O limiar de esforço percebido (LEP) corresponde à potência crítica e a um indicador de máximo estado estável de consumo de oxigěnio

The perceived exertion has been a target of several investigations, many times with association with objective physiological indicators in exercise. Recently, the identification of the perceived exertion threshold (PET) was proposed in the water running, which presented no difference in relation to the critical velocity. Theoretically, both parameters would be indicators of the maximum steady state of variables such as V̇O2 and blood lactate. The objective of this work was to verify the coincidence between PET, critical power (PCrit) and an indicator of maximum V̇O2 steady state (PCrit') in cycle ergometer. Eight male participants were submitted to progressive effort test in order to determine V̇O2peak (46.7 ± 8.5 ml/kg/min) and to four rectangular tests until exhaustion for the estimation of the critical power model parameters, PET and PCrit'. The hyperbolic relation between mechanical power and time spent for the V̇O2peak to be reached in each test was used for the PCrit' estimation, considered as the asymptote in the power axis, and the portion of the anaerobic work capacity (CTAnaer) depleted up to the establishment of the V̇O2peak (CTAnaer'). In order to identify PET, the straight lines angular coefficients of the perceived exertion in time (ordinate) and the powers used (abscissa) were adjusted to a linear function that provided a point in the power axis in which the perceived exertion would be kept indefinitely stable. The parameters PCrit and CTAnaer were estimated by means of the power-time non-linear equation. In order to compare the estimations of PET, PCrit and PCrit', the analysis of variance ANOVA for repeated measurements was employed, and the associations were established through the Pearson correlation. CTAnaer and CTAnaer' were compared through the t test. PET (180 W ± 61 W), PCrit (174 W ± 43 W) and PCrit' (176 W ± 48 W) were not significantly different and the correlations were of 0.92-0.98. CTAnaer' (14,080 ± 5,219 J) was lower than CTAnaer (22,093 ± 9,042 J). One concludes that the PET predicts the intensity of PCrit and PCrit' with accuracy.

Efeito da cadência de pedalada sobre as respostas metabólica e cardiovascular durante o exercício incremental e de carga constante em indivíduos ativos

The main purpose of this study was to analyze the effect of the pedaling cadence (500 × 100 rpm) on the heart rate (HR) and the blood lactate response during incremental and constant workload exercises in active individuals. Nine active male individuals (20.9 ± 2.9 years old; 73.9 ± 6.5 kg; 1.79 ± 0.9 m) were submitted to two incremental tests, and to 6-8 constant workload tests to determine the intensity corresponding to the maximal steady state lactate (MLSSintens) in both cadences. The maximal power (Pmax) attained during the incremental test, and the MLSSintens were significantly lower at 100 rpm (240.9 ± 12.6 W; 148.1 ± 154.W) compared to 50 rpm (263.9 ± 18.6 W; 186.1 ± 21.2 W), respectively. The HRmax did not change between cadences (50 rpm = 191.1 ± 8.8 bpm; 100 rpm = 192.6 ± 9.9 bpm). Regardless the cadence, the HRmax percentage (70, 80, 90, and 100%) determined the same lactate concentrations during the incremental test. However, when the intensity was expressed in Pmax percentage or in absolute power, the lactate and the HR values were always higher at highest cadences. The HR corresponding to MLSSintens was similar between cadences (50 rpm = 162.5 ± 9.1 bpm; 100 rpm = 160.4 ± 9.2 bpm). Based on these results, it can be conclude that regardless the cadence employed (50 × 100 rpm), the use of the HR to individualize the exercise intensity indicates similar blood lactate responses, and this relationship is also kept in the exercise of constant intensity performed at MLSSintens. On the other hand, the use of the Pmax percentages depend on the cadence used, indicating different physiological responses to a same percentage.

Comparação entre limiar anaeróbio determinado por variáveis ventilatórias e pela resposta do lactato sanguíneo em ciclistas

Many investigations have shown that the coincidence between the ventilatory thresholds and those thresholds using the lactate response does not happen all of the time, suggesting that there is no relationship between the cause-effect between these phenomena. Thus, the present study had as main purpose to compare and correlate the Oxygen consumption (V̇O 2), the power (W), and the heart rate (HR) values attained using protocols to determine the Ventilatory Threshold (VT) and the Individual Anaerobic Threshold (IAT). The sampling was constituted by eight State and National level cyclists (age: 27.88 ± 8.77 years; body mass: 65.19 ± 4.40 kg; height: 169.31 ± 5,77 cm). The IAT was determined starting from a three minutes 50 W warm up with progressive increases of 50 W.3min -1 up to achieving the voluntary exhaustion, when the blood was collected in the last 20 seconds of each phase, and during the recovering period. In order to determine the VT, it was used the same protocol used to determine the IAT, but without performing the blood collection. The VT was identified through the changes in the pulmonary ventilation, as well as of the ventilatory equivalent of the O 2 and CO 2. The t-Student test showed no significant statistical difference in any of the attained variables. The associations found were high and significant. The V̇O 2 (ml.kg -1.min. -1), P (W), and HR (bpm) corresponding to the VT and IAT, as well as the associations between variables were respectively: 48.00 ± 3.82 vs. 48.08 ± 3.71 (r = 0.90); 256.25 ± 32.04 vs. 246.88 ± 33.91 (r = 0.84); 173.75 ± 9.18 vs. 171.25 ± 12.02 (r = 0.97). According to the results attained, it can be concluded that the IAT and the VT produce similar V̇O 2, W, and HR values, favoring the adoption of the VT because it is a non-invasive method to determine the anaerobic threshold in cyclists.

Long-term creatine supplementation improves the aerobic capacity of horses

The aim of the present study was to investigate the effect of long-term oral supplementation of creatine on the physiological responses to aerobic training. Twelve purebred Arabian horses were submitted to aerobic training for 90 days, with and without creatine supplementation which consisted of the daily administration of 75g of creatine monohydrate mixed into the ration for 90 days of training. Physical conditioning was conducted on a high performance treadmill and training intensity was stipulated by calculating the V 4 (velocity at which blood lactate reaches 4mmol L -1) determined monthly for each animal. The individual intensity of physical force at 80% of aerobic threshold was established. An incremental exercise test was used to set the individual V4. After a warm up period of 4 min at 4m s -1), the speed was increased at 2min intervals to 6, 8 and 10m s -1). The blood samples were collected 15s before the end of each step to determine the concentration of lactate, packed cell volume, hemoglobin and red cell values. The results demonstrated a significant increase (P<0.05) in V4 in the groups that received creatine supplementation for 60 days or more when compared to the animals without creatine supplememntation. The other hematological variables were similar to all groups. The results showed that the prolonged creatine supplementation may have a beneficial al effect on the equine athletic performance.

Aerobic Training, But Not Creatine, Modifies Longissimus Dorsi Muscle Composition

The goal of this study was to investigate by means of an ultrasound examination the composition of the longissimus dorsi muscle in 12 purebred Arabian horses submitted to aerobic training for 90 days, with and without creatine supplementation. Creatine supplementation was carried out by daily administration of 75 g creatine monohydrate mixed into the ration during 90 days of training. Physical conditioning was conducted on a high-performance treadmill, and training intensity was stipulated by calculating the velocity at which blood lactate reaches 4 mmol/l, determined monthly for each animal. The individual intensity of physical force was established at 80% of velocity that resulted in a blood lactate level of 4 mmol/l. The cross-sectional area and the thickness of the layer of fat of the longissimus dorsi muscle were measured for each group at the end of 8 months of inactivity and after 30, 60, and 90 days of training without (control groups) or with creatine supplementation (experimental groups). The results showed that aerobic training combined with or without creatine supplementation caused significant longissimus dorsi hypertrophy and reduction in the thickness of the fat layer. No beneficial effect from prolonged creatine supplementation on the body composition of horses was detected. © 2007 Elsevier Inc. All rights reserved.

Exercise at anaerobic threshold intensity and insulin secretion by isolated pancreatic islets of rats

To evaluate the effect of acute exercise and exercise training at the anaerobic threshold (AT) intensity on aerobic conditioning and insulin secretion by pancreatic islets, adult male Wistar rats were submitted to the lactate minimum test (LMT) for AT determination. Half of the animals were submitted to swimming exercise training (trained), 1 h/day, 5 days/week during 8 weeks, with an overload equivalent to the AT. The other half was kept sedentary. At the end of the experimental period, the rats were submitted to an oral glucose tolerance test and to another LMT. Then, the animals were sacrificed at rest or immediately after 20 minutes of swimming exercise at the AT intensity for pancreatic islets isolation. At the end of the experiment mean workload (% bw) at AT was higher and blood lactate concentration (mmol/L) was lower in the trained than in the control group. Rats trained at the AT intensity showed no alteration in the areas under blood glucose and insulin during OGTT test. Islet insulin content of trained rats was higher than in the sedentary rats while islet glucose uptake did not differ among the groups. The static insulin secretion in response to the high glucose concentration (16.7 mM) of the sedentary group at rest was lower than the sedentary group submitted to the acute exercise and the inverse was observed in relation to the trained groups. physical training at the AT intensity improved the aerobic condition and altered insulin secretory pattern by pancreatic islets. © 2010 Landes Bioscience.

Determination of critical velocity and anaerobic capacity of running rats

The aim of this study was to validate a non-invasive protocol to determine aerobic and anaerobic capacity of treadmill running rats. Thirteen male Wistar rats (90 days old) were submitted to 4 exercise tests, consisting of running at 25, 30, 35 and 40 m min-1, continuously until exhaustion. For the critical velocity (CV) and anaerobic running capacity (ARC) estimations, the hyperbolic curve (velocity versus time to exhaustion (tlim)) was linearized to V= CV+ARC/tlim, where the CV and ARC were linear and slope coefficients, respectively. In order to verify if the CV was the maximal aerobic intensity, the rats were submitted to the maximal lactate steady state test (MLSS) composed of three 25-minute tests of continuous running trials at 15, 20 and 25 m min-1, with blood collection every 5 minutes. The CV was obtained at 22.8±0.7 m min-1 and the ARC, at 26.80±2.77 m. The MLSS was observed at 20m min-1, with blood lactate 3.84 ± 0.31 mmol L-1. There was a progressive increase in lactate concentration at 25 m min-1. The CV and MLSS were different, but presented a high and significant correlation (r=0.81). These results indicate that the non-invasive protocol can be used for physical evaluation of aerobic running rats, but the ARC should still be further investigated.

Endurance swimming periodized training in rats

The aim of this study was to develop an experimental protocol for endurance swimming periodization training in rats similar to high performance training in humans, and compare it to continuous training. Three groups of male Wistar rats (90 days old) were allocated to Sedentary Control (SC); Continuous Training (CT); and Periodized Experimental Training (PET) groups. PET and CT trained 5 days/week, over five weeks, CT: continuous training supporting a 5% body mass (bm) load for 40 min/day; PET: training subdivided into basic, specific, and taper periods, with overload changed daily (volume-intensity, continuous, and interval training). Total training overload was quantified (% bm X exercise time in training session) and equalized for the two trained groups. Glucose ([ 3H]2-deoxyglucose) uptake, incorporation to glycogen (synthesis), glucose oxidation (CO 2 production), and lactate production from [U- 14C]glucose by soleus muscle strips incubated in presence of insulin (100μU/mL) were evaluated 48h after the last training session. The load equivalent at 5.5mM blood lactate concentration ([La-5.5]) was determined in the incremental test. Lactate production was similar in all groups. PET presented higher glucose uptake (59%) than SC, and higher glycogen synthesis (51 and 22%) and glucose oxidation (147 and 178%) than SC and CT, respectively. CT presented higher glycogen synthesis rates (23%) than SC. Load [La-5.5] was similar between trained groups and higher than SC. PET presented higher values for glucose metabolism than CT and SC. These results open up new perspectives for studying training methods used in high performance sport through swimming exercise in rats.

Non-exhaustive test for aerobic capacity determination in running rats

A simple and applicable method for non-exhaustive aerobic evaluation in running rats is described. Wistar rats were submitted to running test at different velocities (10, 15, 20, 25 m/min) with 48 h recovery among them. At each velocity, the rats ran two bouts of 5 min with 2 min of rest between bouts. Blood samples were collected at the end of each bout for lactate determination. For each intensity, delta lactate was calculated and using deltas obtained by four tests, an individual linear interpolation was plotted. The y-intercept of linear interpolation was the null delta lactate equivalent to the critical velocity (CV). To verify the lactate stabilization at CV, the animals were submitted to 25 min of continuous exercise (15, 20, 25 m/min), with blood collection every 5 min. The estimated CV was 16.6±0.7 m/min, with significant linear regressions (R=0.90±0.03). The rats presented maximal lactate steady state (MLSS) at 3.9±0.4 mmol/L, at 20 m/min. The CV was less than MLSS but significantly correlated with this parameter (r=0.78). This non-exhaustive test seems to be valid for the aerobic evaluation of sedentary rats and this protocol underestimates the MLSS in 20%. This test seems to be the interesting method for the evaluation of rats submitted to acute exercise or physical training.

Effect of Cycling Exercise at Different Pedal Cadences on Subsequent Muscle Strength

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

How narrow is the spectrum of submaximal speeds in swimming?

The purpose of this study was to identify the boundary of submaximal speed zones (i.e., exercise intensity domains) between maximal aerobic speed (S-400) and lactate threshold (LT) in swimming. A 400-m all-out test, a 7 × 200 m incremental step test, and two to four 30-minute submaximal tests were performed by 12 male endurance swimmers (age = 24.5 ± 9.6 years; body mass = 71.3 ± 9.8 kg) to determine S-400, speed corresponding to LT, and maximal lactate steady state (MLSS). S-400 was 1.30 ± 0.09 m·s -1 (400 m-5:08 minutes:seconds). The speed at LT (1.08 ± 0.02 m·s-1; 83.1 ± 2.2 %S-400) was lower than the speed at MLSS (1.14 ± 0.02 m·s-1; 87.5 ± 1.9 %S-400). Maximal lactate steady state occurred at 26 ± 10% of the difference between the speed at LT and S-400. Mean blood lactate values at the speeds corresponding to LT and MLSS were 2.45 ± 1.13 mmol·L-1 and 4.30 ± 1.32 mmol·L-1, respectively. The present findings demonstrate that the range of intensity zones between LT and MLSS (i.e., heavy domain) and between MLSS and S-400 (i.e., severe domain) are very narrow in swimming with LT occurring at 83% S-400 in trained swimmers. Precision and sensitivity of the measurement of aerobic indexes (i.e., LT and MLSS) should be considered when conducting exercise training and testing in swimming. © 2013 National Strength and Conditioning Association.

Overall and differentiated session ratings of perceived exertion at different time points following a circuit weight training workout

Session ratings of perceived exertion (SRPE) have been considered to provide a quantitative evaluation of the entire exercise session in different types of resistance training. In this study we investigated the ability of SRPE to assess exercise strain in a circuit weight training (CWT) workout and the influence of time lag to report SRPE. Ten healthy male volunteers (22.3±2.8 years, 72.5±6.5kg, and 175±5cm) completed a CWT session involving three circuits of five multiple joint exercises with single sets of 20 repetitions at 30% one repetition maximum (1-RM). Heart rate [63.7-75.0% maximum heart rate (%HRmax)], blood lactate (5.6-7.6mM) as well as overall, chest, and active muscle RPE increased significantly (p<0.05) throughout the CWT, but no significant differences were found between ratings of perceived exertion (RPE) types. Overall, chest and active muscle SRPE were accessed 10 minutes, 20 minutes, and 30 minutes after the workout, with no significant main effects or SRPE type×time interaction being found (p>0.05). Finally, no significant differences (p>0.05) were observed between averaged SRPE and RPE responses (overall: 3.7±0.6 vs. 3.5±0.9; chest: 3.8±0.7 vs. 3.6±0.8; active muscle; 3.7±0.7 vs. 3.5±0.7). These results suggest SRPE, irrespective of the moment at which it is taken, to be a useful tool for assessing global exercise strain in a CWT workout, providing coaches, physicians, and exercisers a practical way for monitoring this type of resistance training. © 2013.

Características aeróbias e anaeróbias de mesatenistas brasileiros treinados

O objetivo deste estudo foi determinar, em mesatenistas bem treinados, as aptidões aeróbia e anaeróbia. Participaram do presente estudo oito mesatenistas brasileiros treinados do sexo masculino (18±2 anos). Os sujeitos foram submetidos a um teste incremental específico para determinação do consumo pico de oxigênio (VO2PICO), intensidade associada ao VO2PICO (iVO2PICO) e do ponto de compensação respiratório (PCR) e a dois testes de esforço repetitivo, sendo o teste de RAST e o índice anaeróbio alático (IAA), para determinação dos índices anaeróbios. O VO2PICO correspondeu a 50,5±4,4ml kg-1 min-1 , a iVO2PICO a 52,1±9,6 bolas min-1 e o PCR a 44,9±8,0 bolas min-1. No RAST, a potência pico (PP) e a potência média (PM) relativa corresponderam a 9,0±1,3W kg-1 e 7,0±0,9W kg-1, respectivamente, enquanto que o IAA foi 1,14±0,51 mM/m s-1 . Esses valores de VO2PICO e dos parâmetros anaeróbios quando comparados a valores de outros esportes com raquetes caracterizaram que mesatenistas brasileiros treinados apresentam potência aeróbia moderada e potência anaeróbia é baixa.

Efeitos de uma pré temporada em parâmetros anaeróbios e comparação de parâmetros aeróbios e anaeróbios de futebolistas de diferentes categorias

Pós-graduação em Fisioterapia - FCT

Coordenação da ação dos braços no nado crawl analisada em diferentes intensidades, nos exercícios contínuo e intermitente

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)