THE EFFECT OF BCAA ON ISOMETRIC FORCE FOLLOWING ENDURANCE EXERCISE IN A HOT ENVIRONMENT

The effect of dietary supplements on core temperature and sweating responses in hot environmental conditions: a meta-analysis and meta-regression

Dietary supplements are widely used among individuals exposed to hot environments, but whether their consumption confers any thermoregulatory effect is unclear. Therefore, we systematically evaluated the effect of dietary supplementation on key aspects of thermoregulation [core temperature (Tcore) and sweating responses] in the heat. Three databases were searched in April 2024. After screening, 124 peer-reviewed articles were identified for inclusion within three separate meta-analyses: 1) peak Tcore; 2) whole body sweat rate (WBSR); 3) local sweat rate (LSR). The moderating effect of several variables (e.g., training and heat acclimation status), known to influence thermoregulatory function, were assessed via subanalysis and meta-regression. There was no overall effect of the differing supplement types on WBSR (P = 0.405) and LSR (P = 0.769), despite taurine significantly increasing WBSR (n = 3, Hedges' g = 0.79, P = 0.006). Peak Tcore was significantly affected by supplement type (P = 0.011), primarily due to caffeine's "small" significant positive effect (n = 30; Hedges' g = 0.44, P < 0.001) and taurine's (n = 3, Hedges' g = -0.66, P = 0.043) and oligonol's (n = 3; Hedges' g = -0.50, P = 0.014) "medium" significant negative effects. Dietary supplements, such as amino acids (e.g., taurine), some antioxidants and anti-inflammatories (e.g., oligonol) conferred the greatest thermoregulatory benefits during heat exposure. Taurine ingestion in such conditions may lower heat strain, which is likely through its augmentation of thermal sweating. Conversely, caffeine intake may potentially pose the greatest risk in the heat due to its effect on Tcore.NEW & NOTEWORTHY The effects of dietary supplements on core temperature and sweating responses when ingested in the heat varied greatly. Some supplements demonstrated the potential to improve thermoregulatory capacity (e.g., select amino acids, anti-oxidants and anti-inflammatories), while others had no or even deleterious effects on thermal balance (e.g., caffeine). These findings have implications for those ingesting dietary supplements for their health and/or performance effects during exposure to hot environmental conditions. Certain supplements should possibly be avoided in the heat, while others may elicit a thermoregulatory benefit.

Reduced running performance and greater perceived exertion, but similar post-exercise neuromuscular fatigue in tropical natives subjected to a 10 km self-paced run in a hot compared to a temperate environment

Environmental heat stress impairs endurance performance by enhancing exercise-induced physiological and perceptual responses. However, the time course of these responses during self-paced running, particularly when comparing hot and temperate conditions, still needs further clarification. Moreover, monitoring fatigue induced by exercise is paramount to prescribing training and recovery adequately, but investigations on the effects of a hot environment on post-exercise neuromuscular fatigue are scarce. This study compared the time course of physiological and perceptual responses during a 10 km self-paced treadmill run (as fast as possible) between temperate (25°C) and hot (35°C) conditions. We also investigated the changes in countermovement jump (CMJ) performance following exercise in these two ambient temperatures. Thirteen recreational long-distance runners (11 men and 2 women), inhabitants of a tropical region, completed the two experimental trials in a randomized order. Compared to 25°C, participants had transiently higher body core temperature (TCORE) and consistently greater perceived exertion while running at 35°C (p < 0.05). These changes were associated with a slower pace, evidenced by an additional 14 ± 5 min (mean ± SD) to complete the 10 km at 35°C than at 25°C (p < 0.05). Before, immediately after, and 1 h after the self-paced run, the participants performed CMJs to evaluate lower limb neuromuscular fatigue. CMJ height was reduced by 7.0% (2.3 ± 2.4 cm) at 1 h after the race (p < 0.05) compared to pre-exercise values; environmental conditions did not influence this reduction. In conclusion, despite the reduced endurance performance, higher perceived exertion, and transiently augmented TCORE caused by environmental heat stress, post-exercise neuromuscular fatigue is similar between temperate and hot conditions. This finding suggests that the higher external load (faster speed) at 25°C compensates for the effects of more significant perceptual responses at 35°C in inducing neuromuscular fatigue.

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 (β 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.

Active warm-up and time-of-day effects on repeated-sprint performance and post-exercise recovery

PURPOSE

This study investigated the effects of both an active warm-up and the time-of-day variation on repeated-sprint performance. A second objective was to compare the post-exercise recovery between the experimental conditions.

METHODS

Eleven male participants performed ten maximal cycling sprints (6 s each, with a 30-s interval between them) in the morning and late afternoon, either after a warm-up or control condition. The warm-up consisted of cycling for 10 min at 50% of the peak aerobic power.

RESULTS

Rest measurements of rectal, muscle, and skin temperatures were higher in the afternoon compared to the morning (p < 0.05), with no significant differences in heart rate (p = 0.079) and blood lactate concentration (p = 0.300). Warm-up increased muscle temperature, heart rate, and lactate, and reduced skin temperature (all p < 0.001), though no significant differences were observed for rectal temperature (p = 0.410). The number of revolutions (p = 0.034, η_p² = 0.375), peak (p = 0.034, η_p² = 0.375), and mean (p = 0.037, η_p² = 0.365) power of the first sprint (not the average of ten sprints) were higher in the afternoon compared to the morning, regardless of warm-up. However, beneficial performance effects of warming up were evident for the first (p < 0.001) and the average of ten sprints (p < 0.05), regardless of time of day. More remarkable changes during the 60-min post-exercise were observed for rectal temperature (p = 0.005) and heart rate (p = 0.010) in the afternoon than in the morning.

CONCLUSION

Warming-up and time-of-day effects in enhancing muscular power are independent. Although warm-up ensured further beneficial effects on performance than the time-of-day variation, a faster post-exercise recovery was observed in the late afternoon.

Protective Effect of Amino Acids on the Muscle Injury of Aerobics Athletes after Endurance Exercise Based on CT Images

During the training process, the aerobics athletes gradually increase their technical movements, the appreciation of the movements has been gradually improved, and the injuries of the athletes themselves have also gradually become serious. Based on CT image analysis, we study the protective effect of amino acids on aerobics athletes' muscle injury after endurance exercise. There are three major substance metabolism disorders in patients with muscle sclerosis, which are mainly manifested as decreased glucose tolerance and insulin resistance. Some patients develop muscle-derived diabetes. At the same time, the synthesis of lipids such as cholesterol and apolipoproteins decreases, the production of ketone bodies increases and the body uses more ketones for energy. The BCAA/AAA factor refers to the branched-chain amino acid/aromatic amino acid (BCAA/AAA) value. In amino acid metabolism, plasma albumin decreased significantly, the ratio of amino acids was unbalanced, and BCAA/AAA decreased, which was more likely to induce muscular encephalopathy. Using computer tomography (CT) to study the protective effect of amino acids on muscle injury, 32 aerobics athletes were randomly divided into an intervention group (Ig) and a control group (CG), each with 16 people. After 64-slice spiral CT scanning of muscles and three-dimensional reconstruction, the intervention group and the control group participated in aerobic endurance training 3 weeks in advance to establish a muscle microinjury model. The intervention group took the preprepared BCAA, while the control group did not take it. After three weeks of training, there will be one hour and three hours of aerobics competition. We need to detect changes in blood glucose (BS), creatine kinase (SCK), lactate dehydrogenase (LD), alanine (ALA), and alanine aminotransferase (AA) before and after exercise and 1 hour after exercise and record AVS athletes' pain analysis table. We successfully established the muscle injury model, letting all athletes' VAS score in 6-8 points; after 1 hour of exercise, the measurement results were the same as those of 2 hours. Therefore, after endurance training, the blood glucose content of the intervention group gradually decreased and returned to the original level after 2 hours of exercise, while the control group was lower than the level of exercise after 2 hours of exercise; the content of alanine in the two groups decreased more after 2 hours of exercise; the results of serum creatine kinase in the intervention group were higher than those in the control group after exercise. In the intervention group, lactate dehydrogenase increased rapidly at 2 hours after exercise; the alanine aminotransferase in the intervention group increased after exercise, but there was no significant change in the control group. It is also concluded that the longer the exercise time and the more energy consumption, the more effective the branched-chain amino acids supplement will be. The obtained imaging data can provide a more intuitive and accurate basis for the scientific selection of athletes, and amino acids can promote the synthesis of hormones, accelerate the synthesis of proteins and other products, reduce the content of creatine kinase in the blood, and protect the rapid recovery of muscle damage.

Mechanisms of Physical Fatigue and its Applications in Nutritional Interventions

Physical fatigue during exercise can be defined as an impairment of physical performance. Multiple factors have been found contributing to physical fatigue, including neurotransmitter-mediated defense action, insufficient energy supply, and induction of oxidative stress. These mechanistic findings provide a sound theoretical rationale for nutritional intervention since most of these factors can be modulated by nutrient supplementation. In this review, we summarize the current evidence regarding the functional role of nutrients supplementation in managing physical performance and propose the issues that need to be addressed for better utilization of nutritional supplementation approach to improve physical performance.