Changes in Factors Regulating Serum Sodium Homeostasis During Two Ultra-Endurance Mountain Races of Different Distances: 69km vs. 121km

Overdrinking and non-osmotic arginine vasopressin release are the main risk factors for exercise-associated hyponatremia (EAH) in ultra-marathon events. However, particularly during ultra-marathon running in mountainous regions, eccentric exercise and hypoxia, which have been shown to modulate inflammation, hormones regulating fluid homeostasis (hypoxia), and oxidative stress, could contribute to serum sodium changes in a dose-dependent manner. To the best of our knowledge, the contribution of these factors, the extent of which depends on the duration and geographical location of the race, has not been well studied. Twelve male participants (11 finishers) of the short (69km, 4,260m elevation-gain) and 15 male participants (seven finishers) of the long (121km, 7,554m elevation-gain) single-stage Südtirol Ultra Sky-Race took part in this observational field study. Venous blood was drawn immediately before and after the race. Analyses included serum sodium concentration, copeptin (a stable marker for vasopressin), markers of inflammation, muscle damage and oxidative stress. Heart rate was measured during the race and race time was obtained from the race office. During the short and the long competition two and one finishers, respectively showed serum sodium concentrations >145mmol/L. During the long competition, one athlete showed serum sodium concentrations <135mmol/L. Only during the short competition percent changes in serum sodium concentrations of the finishers were related to percent changes in body mass (r=−0.812, p=0.002), total time (r=−0.608, p=0.047) and training impulse (TRIMP) (r=−0.653, p=0.030). Data show a curvilinear (quadratic) relationship between percent changes in serum sodium concentration and body mass with race time when including all runners (short, long, finishers and non-finishers). The observed prevalence of hypo- and hypernatremia is comparable to literature reports, as is the relationship between serum sodium changes and race time, race intensity and body mass changes of the finishers of the short race. The curvilinear relationship indicates that there might be a turning point of changes in serum sodium and body mass changes after a race time of approximately 20h. Since the turning point is represented mainly by non-finishers, regardless of race duration slight decrease in body mass and a slight increase in serum sodium concentration should be targeted to complete the race. Drinking to the dictate of thirst seems an adequate approach to achieve this goal.

Analysis of Food Habits during Pandemic in a Polish Population-Based Sample of Primary School Adolescents: Diet and Activity of Youth during COVID-19 (DAY-19) Study

The improper dietary behaviors of children and adolescents during the COVID-19 pandemic, which are associated with lockdowns and reduced physical activity, are a complex problem, potentially resulting in increased risk of diet-related diseases, including overweight and obesity and their consequences. The aim of the study was to assess the food habits during the COVID-19 pandemic and to define their association with physical activity and body mass changes in a Polish population of primary school adolescents within the Diet and Activity of Youth During COVID-19 (DAY-19) Study. The DAY-19 Study was conducted in June 2020 in a national cohort of 1334 primary school students aged 10–16 years, recruited based on a stratified random sampling of schools (sampling counties from voivodeships and schools from counties). The Adolescent Food Habits Checklist (AFHC) was used to assess food habits, associated with food purchase, preparation, and consumption, which in the studied group were analyzed separately for the period before (retrospective data) and during the COVID-19 pandemic (prospective data). The recognizable physical activity changes and recognizable body mass changes were also assessed (retrospective data) and respondents were classified as those declaring that their physical activity and body mass decreased, remained stable, or increased during the COVID-19 pandemic. It was observed that during the COVID-19 pandemic the majority of food habits changed in a statistically significant way (p < 0.05). Within food purchase habits, the number of respondents who declared choosing a low-fat lunch away from home decreased, often buying pastries or cakes decreased, and buying a low-fat crisps brand increased (p < 0.05). Within food preparation habits, the number of respondents who declared trying to keep overall fat intake down increased, trying to keep overall sugar intake down increased, eating at least one serving of vegetables or salad with evening meal increased, and usually including some chocolate and/or biscuits in a packed lunch decreased (p < 0.05). Within food consumption habits, the number of respondents who declared making sure that they eat at least one serving of fruit a day increased, eating at least three servings of fruit most days increased, making sure that they eat at least one serving of vegetables or salad a day increased, trying to ensure that they eat plenty of fruit and vegetables increased, often choosing a fruit when they have a snack between meals increased, eating at least three servings of fruit most days increased, and generally trying to have a healthy diet increased (p < 0.05). It was concluded that in the period of the COVID-19 pandemic and resultant remote education, adolescents in Poland presented different food habits than before, while the majority of changes were positive. The positive food purchase, preparation, and consumption habits were observed mainly in sub-groups of adolescents declaring decreased body mass or increased physical activity during the COVID-19 pandemic. It may be suggested that physical activity may support positive changes of dietary behaviors and while combined positive changes of diet and increased physical activity, they may effectively promote body mass reduction in adolescents.

The thirst sensation failure in keeping body water balance delivered by the modern civilization should be corrected by wearable technologies

A thirst sensation as an evolutionary developed signal for behavioural compensating the lost water balance is frequently compromised at present by palatable additions and stimulants in food and drinks. This situation aggravates the risks for people’s health but many suggested indicators of hydration status are not precise due to lacking a reference to individual homeostatic setpoints. The present study was conducted using a wearable device measuring bioimpedance in three samples with an ambulatory and two laboratory protocols (4016, 13, and 29 subjects) with different successive sessions of circadian and interventional modulations of hydration status with control of contemporary short-term body mass changes as a reference of the status change. Results showed high concordance of short-term fluctuations in body mass and a skin reactance component of the bioimpedance measurements. Circadian components of this bioimpedance measure are suggested as the individual reference to track individual hydration status for correcting thirst signal failures.

Heterothermy as the Norm, Homeothermy as the Exception: Variable Torpor Patterns in the South American Marsupial Monito del Monte (Dromiciops gliroides)

Hibernation (i.e., multiday torpor) is considered an adaptive strategy of mammals to face seasonal environmental challenges such as food, cold, and/or water shortage. It has been considered functionally different from daily torpor, a physiological strategy to cope with unpredictable environments. However, recent studies have shown large variability in patterns of hibernation and daily torpor (“heterothermic responses”), especially in species from tropical and subtropical regions. The arboreal marsupial “monito del monte” (Dromiciops gliroides) is the last living representative of the order Microbiotheria and is known to express both short torpor episodes and also multiday torpor depending on environmental conditions. However, only limited laboratory experiments have documented these patterns in D. gliroides. Here, we combined laboratory and field experiments to characterize the heterothermic responses in this marsupial at extreme temperatures. We used intraperitoneal data loggers and simultaneous measurement of ambient and body temperatures (TA and TB, respectively) for analyzing variations in the thermal differential, in active and torpid animals. We also explored how this differential was affected by environmental variables (TA, natural photoperiod changes, food availability, and body mass changes), using mixed-effects generalized linear models. Our results suggest that: (1) individuals express short bouts of torpor, independently of TA and even during the reproductive period; (2) seasonal torpor also occurs in D. gliroides, with a maximum bout duration of 5 days and a mean defended TB of 3.6 ± 0.9°C (one individual controlled TB at 0.09°C, at sub-freezing TA); (3) the best model explaining torpor occurrence (Akaike information criteria weight = 0.59) discarded all predictor variables except for photoperiod and a photoperiod by food interaction. Altogether, these results confirm that this marsupial expresses a dynamic form of torpor that progresses from short torpor to hibernation as daylength shortens. These data add to a growing body of evidence characterizing tropical and sub-tropical heterothermy as a form of opportunistic torpor, expressed as daily or seasonal torpor depending on environmental conditions.

Polymorphism of winter phenotype in Siberian hamster: consecutive litters do not differ in photoresponsiveness but prolonged acclimation to long photoperiod inhibits winter molt

Background The theory of delayed life history effects assumes that phenotype of adult individual results from environmental conditions experienced at birth and as juvenile. In seasonal environments, being born late in the reproductive season affects timing of puberty, body condition, longevity, and fitness. We hypothesized that late-born individuals are more prone to respond to short photoperiod (SP) than early born ones. We used Siberian hamsters Phodopus sungorus, a model species characterized by high polymorphism of winter phenotype. We experimentally distinguished the effect of litter order (first or third) from the effect of exposure to long photoperiod (LP) before winter (3 months or 5 months) by manipulating the duration of LP acclimation in both litters. We predicted that, irrespective of the litter order, individuals exposed to long photoperiod for a short time have less time to gather energy resources and consequently are more prone to developing energy-conserving phenotypes. To assess effect of litter order, duration of acclimation to long days, and phenotype on basal cost of living we measured basal metabolic rate (BMR) of hamsters. Results Individuals born in third litters had faster growth rates and were bigger than individuals from first litters, but these differences vanished before transfer to SP. Litter order or duration of LP acclimation had no effects on torpor use or seasonal body mass changes, but prolonged acclimation to LP inhibited winter molting both in first and third litters. Moreover, individuals that did not molt had significantly higher BMR in SP than those which molted to white fur. Although one phenotype usually predominated within a litter, littermates were often heterogeneous. We also found that over 10% of individuals presented late response to short photoperiod. Conclusions Our data indicate that duration of postnatal exposure to LP may define propensity to photoresponsiveness, regardless of the litter in which animal was born. Existence of littermates presenting different phenotypes suggests a prudent reproductive strategy of investing into offspring of varied phenotypes, that might be favored depending on environmental conditions. This strategy could have evolved in response to living in stochastic environment.

Examination of Body Mass Changes Among Division I Collegiate Football Players With Sickle Cell Trait

American football athletes are frequently hypohydrated before and during activity. Hypohydration increases the risk of exertional sickling in student-athletes with sickle cell trait (SCT). The authors examined weight charts from the 2010/2011 to 2018/2019 seasons at one Division I institution to determine if differences in percentage body mass losses (%BML) exist between those with and without SCT. Seventeen student-athletes with SCT and 17 matched-controls were included. A Bonferroni correction was applied to account for multiple comparisons (0.05/8), resulting in p < .006 considered significant. There was a significant difference for %BML between groups (SCT: 0.84 ± 0.65% vs. control: 1.21 ± 0.71%; p = .002) but not for the number of days %BML exceeded 2% (SCT: 0 ± 1 vs. control: 1 ± 1; p = .016). Implementation of proper hydration strategies minimized %BML in athletes with SCT, decreasing the risk of hypohydration and exertional sickling. The same strategies ensured all players remained below threshold to optimize performance and reduce heat illness risk.