Author's Reply to Goulet: Comment on: "Drinking Strategies: Planned Drinking Versus Drinking to Thirst''

Risk of Dehydration Due to Sweating While Wearing Personal 2 Protective Equipment in COVID-19 Clinical Care: A Pilot Study

Objective: The objectives of this study were (a) to determine the physical impact of the personal protective equipment (PPE) used in COVID-19 care, specifically the impact on the hydration state of the temperature and the comfort of the healthcare workers who use it, and (b) to show the high-fidelity simulated environment as an appropriate place to test the experimental designs to be developed in real environments for COVID-19. Background: All healthcare staff use full PPE in the care of COVID-19 patients. There are problems, such as excessive sweating, which have not been quantified thus far. Methods: A descriptive pilot design was used in a simulated high-fidelity setting. There was paired activity, with mild–moderate physical activity, between 45 and 60 min continuously, with the COVID-19 PPE. Sixteen intensive care nurses were selected. The before–after differential of weight, thirst, weight use of the PPE, body temperature, thermal body image, general and facial warmth sensation, and perspiration sensation were measured. Results: All subjects lost weight in the form of sweat with both PPEs during the simulation scenario, with a mean of 200 g (0.28% of initial weight), and increased thirst sensation. Body thermal image increased by 0.54 °C in people using the full COVID-19 PPE. Conclusions: The use of PPE in the management of critically ill COVID-19 patients generates weight loss related to excessive sweating. The weight loss shown in this pilot test is far from the clinical limits of dehydration. The use of ventilated PPE, such as PAPR, reduce the body temperature and heat sensation experienced by the users of it; at the same time, it improves the comfort of those who wear it. The simulated environment is a suitable place to develop the piloting of applicable research methodologies in future studies in a real environment.

Nutritional approaches to counter performance constraints in high-level sports competition

New Findings

What is the topic of this review?

The nutritional strategies that athletes use during competition events to optimize performance and the reasons they use them.

What advances does it highlight?

A range of nutritional strategies can be used by competitive athletes, alone or in combination, to address various event‐specific factors that constrain event performance. Evidence for such practices is constantly evolving but must be combined with understanding of the complexities of real‐life sport for optimal implementation.

Abstract

High‐performance athletes share a common goal despite the unique nature of their sport: to pace or manage their performance to achieve the highest sustainable outputs over the duration of the event. Periodic or sustained decline in the optimal performance of event tasks, involves an interplay between central and peripheral phenomena that can often be reduced or delayed in onset by nutritional strategies. Contemporary nutrition practices undertaken before, during or between events include strategies to ensure the availability of limited muscle fuel stores. This includes creatine supplementation to increase muscle phosphocreatine content and consideration of the type, amount and timing of dietary carbohydrate intake to optimize muscle and liver glycogen stores or to provide additional exogenous substrate. Although there is interest in ketogenic low‐carbohydrate high‐fat diets and exogenous ketone supplements to provide alternative fuels to spare muscle carbohydrate use, present evidence suggests a limited utility of these strategies. Mouth sensing of a range of food tastants (e.g., carbohydrate, quinine, menthol, caffeine, fluid, acetic acid) may provide a central nervous system derived boost to sports performance. Finally, despite decades of research on hypohydration and exercise capacity, there is still contention around their effect on sports performance and the best guidance around hydration for sporting events. A unifying model proposes that some scenarios require personalized fluid plans while others might be managed by an ad hoc approach (ad libitum or thirst‐driven drinking) to fluid intake.

Changes in Hydration Factors Over the Course of Heat Acclimation in Endurance Athletes

The purpose of this study was to examine the effect of heat acclimation (HA) on thirst levels, sweat rate, and percentage of body mass loss (%BML), and changes in fluid intake factors throughout HA induction. Twenty-eight male endurance athletes (mean ± SD; age, 35 ± 12 years; body mass, 73.0 ± 8.9 kg; maximal oxygen consumption, 57.4 ± 6.8 ml·kg-1·min-1) completed 60 min of exercise in a euhydrated state at 58.9 ± 2.3% velocity of maximal oxygen consumption in the heat (ambient temperature, 35.0 ± 1.3 °C; relative humidity, 48.0 ± 1.3%) prior to and following HA where thirst levels, sweat rate, and %BML were measured. Then, participants performed 5 days of HA while held at hyperthermia (38.50-39.75 °C) for 60 min with fluid provided ad libitum. Sweat volume, %BML, thirst levels, and fluid intake were measured for each session. Thirst levels were significantly lower following HA (pre, 4 ± 1; post, 3 ± 1, p < .001). Sweat rate (pre, 1.76 ± 0.42 L/hr; post, 2.00 ± 0.60 L/hr, p = .039) and %BML (pre, 2.66 ± 0.53%; post, 2.98 ± 0.83%, p = .049) were significantly greater following HA. During HA, thirst levels decreased (Day 1, 4 ± 1; Day 2, 3 ± 2; Day 3, 3 ± 2; Day 4, 3 ± 1; Day 5, 3 ± 1; p < .001). However, sweat volume (Day 1, 2.34 ± 0.67 L; Day 2, 2.49 ± 0.58 L; Day 3, 2.67 ± 0.63 L; Day 4, 2.74 ± 0.61 L; Day 5, 2.74 ± 0.91 L; p = .010) and fluid intake (Day 1, 1.20 ± 0.45 L; Day 2, 1.52 ± 0.58 L; Day 3, 1.69 ± 0.63 L; Day 4, 1.65 ± 0.58 L; Day 5, 1.74 ± 0.51 L; p < .001) increased. In conclusion, thirst levels were lower following HA even though sweat rate and %BML were higher. Thirst levels decreased while sweat volume and fluid intake increased during HA induction. Thus, HA should be one of the factors to consider when planning hydration strategies.

Rehydration during Endurance Exercise: Challenges, Research, Options, Methods

During endurance exercise, two problems arise from disturbed fluid-electrolyte balance: dehydration and overhydration. The former involves water and sodium losses in sweat and urine that are incompletely replaced, whereas the latter involves excessive consumption and retention of dilute fluids. When experienced at low levels, both dehydration and overhydration have minor or no performance effects and symptoms of illness, but when experienced at moderate-to-severe levels they degrade exercise performance and/or may lead to hydration-related illnesses including hyponatremia (low serum sodium concentration). Therefore, the present review article presents (a) relevant research observations and consensus statements of professional organizations, (b) 5 rehydration methods in which pre-race planning ranges from no advanced action to determination of sweat rate during a field simulation, and (c) 9 rehydration recommendations that are relevant to endurance activities. With this information, each athlete can select the rehydration method that best allows her/him to achieve a hydration middle ground between dehydration and overhydration, to optimize physical performance, and reduce the risk of illness.