Heart rate variability in athletes and nonathletes at rest and during head-up tilt

The purpose of the present study was to determine if autonomic heart rate modulation, indicated by heart rate variability (HRV), differs during supine rest and head-up tilt (HUT) when sedentary and endurance-trained cyclists are compared. Eleven sedentary young men (S) and 10 trained cyclists (C) were studied. The volunteers were submitted to a dynamic ECG Holter to calculate HRV at rest and during a 70º HUT. The major aerobic capacity of athletes was expressed by higher values of at anaerobic threshold and peak conditions (P < 0.05). At rest the athletes had lower heart rates (P < 0.05) and higher values in the time domain of HRV compared with controls (SD of normal RR interval, SDNN, medians): 59.1 ms (S) vs 89.9 ms (C), P < 0.05. During tilt athletes also had higher values in the time domain of HRV compared with controls (SDNN, medians): 55.7 ms (S) vs 69.7 ms (C), P < 0.05. No differences in power spectral components of HRV at rest or during HUT were detected between groups. Based on the analysis of data by the frequency domain method, we conclude that in athletes the resting bradycardia seems to be much more related to changes in intrinsic mechanisms than to modifications in autonomic control. Also, HUT caused comparable changes in sympathetic and parasympathetic modulation of the sinus node in both groups.

Protein turnover, amino acid requirements and recommendations for athletes and active populations

Skeletal muscle is the major deposit of protein molecules. As for any cell or tissue, total muscle protein reflects a dynamic turnover between net protein synthesis and degradation. Noninvasive and invasive techniques have been applied to determine amino acid catabolism and muscle protein building at rest, during exercise and during the recovery period after a single experiment or training sessions. Stable isotopic tracers (13C-lysine, 15N-glycine, ²H5-phenylalanine) and arteriovenous differences have been used in studies of skeletal muscle and collagen tissues under resting and exercise conditions. There are different fractional synthesis rates in skeletal muscle and tendon tissues, but there is no major difference between collagen and myofibrillar protein synthesis. Strenuous exercise provokes increased proteolysis and decreased protein synthesis, the opposite occurring during the recovery period. Individuals who exercise respond differently when resistance and endurance types of contractions are compared. Endurance exercise induces a greater oxidative capacity (enzymes) compared to resistance exercise, which induces fiber hypertrophy (myofibrils). Nitrogen balance (difference between protein intake and protein degradation) for athletes is usually balanced when the intake of protein reaches 1.2 g·kg-1·day-1 compared to 0.8 g·kg-1·day-1 in resting individuals. Muscular activities promote a cascade of signals leading to the stimulation of eukaryotic initiation of myofibrillar protein synthesis. As suggested in several publications, a bolus of 15-20 g protein (from skimmed milk or whey proteins) and carbohydrate (± 30 g maltodextrine) drinks is needed immediately after stopping exercise to stimulate muscle protein and tendon collagen turnover within 1 h.

Isokinetic assessment of the flexor-extensor balance of the knee in athletes with total rupture of the anterior cruciate ligament

The purpose of this study was to assess the flexor-extensor group of muscles of the knee in young athletes diagnosed with a total rupture of the anterior cruciate ligament (ACL). Eighteen knees of 18 athletes (14 men and 4 women) with an average age of 21.6 years (range 16-32 years) were assessed with a Cybex 6000 model isokinetic apparatus. The average interval between occurrence of the injury and assessment was 10.2 months (range 2 - 48 months). There was an associated meniscal injury in eight of the knees. Athletes with any other kind of associated injury, limitation, or blockage of the movement of the joint, significant pain during the exam, or interval between injury and exam of less than two months were excluded from the study. The parameters studied were the peak torque-velocity and flexor-extensor relationships at the constant angular velocities of 60°/sec and 240°/sec. Previous warming-up was done by means of an ergometric bicycle and adaptation with 3 submaximal repetitions. The contra-lateral side, which presented no injury, was used as control. Peak torque (PT) at the constant velocity of 60°/sec was greater than that at 240°/sec for knees with and without injuries. However, there was no significant difference between the injured and uninjured sides at 60°/sec or at 240°/sec. The average value for the flexor-extensor relationship at 60°/sec on the injured was 60% (( 6), compared to 57% (( 10) on the contra-lateral side. At 240°/sec, the average value was 75% ((10) on the injured side, and 65% ((12) on the contra-lateral side. In conclusion, despite the complete rupture of the ACL of one knee, the average values for the flexor-extensor relationship were similar on the injured and uninjured sides at the velocity of 60°/sec. As the velocity increased, an increase in the values for the flexor-extensor relationship of the knee also occurred, indicating a tendency of the performance of the flexor muscle group to approach that of the extensor muscle group, and this tendency was more pronounced on the side of the injury.

Isokinetic dynamometry of knee flexors and extensors: comparative study among non-athletes, jumper athletes and runner athletes

Participation in intensive sports activities leads to muscular specializations that may generate alterations in involved articular forces and cause static (posture) and dynamic changes (alterations of articular stability, coordination, etc.). Prevention of injury requires specific functional muscular evaluation in all athletes and for any kind of sport. OBJECTIVE: To dynamically evaluate, through isokinetic tests, the peak torque, total work, and average power of the knee flexor and extensor muscles of jumper and runner athletes and compare them to those of a non-athletic population, evaluating dominance and balance between agonistic and antagonistic muscle groups. RESULTS: In the non-athlete group, we noted a higher asymmetry between the dominant and nondominant members. The jumpers had the highest values of the evaluated parameters of all groups, whereas parameters for the runners were intermediate between non-athletes and jumpers.

Hepatitis C among former athletes: association with the use of injectable stimulants in the past

This study was performed with the purpose of testing the hypothesis that the high prevalence of hepatitis C among former athletes is associated with their past use of injectable stimulants. The study involved the participation of 208 former professional and amateur soccer and basketball players from the region of Ribeirão Preto, Brazil, who answered a questionnaire regarding their exposure to risk factors, including the use of injectable stimulants in the time they were engaged in sporting activities. ELISA tests were used to detect infection by the hepatitis C virus, and confirmed with PCR and genotyping for the positive cases. It was observed that the former use of injectable stimulants was a practice disseminated among the participants (24.5%), reaching 50.8% in the professionals. The overall prevalence for hepatitis C was 7.2%, with values of 11% among professionals and 5.5% among amateurs. In both categories, the presence of infection was markedly higher among those who admitted past use of injectable stimulants when compared to those who denied such practice (36% and 0.8% among amateurs; 21.9% and 0% among professionals, respectively). Multivariate analysis showed that the use of those substances was the only variable associated with the risk of hepatitis C. This confirms previous observations, performed with reduced sample sizes and without comparison groups, which indicated that the use of injectable vitamins was a risk factor of hepatitis C among former athletes.

Do hematologic constituents really increase due to endurance exercise in horses?

The aim of this study was to evaluate the behavior of blood constituents in a group of horses that successfully completed long endurance rides in tropical conditions. Jugular vein puncture was done to collect blood before, during and after rides. Data were analyzed using a mathematic approach, based on the hematocrit and blood volume where the percentual change in plasma volume was used to correct the values of each variable analyzed. Significance was inferred when P<0.05. The proposed mathematical model to assess blood constituents concentrations allowed the observation of a different pattern of the variables behavior, pointing out that the approach followed by the authors could be more sensitive than ones that did not take this routine. In conclusion, the method used in this study enabled to monitor the physiological processes that actually occur during endurance effort in tropical conditions.

Venous hemogasometry of equines finalists in 90 km endurance races

Front of exercise, the organic systems may suffer water-electrolyte and acid-base imbalances, particularly in the case of blood gases, demonstrating variations from different causes, whether respiratory and/or metabolic. Understanding the physiological adaptations to exercise is essential in the search for the optimum performance. In this way, this study measured the venous blood gases (pO2, pCO2), as well as the oxygen saturation (SatO2) in healthy equines, Arabian horses finalists in 90km endurance races. A total of fourteen Arabian horses were evaluated, nine males and five females, between six and 12 years old, finalists in 90km endurance races. There was a significant reduction in pO2, pCO2 and SatO2 after the exercise, however, the values remained within the normality range, and did not change the athletic performance of the animals, indicating a temporary alteration, assuming thus a character of physiological response to the exercise performed. The equines, finalists in 90 Km endurance races, demonstrated efficient ventilatory process, without any alterations in the athletic performance, being adapted to the type of exercise imposed.

The acute effects of strength, endurance and concurrent exercises on the Akt/mTOR/p70S6K1 and AMPK signaling pathway responses in rat skeletal muscle

The activation of competing intracellular pathways has been proposed to explain the reduced training adaptations after concurrent strength and endurance exercises (CE). The present study investigated the acute effects of CE, strength exercises (SE), and endurance exercises (EE) on phosphorylated/total ratios of selected AMPK and Akt/mTOR/p70S6K1 pathway proteins in rats. Six animals per exercise group were killed immediately (0 h) and 2 h after each exercise mode. In addition, 6 animals in a non-exercised condition (NE) were killed on the same day and under the same conditions. The levels of AMPK, phospho-Thr172AMPK (p-AMPK), Akt, phospho-Ser473Akt (p-Akt), p70S6K1, phospho-Thr389-p70S6K1(p-p70S6K1), mTOR, phospho-Ser2448mTOR (p-mTOR), and phospho-Thr1462-TSC2 (p-TSC2) expression were evaluated by immunoblotting in total plantaris muscle extracts. The only significant difference detected was an increase (i.e., 87%) in Akt phosphorylated/total ratio in the CE group 2 h after exercise compared to the NE group (P = 0.002). There were no changes in AMPK, TSC2, mTOR, or p70S6K1 ratios when the exercise modes were compared to the NE condition (P ≥ 0.05). In conclusion, our data suggest that low-intensity and low-volume CE might not blunt the training-induced adaptations, since it did not activate competing intracellular pathways in an acute bout of strength and endurance exercises in rat skeletal muscle.

Factors associated with dietary supplement use by people who exercise at gyms

OBJECTIVE To assess the factors associated with the use of dietary supplements by people who exercise at gyms.METHODS A cross-sectional study with a sample defined by convenience, considering the number of gyms registered in the Conselho Regional de Educação Física (Regional Council of Physical Education) of Sao Luis, MA, Northeastern Brazil, from July 2011 to July 2012. The final sample comprised 723 individuals who exercise at gyms. The dependent variable was supplement use, and the explanatory variables were length of time and motivation of the physical exercises, duration, goal and self-perception of training, weekly frequency of gym attendance, sex, age, educational attainment, self-perception of body weight, smoking and self-perception of diet. The association between variables was analysed by hierarchical Poisson regression based on a theoretical model.RESULTS Supplement use was reported by 64.7% of the participants. Most of the sample was male (52.6%). The most frequent age group was 20 to 39 years (74.4%). Most participants (46.1%) had been exercising for over a year. The following variables were associated with supplement use: self-perceiving body weight as below ideal (p < 0.001), smoking (p < 0.001), exercising for 7 to 12 months (p = 0.028) or more than one year (p < 0.001), spending more than two hours at the gym (p = 0.051), and perceiving training as moderate (p = 0.024) or intense (p = 0.001).CONCLUSIONS The use of supplements lacks proper professional guidance, being motivated by individuals unsatisfied with their low body weight and who perceive their workout as intense, which raises the need for monitoring this population.

Pulmonary function and aerobic capacity in asymptomatic bariatric candidates with very severe morbid obesity

PURPOSE: Aerobic capacity and respiratory function may be compromised in obesity, but few studies have been done in highly obese bariatric candidates. In a prospective study, these variables were documented in the preoperative period, aiming to define possible physiologic limitations in a apparently healthy and asymptomatic population. METHOD: Forty-six consecutively enrolled adults (age 39.6 ± 8.4 years, 87.0% females, body mass index /BMI 49.6 ± 6.3 kg/m² ) were analyzed. Ventilatory variables were investigated by automated spirometry, aerobic capacity was estimated by a modified Bruce test in an ergometric treadmill, and body composition was determined by bioimpedance analysis. RESULTS: Total fat was greatly increased (46.4 ± 4.6% of body weight) and body water reduced (47.3 ± 4.6 % body weight), as expected for such obese group. Spirometric findings including forced vital capacity of 3.3 ± 0.8 L and forced expiratory volume-1 second of 2.6 ± 0.6 L were usually acceptable for age and gender, but mild restrictive pulmonary insufficiency was diagnosed in 20.9%. Aerobic capacity was more markedly diminished, as reflected by very modest maximal time (4.5 ± 1.1 min) and distance (322 ±142 m) along with proportionally elevated maximal oxygen consumption (23.4 ± 9.5 mL/kg/min) achieved by these subjects during test exercise. CONCLUSIONS: 1) Cardiopulmonary evaluation was feasible and well-tolerated in this severely obese population; 2) Mean spirometric variables were not diminished in this study, but part of the population displayed mild restrictive changes; 3) Exercise tolerance was very negatively influenced by obesity, resulting in reduced endurance and excessive metabolic cost for the treadmill run; 4) More attention to fitness and aerobic capacity is recommended for seriously obese bariatric candidates;

Comparação do comportamento de risco para transtornos alimentares entre adolescentes atletas e não atletas

RESUMO Objetivo Comparar o comportamento de risco para transtornos alimentares (CRTA) entre não atletas e atletas de esportes estéticos, endurance ou com divisão de classe de peso. Métodos Participaram 187 adolescentes atletas e 200 sujeitos que compuseram o grupo de não atletas. Foi utilizado o Eating Attitudes Test (EAT-26) para avaliar o CRTA. Conduziu-se análise multivariada de covariância para comparar as subescalas do EAT-26 segundo o grupo e o sexo. Resultados Os resultados demonstraram que todos os escores das subescalas do EAT-26 foram maiores no sexo feminino quando comparado ao masculino, independente do grupo (p < 0,05). Ademais, as subescalas do EAT-26 foram semelhantes entre atletas e não atletas do sexo feminino, e no masculino evidenciaram-se maiores pontuações para as subescalas Dieta e Autocontrole Oral no grupo de não atletas quando comparado aos atletas (p < 0,05). Conclusão Os atletas não apresentaram maiores escores nas subescalas do EAT-26 quando comparados ao grupo de não atletas.

Respostas cardiorrespiratórias durante exercício em portadores de transplante cardíaco. Análise ergoespirométrica comparativa com indivíduos normais

OBJETIVO: Avaliar as respostas cardiorrespiratórias dos portadores de transplante cardíaco (TxC). MÉTODOS: Submeteram-se a testes ergoespirométricos 9 portadores de TxC (GI), pareados por sexo, idade, peso e altura, com 9 indivíduos sedentários, aparentemente sadios (GII). Os pacientes eram do sexo masculino, com idade de 48±12 anos, com TFI (NYHA) após 23±21 meses TxC. Faziam uso regular de ciclosporina, azatioprina, prednisona, dipiridamol e anti-hipertensivos. Os testes foram limitados por sintomas e interrompidos por exaustão. RESULTADOS: No pico do exercício, o GI apresentou desempenho significativamente inferior ao GII quanto ao VO2, VE, VEO2, FC, tempo de endurance e potência. No limiar anaeróbio, o GI apresentou VO2, tempo de endurance e potência significativamente inferior a do GII. Na potência de 40W o desempenho dos dois grupos foi similar. CONCLUSÃO: O GI apresentou desempenho cardiorrespiratório significativamente inferior no pico do exercício e similar na potência de 40W em relação ao GII, evidenciando os benefícios do TxC para cardiopatas em atividades habituais

Efeitos do exercício aeróbico e anaeróbico em variáveis de risco cardíaco em adultos com sobrepeso

FUNDAMENTO: O exercício físico aeróbico é importante aliado no combate aos fatores de risco cardiovascular. No entanto, os efeitos de exercícios de alta intensidade sobre tais fatores ainda são pouco conhecidos. OBJETIVO: Comparar os efeitos de protocolos de exercícios aeróbico e anaeróbico sobre fatores associados ao risco cardíaco. MÉTODOS: Vinte e dois indivíduos com idade média de 40±8 anos foram alocados nos grupos: controle (CO), treinamento de endurance (ET) e treinamento intermitente (IT). Os protocolos tiveram duração de 12 semanas, três vezes por semana; e intensidades de 10% abaixo e 20% acima do limiar anaeróbico (LAn). Foram medidas: massa corporal total (MCT), índice de massa corporal (IMC), circunferências de cintura (CINT) e quadril (QUA) e a composição corporal, além das concentrações plasmáticas de glicose (GLI), colesterol total (CHO) e triglicérides (TG); ainda foram calculados a razão cintura-quadril (PCCQ) e o índice de conicidade (Índice C). RESULTADOS: As variáveis de MCT, IMC, CINT, GLI e a composição corporal apresentaram alterações significativas nos grupos ET e IT. Os valores de CHO e QUA foram significativamente reduzidos no grupo ET, enquanto a PCCQ mostrou redução significativa no grupo IT. O LAn e o índice C, no grupo IT foram significativamente diferentes em relação a ET. CONCLUSÃO: Tendo em vista as diferenças encontradas nas respostas das variáveis estudadas, em razão do treinamento empregado, concluímos que um programa de exercício que contemple atividades de alta e baixa intensidades seja mais completo para garantir a redução de maior número de variáveis de risco cardíaco.

Resistance Exercise Restores Endothelial Function and Reduces Blood Pressure in Type 1 Diabetic Rats

Background: Resistance exercise effects on cardiovascular parameters are not consistent. Objectives: The effects of resistance exercise on changes in blood glucose, blood pressure and vascular reactivity were evaluated in diabetic rats. Methods: Wistar rats were divided into three groups: control group (n = 8); sedentary diabetic (n = 8); and trained diabetic (n = 8). Resistance exercise was carried out in a squat device for rats and consisted of three sets of ten repetitions with an intensity of 50%, three times per week, for eight weeks. Changes in vascular reactivity were evaluated in superior mesenteric artery rings. Results: A significant reduction in the maximum response of acetylcholine-induced relaxation was observed in the sedentary diabetic group (78.1 ± 2%) and an increase in the trained diabetic group (95 ± 3%) without changing potency. In the presence of NG-nitro-L-arginine methyl ester, the acetylcholine-induced relaxation was significantly reduced in the control and trained diabetic groups, but not in the sedentary diabetic group. Furthermore, a significant increase (p < 0.05) in mean arterial blood pressure was observed in the sedentary diabetic group (104.9 ± 5 to 126.7 ± 5 mmHg) as compared to that in the control group. However, the trained diabetic group showed a significant decrease (p < 0.05) in the mean arterial blood pressure levels (126.7 ± 5 to 105.1 ± 4 mmHg) as compared to the sedentary diabetic group. Conclusions: Resistance exercise could restore endothelial function and prevent an increase in arterial blood pressure in type 1 diabetic rats.