Comparação entre métodos invasivos e não invasivo de determinação da capacidade aeróbia em futebolistas profissionais

O Limiar Anaeróbio (Lan) pode ser determinado por protocolos que utilizam concentrações fixas de lactato sanguíneo como o OBLA (Onset of Blood Lactate Accumulation) e os que utilizam procedimentos mais individualizados, como o Lactato Mínimo (Lacmin). Independente do método, a mensuração da capacidade aeróbia através do Lan nesses casos exige a utilização de equipamentos sofisticados, além do elevado custo por atleta, o que torna sua aplicação limitada. Como alternativa, um dos testes não invasivos mais empregados no meio esportivo é o de 12 minutos proposto por Cooper. O objetivo principal do presente estudo foi comparar a intensidade de exercício obtida pelo teste de 12min com as intensidades correspondentes ao Lan obtido pelo protocolo adaptado ao de Tegtbur et al. (1993) (Lac minat) e pelo OBLA em futebolistas profissionais. Para tanto participaram 16 atletas pertencentes a uma equipe profissional filiada à série A3 do futebol paulista. Cada atleta foi avaliado nos três protocolos, com intervalo mínimo de 48 e máximo de 72 horas. Os resultados mostraram diferença (p < 0,05) entre as velocidades (km.h-1) obtidas pelo teste de Cooper (15,09 ± 0,94) e OBLA (14,28 ± 1,02); entretanto, esses testes apresentaram correlação significativa. Cooper e OBLA não apresentaram correlação com o Lac minat, mas as velocidades foram similares com esse protocolo. Dessa maneira, a partir da análise de regressão entre os valores de Cooper e OBLA foi possível determinar uma equação de correção que permita, através do teste de Cooper, a obtenção da intensidade correspondente ao Lan determinado pelo OBLA em futebolistas profissionais.

Capacidade aeróbia de ratos alimentados com dieta rica em frutose

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

Capacidade funcional, desempenho e solicitação metabólica em futebolistas profissionais durante situação real de jogo monitorados por análise cinematográfica

Foi objetivo deste estudo caracterizar a relação entre o nível de aptidão física, desempenho e solicitação metabólica em futebolistas durante situação real de jogo. Seis jogadores de futebol profissional com média de idade de 20,8 ± 2,6 anos (17-25), peso 70,4 ± 7,5kg (63-81,3) e altura 173,3 ± 9,7cm (166-188), foram submetidos a testes de aptidão física em campo e análise cinematográfica durante a partida. Os testes de aptidão física foram realizados em campo, com medições de lactato sanguíneo. A via metabólica alática foi avaliada por meio de cinco corridas na distância de 30m, em velocidade máxima, com pausa passiva de um minuto entre cada corrida. As concentrações de lactato foram medidas no 1º, 3º e 5º minuto após o término das cinco corridas. Para detecção do limiar anaeróbio foram realizadas 3 corridas de 1.200m nas intensidades de 80, 85 e 90% da velocidade máxima para essa distância, com intervalo passivo de 15 minutos entre cada corrida. As dosagens de lactato sanguíneo foram feitas no 1º, 3º e 5º minuto de repouso passivo após cada corrida. Os futebolistas foram submetidos à filmagem individual durante o transcorrer do jogo e as concentrações de lactato foram medidas antes, no intervalo e no final da partida para análise da solicitação energética e metabólica, respectivamente. Os seguintes resultados foram verificados: 1) o limiar anaeróbio em velocidade de corrida, correspondente à concentração de lactato sanguíneo de 4mmol.L_1 foi encontrado aos 268 ± 28m.min_1 ou 16,1 ± 1,6km.h_1; 2) a velocidade média e a concentração de lactato máximo nas corridas de 30m foram de 6,9 ± 0,2m.s_1 e 4,5 ± 1,0mmol.L_1, respectivamente; 3) a distância total percorrida foi de 10.392 ± 849m, sendo 5.446 ± 550m para o primeiro e 4.945 ± 366m para o segundo tempo, respectivamente; 4) os valores médios encontrados nas concentrações de lactato sanguíneo foram de 1,58 ± 0,37; 4,5 ± 0,42 e 3,46 ± 1,54mmol.L_1 antes, no intervalo do primeiro para o segundo tempo e ao final da a,respectivamente; e 5) a distância média total atingida ao final das partidas pelos jogadores de meio-campo (10.910 ± 121m) foi ligeiramente maior que a percorrida pelos atacantes (10.377 ± 224m) e defensores (9.889 ± 102m), mas não significativa. Houve correlação negativa (r =- 0,84; p < 0,05) entre o limiar anaeróbio (268 ± 28m.min_1 ou 16,1 ± 1,6km.h_1) e a concentração de lactato sanguíneo (4,5 ± 0,4 mmol.L_1) no primeiro tempo do jogo. Portanto, os resultados sugerem que a capacidade aeróbia é um determinante importante para suportar a longa duração da partida e recuperar mais rapidamente os futebolistas dos esforços realizados em alta intensidade, com o desenvolvimento de concentrações de lactato sanguíneo menores ao final do primeiro e segundo tempo das partidas.

Anaerobic capacity may not be determined by critical power model in elite table tennis players

The aim of the present study was to verify the applicability of anaerobic work capacity (AWC) determined from the critical power model in elite table tennis players. Eight male international level table tennis players participated in the study. The tests undertaken were: 1) A critical frequency test used to determinate the anaerobic work capacity; 2) Wingate tests were performed using leg and arm ergometers. AWC corresponded to 99.5 +/- 29.1 table tennis balls. AWC was not related to peak (r = -0.25), mean (r = -0.02), relative peak (r = -0.49) or relative mean power (r = 0.01), nor fatigue index (r = -0.52) (Wingate leg ergometer). Similar correlations for peak (r = -0.34), mean (r = -0.04), relative peak (r = -0.49), relative mean power (r = -0.14) and peak blood lactate concentration (r = -0.08) were determined in the Wingate arm ergometer test. Based on these results the AWC determined by a modified critical power test was not a good index for measurement of anaerobic capacity in table tennis players.

PHYSIOLOGICAL and PERCEIVED EXERTION RESPONSES AT INTERMITTENT CRITICAL POWER and INTERMITTENT MAXIMAL LACTATE STEADY STATE

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

THE INFLUENCE of RESTING PERIOD LENGTH on JUMPING PERFORMANCE

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

The rating of perceived exertion predicts intermittent vertical jump demand and performance

The aims of this study were (a) to assess the ability of the rating of perceived exertion (RPE) to predict performance (i.e. number of vertical jumps performed to a fixed jump height) of an intermittent vertical jump exercise, and (b) to determine the ability of RPE to describe the physiological demand of such exercise. Eight healthy men performed intermittent vertical jumps with rest periods of 4, 5, and 6s until fatigue. Heart rate and RPE were recorded every five jumps throughout the sessions. The number of vertical jumps performed was also recorded. Random coefficient growth curve analysis identified relationships between the number of vertical jumps and both RPE and heart rate for which there were similar slopes. In addition, there were no differences between individual slopes and the mean slope for either RPE or heart rate. Moreover, RPE and number of jumps were highly correlated throughout all sessions (r=0.97-0.99; P0.001), as were RPE and heart rate (r=0.93-0.97; P0.001). The findings suggest that RPE can both predict the performance of intermittent vertical jump exercise and describe the physiological demands of such exercise.

L-carnitine as an ergogenic aid for patients with chronic obstructive pulmonary disease submitted to whole-body and respiratory muscle training programs

The effects of adding L-carnitine to a whole-body and respiratory training program were determined in moderate-to-severe chronic obstructive pulmonary disease (COPD) patients. Sixteen COPD patients (66 ± 7 years) were randomly assigned to L-carnitine (CG) or placebo group (PG) that received either L-carnitine or saline solution (2 g/day, orally) for 6 weeks (forced expiratory volume on first second was 38 ± 16 and 36 ± 12%, respectively). Both groups participated in three weekly 30-min treadmill and threshold inspiratory muscle training sessions, with 3 sets of 10 loaded inspirations (40%) at maximal inspiratory pressure. Nutritional status, exercise tolerance on a treadmill and six-minute walking test, blood lactate, heart rate, blood pressure, and respiratory muscle strength were determined as baseline and on day 42. Maximal capacity in the incremental exercise test was significantly improved in both groups (P < 0.05). Blood lactate, blood pressure, oxygen saturation, and heart rate at identical exercise levels were lower in CG after training (P < 0.05). Inspiratory muscle strength and walking test tolerance were significantly improved in both groups, but the gains of CG were significantly higher than those of PG (40 ± 14 vs 14 ± 5 cmH2O, and 87 ± 30 vs 34 ± 29 m, respectively; P < 0.05). Blood lactate concentration was significantly lower in CG than in PG (1.6 ± 0.7 vs 2.3 ± 0.7 mM, P < 0.05). The present data suggest that carnitine can improve exercise tolerance and inspiratory muscle strength in COPD patients, as well as reduce lactate production.

Valores sangüíneos de chumbo em bovinos nelore suplementados com sal mineral naturalmente contaminado por chumbo

A pesquisa foi realizada em 8 propriedades rurais com regime de criação extensiva, situadas às margens da represa de Barra Bonita, no município de Anhembi, estado de São Paulo. Amostras de sal mineral, capim e sangue animal foram colhidas para análise laboratorial, para se investigar a presença de chumbo. Foram utilizados 160 bovinos, machos e fêmeas, da raça Nelore, divididos em dois grupos de 80 animais. A finalidade precípua foi realizar um estudo comparativo entre os dois grupos, sendo que no primeiro os animais recebiam sal mineral sabidamente contaminado com chumbo. O segundo grupo serviu como lote para efeito comparativo. O critério de comparação foi a análise sangüínea que revelou valores aquém do limite de tolerância biológico atribuído à espécie bovina, em ambos os grupos. Os resultados permitem a conclusão de que, aos níveis de chumbo detectados nas amostras mineralizadas, ainda não há risco de efeito cumulativo e tóxico para os bovinos avaliados.

Effect of the passive recovery period on the lactate minimum speed in sprinters and endurance runners

The objective of this study was to verify the effect of the passive recovery time following a supramaximal sprint exercise and the incremental exercise test on the lactate minimum speed (LMS). Thirteen sprinters and 12 endurance runners performed the following tests: 1) a maximal 500 m sprint followed by a passive recovery to determine the time to reach the peak blood lactate concentration; 2) after the maximal 500 m sprint, the athletes rested eight mins, and then performed 6 x 800 m incremental test, in order to determine the speed corresponding to the lower blood lactate concentration (LMS1) and; 3) identical procedures of the LMS1, differing only in the passive rest time, that was performed in accordance with the time to peak lactate (LMS2). The time (min) to reach the peak blood lactate concentration was significantly higher in the sprinters (12.76+/-2.83) than in the endurance runners (10.25+/-3.01). There was no significant difference between LMS1 and LMS2, for both endurance (285.7+/-19.9; 283.9+/-17.8 m/min; r= 0.96) and sprint runners (238.0+/-14.1; 239.4+/-13.9 m/min; r= 0.93), respectively. We can conclude that the LMS is not influenced by a passive recovery period longer than eight mins (adjusted according with the time to peak blood lactate), although blood lactate concentration may differ at this speed. The predominant type of training (aerobic or anaerobic) of the athletes does not seem to influence the phenomenon previously described.

Maximal lactate steady state in running mice: Effect of exercise training

1. Maximal lactate steady state (MLSS) corresponds to the highest blood lactate concentration (MLSSc) and workload (MLSSw) that can be maintained over time without continual blood lactate accumulation and is considered an important marker of endurance exercise capacity. The present study was undertaken to determine MLSSw and MLSSc in running mice. In addition, we provide an exercise training protocol for mice based on MLSSw.2. Maximal lactate steady state was determined by blood sampling during multiple sessions of constant-load exercise varying from 9 to 21 m/min in adult male C57BL/6J mice. The constant-load test lasted at least 21 min. The blood lactate concentration was analysed at rest and then at 7 min intervals during exercise.3. The MLSSw was found to be 15.1 +/- 0.7 m/min and corresponded to 60 +/- 2% of maximal speed achieved during the incremental exercise testing. Intra- and interobserver variability of MLSSc showed reproducible findings. Exercise training was performed at MLSSw over a period of 8 weeks for 1 h/day and 5 days/week. Exercise training led to resting bradycardia (21%) and increased running performance (28%). of interest, the MLSSw of trained mice was significantly higher than that in sedentary littermates (19.0 +/- 0.5 vs 14.2 +/- 0.5 m/min; P = 0.05), whereas MLSSc remained unchanged (3.0 mmol/L).4. Altogether, we provide a valid and reliable protocol to improve endurance exercise capacity in mice performed at highest workload with predominant aerobic metabolism based on MLSS assessment.

Protein malnutrition does not impair glucose metabolism adaptations to exercise-training

Malnutrition is a common health problem in developing countries and is associated with alterations in glucose metabolism. In the present study we examine the effects of chronic aerobic exercise on some aspects of glucose metabolism in protein-deficient rats. Two groups of adult rats (90 days old) were used: Normal protein group (17%P)- kept on a normal protein diet during intra-uterine and postnatal life and Low protein group (6%P)- kept on a low protein diet during intrauterine and post natal life. After weaning (21 days old), half of the 17%P and 6%P rats were assigned to a Sedentary (Sed) or an Exercise-trained (Exerc = swimming, 1 hr/day, 5 days/week, supporting an overload of 5% of body weight) subgroup. The area under blood glucose concentration curve (Delta G) after an oral glucose load was higher in 17%P Sed rats (20%) than in other rats and lower in 6%P Exerc (11%) in relation to 6% Sed rats. The post-glucose increase in blood insulin (Delta I) was also higher in 17%P Sed (9%) than in other rats. on the other hand, the glucose disappearance rate after exogenous subcutaneous insulin administration (Kitt) was lower in 17%P Sed rats (66%) than in other rats. Glucose uptake by soleus muscle was higher in Exerc rats (30%) than in Sed rats. Soleus muscle glycogen synthesis was reduced in 6%P Sed rats (41%) compared to 17%P Sed rats but was restored in 6%P Exerc rats. Glycogen concentration was elevated in Exerc (32%) rats in comparison to Sed rats. The present results indicate that glucose-induced insulin release is reduced in rats fed low protein diet. This defect is counteracted by an increase in the sensitivity of the target tissues to insulin and glucose homeostasis is maintained. This adaptation allows protein deficient rats to preserve the ability to appropriately adapt to aerobic physical exercise training. (C) 2000 Elsevier B.V.

Interval training at 95% and 100% of the velocity at VO2 max: effects on aerobic physiological indexes and running performance

The objective of this study was to analyze the effect of two different high-intensity interval training (HIT) programs on selected aerobic physiological indices and 1500 and 5000 m running performance in well-trained runners. The following tests were completed (n = 17): (i) incremental treadmill test to determine maximal oxygen uptake (VO2max), running velocity associated with VO2 max (VVO2max), and the velocity corresponding to 3.5 mmol/L of blood lactate concentration (vOBLA); (ii) submaximal constant-intensity test to determine running economy (RE); and (iii) 1500 and 5000 m time trials on a 400 m track. Runners were then randomized into 95% vVO(2max) or 100% vVO(2max) groups, and undertook a 4 week training program consisting of 2 HIT sessions (performed at 95% or 100% vVO(2max), respectively) and 4 submaximal run sessions per week. Runners were retested on all parameters at the completion of the training program. The VO2 max values were not different after training for both groups. There was a significant increase in post-training vVO(2 max), RE, and 1500 in running performance in the 100% vVO(2 max) group. The vOBLA and 5000 m running performance were significantly higher after the training period for both groups. We conclude that vOBLA and 5000 m running performance can be significantly improved in well-trained runners using a 4 week training program consisting of 2 HIT sessions (performed at 95% or 100% vVO(2max)) and 4 submaximal run sessions per week. However, the improvement in vVO(2 max), RE, and 1500 in running performance seems to be dependent on the HIT program at 100% vVO(2 max).

Protein deficiency during pregnancy and lactation impairs glucose-induced insulin secretion but increases the sensitivity to insulin in weaned rats

We studied glucose homeostasis in rat pups from darns fed on a normal-protein (170 g/kg) (NP) diet or a diet containing 60 g protein/kg (LP) during fetal life and the suckling period. At birth, total serum protein, serum albumin and serum insulin levels were similar in both groups. However, body weight and serum glucose levels in LP rats were lower than those in NP rats. At the end of the suckling period (28 d of age), total serum protein, serum albumin and serum insulin were significantly lower and the liver glycogen and serum free fatty acid levels were significantly higher in LP rats compared with NP rats. Although the fasting serum glucose level was similar in both groups, the area under the blood glucose concentration curve after a glucose load was higher for NP rats (859 (SEM 58) mmol/l per 120 min for NP rats v. 607 (SEM 52) mmol/l per 120 min for LP rats; P < 0.005). The mean post-glucose increase in insulin was higher for NP rats (30 (SEM 4.7) nmol/l per 120 min for NP rats v. 17 (SEM 3.9) nnol/l per 120 min for LP rats; P < 0.05). The glucose disappearance rate for NP rats(0.7 (SEM 0.1) %/min) was lower than that for LP rats (1.6 (SEM 0.2) %/min; P < 0.001). Insulin secretion from isolated islets (1 h incubation) in response to 16.7 mmol glucose/l was augmented 14-fold in NP rats but only 2.6-fold in LP rats compared with the respective basal secretion (2.8 mmol/l; P <0.001). These results indicate that in vivo as well as in vitro insulin secretion in pups from dams maintained on a LP diet is reduced. This defect may be counteracted by an increase in the sensitivity of target tissues to insulin.

Effects of Strength Training on Running Economy

The objective of this study was to compare the effect of different strength training protocols added to endurance training on running economy (RE). Sixteen well-trained runners (27.4 +/- 4.4 years; 62.7 +/- 4.3 kg; 166.1 +/- 5.0 cm), were randomized into two groups: explosive strength training (EST) (n = 9) and heavy weight strength training (HWT) (n = 7) group. They performed the following tests before and after 4 weeks of training: 1) incremental treadmill test to exhaustion to determine of peak oxygen uptake and the velocity corresponding to 3.5 mM of blood lactate concentration; 2) submaximal constant-intensity test to determine RE; 3) maximal countermovernent jump test and; 4) one repetition maximal strength test in leg press. After the training period, there was an improvement in RE only in the HWT group (HWT = 47.3 +/- 6.8 vs. 44.3 +/- 4.9 ml.kg(-1) -min(-1); EST = 46.4 +/- 4.1 vs. 45.5 +/- 4.1 ml.kg(-1) .min(-1)). In conclusion, a short period of traditional strength training can improve RE in well-trained runners, but this improvement can be dependent on the strength training characteristics. When comparing to explosive training performed in the same equipment, heavy weight training seems to be more efficient for the improvement of RE.