major role during the endurance events of the 2019 IAAF world championships, the 2020 summer Olympics and many other sports events. Here, various countermeasures with scientific evidence are put in perspective of their practical application. This manuscript is not a comprehensive review, but rather a set of applied recommendations built upon sound scientific reasoning and experience with elite athletes. The primary recommendation for an athlete who will be competing in the heat, will be to train in the heat. This acclimatization phase should last for 2 weeks and be programmed to accommodate the taper and travel requirements. Despite extensive laboratory-based research, hydration strategies within athletics are generally dictated by the race characteristics. The main opportunities for hydration are during the preparation and recovery phases. In competition, depending on thirst, feeling, and energy requirements, water may be ingested or poured. The athletes should also adapt their warm-up routines to the environmental conditions, as it may do more harm than good. Avoiding harm includes limiting unnecessary heat exposure before the event, warming-up with cooling aids such as ice-vest or cold/iced drinks, and avoiding clothing or accessories limiting sweat evaporation. From a medical perspective, exertional heat stroke should be considered immediately when an athlete collapses or struggles during exercise in the heat with central nervous system disorders. Once a rectal temperature >40.5 • C is confirmed, cooling (via cold water immersion) should be undertaken as soon as possible (cool first/transport second).

Objectives To investigate whether self-reported health complaints and choice of heat stress prevention strategies during the taper predicted peaking at an athletics championship in hot conditions. Design Cohort study. Methods Data on health and heat stress prevention were collected before the 2015 World Athletics Championship in Beijing, China. Peaking was defined using the athlete’s pre-competition ranking and final competition rank. Baseline and endpoint data were fitted into multiple logic regression models. Results Two hundred forty-five (29%) of 841 eligible athletes participated. Both sprint/power (Odds ratio (OR) 0.33 (95% Confidence interval (CI) 0.11 to 0.94), P = 0.038) and endurance/combined events (OR 0.38 (95% CI 0.14 to 1.00), P = 0.049) athletes having sustained concern-causing health complaints during the taper were less likely to peak. Endurance/combined events athletes who chose pre-cooling to mitigate heat stress were less likely to peak (OR 0.35 (95% CI 0.15 to 0.80), P = 0.013), while sprint/power athletes reporting a sudden-onset injury complaint during the taper displayed increased peaking (OR 4.47 (95% CI 1.28 to 15.59), P = 0.019). Conclusions Health complaints that caused the athlete concern during the taper were predictive of failure to peak at a major athletics competition. Sprint/power athletes who experienced an acute injury symptom during the taper appeared to benefit from rest. Pre-cooling strategies seem to require further validation during real-world endurance/combined events. It appears that athletics athletes’ self-reported health should be monitored during the taper, concerns addressed, and heat stress prevention strategies individually tested before championships in hot conditions.

Objectives To determine the effects of heat stress on ankle proprioception and running gait pattern. Design Counterbalanced repeated measures. Methods 12 trained runners performed a proprioception test (active movement discrimination) before and immediately after a 30 min, self-paced treadmill run in HOT (39 °C) and COOL (22 °C) ambient conditions. Velocity was imposed during the first and last minute (70% of maximal aerobic velocity, 13.3 ± 0.8 km h−1) for determination of running mechanics and spring–mass characteristics. Results Rectal (39.7 ± 0.4 vs. 39.4 ± 0.4 °C), skin (36.3 ± 1.1 vs. 31.8 ± 1.1 °C) and average body (38.3 ± 0.2 vs. 36.4 ± 0.4 °C) temperatures together with heart rate (178 ± 8 vs. 174 ± 6 bpm) and thermal discomfort (6.5 ± 0.5 vs. 4.3 ± 1.3) were all higher at the end of the HOT compared to COOL run (all p 0.05). Conclusions Heat stress exacerbates thermal, cardiovascular and perceptual responses, while running velocity was slower during a 30 min self-paced treadmill run. Heat stress also impairs ankle proprioception during an active movement discrimination task, but it has no influence on gait pattern assessed at a constant, sub-maximal velocity. The authors thank Clint Hansen for his methodological input. The authors thank Mohammed Aziz Farooq for his support with the statistical analysis. The authors thank the participants for their involvement. The results of this study are presented clearly, honestly, and without fabrication, falsification, or inappropriate data manipulation. This study was internally funded by Aspetar Orthopedic and Sports Medicine Hospital . This project was conducted using an instrumented treadmill that was funded by QNRF (NPRP 4-760-3-217). Scopus

Current epidemiological studies in elite alpine skiers are mostly limited to retrospective surveys on in-season injury. The aim of this study was to determine the risk and pattern of injury in elite alpine skiers during the winter competitive season (WCS) and the summer off-season (SOS). European Cup skiers were prospectively followed during 5 complete years. A total of 133 skier-seasons (79 males and 54 females) completed the study. All acute and overuse injuries that required medical attention were registered, representing a total of 166 injuries. Absolute injury incidence was 124.8 (95% CI [106-145]) injuries per 100 athletes per complete season and was higher during the WCS compared with the SOS, albeit in a smaller magnitude than expected (relative risk ratio (RR) 1.44 [1.06-1.96]). The absolute incidence of severe injuries (ie, time-loss >28 days) was twofold higher during WCS compared with SOS (RR 2.19 [1.21-3.95]). Most common injuries during the 2013-2015 seasons were knee followed by back (absolute incidences 56 [38-80] and 20 [10-36], respectively; RR 2.82 [1.42-5.61]), but this difference disappeared after 2015 (absolute incidences 25.6 [15.7-39.6] and 23.1 [13.7-36.5], respectively; RR 1.11 [0.59-2.10]). In summary, we found that 98 (59%) injuries occurred during WCS and 68 (41%) during SOS over 5 years. These results demonstrate the necessity to record injuries during the entire year to avoid a significant underestimation of the injury incidence. In addition, the current data showed an evolution of injury pattern over time and since previous reports, with back injuries being the main concern along knee joint injuries.

The Tokyo 2020 Olympic Games is expected to be among the hottest Games in modern history, increasing the chances for exertional heat stroke (EHS) incidence, especially in non-acclimatised athletes/workers/spectators. The urgent need to recognise EHS symptoms to protect all attendees’ health has considerably accelerated research examining the most effective cooling strategies and the development of wearable cooling technology and real-time temperature monitoring. While these technological advances will aid the early identification of EHS cases, there are several potential ethical considerations for governing bodies and sports organisers. For example, the impact of recently developed cooling wearables on health and performance is unknown. Concerning improving athletic performance in a hot environment, there is uncertainty about this technology’s availability to all athletes. Furthermore, the real potential to obtain real-time core temperature data will oblige medical teams to make crucial decisions around their athletes continuing their competitions or withdraw. Therefore, the aim of this review is (1) to summarise the practical applications of the most novel cooling strategies/technologies for both safety (of athletes, spectators and workers) and performance purposes, and (2) to inform of the opportunities offered by recent technological developments for the early recognition and diagnosis of EHS. These opportunities are presented alongside several ethical dilemmas that require sports governing bodies to react by regulating the validity of recent technologies and their availability to all.

Purpose Assess exertional heat illness (EHI) history and preparedness in athletes competing in a World Athletics Championships under hot/humid conditions and identify the factors associated with preparedness strategies. Methods Of the 207 registered national teams invited to participate in the study, 50 (24%) accepted. The 957 athletes (49% of all 1965 registered) in these teams were invited to complete a precompetition questionnaire evaluating EHI history, heat stress prevention (heat acclimatisation, precooling and hydration) and recovery. Responses from 307 (32%) athletes were separated in field events, sprints, middle-distance and long-distance running, and decathlon/heptathlon for analysis. Results 48% of athletes had previously experienced EHI symptoms and 8.5% had been diagnosed with EHI. 15% heat acclimatised (similar to 20 days) before the championships. 52% had a precooling strategy, ice slurry ingestion (24%) being the most prevalent and women using it more frequently than men (p=0.005). 96% of athletes had a fluid consumption strategy, which differed between event categories (pamp;lt;0.001). The most common volumes planned on being consumed were 0.5-1 L (27.2%) and amp;gt;= 2 L (21.8%), water being the most frequent. 89% of athletes planned on using at least one recovery strategy. Female sex (p=0.024) and a previous EHI diagnosis increased the likelihood of using all 3 prevention strategies (pamp;lt;0.001). Conclusions At a World Championships with expected hot/humid conditions, less than one-fifth of athletes heat acclimatised, half had a precooling strategy and almost all a hydration plan. Women, and especially athletes with an EHI history, were more predisposed to use a complete heat stress prevention strategy. More information regarding heat acclimatisation should be provided to protect athlete health and optimise performance at major athletics competitions in the heat. Funding Agencies|IAAF Medical and Anti-Doping Commission and Department

Aim: Intestinal temperature telemetry systems are promising monitoring and research tools in athletes. However, the additional equipment that must be carried to continuously record temperature data limits their use to training. The purpose of this study was to assess the validity and reliability of a new gastrointestinal temperature data logging and telemetry system (e-Celsius™) during water bath experimentation and exercise trials. Materials and Methods: Temperature readings of 23 pairs of e-Celsius (TeC) and VitalSense (TVS) ingestible capsules were compared to rectal thermistor responses (Trec) at 35, 38.5 and 42°C in a water bath. Devices were also assessed in vivo during steady-state cycling (n = 11) and intermittent running (n = 11) in hot conditions. Results: The water bath experiment showed TVS and TeC under-reported Trec (P

International audience; This study examined the effects of acute hypoxia on maximal and explosive torque and fatigability in knee extensors of skiers. Twenty-two elite male alpine skiers performed 35 maximal, repeated isokinetic knee extensions at 180 degrees s(-1) (total exercise duration 61.25 s) in normoxia (NOR, FiO(2) 0.21) and normobaric hypoxia (HYP, FiO(2) 0.13) in a randomized, single-blind design. Peak torque and rate of torque development (RTD) from 0 to 100 ms and associated Vastus Lateralis peak EMG activity and rate of EMG rise (RER) were determined for each contraction. Relative changes in deoxyhemoglobin concentration of the VL muscle were monitored by near-infrared spectroscopy. Peak torque and peak EMG activity did not differ between conditions and decreased similarly with fatigue (p < 0.001), with peak torque decreasing continuously but EMG activity decreasing significantly after 30 contractions only. Compared to NOR, RTD, and RER values were lower in HYP during the first 12 and 9 contractions, respectively (both p < 0.05). Deoxyhemoglobin concentration during the last five contractions was higher in HYP than NOR (p = 0.050) but the delta between maximal and minimal deoxyhemoglobin for each contraction was similar in HYP and NOR suggesting a similar muscle O-2 utilization. Post-exercise heart rate (138 +/- 24 bpm) and blood lactate concentration (5.8 +/- 3.1 mmol. l(-1)) did not differ between conditions. Arterial oxygen saturation was significantly lower (84 +/- 4 vs. 98 +/- 1%, p < 0.001) and ratings of perceived exertion higher (6 +/- 1 vs. 5 +/- 1, p < 0.001) in HYP than NOR. In summary, hypoxia limits RTD via a decrease in neural drive in elite alpine skiers undertaking maximal repeated isokinetic knee extensions, but the effect of hypoxic exposure is negated as fatigue develops. Isokinetic testing protocols for elite alpine skiers should incorporate RTD and RER measurements as they display a higher sensitivity than peak torque and EMG activity.

The aim of this study was to determine the time course of physiological adaptations and their relationship with performance improvements during 2 weeks of heat acclimatization. Nine trained cyclists completed 2 weeks of training in naturally hot environment (34 ± 3 °C; 18 ± 5% relative humidity). On days 1, 6, and 13, they performed standardized heat response tests (HRT-1, 2, 3), and 43.4-km time trials in the heat (TTH-1, 2, 3) were completed on days 2, 7, and 14. Within the first 5–6 days, sweat sodium concentration decreased from 75 ± 22 mmol/L to 52 ± 24 mmol/L, sweat rate increased (+20 ± 15%), and resting hematocrit decreased (−5.6 ± 5.4%), with no further changes during the remaining period. In contrast, power output during TTHs gradually improved from TTH-1 to TTH-2 (+11 ± 8%), and from TTH-2 to TTH-3 (+5 ± 4%). Individual improvements in performance from TTH-1 to TTH-2 correlated with individual changes in hematocrit (assessed after the corresponding HRT; r = −0.79, P

This study examined the influence of hyperthermia on middle cerebral artery mean blood velocity (MCA Vmean). Eleven cyclists undertook a 750 kJ self-paced time trial in HOT (35 °C) and COOL (20 °C) conditions. Exercise time was longer in HOT (56 min) compared with COOL (49 min; P

This study investigated if well-trained cyclists improve and performance in cool conditions following heat acclimatization through natural outdoor training in hot conditions. Eighteen trained male cyclists were tested for physiological adaptations, , peak aerobic power output, exercise efficiency, and outdoor time trial (TT) performance (43.4 km in cool environment, ∼5–13 °C) before and after 2 weeks of training in a cool (CON, n = 9) or hot (∼35 °C, HA, n = 9) environment. After heat acclimatization, TT performance in the heat was improved by 16%; however, there was no change in the HA group in (4.79 ± 0.21 L/min vs 4.82 ± 0.35 L/min), peak aerobic power output (417 ± 16 W vs 422 ± 17 W), and outdoor TT performance in cool conditions (300 ± 14 W/69 ± 3 min vs 302 ± 9 W/69 ± 4 min). The present study shows that 2 weeks of heat acclimatization was associated with marked improvements in TT performance in the heat. However, for the well-trained endurance athletes, this did not transfer to an improved aerobic exercise capacity or outdoor TT performance in cool conditions.

We assessed neuromuscular fatigue and recovery of the plantar flexors after playing football with or without severe heat stress. Neuromuscular characteristics of the plantar flexors were assessed in 17 male players at baseline and ∼30 min, 24, and 48 h after two 90-min football matches in temperate (∼20 °C and 55% rH) and hot (∼43 °C and 20% rH) environments. Measurements included maximal voluntary strength, muscle activation, twitch contractile properties, and rate of torque development and soleus EMG (i.e., root mean square activity) rise from 0 to 30, -50, -100, and -200 ms during maximal isometric contractions for plantar flexors. Voluntary activation and peak twitch torque were equally reduced (-1.5% and -16.5%, respectively; P

Hyperthermia has been shown to affect both central and peripheral nervous systems. However, the consequences of these alterations on the proprioceptive mechanisms underlying human movement control remain unclear. The aim of this study was to investigate the effect of passive hyperthermia on various measures of proprioception and balance, two key components of injury prevention and movement efficiency.After a familiarization session, 14 volunteers (8 males, 6 females) completed two experimental sessions in temperate (CON, 24°C) and hot (HOT, 44°C-50°C) conditions, in a counterbalanced order. Participants were tested for neural function (electrically evoked M-wave and Hoffman reflex, Soleus), active movement discrimination (five positions, 50 trials, dorsiflexion), dynamic balance (Star Excursion Balance Test, three directions), and static balance (single-leg stance).Both rectal (39.0°C ± 0.3°C vs 36.9°C ± 0.6°C) and mean skin (37.9°C ± 1.0°C vs 32.0°C ± 2.7°C) temperatures were significantly higher in HOT than CON (P0.05). Hyperthermia significantly reduced the Hoffman reflex (P0.05) but not the M-wave (P0.05) amplitudes, increased the mean error for active movement discrimination (0.58°± 0.13° vs 0.50° ± 0.11°, +17%, P0.05), decreased the average distance reached in the posteromedial direction during dynamic balance (88.6 ± 7.9 cm vs 90.9 ± 6.1 cm, P0.05), and increased the contact area of the foot (126 ± 14 cm vs 122 ± 13 cm, +2.7%, P0.05) and the center of pressure excursion (64 ± 14 vs 57 ± 9 cm, +11.1%, P0.10) during single-leg stance.The current study suggests that hyperthermia impairs the proprioception and balance parameters measured. These observations might be due to heat-induced alterations in efferent and afferent signals to and from the muscle.

Most professional and recreational athletes perform pre-conditioning exercises, often collectively termed a 'warm-up' to prepare for a competitive task. The main objective of warming-up is to induce both temperature and non-temperature related responses to optimize performance. These responses include increasing muscle temperature, initiating metabolic and circulatory adjustments, and preparing psychologically for the upcoming task. However, warming-up in hot and/or humid ambient conditions increases thermal and circulatory strain. As a result, this may precipitate neuromuscular and cardiovascular impairments limiting endurance capacity. Preparations for competing in the heat should include an acclimatization regimen. Athletes should also consider cooling interventions to curtail heat gain during the warm-up and minimize dehydration. Indeed, although it forms an important part of the pre-competition preparation in all environmental conditions, the rise in whole-body temperature should be limited in hot environments. This review provides recommendations on how to build an effective warm-up following a 3 stage RAMP model (Raise, Activate and Mobilize, Potentiate), including general and context specific exercises, along with dynamic flexibility work. In addition, this review provides suggestion to manipulate the warm-up to suit the demands of competition in hot environments, along with other strategies to avoid heating-up.

Introduction: We examined the extent to which fatiguing cycling exercise in the heat influences contractile function in modulating the force–frequency relationship. Methods: Before (∽37.0°C) and after (∽38.5°C) exercise (ExH) and passive (PaH) hyperthermia, an 8-s train of stimulation at 10, 20, 50, and 100 Hz (2 s per frequency) and a potentiated twitch were evoked on the relaxed knee extensors using percutaneous stimulation. Results: ExH and PaH produced a decrease in the 20:50 Hz force ratio, indicative of low-frequency fatigue (P

Purpose:To examine the physiological and performance responses to a heat-acclimatization camp in highly trained professional team-sport athletes.Methods:Eighteen male Australian Rules Football players trained for 2 wk in hot ambient conditions (31–33°C, humidity 34–50%). Players performed a laboratory-based heat-response test (24-min walk + 24 min seated; 44°C), a YoYo Intermittent Recovery Level 2 Test (YoYoIR2; indoor, temperate environment, 23°C) and standardized training drills (STD; outdoor, hot environment, 32°C) at the beginning and end of the camp.Results:The heat-response test showed partial heat acclimatization (eg, a decrease in skin temperature, heart rate, and sweat sodium concentration, P < .05). In addition, plasma volume (PV, CO rebreathing, +2.68 [0.83; 4.53] mL/kg) and distance covered during both the YoYoIR2 (+311 [260; 361] m) and the STD (+45.6 [13.9; 77.4] m) increased postcamp (P < .01). None of the performance changes showed clear correlations with PV changes (r < .24), but the improvements in running STD distance in hot environment were correlated with changes in hematocrit during the heat-response test (r = –.52, 90%CI [–.77; –.12]). There was no clear correlation between the performance improvements in temperate and hot ambient conditions (r < .26).Conclusion:Running performance in both hot and temperate environments was improved after a football training camp in hot ambient conditions that stimulated heat acclimatization. However, physiological and performance responses were highly individual, and the absence of correlations between physical-performance improvements in hot and temperate environments suggests that their physiological basis might differ.

New findings • What is the central question of this study? We examined whether passive hyperthermia exacerbates central fatigue due to an increase in peak muscle relaxation rate, and whether exercise-induced hyperthermia attenuates this response because of a reduction in contractile speed related to peripheral fatigue. • What is the main finding and its importance? Exercise and passive hyperthermia increase muscle relaxation rate. An increase from moderate to severe passive hyperthermia enhances this rate, but without exacerbating force loss or voluntary muscle and cortical activation, relative to exercise. The centrally mediated rate of activation appears sufficient to overcome the increase in peak muscle relaxation. This study examined whether central fatigue was exacerbated by an increase in muscle contractile speed caused by passive hyperthermia (PaH) and whether exercise-induced hyperthermia (ExH) combined with related peripheral fatigue influenced this response. The ExH was induced by cycling at 60% of maximal oxygen uptake in 38°C conditions and the PaH by sitting in a 48°C climate chamber. Ten men performed brief (∼5 s) and sustained (30 s) maximal voluntary isometric contractions (MVCs) of the knee extensors at baseline (CON, ∼37.1°C) and during moderate (MOD, ∼38.5°C) and severe (SEV, ∼39.5°C) hyperthermia. Motor nerve and transcranial magnetic stimulation were used to assess voluntary muscle and cortical activation level, along with contractile properties. Brief MVC force decreased to a similar extent during SEV-ExH (−8%) and SEV-PaH (−6%; P < 0.05 versus CON). Sustained MVC force also decreased during MOD-ExH (−10%), SEV-ExH (−13%) and SEV-PaH (−7%; P < 0.01 versus CON). Motor nerve and cortical activation were reduced on reaching MOD (∼3%) and SEV (∼5%) ExH and PaH during the brief and sustained MVCs (P < 0.01 versus CON). Peak twitch force decreased on reaching SEV-ExH and SEV-PaH (P < 0.05 versus CON). Following transcranial magnetic stimulation, during the brief and sustained MVCs the peak muscle relaxation rate increased in ExH and PaH (P < 0.01 versus CON). The increase was greatest during the sustained contraction in SEV-PaH (P < 0.01), but this did not exacerbate central fatigue relative to ExH. These results indicate that during fatiguing cycling exercise in the heat, quadriceps peak relaxation rate increases. However, the centrally mediated rate of activation appears sufficient to overcome even the largest increase in muscle relaxation rate, seen during SEV-PaH.

Objectives To determine preparticipation predictors of injury and illness at a major Athletics championship. Methods A cohort study design was used. Before the 2015 International Association of Athletics Federations World Championships in Athletics, all 207 registered national teams were approached about partaking in a study of preparticipation health; 50 teams accepted. The athletes (n=957) in the participating teams were invited to complete a preparticipation health questionnaire (PHQ). New injuries and illnesses that occurred at the championships were prospectively recorded. Logistic regression analyses were performed with simple and multiple models using any in-championship injury and in-championship illness as outcomes. Results The PHQ was completed by 307 (32.1%) of the invited athletes; 116 athletes (38.3%) reported an injury symptom during the month before the championships, while 40 athletes (13%) reported an illness symptom. 20 (6.5%) of the participating athletes sustained a health problem during the championships. Endurance athletes were almost 10-fold more likely to sustain an in-championship illness than speed/power athletes (OR, 9.88; 95% CI 1.20 to 81.31; p=0.033). Participants reporting a preparticipation gradual-onset injury symptom were three times more likely (OR, 3.09; 95% CI 1.08 to 8.79; p=0.035) and those reporting an illness symptom causing anxiety were fivefold more likely (OR, 5.56; 95% CI 1.34 to 23.15; p=0.018) to sustain an in-championship injury. Summary and conclusions Analyses of preparticipation predictors of injury and illness at a major Athletics championship suggest that endurance athletes require particular clinical attention. Preparticipation symptoms causing anxiety are interesting predictors for in-championship health problems.

Purpose:To determine the effect of cold ambient conditions on proprioception and cognitive function in elite alpine skiers.Methods:22 high-level alpine skiers and 14 control participants performed a proprioceptive-acuity (active movement-extent discrimination) and a cognitive (planning task) test in cold (8°C) and temperate (24°C) ambient conditions.Results:All participants displayed an increase in thermal discomfort and the amount of negative affects in the cold environment (all P < .05). Average proprioceptive acuity was significantly better in the elite skiers (0.46° ± 0.12°) than in the control group (0.55° ± 0.12°) (P < .05) and was not affected by cold ambient conditions, except for a shift in the pattern of error (over- vs underestimation, P < .05). Cognitive performance was similar between elite skiers and control participants in temperate environments but decreased in the cold in the control group only (P < .05) becoming lower than in elite skiers (P < .05).Conclusion:Elite alpine skiers showed a significantly better proprioceptive acuity than a control population and were able to maintain their performance during a cognitive task in a cold environment.

Challenging environmental conditions, including heat and humidity, cold, and altitude, pose particular risks to the health of Olympic and other high-level athletes. As a further commitment to athlete safety, the International Olympic Committee (IOC) Medical Commission convened a panel of experts to review the scientific evidence base, reach consensus, and underscore practical safety guidelines and new research priorities regarding the unique environmental challenges Olympic and other international-level athletes face. For non-aquatic events, external thermal load is dependent on ambient temperature, humidity, wind speed and solar radiation, while clothing and protective gear can measurably increase thermal strain and prompt premature fatigue. In swimmers, body heat loss is the direct result of convection at a rate that is proportional to the effective water velocity around the swimmer and the temperature difference between the skin and the water. Other cold exposure and conditions, such as during Alpine skiing, biathlon and other sliding sports, facilitate body heat transfer to the environment, potentially leading to hypothermia and/or frostbite; although metabolic heat production during these activities usually increases well above the rate of body heat loss, and protective clothing and limited exposure time in certain events reduces these clinical risks as well. Most athletic events are held at altitudes that pose little to no health risks; and training exposures are typically brief and well-tolerated. While these and other environment-related threats to performance and safety can be lessened or averted by implementing a variety of individual and event preventative measures, more research and evidence-based guidelines and recommendations are needed. In the mean time, the IOC Medical Commission and International Sport Federations have implemented new guidelines and taken additional steps to mitigate risk even further.