Ad libitum ice slurry ingestion and half-marathon performance in a hot environment: A study comparing the effects of the amount and moment of ingestion between ice slurry and water at 37 °C.

Ice slurry ingestion during prolonged exercises may improve performance in hot environments; however, the ideal amount and timing of ingestion are still uncertain. We determined whether ad libitum ice slurry ingestion influences physiological and perceptual variables and half-marathon performance while comparing the effects of the amount and moment of ingestion between ice slurry and water at 37 °C. Ten trained participants (28 ± 2 years; mean and SD) were required to run two half marathons while consuming either ice slurry (-1 °C; Ad-1) or water (37 °C; 37 CE) ad libitum. They then performed two other half marathons where, during one, they were required to ingest an amount of water equivalent to the amount consumed during the Ad-1 trial (Pro37), and in the other, to ingest ice slurry in the amount consumed during the 37 CE trial (Pro-1). During the half marathons, dry-bulb temperature and relative humidity were controlled at 33.1 ± 0.3 °C and 60 ± 3%, respectively. Ad-1 ingestion (349.6 ± 58.5 g) was 45% less than 37 CE ingestion (635.5 ± 135.8 g). Physical performance, heart rate, perceived exertion, body temperatures, and thermal perception were not influenced by the temperature or amount of beverage ingestion. However, a secondary analysis suggested that lower beverage ingestion was associated with improved performance (Ad-1 + Pro37 vs. 37 CE + Pro-1: -4.0 min, Cohen's d = 0.39), with a significant relationship between lower beverage ingestion and faster running time (b = 0.02, t = 4.01, p < 0.001). In conclusion, ice slurry ingestion does not affect performance or physiological or perceptual variables during a half marathon in a hot environment. Preliminary evidence suggests that lower beverage ingestion (ice slurry or warm water) is associated with improved performance compared to higher ingestion.

Core body temperatures of rats subjected to treadmill exercise to fatigue or exhaustion: The journal Temperature toolbox.

This study systematically reviewed the literature reporting the changes in rats' core body temperature (TCORE) induced by either incremental- or constant-speed running to fatigue or exhaustion. In addition, multiple linear regression analyses were used to determine the factors contributing to the TCORE values attained when exercise was interrupted. Four databases (EMBASE, PubMed, SPORTDiscus, and Web of Science) were searched in October 2021, and this search was updated in August 2022. Seventy-two studies (n = 1,538 rats) were included in the systematic review. These studies described heterogeneous experimental conditions; for example, the ambient temperature ranged from 5 to 40°C. The rats quit exercising with TCORE values varying more than 8°C among studies, with the lowest and highest values corresponding to 34.9°C and 43.4°C, respectively. Multiple linear regression analyses indicated that the ambient temperature (p < 0.001), initial TCORE (p < 0.001), distance traveled (p < 0.001; only incremental exercises), and running speed and duration (p < 0.001; only constant exercises) contributed significantly to explaining the variance in the TCORE at the end of the exercise. In conclusion, rats subjected to treadmill running exhibit heterogeneous TCORE when fatigued or exhausted. Moreover, it is not possible to determine a narrow range of TCORE associated with exercise cessation in hyperthermic rats. Ambient temperature, initial TCORE, and physical performance-related variables are the best predictors of TCORE at fatigue or exhaustion. From a broader perspective, this systematic review provides relevant information for selecting appropriate methods in future studies designed to investigate exercise thermoregulation in rats.

Predicting the body core temperature of recreational athletes at the end of a 10 km self-paced run under environmental heat stress.

NEW FINDINGS: What is the central question of this study? The aim was to identify the factors predicting the body core temperature of athletes at the end of a 10 km self-paced run in a hot environment. What is the main finding and its importance? Hyperthermia in athletes subjected to self-paced running depends on several factors, highlighting the integrated control of core temperature during exercise under environmental heat stress. Five of the seven variables that significantly predicted core temperature are not invasive and, therefore, practical for use outside the laboratory environment: heart rate, sweat rate, wet-bulb globe temperature, running speed and maximal oxygen consumption. ABSTRACT: Measurement of body core temperature (Tcore ) is paramount to determining the thermoregulatory strain of athletes. However, standard measurement procedures of Tcore are not practical for extended use outside the laboratory environment. Therefore, determining the factors that predict Tcore during a self-paced run is crucial for creating more effective strategies to minimize the heat-induced impairment of endurance performance and reduce the occurrence of exertional heatstroke. The aim of this study was to identify the factors predicting Tcore values attained at the end of a 10 km time trial (end-Tcore ) under environmental heat stress. Initially, we extracted data obtained from 75 recordings of recreationally trained men and women. Next, we ran hierarchical multiple linear regression analyses to understand the predictive power of the following variables: wet-bulb globe temperature, average running speed, initial Tcore , body mass, differences between Tcore and skin temperature (Tskin ), sweat rate, maximal oxygen uptake, heart rate and change in body mass. Our data indicated that Tcore increased continuously during exercise, attaining 39.6 ± 0.5°C (mean ± SD) after 53.9 ± 7.5 min of treadmill running. This end-Tcore value was primarily predicted by heart rate, sweat rate, differences between Tcore and Tskin , wet-bulb globe temperature, initial Tcore , running speed and maximal oxygen uptake, in this order of importance (ß power values corresponded to 0.462, -0.395, 0.393, 0.327, 0.277, 0.244 and 0.228, respectively). In conclusion, several factors predict Tcore in athletes subjected to self-paced running under environmental heat stress. Moreover, considering the conditions investigated, heart rate and sweat rate, two practical (non-invasive) variables, have the highest predictive power.

Determinants of body core temperatures at fatigue in rats subjected to incremental-speed exercise: The prominent roles of ambient temperature, distance traveled, initial core temperature, and measurement site.

Understanding the factors that underlie the physical exercise-induced increase in body core temperature (TCORE) is essential to developing strategies to counteract hyperthermic fatigue and reduce the risk of exertional heatstroke. This study analyzed the contribution of six factors to TCORE attained at fatigue in Wistar rats (n = 218) subjected to incremental-speed treadmill running: ambient temperature (TAMB), distance traveled, initial TCORE, body mass, measurement site, and heat loss index (HLI). First, we ran hierarchical multiple linear regression analyses with data from different studies conducted in our laboratory (n = 353 recordings). We observed that TAMB, distance traveled, initial TCORE, and measurement site were the variables with predictive power. Next, regression analyses were conducted with data for each of the following TCORE indices: abdominal (TABD), brain cortex (TBRAIN), or colonic (TCOL) temperature. Our findings indicated that TAMB, distance traveled (i.e., an exercise performance-related variable), initial TCORE, and HLI predicted the three TCORE indices at fatigue. Most intriguingly, HLI was inversely related to TABD and TBRAIN but positively associated with TCOL. Lastly, we compared the temperature values at fatigue among these TCORE indices, and the following descendent order was noticed - TCOL, TABD, and TBRAIN - irrespective of TAMB where experiments were conducted. In conclusion, TCORE in rats exercised to fatigue depends primarily on environmental conditions, performance, pre-exercise TCORE, and measurement site. Moreover, the influence of cutaneous heat loss on TCOL is qualitatively different from the influence on TABD and TBRAIN, and the temperature values at fatigue are not homogenous within the body core.

Evaluation of hydration status by urine, body mass variation and plasma parameters during an official half-marathon.

BACKGROUND: The aim of this study was to verify the agreement of urine, body mass variations and plasma parameters to determine the hydration status of 14 male runners (29±4 years and 54.3±5.5 mLO2/kg/min) in an official 21.1 km road race. METHODS: The mean dry-bulb temperature and air relative humidity during the road race were 25.1±2.1 °C and 54.7±2.2%, respectively. The volume of water ingested by the runners was monitored using marked volumetric plastic bottles provided at the hydration stations located at 0, 2.5, 5.0, 7.5, 10.5, 14.0, 16.0 and 18.5 km from the starting line. Hydration status was assessed using urine specific gravity (USG), urine osmolality (UOSM) and plasma osmolality (POSM). Furthermore, body mass variation (∆BM) was assessed by comparing body mass (BM) immediately prior and after the race. Total sweat was estimated by ∆BM, added water volume ingested and deducted blood volume collected. The sweat rate was calculated through total sweat and total exercise time. RESULTS: The mean water intake was 0.82±0.40 L, and the mean sweat rate and total sweating were 1440.11±182.13 mL/h and 2.67±0.23 L. After the race, the BM reduced by 1.7±0.4 kg. The ∆BM was -2.41±0.47%, and the plasma volume variation was -9.79±4.6% between pre- and post-running measurements. Despite the POSM increased post-race compared to pre-race, the UOSM and USG did not change. No significant correlations were found between POSM variation with UOSM variation (r=-0.08; P=0.71), USG variation (r=-0.11; P=0.78) or ∆BM (r=0.09; P=0.77). CONCLUSIONS: In conclusion, this study shows that both ∆BM and ∆POSM indicated a hypohydration state after exercise even though the ∆BM did not correlate significantly with ∆POSM. These results demonstrate that ∆BM is a practical method and can be sufficiently sensitive to evaluate the hydration state, but it should be utilized with caution.

Indole alkaloids from Tabernaemontana australis (Muell. Arg) Miers that inhibit acetylcholinesterase enzyme.

Ten indole alkaloids from the chloroform extract of stalk of Tabernaemontana australis (Muell. Arg) Miers were tentatively identified by GC-MS, viz., coronaridine (1), voacangine (2), voacangine hydroxyindolenine (3), rupicoline (4), ibogamine (5), ibogaine (6), ibogaline (7), desethyl-voacangine (8), voachalotine (9), and affinisine (10). Of these, the first four were isolated by silica gel open column chromatography, identified by uni- and bidimensional NMR, IR, MS and showed anti-cholinesterasic activity at the same concentration as the reference compounds physostigmine and galanthamine (detection limit of 0.01mM) by TLC assay using the modified Ellman's method.