Hydration for the Tokyo Olympics: to thirst or not to thirst?

The Physiological Requirements of and Nutritional Recommendations for Equestrian Riders

Equestrian sport is under-researched within the sport science literature, creating a possible knowledge vacuum for athletes and support personnel wishing to train and perform in an evidence-based manner. This review aims to synthesise available evidence from equitation, sport, and veterinary sciences to describe the pertinent rider physiology of equestrian disciplines. Estimates of energy expenditure and the contribution of underpinning energy systems to equestrian performance are used to provide nutrition and hydration recommendations for competition and training in equestrian disciplines. Relative energy deficiency and disordered eating are also considered. The practical challenges of the equestrian environment, including competitive, personal, and professional factors, injury and concussion, and female participation, are discussed to better highlight novelty within equestrian disciplines compared to more commonly studied sports. The evidence and recommendations are supported by example scenarios, and future research directions are outlined.

Autonomous wearable sweat rate monitoring based on digitized microbubble detection

Advancements in wearable bioanalytical microsystems have enabled diurnal and (semi)continuous monitoring of physiologically-relevant indices that are accessible through probing sweat. To deliver an undistorted and physiologically-meaningful interpretation of these readings, tracking the sweat secretion rate is essential, because it allows for calibrating the biomarker readings against variations in sweat secretion and inferring the body's hydration/electrolyte homeostasis status. To realize an autonomous wearable solution with intrinsically high signal-to-noise ratio sweat rate sensing capabilities, here, we devise a digitized microbubble detection mechanism-delivered by a hybrid microfluidic/electronic system with a compact footprint. This mechanism is based on the intermittent generation of microliter-scale bubbles via electrolysis and the instantaneous measurement of their time-of-flight (and thus, velocity) via impedimetric sensing. In this way, we overcome the limitations of previously proposed sweat rate sensing modalities that are inherently susceptible to non-targeted secretion characteristics (pH, conductivity, and temperature), constrained by volume, or lack system integration for autonomous on-body operation. By deploying our solution in human subject trials, we validate the utility of our solution for seamless monitoring of exercise- and iontophoretically-induced sweat secretion profiles.

Impact of different climatic conditions on peak core temperature of elite athletes during exercise in the heat: a Thermo Tokyo simulation study

Objectives

To evaluate how separate and combined climatic parameters affect peak core temperature during exercise in the heat using computer simulations fed with individual data.

Methods

The impact of eight environmental conditions on rectal temperature (T_re) was determined for exercise under heat stress using the Fiala-thermal-Physiology-and-Comfort simulation model. Variations in ambient temperature (T_a±6°C), relative humidity (RH±15%) and solar radiation (SR+921 W/m²) were assessed in isolation and combination (worst-case/best-case scenarios) and compared with baseline (T_a32°C, RH 75%, SR 0 W/m²). The simulation model was fed with personal, anthropometric and individual exercise characteristics.

Results

54 athletes exercised for 46±10 min at baseline conditions and achieved a peak core temperature of 38.9±0.5°C. Simulations at a higher T_a (38°C) and SR (921 W/m²) resulted in a higher peak T_re compared with baseline (+0.6±0.3°C and +0.5±0.2°C, respectively), whereas a higher RH (90%) hardly affected peak T_re (+0.1±0.1°C). A lower T_a (26°C) and RH (60%) reduced peak T_re by −0.4±0.2°C and a minor −0.1±0.1°C, respectively. The worst-case simulation yielded a 1.5±0.4°C higher T_re than baseline and 2.0±0.7°C higher than the best-case condition.

Conclusion

Combined unfavourable climatic conditions produce a greater increase in peak core temperature than the sum of its parts in elite athletes exercising in the heat.

Case Report: Countermeasures Against Heat and Coronavirus for Japanese Athletes at the Tokyo 2020 Olympics and Paralympic Games

The Tokyo 2020 Olympics and Paralympic Games were held in the hottest environment in the history of the games. Additionally, the worldwide coronavirus disease 2019 (COVID-19) pandemic necessitated daily polymerase chain reaction (PCR) testing during the games, wearing a mask became mandatory publicly, and it was an unheard and unique Olympic with no spectators. Heat acclimation, hydration, and body cooling are essential for safe and high-performance activities in hot environments. In 2015, the Japan Institute of Sports Sciences launched the “Heat Countermeasure Project” to conduct experiments and practical research on heat countermeasures and investigate issues related to heat countermeasures in each athletic event. The results obtained were proposed to various Japan national sports teams, and support for heat countermeasures for the Tokyo 2020 games was promoted in consultation with national federations. Furthermore, due to the COVID-19 pandemic, infectious disease countermeasures for the Tokyo 2020 Games during support were a must. Moreover, athletes, coaches, and team staff could not avoid implementing heat countermeasures while adopting measures against infectious diseases. This study aimed to clarify the issues faced with heat countermeasures and report on heat acclimation training and cooling support efforts, considering measures against infectious diseases.

Performance and thermoregulation of Dutch Olympic and Paralympic athletes exercising in the heat: Rationale and design of the Thermo Tokyo study: The journal Temperature toolbox

The environmental conditions during the Tokyo Olympic and Paralympic Games are expected to be challenging, which increases the risk for participating athletes to develop heat-related illnesses and experience performance loss. To allow safe and optimal exercise performance of Dutch elite athletes, the Thermo Tokyo study aimed to determine thermoregulatory responses and performance loss among elite athletes during exercise in the heat, and to identify personal, sports-related, and environmental factors that contribute to the magnitude of these outcomes. For this purpose, Dutch Olympic and Paralympic athletes performed two personalized incremental exercise tests in simulated control (15°C, relative humidity (RH) 50%) and Tokyo (32°C, RH 75%) conditions, during which exercise performance and (thermo)physiological parameters were obtained. Thereafter, athletes were invited for an additional visit to conduct anthropometric, dual-energy X-ray absorptiometry (DXA), and 3D scan measurements. Collected data also served as input for a thermophysiological computer simulation model to estimate the impact of a wider range of environmental conditions on thermoregulatory responses. Findings of this study can be used to inform elite athletes and their coaches on how heat impacts their individual (thermo)physiological responses and, based on these data, advise which personalized countermeasures (i.e. heat acclimation, cooling interventions, rehydration plan) can be taken to allow safe and maximal performance in the challenging environmental conditions of the Tokyo 2020 Olympic and Paralympic Games.

Exercise Performance and Thermoregulatory Responses of Elite Athletes Exercising in the Heat: Outcomes of the Thermo Tokyo Study

Objective

We examined the impact of simulated Tokyo 2020 environmental condition on exercise performance, thermoregulatory responses and thermal perception among Dutch elite athletes.

Methods

105 elite athletes from different sport disciplines performed two exercise tests in simulated control (15.9 ± 1.2 °C, relative humidity (RH) 55 ± 6%) and Tokyo (31.6 ± 1.0 °C, RH 74 ± 5%) environmental conditions. Exercise tests consisted of a 20-min warm-up (70% HR_max), followed by an incremental phase until volitional exhaustion (5% workload increase every 3 min). Gastrointestinal temperature (T_gi), heart rate, exercise performance and thermal perception were measured.

Results

Time to exhaustion was 16 ± 8 min shorter in the Tokyo versus the control condition (− 26 ± 11%, whereas peak power output decreased with 0.5 ± 0.3 W/kg (16 ± 7%). Greater exercise-induced increases in T_gi (1.8 ± 0.6 °C vs. 1.5 ± 0.5 °C, p < 0.001) and higher peak T_gi (38.9 ± 0.6 °C vs. 38.7 ± 0.4 °C, p < 0.001) were found in the Tokyo versus control condition. Large interindividual variations in exercise-induced increase in T_gi (range 0.7–3.5 °C) and peak T_gi (range 37.6–40.4 °C) were found in the Tokyo condition, with greater T_gi responses in endurance versus mixed- and skill-trained athletes. Peak thermal sensation and thermal comfort scores deteriorated in the Tokyo condition, with aggravated responses for power versus endurance- and mixed-trained athletes.

Conclusion

Large performance losses and T_gi increases were found among elite athletes exercising in simulated Tokyo conditions, with a substantial interindividual variation and significantly different responses across sport disciplines. These findings highlight the importance of an individual approach to optimally prepare athletes for safe and maximal exercise performance during the Tokyo Olympics.

Supplementary Information

The online version contains supplementary material available at 10.1007/s40279-021-01530-w.

Apparent temperature and heat-related illnesses during international athletic championships: A prospective cohort study

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 15℃ and 37℃, 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/°C; 95%CI 0.08-0.16) and was found to double from 25 to 35°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.