Respostas inflamatória, hematológica, de estresse oxidativo, prejuízo muscular e composição corporal em ultramaratona de 217 km

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Efeito do nadar sobre o desempenho do pedal e corrida no triathlon super-sprint

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Maximal power output during incremental cycling test is dependent on the curvature constant of the power-time relationship

The aim of this study was to investigate whether the maximal power output (Pmax) during an incremental test was dependent on the curvature constant (W') of the power-time relationship. Thirty healthy male subjects (maximal oxygen uptake = 3.58 ± 0.40 L·min(-1)) performed a ramp incremental cycling test to determine the maximal oxygen uptake and Pmax, and 4 constant work rate tests to exhaustion to estimate 2 parameters from the modeling of the power-time relationship (i.e., critical power (CP) and W'). Afterwards, the participants were ranked according to their magnitude of W'. The median third was excluded to form a high W' group (HIGH, n = 10), and a low W' group (LOW, n = 10). Maximal oxygen uptake (3.84 ± 0.50 vs. 3.49 ± 0.37 L·min(-1)) and CP (213 ± 22 vs. 200 ± 29 W) were not significantly different between HIGH and LOW, respectively. However, Pmax was significantly greater for the HIGH (337 ± 23 W) than for the LOW (299 ± 40 W). Thus, in physically active individuals with similar aerobic parameters, W' influences the Pmax during incremental testing.

Bioenergetics and neuromuscular determinants of the time to exhaustion at velocity corresponding to (V) over dotO(2)max in recreational long-distance runners

Bertuzzi, R, Bueno, S, Pasqua, LA, Acquesta, FM, Batista, MB, Roschel, H, Kiss, MAPDM, Serrao, JC, Tricoli, V, and Ugrinowitsch, C. Bioenergetics and neuromuscular determinants of the time to exhaustion at velocity corresponding to (V) over dotO(2)max in recreational long-distance runners. J Strength Cond Res 26(8): 2096-2102, 2012-The purpose of this study was to investigate the main bioenergetics and neuromuscular determinants of the time to exhaustion (T-lim) at the velocity corresponding to maximal oxygen uptake in recreational long-distance runners. Twenty runners performed the following tests on 5 different days: (a) maximal incremental treadmill test, (b) 2 submaximal tests to determine running economy and vertical stiffness, (c) exhaustive test to measured the T-lim, (d) maximum dynamic strength test, and (e) muscle power production test. Aerobic and anaerobic energy contributions during the T-lim test were also estimated. The stepwise multiple regression method selected 3 independent variables to explain T-lim variance. Total energy production explained 84.1% of the shared variance (p = 0.001), whereas peak oxygen uptake ((V) over dotO(2)peak) measured during T-lim and lower limb muscle power ability accounted for the additional 10% of the shared variance (p = 0.014). These data suggest that the total energy production, (V) over dotO(2)peak, and lower limb muscle power ability are the main physiological and neuromuscular determinants of T-lim in recreational long-distance runners.

Effects of excess body mass on strength and fatigability of quadriceps in postmenopausal women

Objective: Obesity is a major public health problem leading to, among other things, reduced functional capacity. Moreover, obesity-related declines in functional capacity may be compounded by the detrimental consequences of menopause. The aim of this study was to understand the potential effects of excess body mass on measures of functional capacity in postmenopausal women. Methods: Forty-five postmenopausal women aged 50 to 60 years were divided into two groups according to body mass index (BMI): obese (BMI, >= 30 kg/m(2); n = 19) and nonobese (BMI, 18.5-29.9 kg/m(2); n = 26). To determine clinical characteristics, body composition, bone mineral density, and maximal exercise testing was performed, and a 3-day dietary record was estimated. To assess quadriceps function, isokinetic exercise testing at 60 degrees per second (quadriceps strength) and at 300 degrees per second (quadriceps fatigue) was performed. Results: The absolute value of the peak torque was not significantly different between the groups; however, when the data were normalized by body mass and lean mass, significantly lower values were observed for obese women compared with those in the nonobese group (128% +/- 25% vs 155% +/- 24% and 224% +/- 38% vs 257% +/- 47%, P < 0.05). The fatigue index did not show any significant difference for either group; however, when the data were normalized by the body mass and lean mass, significantly lower values were observed for obese women (69% +/- 16% vs 93% +/- 18% and 120% +/- 25% vs. 135% +/- 23%, P < 0.01). Conclusions: Our results show that despite reduced muscle force, the combination of obesity and postmenopause may be associated with greater resistance to muscle fatigue.

Effects of acute creatine supplementation on iron homeostasis and uric acid-based antioxidant capacity of plasma after wingate test

Background: Dietary creatine has been largely used as an ergogenic aid to improve strength and athletic performance, especially in short-term and high energy-demanding anaerobic exercise. Recent findings have also suggested a possible antioxidant role for creatine in muscle tissues during exercise. Here we evaluate the effects of a 1-week regimen of 20 g/day creatine supplementation on the plasma antioxidant capacity, free and heme iron content, and uric acid and lipid peroxidation levels of young subjects (23.1 +/- 5.8 years old) immediately before and 5 and 60 min after the exhaustive Wingate test. Results: Maximum anaerobic power was improved by acute creatine supplementation (10.5 %), but it was accompanied by a 2.4-fold increase in pro-oxidant free iron ions in the plasma. However, potential iron-driven oxidative insult was adequately counterbalanced by proportional increases in antioxidant ferric-reducing activity in plasma (FRAP), leading to unaltered lipid peroxidation levels. Interestingly, the FRAP index, found to be highly dependent on uric acid levels in the placebo group, also had an additional contribution from other circulating metabolites in creatine-fed subjects. Conclusions: Our data suggest that acute creatine supplementation improved the anaerobic performance of athletes and limited short-term oxidative insults, since creatine-induced iron overload was efficiently circumvented by acquired FRAP capacity attributed to: overproduction of uric acid in energy-depleted muscles (as an end-product of purine metabolism and a powerful iron chelating agent) and inherent antioxidant activity of creatine.

Circulating plasma surfactant protein type B as biological marker of alveolar-capillary barrier damage in chronic heart failure

BACKGROUND: Surfactant protein type B (SPB) is needed for alveolar gas exchange. SPB is increased in the plasma of patients with heart failure (HF), with a concentration that is higher when HF severity is highest. The aim of this study was to evaluate the relationship between plasma SPB and both alveolar-capillary diffusion at rest and ventilation versus carbon dioxide production during exercise. METHODS AND RESULTS: Eighty patients with chronic HF and 20 healthy controls were evaluated consecutively, but the required quality for procedures was only reached by 71 patients with HF and 19 healthy controls. Each subject underwent pulmonary function measurements, including lung diffusion for carbon monoxide and membrane diffusion capacity, and maximal cardiopulmonary exercise test. Plasma SPB was measured by immunoblotting. In patients with HF, SPB values were higher (4.5 [11.1] versus 1.6 [2.9], P=0.0006, median and 25th to 75th interquartile), whereas lung diffusion for carbon monoxide (19.7+/-4.5 versus 24.6+/-6.8 mL/mm Hg per min, P<0.0001, mean+/-SD) and membrane diffusion capacity (28.9+/-7.4 versus 38.7+/-14.8, P<0.0001) were lower. Peak oxygen consumption and ventilation/carbon dioxide production slope were 16.2+/-4.3 versus 26.8+/-6.2 mL/kg per min (P<0.0001) and 29.7+/-5.9 and 24.5+/-3.2 (P<0.0001) in HF and controls, respectively. In the HF population, univariate analysis showed a significant relationship between plasma SPB and lung diffusion for carbon monoxide, membrane diffusion capacity, peak oxygen consumption, and ventilation/carbon dioxide production slope (P<0.0001 for all). On multivariable logistic regression analysis, membrane diffusion capacity (beta, -0.54; SE, 0.018; P<0.0001), peak oxygen consumption (beta, -0.53; SE, 0.036; P=0.004), and ventilation/carbon dioxide production slope (beta, 0.25; SE, 0.026; P=0.034) were independently associated with SPB. CONCLUSIONS: Circulating plasma SPB levels are related to alveolar gas diffusion, overall exercise performance, and efficiency of ventilation showing a link between alveolar-capillary barrier damage, gas exchange abnormalities, and exercise performance in HF.

The importance of growth hormone in the regulation of erythropoiesis, red cell mass, and plasma volume in adults with growth hormone deficiency

Total body water (TBW) is reduced in adult GH deficiency (GHD) largely due to a reduction of extracellular water. It is unknown whether total blood volume (TBV) contributes to the reduced extracellular water in GHD. GH and insulin-like growth factor I (IGF-I) have been demonstrated to stimulate erythropoiesis in vitro, in animal models, and in growing children. Whether GH has a regulatory effect on red cell mass (RCM) in adults is not known. We analyzed body composition by bioelectrical impedance and used standard radionuclide dilution methods to measure RCM and plasma volume (PV) along with measuring full blood count, ferritin, vitamin B12, red cell folate, IGF-I, IGF-binding protein-3, and erythropoietin in 13 adult patients with GHD as part of a 3-month, double blind, placebo-controlled trial of GH (0.036 U/kg.day). TBW and lean body mass significantly increased by 2.5 +/- 0.53 kg (mean +/- SEM; P < 0.004) and 3.4 +/- 0.73 kg (P < 0.004), respectively, and fat mass significantly decreased by 2.4 +/- 0.32 kg (P < 0.001) in the GH-treated group. The baseline RCM of all patients with GHD was lower than the predicted normal values (1635 +/- 108 vs. 1850 +/- 104 mL; P < 0.002). GH significantly increased RCM, PV, and TBV by 183 +/- 43 (P < 0.006), 350 +/- 117 (P < 0.03), and 515 +/- 109 (P < 0.004) mL, respectively. The red cell count increased by 0.36 +/- 0.116 x 10(12)/L (P < 0.03) with a decrease in ferritin levels by 39.1 +/- 4.84 micrograms/L (P < 0.001) after GH treatment. Serum IGF-I and IGF-binding protein-3 concentrations increased by 3.0 +/- 0.43 (P < 0.001) and 1.3 +/- 0.15 (P < 0.001) SD, respectively, but the erythropoietin concentration was unchanged after GH treatment. No significant changes in body composition or blood volume were recorded in the placebo group. Significant positive correlations could be established between changes in TBW and TBV, lean body mass and TBV (r = 0.78; P < 0.04 and r = 0.77; P < 0.04, respectively), and a significant negative correlation existed between changes in fat mass and changes in TBV in the GH-treated group (r = -0.95; P < 0.02). We conclude that 1) erythropoiesis is impaired in GHD; 2) GH stimulates erythropoiesis in adult GHD; and 3) GH increases PV and TBV, which may contribute to the increased exercise performance seen in these patients.

B-type natriuretic peptide for diagnosis and treatment of congestive heart failure

BACKGROUND Prognostic classification of congestive heart failure (CHF) is difficult and only possible with the help of additional diagnostic tools. B-type natriuretic peptide (BNP) has been used as a diagnostic and prognostic marker for patients (pts) with CHF. In this study, the clinical value of BNP for stratification and treatment of pts with CHF was evaluated. PATIENTS AND METHODS 33 out-pts with CHF (age 57 +/- 12 years) were included. Left-ventricular (LV) ejection fraction (EF) was 27 +/- 8% (mean +/- SD) and NYHA-class 2.4 +/- 0.7. Following parameters were measured: BNP and sodium from blood samples, exercise performance from 6-minute walking test (6MWT, meters) (n = 18), LV end-diastolic diameter (LVEDD) and LV mass (LVM) from 2D-echocardiography (n = 33), as well as LV end-diastolic pressure (LVEDP, n = 23) and systemic vascular resistance (SVR, n = 20) from heart-catheterisation. Ten pts were hospitalised in the preceding 6 months because of worsening CHF or for optimisation of medical therapy. BNP was measured at the beginning and end of the hospital-stay. Follow-up was for 1 year. RESULTS Pts with a high NYHA-class had a higher BNP (pg/ml) than those with a low NYHA- class: NYHA I 51 +/- 20, II 281 +/- 223, III 562+/-346 and IV 1061 +/- 126 pg/ml (p = 0.002). BNP correlated with LVEDP (r = 0.50, p <0.02), SVR (r =0.49, p <0.03) and inversely with 6MWT (r =-0.60, p <0.009), LVEF (r = -0.49, p <0.004) and sodium (r = -0.36, p = 0.04). In the hospitalised pts, mean BNP (pg/ml) was 881 +/- 695 at admission,and 532 +/- 435 at discharge (n.s.). Decrease in BNPduring hospitalisation paralleled weight-loss and was significantly greater in patients with >1000 pg/ml BNP at admission (n = 5) as compared to the 5 patients with BNP <1000 (p <0.03). Patients with an adverse event during 1-year follow-up had significantly higher BNP both at steady-state (603 +/-359 pg/ml) and at time of decompensation than patients with a favourable outcome (227 +/- 218 pg/ml,p <0.001). CONCLUSIONS BNP correlates well with the clinical severity of CHF (NYHA-class) and is directly related to filling pressure (LVEDP), LV function(LVEF) and exercise performance (6 MWT). Furthermore, BNP has prognostic impact with regard to adverse clinical events.

Effects of Anxiety on Anticipation and Visual Search in Dynamic, Time-Constrained Situations

We tested the predictions of Attentional Control Theory (ACT) by examining how anxiety affects visual search strategies, performance efficiency, and performance effectiveness using a dynamic, temporal-constrained anticipation task. Higher and lower skilled players viewed soccer situations under 2 task constraints (near vs. far situation) and were tested under high (HA) and low (LA) anxiety conditions. Response accuracy (effectiveness) and response time, perceived mental effort, and eye-movements (all efficiency) were recorded. A significant increase in anxiety was evidenced by higher state anxiety ratings on the MRF-L scale. Increased anxiety led to decreased performance efficiency because response times and mental effort increased for both skill groups whereas response accuracy did not differ. Anxiety influenced search strategies, with higher skilled players showing a decrease in number of fixation locations for far situations under HA compared with LA condition when compared with lower skilled players. Findings provide support for ACT with anxiety impairing processing efficiency and, potentially, top-down attentional control across different task constraints.

Joint effects of pulmonary function and aerobic power on survival in a cohort of healthy adults

Objective measurements of physical fitness and pulmonary function are related individually to long-term survival, both in healthy people and in those who are ill. These factors are furthermore known to be related to one another physiologically in people with pulmonary disease, because advanced pulmonary disease causes ventilatory limitation to exercise. Healthy people do not have ventilatory limitation to exercise, but rather have ventilatory reserve. The relationship between pulmonary function and exercise performance in healthy people is minimal. Exercise performance has been shown to modify the effect of pulmonary function on mortality in people with chronic obstructive pulmonary disease, but the relationship between these factors in healthy people has not been studied and is not known. The purpose of this study is to quantify the joint effects of pulmonary function and exercise performance as these bear on mortality in a cohort of healthy adults. This investigation is an historical cohort study over 20 years of follow-up of 29,624 adults who had complete preventive medicine, spirometry and treadmill stress examinations at the Cooper Clinic in Dallas, Texas.^ In 20 years of follow-up, there were 738 evaluable deaths. Forced expiratory volume in one second (FEV$\sb1$) percent of predicted, treadmill time in minutes percent of predicted, age, gender, body mass index, baseline smoking status, serum glucose and serum total cholesterol were all significant, independent predictors of mortality risk. There were no frank interactions, although age had an important increasing effect on the risk associated with smoking when other covariates were controlled for in a proportional-hazards model. There was no confounding effect of exercise performance on pulmonary function. In agreement with the pertinent literature on independent effects, each unit increase in FEV$\sb1$ percent predicted was associated with about eight tenths of a percent reduction in adjusted mortality rate. The concept of physiologic reserve is useful in interpretation of the findings. Since pulmonary function does not limit exercise tolerance in healthy adults, it is reasonable to expect that exercise tolerance would not modify the effect of pulmonary function on mortality. Epidemiologic techniques are useful for elucidating physiological correlates of mortality risk. ^

Abdominal muscle recruitment during a range of voluntary exercises

Various exercises are used to retrain the abdominal muscles in the management of low back pain and other musculoskeletal disorders. However. few studies have directly investigated the activity of all the abdominal muscles or the recruitment of regions of the abdominal muscles during these manoeuvres. This study examined the activity of different regions of transversus abdominis (TrA), obliquus internus (OI) and externus abdominis (OE), and rectus abdominis (RA), and movement of lumbar spine, pelvis and abdomen during inward movement of the lower abdominal wall, abdominal bracing, pelvic tilting, and inward movement of the lower and upper abdominal wall. Inward movement of the lower abdominal wall in supine produced greater activity of TrA compared to OI. OE and RA. During posterior pelvic tilting. middle OI was most active and with abdominal bracing. OE was predominately recruited. Regions of TrA were recruited differentially and in inverse relationship between lumbopelvic motion and TrA electromyography (EMG) was found. This study indicates that inward movement of the abdominal wall in supine produces the most independent activity of TrA relative to the other abdominal muscle, recruitment varies between regions of TrA, and observation of abdominal and lumbopelvic motion may assist in evalation of exercise performance. (c) 2004 Elsevier Ltd. All rights reserved.

Physiological role of carnosine in contracting muscle

High-intensity exercise leads to reductions in muscle substrates (ATP, PCr, and glycogen) and a subsequent accumulation of metabolites (ADP, Pi, H+, and M2+) with a possible increase in free radical production. These factors independently and collectively have deleterious effects on muscle, with significant repercussions on high-intensity performance or training sessions. The effect of carnosine on overcoming muscle fatigue appears to be related to its ability to buffer the increased H+ concentration following high-intensity work. Carnosine, however, has other roles such as an antioxidant, a metal chelator, a Ca2+ and enzyme regulator, an inhibitor of protein glycosylation and protein-protein cross-linking. To date, only 1 study has investigated the effects of carnosine supplementation (not in pure form) on exercise performance in human subjects and found no improvement in repetitive high-intensity work. Much data has come from in vitro work on animal skeletal muscle fibers or other components of muscle contractile mechanisms. Thus further research needs to be carried out on humans to provide additional understanding on the effects of carnosine in vivo.

Awareness and use of caffeine by athletes competing at the 2005 Ironman Triathlon World Championships

This study assessed the knowledge, prevalence, and quantity of caffeine use by athletes competing at the 2005 Ironman Triathlon World Championships. Caffeine-related questionnaires were self-administered to 140 (105 male and 35 female, 40.3 +/- 10.7 y) athletes representing 16 countries. Fifty of these athletes further consented to immediate post-race blood samples for analysis of plasma caffeine and paraxanthine using high-performance liquid chromatography (HPLC). Seventy-two percent of 70 athletes correctly identified caffeine as being an unrestricted substance in triathlon. The majority of athletes [125 (89%)] were planning on using a caffeinated substance immediately prior to or throughout the race. Cola drinks (78%), caffeinated gels (42%), coffee (usually pre-race) (37%), energy drinks (13%), and NoDoz tablets (9%) were the most popular caffeinated choices. Mean standard deviation (and range) post race plasma caffeine and paraxanthine levels were 22.3 +/- 20 mu mol/L (1.7 to 98.4) and 9.4 +/- 6 mu mol/L (1.8 to 28.9), respectively. Seven athletes (14%) finished with plasma caffeine levels >= 40 mu mol/L. Plasma values from elite athletes did not differ from age group competitors. Despite the prevalence of its consumption and the training experience of this athletic group, over one quarter of athletes remained either confused or uninformed about caffeine's legality. Levels of plasma caffeine taken immediately post race indicated that athletes typically finish with quantities of caffeine that have been shown to improve endurance performance (i.e., approximate to 20 mu mol/L or a dose of >= 3 mg/kg body weight).

Normative reference values for the 20-meter shuttlerun test in a population-based sample of schoolchildren in Bogota, Colombia: The FUPRECOL Study

Our aim was to determine the normative reference values of cardiorespiratory fitness (CRF) and to establish the proportion of subjects with low CRF suggestive of future cardio-metabolic risk.