Fatigue during prolonged exercise is related to brain monoamines concentrations, but the mechanisms underlying this relationship have not been fully elucidated. We investigated the effects of increased central tryptophan (TRP) availability on physical performance and thermoregulation in running rats that were pretreated with parachlorophenylalanine (p-CPA), an inhibitor of the conversion of TRP to serotonin. On the 3 days before the experiment, adult male Wistar rats were treated with intraperitoneal (ip) injections of saline or p-CPA. On the day of the experiment, animals received intracerebroventricular (icv) injections of either saline or TRP (20.3 mM) and underwent a submaximal exercise test until fatigue.

To assess the effects of increased hypothalamic tryptophan (TRP) availability on 5-HT content in preoptic area on thermoregulation and work production during exercise on treadmill, 20.3 M of L-TRP (n = 7) or 0.15 M NaCl (n = 6) was injected into the lateral cerebral ventricle of male Wistar rats immediately before the animals started running (18 m min −1 5% inclination). Exercise time to fatigue (min), and workload (kgm) were analysed. Core temperature was measured by telemetry. At fatigue, brains were quickly removed and preoptic area (POA), hypothalamus (HP), frontal cortex (FC), hippocampi (HC) were rapidly dissected and frozen immediately in dry ice. Serotonin (5-HT) and 5-hydroxyindoleacetic acid (5-HIAA) were measured by HPLC. TRP-exercised rats showed the highest content of 5-HT in the POA and the lowest in the hippocampi compared to the rested and SAL-exercised rats. An inverse relationship between TF and a direct correlation with body temperature changes and POA-5HT levels were observed. A correlation between HC 5-HT content and TF was also found. However, there was no correlation between HC 5-HT content and changes in Tb at fatigue. Finally, our results bring further evidences that increased 5-HT content in POA is involved with an increase in heat production during exercise. In addition, the direct correlation of 5-HT level in hippocampi and TF of TRP-exercised rats suggests that this brain area is also related to motor activity control during exercise. In conclusion, our data indicated that tryptophan-induced central fatigue in exercising rats is related to serotonin content in preoptic area.

Prímola-Gomes TN, Campos LA, Lauton-Santos S, Balthazar CH, Guatimosim S, Capettini LS, Lemos VS, Coimbra CC, Soares DD, Carneiro-Jú nior MA, Quintão-Jú nior JF, Souza MO, Cruz JS, Natali AJ. Exercise capacity is related to calcium transients in ventricular cardiomyocytes. aim of the present study was to evaluate the Ca 2ϩ handling and contractility properties of cardiomyocytes isolated from rats with high intrinsic aerobic exercise capacity. Standard-performance (SP) and high-performance (HP) rats were categorized with a treadmill progressive exercise test according to the exercise time to fatigue (TTF). The SP group included rats with TTF between 16.63 and 46.57 min, and the HP group included rats with TTF Ͼ46.57 min. Isolated ventricular cardiomyocytes were dissociated from the hearts of SP and HP rats, and intracellular global Ca 2ϩ ([Ca 2ϩ ]i) transients were measured. The [Ca 2ϩ ]i transient peak was increased in the HP group relative to the SP group (5.54 Ϯ 0.31 vs. 4.18 Ϯ 0.12 F/F0; P Յ 0.05) and was positively correlated with the TTF attained during the progressive test (r ϭ 0.81). We also performed contractility measurements in isolated cardiomyocytes and found higher amplitude of contraction in the HP group compared with the SP group (6.7 Ϯ 0.2 vs. 6.0 Ϯ 0.3% resting cell length; P Յ 0.05). To reinforce the intrinsic differences between SP and HP rats, we performed Western blot experiments and observed increased expression of sarco-(endo)plasmic reticulum Ca 2ϩ -ATPase type 2a (1.30 Ϯ 0.07 vs. 1.74 Ϯ 0.18 arbitrary units; P Յ 0.05) and ryanodine receptor type 2 (1.86 Ϯ 0.13 vs. 3.57 Ϯ 0.12 arbitrary units; P Յ 0.05) in HP rats. In summary, our data showed important intrinsic differences in cardiomyocyte properties that could explain some of the divergence observed in rats with high intrinsic aerobic exercise capacity. intrinsic exercise aerobic capacity; confocal microscopy Address for reprint requests and other correspondence: A. J. Natali, Av.

In order to verify the effects of heat and exercise acclimation (HA) on resting and exercise-induced expression of plasma and leukocyte heat shock protein 72 (Hsp72) in humans, nine healthy young male volunteers (25.0 ± 0.7 years; 80.5 ± 2.0 kg; 180 ± 2 cm, mean ± SE) exercised for 60 min in a hot, dry environment (40 ± 0°C and 45 ± 0% relative humidity) for 11 days. The protocol consisted of running on a treadmill using a controlled hyperthermia technique in which the work rate was adjusted to elevate the rectal temperature by 1°C in 30 min and maintain it elevated for another 30 min. Before and after the HA, the volunteers performed a heat stress test (HST) at 50% of their individual maximal power output for 90 min in the same environment. Blood was drawn before (REST), immediately after (POST) and 1 h after (1 h POST) HST, and plasma and leukocytes were separated and stored. Subjects showed expected adaptations to HA: reduced exercise rectal and mean skin temperatures and heart rate, and augmented sweat rate and exercise tolerance. In HST1, plasma Hsp72 increased from REST to POST and then returned to resting values 1 h POST (REST: 1.11 ± 0.07, POST: 1.48 ± 0.10, 1 h POST: 1.22 ± 0.11 ng mL−1; p −1; p > 0.05). HA increased resting levels of intracellular Hsp72 (HST1: 1 ± 0.02 and HST2: 4.2 ± 1.2 density units, p p p > 0.05). Regression analysis showed that the lower the pre-exercise expression of intracellular Hsp72, the higher the exercise-induced increase (R = −0.85, p 

Introduction: Fatigue due to endurance exercise results from both peripheral and central changes, and may influence subsequent performance during a strength task. The increase in serotonin concentration is one of the central factors associated with endurance exercise-induced fatigue, particularly in hot environments. A nutritional strategy employed to reduce serotonergic activation is supplementation with branched-chain amino acids (BCAA). Objective: To investigate whether BCAA supplementation attenuates the reduction in isometric force caused by prior endurance exercise in a hot environment. Methods: Nine volunteers (aged 25.4 ± 1.2 years) performed a 2-min maximal voluntary isometric contraction (MVCISO) of upper limb muscles before and after an endurance exercise on a cycle ergometer at 40% of the maximal aerobic power. The volunteers underwent three experimental trials: 1) endurance exercise in a temperate environment (23°C and 60% RH); exercise in a hot environment (35°C and 60...

Introduction: Fatigue due to endurance exercise results from both peripheral and central changes, and may influence subsequent performance during a strength task. The increase in serotonin concentration is one of the central factors associated with endurance exercise-induced fatigue, particularly in hot environments. A nutritional strategy employed to reduce serotonergic activation is supplementation with branched-chain amino acids (BCAA). Objective: To investigate whether BCAA supplementation attenuates the reduction in isometric force caused by prior endurance exercise in a hot environment. Methods: Nine volunteers (aged 25.4 ± 1.2 years) performed a 2-min maximal voluntary isometric contraction (MVCISO) of upper limb muscles before and after an endurance exercise on a cycle ergometer at 40% of the maximal aerobic power. The volunteers underwent three experimental trials: 1) endurance exercise in a temperate environment (23°C and 60% RH); exercise in a hot environment (35°C and 60...

Different methodological approaches have been used to conduct experiments with rats subjected to treadmill running. Some experimenters have exposed rats to the treadmill setup before initiating exercise to minimize the influences of handling and being placed in an anxiety-inducing environment on the physiological responses to subsequent running. Other experimenters have subjected rats to exercise immediately after placing them on the treadmill. Thus, the present study aimed to evaluate the effects of pre-exercise exposure to the treadmill on physical performance and cardiovascular and thermoregulatory responses during subsequent exercise. Male Wistar rats were subjected to fatiguing incremental-speed exercise at 24°C immediately after being placed on the treadmill or after being exposed to the treadmill for 70 min following removal from their home cages. Core body temperature (T), tail-skin temperature (T), heart rate (HR) and mean arterial pressure (MAP) were recorded throughout th...

Background Cocoa flavanols (CFs) have antioxidant and anti-inflammatory capacities and can improve vascular function. It has recently been suggested that CF intake may improve exercise performance and recovery. This systematic review aimed to evaluate the literature on the effects of CF intake on exercise performance and recovery and exercise-induced changes in vascular function, cognitive function, oxidative stress, inflammation, and metabolic parameters. Methods Two electronic databases (Pubmed and Web of Science) were searched for studies examining the combination of CF intake and exercise in humans (up to 28 March 2017). Articles were included if the exact amount of CFs was mentioned. The methodological quality and level of bias of the 13 included studies was assessed according to the checklist for randomized controlled trials from the Dutch Cochrane center. Results Acute, sub-chronic (2 weeks) and chronic (3 months) CF intake reduced exercise-induced oxidative stress. Evidence on the effect of CF on exercise-induced inflammation and platelet activation was scarce. Acute CF intake reduced and tempered the exercise-induced increase in blood pressure in obese participants. Acute and subchronic CF intake altered fat and carbohydrate metabolism during exercise. Acute and sub-chronic CF intake did not have ergogenic effects in athletes, while chronic CF intake improved mitochondrial efficiency in untrained participants. While combining sub-chronic CF intake and exercise training improved cardiovascular risk factors and vascular function, evidence on the synergistic effects of CF and exercise training on oxidative stress, inflammation, and fat and glucose metabolism was lacking. Conclusion CF intake may improve vascular function, reduce exercise-induced oxidative stress, and alter fat and carbohydrate utilization during exercise, but without affecting exercise performance. There is a strong need for future studies examining the synergetic effect of chronic CF intake and exercise training.

Different variables can be used for the identification and monitoring of aerobic capacity in collective sports, with the anaerobic threshold (AT) being commonly used in long-duration team sports such as soccer, basketball, and handball. The aim of this study was ...

Among the many parameters used to evaluate the intensity of a physical activity, the energy expenditure is considered within the principal ones. The purpose of the current research was to compare the energy expenditure estimation of soccer players in the Under-20 league (U-20) with results of professional soccer players described in the literature. Eleven soccer players from the first-division Brazilian soccer were evaluated in 12 matches of an official championship. The relationship between HR and oxygen uptake was established in a laboratory. Right after such procedures, the energy expenditure was calculated from the VO2 rates that were found by an equation of linear regression, which were subsequently substituted by the rates given in kilocalories. The energy expenditure of a soccer match was estimated as 17.11 ± 1.45 kcal.min-1 or 13.1 ± 1.68 METs, which corresponded to a total average expenditure of 1539.86 ± 130.07 kcal during a complete match. Therefore, the conclusion is that soccer players of an Under-20 category present high values for energy expenditure during the matches of an official championship.

Group-housed Sprague-Dawley (SD) rats exposed for 1 h to 2,5-dihydro-2,4,5-trimethylthiazoline (TMT, a component of fox feces) 3 did not display changes in hippocampal serotonin (5-HT) metabolism and [ H]5-HT reuptake, compared to water or butyric acid. Such an observation extended to isolated SD and Fischer 344 rats. When group-housed SD rats were tested 1 week after a 1-h exposure to TMT, 3 3 hippocampal 5-HT metabolism, [ H]5-HT reuptake, and [ H]paroxetine binding at the 5-HT transporter remained unchanged. This study questions TMT as a specific predatory stimulus as both butyric acid and TMT increased plasma corticosterone levels whilst leaving intact open field behaviour (at least in group-housed SD rats).

Obesity, defined as an excess in body fat, is a multifactorial disease involving both genetic and environmental risk factors. Early diagnosis and interventions during critical periods of development of obesity-childhood and adolescence-have been recommended, aiming at preventing unfavorable outcomes at a later age. This cross-sectional study sought to characterize the lipid profile, glucose, adiponectin, leptin and ghrelin in schoolchildren between six and nine years of age with overweight and obesity in the city of Ouro Preto (MG). The data was analyzed with the Shapiro Wilk normality test, groups comparisons were made with either a parametric (T test) or a nonparametric (Mann Whitney) test, adopting confidence intervals of 95% and a significance level of ≤ 0.05. The average age of the school population was 7.8 ± 1.1 years, with a prevalence of 8.9% of overweight and 3% of obesity. Hypercholesterolemia was found in 5.5%, HDL was abnormal in 98.7%, LDL levels were borderline in 32.4% and altered glucose levels were present in 46.6% of the children. In stratified analysis by gender, higher values of leptin in girls (p = 0.032) and ghrelin in boys (p = 0.033) were found, with no difference for the other variables. The results show that overweight/obesity among schoolchildren should be considered a significant health problem in this population, highlighting the importance of implementing early intervention programs. Uncovering the precursors of childhood obesity could lead to interventions so as to prevent or mitigate its consequences in youth and adulthood.

Introduction: Child obesity has important consequences on the child's health and is related to the risk of developing chronic diseases. That brings up the need for research assessing the impact of obesity-and overweight-reduction programs with close attention to methodology aspects and precise indicators of the impact of such programs. Goal: Assessing the impact of a physical activity program on the plasma concentrations of adiponectin, leptin, and ghrelin in overweight and obese schoolchildren. Methods: Randomized controlled trial, double-blind, with 6-to 9-year-old overweight and obese schoolchildren. A sample of 79 schoolchildren randomly distributed into control and intervention groups was subjected to a physical activity program. The levels of adiponectin, leptin, ghrelin, body mass index, body fat percentage, anthropometry, lipid profile and glycemia were evaluated. The program's impact was assessed through multivariate linear regression models. Result: When comparing the groups, a significant difference was found for adiponectin, which shows an increase in the proportion of subjects with higher adiponectin concentrations for the intervention group and a reduction in body mass index and body fat percentage. Conclusion: The impact of the intervention program was positive in increasing adiponectin levels associated with a reduction in body mass index and body fat percentage.

Resumo-Diferentes variáveis podem ser utilizadas para a identificação e monitoramento da capacidade aeróbia em esportes coletivos, sendo o limiar anaeróbio (LAN) muito utilizado em atividades como futebol, basquete, handebol entre outros. O objetivo do estudo foi determinar a intensidade do LAN de jogadores de futebol de diferentes categorias, avaliando os parâmetros velocidade, freqüência cardíaca (FC) e percentual da FC máxima (%FCmáx), bem como comparar estas intensidades entre as categorias. Participaram do estudo 19 jogadores da categoria sub-17, 12 jogadores Sub-20 e 14 profissionais. O LAN foi determinado a partir da intensidade de 4mM obtida em um teste de campo. Este consistiu em corridas de 1000m, em velocidades constantes a cada tentativa. A FC e lactato ([Lactato]) obtidos no teste foram analisados através de interpolação linear. Foram determinados a velocidade, a FC e %FCmáx correspondentes à intensidade do LAN. Identificou-se que a FCmáx dos jogadores Sub-17 (202 ± 7bpm) foi maior quando comparada à categoria Profissional (193 ± 10bpm) (p<0,05). O LAN expresso em %FCmáx dos jogadores Sub-17 (87,0 ± 1,1) e Sub-20 (86,3 ± 0,8) foi menor quando comparado à categoria Profissional (91,2 ± 1,1) (p<0,05). A intensidade média do LAN foi 87% FCmáx. Não foram identificadas diferenças entre as categorias quando o LAN foi considerado em bpm e como velocidade de corrida. Concluiu-se que a intensidade do LAN neste grupo pode ser considerada alta, sendo que os jogadores profissionais apresentam LAN mais alto em comparação com as categorias Sub-17 e Sub-20.

This study investigated the influence of aerobic capacity on the activation of the central serotonergic system and exercise fatigue in young men that ingested a selective serotonin reuptake inhibitor and were then subjected to moderate-intensity physical exercise. The maximal oxygen consumption of sixteen volunteers was measured during an incremental test. The volunteers were divided into two groups: subjects with higher (HAC) and lower (LAC) aerobic capacities. The volunteers were subjected to four experimental trials in which they ingested either placebo or paroxetine (10, 20 or 40 mg) and, 4.5 h later, cycled at 60% of their maximal power output until reaching fatigue. None of the three paroxetine doses influenced the total exercise time in the LAC group. However, for the HAC group, the time to fatigue in the 20 mg paroxetine condition was 15% less than that in the placebo condition (76.3 ± 5.1 min vs. 90.0 ± 7.9 min; p &lt; 0.05). The time to fatigue was higher in the HAC group ...