The objective of this study was to assess cardiovascular, respiratory, and metabolic responses during a commonly used dynamic leg press resistance exercise until exhaustion (TEx) at different intensities and compare with critical load (CL). This was a prospective, cross-sectional, controlled, and crossover study. Twelve healthy young men (23±2.5 years old) participated. The subjects carried out three bouts of resistance exercise in different percentages of 1 repetition maximum (60, 75, and 90% 1RM) until TEx. CL was obtained by means of hyperbolic model and linearization of the load-duration function. During all bout intensities, oxygen uptake (VO2), carbon dioxide production (VCO2), ventilation (VE), and respiratory exchange ratio (RER) were obtained. Variations (peak-rest=Δ) were corrected by TEx. In addition, systolic and diastolic blood pressure (SBP and DBP), blood lactate concentration [La-] and Borg scores were obtained at the peak and corrected to TEx. CL induced greater TEx as well as number of repetitions when compared to all intensities (P<0.001). During CL, Borg/TEx, ΔSBP/TEx, ΔDBP/TEx, and [La-] were significantly lower compared with 90% load (P<0.0001). In addition, VO2, VCO2, VE, and RER were higher during CL when compared to 90 or 75%. TEx was significantly correlated with VO2 on CL (r=0.73, P<0.05). These findings support the theory that CL constitutes the intensity that can be maintained for a very long time, provoking greater metabolic and ventilatory demand and lower cardiovascular and fatigue symptoms during resistance exercise.

O objetivo do presente estudo foi analisar as mudanças no limiar de lactato (LL) em ratos submetidos a um programa de treinamento aeróbio em esteira. Vinte e cinco ratos Wistar foram divididos em dois grupos: um grupo controle sedentário (CG), e um grupo treinado (GT) submetido a um treinamento aeróbio durante 5 semanas. Todos os animais foram submetidos a um teste de exercício incremental em esteira, a fim de determinar o LL. Houve um aumento na velocidade máxima de corrida no GT (de 32,25 ± 1,27 para 47,75 ± 3,13 m.min–1 - p = 0,001), e velocidade de corrida no LL (de 26,21 ± 1,15 para 35,30 ± 2,24 m.min–1 - p = 0,004), além da redução na concentração de lactato no LL. O LL pode ser determinado em ratos e o treinamento aeróbio induziu a adaptações fisiológicas oxidativas positivas nos animais.

The aim of the present study was to analyse the lactate threshold (LT) changes in rats submitted to an aerobic treadmill-training programme. Twenty-five Wistar rats were divided into two groups: a sedentary control group (CG), and a trained group (TG) submitted to an aerobic training during 5 weeks. All the animals were submitted to an incremental treadmill exercise test in order to determine LT. There was an increase in the maximum running speed in the TG (from 32.25 ± 1.27 to 47.75 ± 3.13 m.min–1 – p = 0.001), and running speed at LT (from 26.21 ± 1.15 to 35.30 ± 2.24 m.min–1 – p = 0.004), a part from the reduction in blood lactate at LT. LT can be determined in rats, and aerobic training induced positive oxidative physiological adaptations in the animals.

A presença do limiar anaeróbio (LAn) em exercício resistido tem sido objeto de estudo nos últimos anos. O objetivo do estudo foi identificar e comparar o LAn em uma população idosa no leg press (LP) e supino reto (SR). Catorze homens idosos (68.9 ± 4.0 anos, 170.5 ± 0.05 cm e 76.1 ± 7.8 kg) realizaram dois testes incrementais máximos baseados em porcentagens de uma repetição máxima (1RM) para a determinação do LAn no LP e SR. As variáveis lactacidemia, frequência cardíaca (FC) e percepção subjetiva de esforço (PSE) foram coletadas ao final de cada estágio e comparadas entre os exercícios na intensidade referente ao LAn. O nível de significância adotado foi p = .05. O LAn no LP ocorreu em 27.9 ± 5.0% de 1RM, estatisticamente superior ao SR, que foi identificado em 21.5 ± 3.1% de 1RM. No entanto, a lactacidemia foi estatisticamente inferior no LP (1.36 ± 0.40 mmol.L-1) em relação ao SR (1.92 ± 0.38 mmol.L-1). Apesar de intensidades diferentes do LAn entre os exercícios, as variáveis FC e PSE não apresentaram diferenças significativas. Foi possível identificar o LAn em idosos nos aparelhos LP e SR, ocorrendo em intensidades inferiores no SR.

The presence of anaerobic threshold (AT) in resistance exercise has been studied in recent years. The aim of this study was to identify and to compare the AT in elderly population during leg press (LP) and bench press (BP). Fourteen elderly men (68.9 ± 4.0 years, 170.5 ± 0.05 cm e 76.1 ± 7.8 kg) performed two maximal incremental tests based on percentages of one repetition maximum (1RM) for the determination of AT during LP and BP. Blood lactate, heart rate (HR) and rating of perceived exertion (RPE) were measured at the final of each stage and it were compared between the exercises at the intensity of the AT. The level of significance was p = .05. The AT in the LP was 27.9 ± 5.0% of 1RM and in the BP was 21.5 ± 3.1% of 1RM, with statistical differences between the exercises. However, blood lactate was significantly lower on LP (1.36 ± 0.40 mmol.L-1) when compared with BP (1.92 ± 0.38 mmol.L-1). Although the intensity of AT has been different between the exercises, HR and RPE did not presented statistical significant differences. It was possible to identify the AT on elderly population during LP and BP exercises and it occurred in lower intensities for BP.

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.

OBJETIVO: Verificar a atividade e padrão eletroforético da LDH em resposta ao exercício em esteira em ratos submetidos à fotoestimulação por laser de baixa intensidade (780 etam). MÉTODO: Foram utilizados nesse estudo 54 ratos machos jovens (30dias), Winstar, com peso inicial médio de 112 ± 4,7g, os quais foram divididos em quatro grupos: dois permaneceram em repouso, GRC (grupo repouso controle, n= 9) e GRL (grupo repouso laser, n= 10), sendo o segundo irradiado por laser, e outros dois foram submetidos ao treinamento aeróbio e testes de esforço crescente em esteira (em degraus descontínuos) visando à determinação do limiar de anaerobiose (LA) durante 5 semanas, GEC (grupo exercício controle, n= 16) e GEL (grupo exercício laser, n= 19), sendo o último também irradiado por laser. O laser foi aplicado no quadríceps, glúteo máximo, sóleo e tibial anterior (TA), bilateralmente, imediatamente após cada sessão de treinamento, usando: 3,8J/cm², 15mW, 10s, modo contínuo, durante 5 semanas. Amostras de sóleo, TA e coração foram removidas 48 horas após a última sessão de exercício para análise eletroforética e espectrofotométrica. A estatística foi realizada através do teste ANOVA e post-hoc de TUKEY. O nível de significância foi considerado (p< 0,05). RESULTADOS: Foram observadas reduções na atividade da LDH causadas pelo laser (de 19% a 30%), exercício (de 41% a 66%) e as ações combinadas (de 47% a 66%) (p< 0,01). A eletroforese mostrou uma predominância da subunidade B para o sóleo e coração, e uma predominância da subunidade A no TA. CONCLUSÕES: Estes dados sugerem uma melhor resposta adaptativa dos animais ao treinamento aeróbio associado à terapia laser, no que se refere à otimização da via oxidativa.

OBJECTIVE: To analyze the activity and electrophoretic pattern of the enzyme LDH in response to treadmill training, in rats undergoing photostimulation using low-level laser therapy (LLLT) (780 etam). METHOD: Fifty-four 30-day-old male Winstar rats initially weighing 112 ± 4.7g were divided into four groups. Two groups remained at rest: resting control group (RCG, n= 9) and resting LLLT group (RLG, n= 10). The other two groups underwent a five-week treadmill program of aerobic training and non-continuous incremental effort tests, with the aim of determining the anaerobic limit. One of the latter was an exercise control group (ECG, n= 16) and the other was an exercise LLLT group (ELG, n= 19). LLLT was applied to the quadriceps, gluteus maximus, soleus and tibialis anterior, bilaterally, immediately after each training session, using the following: 3.8 J/cm²; 15 mW; time 10 s; continuous mode. Samples of the soleus, tibialis anterior and heart were removed 48 hours after the last exercise session for electrophoretic and spectrophotometric analysis. The statistical analyses used were the ANOVA and post-hoc Tukey tests. The level of statistical significance was set at p< 0.05. RESULTS: Reductions in LDH activity caused by laser (from 19% to 30%), exercise (from 41% to 66%) and combined action (from 47% to 66%) were observed (p< 0.01). Electrophoresis showed predominance of subunit B in the soleus and heart, and predominance of subunit A in the tibialis anterior. CONCLUSION: The data suggest that the animals have an adaptive response to aerobic training with LLLT, towards optimizing the oxidative pathway.