Physiological responses in different intensities of resistance exercise - Critical load and the effects of aging process.

Aim was to identify critical load (CL) in young and elderly apparently healthy male cohorts. To contrast the metabolic, cardiovascular and perceptual responses on CL according to age. We evaluated 12 young (23 ± 3 years) and 10 elderly (70 ± 2 years) apparently healthy active males, who underwent: (1) 1 repetition maximum (1RM) test on a 45° Leg Press; (2) on different days, three high-intensity resistance exercise constant load tests (60%, 75% and 90% 1RM) until fatigue (Tlim). Absolute values of both the CL asymptote and curvature constant (kg) were significantly lower in elderly subjects (P < 0.05). In contrast, elderly subjects demonstrated a significantly higher number of repetitions at CL when compared with young subjects (P < 0.05). As expected, oxygen uptake (VO2) and heart rate (HR) during maximal aerobic exercise testing were significantly reduced in older subjects. However, percent-predicted aerobic capacity were higher in older subjects (P < 0.05). In addition, blood lactate ([La-]) corrected to Tlim and rating of perceived exertion values were greater in younger subjects at all intensities (P < 0.05). These findings, despite reduced force production in older subjects, endurance-related parameters are well preserved according to age-adjusted percent-predicted values in apparently healthy males.

Cardiopulmonary exercise test in type 2 diabetes mellitus in absence of chronic heart failure: reduced lung and heart function / Avaliação cardiopulmonar em portadores de diabetes melitus tipo 2 sem doença cardíaca: redução da função caridorespiratória

Was compared exercise tolerance, respiratory and cardiovascular functions between non--diabetics and type 2 diabetics individuals (T2DM) without chronic heart failure. Thirteen normaglycemic men (non-diabetic group ­ NDG) and eight T2DM (diabetic group ­ DG) performed a cardiopulmonary exercise test (CPX) on motor treadmill (test initiated at 3 km.h-1 with an increment of 1 km.h-1 every two minutes) to evaluate respiratory function, cardiovascular parameters and exercise tolerance. Workload and oxygen uptake ( O2) values at ventilatory threshold were signifi cantly lower for DG (DG: 5.6 ± 0.5 km/h and 13.1 ± 3.8 mL.(kg.min)-1; NDG: 6.5 ± 0.5 km/h and 16.4 ± 2.8 mL.(kg.min)-1; p < 0.05). Peak O2 and workload were signifi cantly lower for DG (22.7 ± 5.7 mL.(kg.min)-1;8.2 ± 0.7 km/h) when compared with NDG (30.8 ± 5.4 mL.(kg.min)-1; 11.6 ± 1.5 km/h). Oxygen uptake effi ciency slope (OUES) and circulatory power were signifi cantly lower (p < 0.05) in DG, although no signifi cant alterations were found in functional capacity and ventilatory effi ciency. T2DM in absence of chronic heart failure presented exercise intolerance and lower cardiorespiratory fi tness. Peak circulatory power and OUES were also reduced in these individuals....(AU)

Foi comparar a tolerância ao exercício, funções respiratória e cardiovascular entre indivíduos não diabéticos e diabéticos tipo 2 sem doenças crônicas cardíacas. Treze homens normoglicêmicos (NDG) e oito homens diabéticos tipo 2 (DG) que realizaram um teste cardiopulmonar de esforço (TCPE) em uma esteira motorizada (o teste iniciou-se em 3km.h-1 com incremento de 1km.h-1 a cada dois minutos) que avaliou a função respiratória, parâmetros cardiovasculares e tolerância ao exercício. Valores de consumo de oxigênio e intensidades na intensidade do limiar ventilatório foram signifi cativamente menores para o DG (DG: 5,6 ± 0,5 km/h-1 e 13,1 ± 3,8 ml.(kg.min)-1; NDG: 6,5 ± 0,5 km/h-1 e 16,4 ± 2,8 ml.(kg.min)-1; p < 0,05). Consumo de oxigênio pico e intensidade associada foram signifi cativamente menores para o DG (DG: 22,7 ± 5,7 ml.(kg.min)-1; 8,2 km/h-1 ± 0,7 km/h-1) quando comparado com o NDG (30,8 ± 5,4 ml.(kg.min)-1; 11,6 ± 1,5 km/h). Oxygen uptake effi ciency slope (OUES) e circulatory power foram signifi cativamente menores para o DG (p < 0,05) embora não foram encontradas diferenças signifi cativas na efi ciência ventilatória. Em indivíduos portadores de diabetes tipo 2, mesmo sem a presença conhecida de doenças cardiovasculares, apresentaram menores níveis de condicionamento cardiorrespiratório e tolerância ao exercício. Circulatory power pico e OUES também foram reduzidos nesses indivíduos....(AU)

Photobiomodulation increases mitochondrial citrate synthase activity in rats submitted to aerobic training.

This study investigated the effects of photobiomodulation by low-laser laser therapy (LLLT) on the activities of citrate synthase (CS) and lactate dehydrogenase (LDH) and the anaerobic threshold (AT) in rats submitted to treadmill exercise. Fifty-four rats were allocated into four groups: rest control (RCG), rest laser (RLG), exercise control (ECG), and exercise laser (ELG). The infrared LLLT was applied daily on the quadriceps, gluteus maximum, soleus, and tibialis anterior muscles. Muscle samples (soleus, tibialis anterior, and cardiac muscles) were removed 48 h after the last exercise session for spectrophotometric analysis of the CS and LDH. The CS activity (µmol/protein) in ELG (16.02 and 0.49) was significantly greater (P < 0.05) than RCG (2.34 and 0.24), RLG (6.25 and 0.17), and ECG (6.76 and 0.26) in the cardiac and soleus muscles, respectively. The LDH activity (in 1 Mm/protein) in soleus muscle was smaller (P < 0.05) for ELG (0.33) compared to ECG (0.97), RLG (0.79), and RCG (1.07). For cardiac muscle, the LDH activity was smaller (P < 0.05) in ELG (1.38) compared to ECG (1.91) and RCG (2.55). The ECG and ELG showed increases in the maximum speed and a shift of the AT to higher effort levels after the training period, but no differences occurred between the exercised groups. In conclusion, the aerobic treadmill training combined with LLLT promotes an increase of oxidative capacity in this rat model, mainly in muscles with greater aerobic capacity.

Critical load: a novel approach to determining a sustainable intensity during resistance exercise.

BACKGROUND: A hyperbolic function as well as a linear relationship between power output and time to exhaustion (Tlim) has been consistently observed during dynamic non-resistive exercises. However, little is known about its concept to resistance exercises (RE), which could be defined as critical load (CL). This study aimed to verify the existence of CL during dynamic RE and to verify the number of workbouts necessary to determine the optimal modeling to achieve it. METHODS: Fifteen healthy men (23±2.5 yrs) completed 1 repetition maximum test (1RM) on a leg press and 3 (60%, 75% and 90% of 1RM) or 4 (+ 30% of 1RM) workbouts protocols to obtain the CL by hyperbolic and linear regression models between Tlim and load performed. Blood lactate and leg fatigue were also measured. RESULTS: CL was obtained during RE and 3 workbouts protocol estimate it at 53% while 4 tests at 38% of 1 RM. However, based on coefficients of determination, 3 protocols provided a better fit than the 4-parameter model, respectively (R2>0.95 vs. >0.77). Moreover, all intensities increased blood lactate and leg fatigue, however, when corrected by Tlim, were significantly lower at CL. CONCLUSIONS: It was possible to determinate CL during dynamic lower limbs RE and that 3 exhaustive workbouts can be used to better estimate the CL, constituting a new concept of determining this threshold during dynamic RE and reducing the physically demanding nature of the protocol. These findings may have important applications for functional performance evaluation and prescription of RE programs.

Circuit resistance training in women with normal weight obesity syndrome: body composition, cardiometabolic and echocardiographic parameters, and cardiovascular and skeletal muscle fitness.

BACKGROUND: Normal weight obesity (NWO) syndrome has been characterized in subjects with normal Body Mass Index (BMI) and high body fat mass percentage (BF%>30 for women) being a risk factor for cardiometabolic dysregulation and cardiovascular mortality. This study evaluated whether circuit resistance training (CRT) improves body composition, heart size and function, cardiometabolic parameters, and cardiorespiratory, cardiovascular and skeletal muscle fitness in women with NWO. METHODS: Data are means (95% Confidence Interval). Twenty-three women participated: 10 NWO-CRT (baseline: BMI=22.4 [21.4-23.3] kg/m2; BF%=44.5 [41.0-48.0]%) performed CRT; and 13 untrained NWO-control (baseline: BMI=21.7 [20.8-22.7] kg/m2; BF%=37.8 [34.6-41.1]%). At baseline and after 10 weeks were performed/measured dual-energy X-ray absorptiometry, echocardiography, blood tests, arterial pressure, exercise testing, and total-overload-by-training-session (TOL). RESULTS: At baseline, the NWO-CRT exhibited larger BF (27.28 [23.9-30.6] kg) than NWO-control (22.41 [19.5-25.3] kg) (P=0.0227). After training, NWO-CRT: reduced 8 kg of BF (P=0.000002); became BF% lower than NWO-control (33.1 [30.1-36.0] <37.0 [34.3-39.6]%, P=0.0423), with 30% of NWO-CRT subjects becoming without-obesity; reduced 3 kg in trunk fat mass (P=0.000005); showed fasting glucose (72.8 [69.4-76.2] mg/dL) smaller than NWO-control (81.7 [78.6-84.8] mg/dL) (P=0.004); increased TOL (5087.5 [4142.5-6032.5] to 6963.3 [6226.4-7700.2] rep.kg, P=0.0004); increased load at VO2peak (122.5 [106.8-138.2] to 137.5 [118.18-156.82] W, P=0.0051); reduced double product/load at VO2peak ratio (277.4 [222.1-332.8] to 237.7 [194.2-281.2] mmHg.bpm/W, P=0.0015); and increased left ventricular mass/body surface area ratio (84.29 [78.98-89.6] to 90.29 [81.45-99.12] g/m2, P=0.0215). CONCLUSIONS: CRT reduced BF% and generated cardiometabolic, cardiac, skeletal muscle and cardiovascular benefits, being a useful strategy to combat the normal weight obesity syndrome in women.

Double product break point estimates ventilatory threshold in individuals with type 2 diabetes.

[Purpose] To verify the identification of the anaerobic threshold through the double product breakpoint (DPBP) method for individuals with type 2 diabetes. [Subjects and Methods] Nine individuals with T2D (7 females; age=63.2 ± 8.9 y) and 10 non-diabetic (ND) (7 females; age=58.3 ± 7.8 y) performed an incremental exercise test on a cycle ergometer. Heart rate (HR), blood pressure (BP) and expired gas were measured at the end of each stage. The ventilatory threshold (VT) and DPBP were considered as the exercise intensities above which an over proportional increases in VE and DP were observed in relation to increasing workload. [Results] No differences were observed between the workloads, HR and VO2 corresponding to the AT identified respectively by VT and DPBP. For the T2D, strong correlations between VT and DBPB workloads (r=0.853), HR (r=0.714), and VO2 (r=0.863) were found. These relationships were similar to those found for the control group (r=0.923; r=0.881; and r=0.863, respectively). [Conclusion] These results demonstrate that the DPBP enables for the prediction of AT and correlated well the VT in both the T2D and ND participants.

Estudo do comportamento cortisol, gh e insulina apos uma sessao de exercicio resistido agudo / Study of the behavior of cortisol, gh and insulin after a session of acute resisted exercise / Estudio del comportamiento de cortisol, gh e insulina despues de uma sesion de ejercicio resistido agudo

INTRODUÇÃO: Muitos trabalhos têm estudado o comportamento hormonal nos exercício resistido, entretanto poucos relacionam os hormônios cortisol, GH e insulina. OBJETIVO: Estudar os ajustes das concentrações plasmáticas dos hormônios cortisol, GH e insulina em exercícios resistidos de mesma intensidade com relação à massas musculares distintas. MÉTODOS: Dez voluntários, com 20,3 ± 4,2 anos, 74,1 ± 10,2 kg de peso, 177,2 ± 4,6 cm de estatura e 23,8 ± 3,2 kg/m2 de IMC, realizaram uma sessão de leg press (LP) e supino reto (SR) com quatro séries com 10 repetições a 70% 1 RM com três minutos de intervalo. Foram coletadas amostras de sangue para dosagem das concentrações plasmáticas de cortisol, GH e insulina em repouso (Pré) e em 0' (Rec. 0'), 30' (Rec. 30') e 90' (Rec. 90') de recuperação. RESULTADOS: As concentrações plasmáticas de cortisol foram significativamente reduzidas ao final da recuperação em LP (2,20±0,37 ng/dl para 1,33±0,38ng/dl) em relação à pré-dosagem. As concentrações de GH e insulina elevaram-se significativamente durante a recuperação. GH em LP foi significativamente maior em Rec. 0' (2,75±3,29 ng/ml para 9,60±5,32 ng/dl) do que em pré. A insulina elevou-se significativamente em Rec. 30' em LP (14,70±7,92 ulU/ml para 21,66 ± 8,61 ulU/ml) e em SR (6,17 ± 2,99 ulU/ml para 19,70 ± 13,8 ulU/ml) em relação à pré. As concentrações plasmáticas de insulina pré em LP foram significativamente superiores a SR (14,70 ulU/ml e 6,17 ± 2,99 ulU/ml). CONCLUSÃO: O exercício resistido promoveu diferentes ajustes nas concentrações hormonais de cortisol, GH e insulina durante o período de recuperação. .

INTRODUCTION: Many works have studied the hormonal behavior in resistance exercise, however, few relate the cortisol, GH and insulin hormones. OBJECTIVE: To study the adjustments of plasma concentrations of the cortisol, GH and insulin hormones in resisted exercises of the same relative intensity with different muscle musses. METHODS: Ten volunteers, aged 20.3 ± 4.2 years, weight 74.1 ± 10.2 Kg, 177.2 ± 4.6 cm of stature and 23.8 ± 3.2 Kg/m2 of BMI, underwent a session of leg press (LP) and bench press (BP) with four sets of 10 repetitions at 70% 1 RM with three minutes apart. We collected blood samples to measure plasma concentrations of cortisol, GH and insulin at rest (Pre) and 0' (Rec. 0'), 30' (Rec. 30') and 90' (Rec. 90') of recovery. RESULTS: Plasma concentrations of cortisol decreased significantly at the end of the recovery in LP (2.20 ± 0.37 ng/dl to 1.33 ± 0.38 ng/dl) compared to pre. The GH and insulin concentrations significantly increased during recovery. GH was significantly higher in LP Rec. 0' (2.75 ± 3.29 ng/ml to 9.60 ± 5.32 ng/dl) than in pre. Insulin was significantly elevated in Rec. 30' in LP (14.70 ± 7.92 ulU/ml to 21.66 ± 8.61 ulU/ml) and BP (6.17 ± 2.99 ulU/ml to 19.70 ± 13.8 ulU/ml) for pre. The plasma insulin concentrations pre PL were significantly higher in the BP (14.70 ulU/ml and 6.17 ± 2.99 ulU/ml). CONCLUSION: Resisted exercise promoted different adjustments in hormone concentrations of cortisol, GH and insulin during the recovery period. .

INTRODUCCIÓN: Muchos trabajos han estudiado el comportamiento hormonal en el ejercicio de resistencia, sin embargo, pocos se refieren el cortisol, GH y las hormonas insulina. OBJETIVO: Estudiar los ajustes de las concentraciones plasmáticas de las hormonas cortisol, GH e insulina en ejercicios resistidos, de igual intensidad, en relación con las masas musculares diferentes. MÉTODOS: Diez voluntarios, con 20,3 ± 4,2 años, 74,1 ± 10,2 kg de peso, 177,2 ± 4,6 cm de estatura y 23,8 ± 3,2 kg/m2 de IMC, realizaron una sesión de leg press (LP) y supino recto (SR) con cuatro series, de 10 repeticiones a 70% 1 RM, con tres minutos de intervalo. Se recolectaron muestras de sangre para dosificación de las concentraciones plasmáticas de cortisol, GH e insulina en reposo (Pré) y en 0' (Rec. 0'), 30' (Rec. 30') y 90' (Rec. 90') de recuperación. RESULTADOS: Las concentraciones plasmáticas de cortisol se redujeron significativamente al final de la recuperación en LP (2,20±0,37 ng/dl para 1,33±0,38ng/dl) en relación con la predosificación. Las concentraciones de GH e insulina aumentaron significativamente durante la recuperación. GH en LP fue significativamente mayor en Rec. 0' (2,75±3,29 ng/ml para 9,60±5,32 ng/dl) en comparación con la predosificación. La insulina se elevó significativamente en Rec. 30' en LP (14,70±7,92 ulU/ml para 21,66 ± 8,61 ulU/ml) y en SR (6,17 ± 2,99 ulU/ml para 19,70 ± 13,8 ulU/ml) en relación con la predosificación. Las concentraciones plasmáticas de insulina, predosificación, en LP fueron significativamente superiores a SR (14,70 ulU/ml y 6,17 ± 2,99 ulU/ml). CONCLUSIÓN: El ejercicio resistido causó diferentes ajustes en las concentraciones hormonales de cortisol, GH e insulina durante el período de recuperación. .

Does aerobic exercise intensity affect health-related parameters in overweight women?

The aim of this study was to compare the effect of a cycling training programme performed at intensity corresponding to the lowest value of the respiratory quotient (RQ) versus at intensity corresponding to the ventilatory threshold (VT), on body composition and health-related parameters in overweight women. Thirty-two sedentary obese women (27-42 years old) were studied in a randomized trial of either RQ (n = 17) or VT (n = 15). RQ and VT training sessions were equalized by time (60 min) and performed in a cycloergometer. Anthropometry, body composition, lipid profile, glucose, basal metabolic rate (BMR) and fitness (maximal oxygen uptake) were evaluated before and after 12 weeks of intervention. Body weight, body mass index, fatness and fitness were improved in both groups (P<0·001). Triglycerides (TG) levels decreased only in response to RQ (P<0·001) and fat-free mass (FFM) to VT (P = 0·002). No differences were observed between groups. Both exercise intensities seem to be effective for improving health in overweight women. However, low-intensity compared with the high-intensity exercise training appears to have additional benefits on TG levels and to maintenance of FFM.

Continuous blood pressure response at different intensities in leg press exercise.

BACKGROUND: Generally, the evaluation of the blood pressure response to resistance exercise has been limited to the evaluation of discontinuous casual blood pressure monitoring, often measured at the end of the exercise. DESIGN: To continuously evaluate the blood pressure response at different intensities of leg press exercise with the same duration and number of repetitions. METHODS: Seven normotensive healthy men performed an incremental test on the leg press machine at relative intensities of one repetition maximum (1RM). The blood pressure and heart rate were measured simultaneously to the incremental exercise by a photoplethysmographic method. RESULTS: The mean ± SD peak values of the heart rate, diastolic blood pressure (DBP) and systolic blood pressure (SBP) were obtained on 70% of 1RM and were 145 ± 20 bpm, 113.1 ± 15.4 mmHg, and 192.4 ± 20.0 mmHg, respectively. The SBP was characterized by a decrease followed by an increase during the sets of exercise. The decrease in the SBP was 12-22 mmHg and took approximately 25 seconds to reach the minimum value before the increase. It was observed for all participants in most of the intensities. The rate of increase in the SBP was not statistically different between the intensities. CONCLUSIONS: Both duration and intensity of exercise have an impact on the blood pressure response. Above 30% of 1RM, the SBP decreases in approximately 20 seconds and starts to increase until the end of the set of leg press exercise.

Effects of ovariectomy and resistance training on oxidative stress markers in the rat liver.

OBJECTIVE: The objective of this study was to assess the effects of resistance training on oxidative stress markers in the livers of ovariectomized rats. METHOD: Adult Sprague-Dawley rats were divided into the following four groups (n = 8 per group): sham-operated sedentary, ovariectomized sedentary, sham-operated resistance training, and ovariectomized resistance training. During the resistance training period, the animals climbed a 1.1-m vertical ladder with weights attached to their tails; the sessions were conducted 3 times per week, with 4-9 climbs and 8-12 dynamic movements per climb. The oxidative stress was assessed by measuring the levels of reduced glutathione and oxidized glutathione, the enzymatic activity of catalase and superoxide dismutase, lipid peroxidation, vitamin E concentrations, and the gene expression of glutathione peroxidase. RESULTS: The results showed significant reductions in the reduced glutathione/oxidized glutathione ratio (4.11±0.65 nmol/g tec), vitamin E concentration (55.36±11.11 nmol/g), and gene expression of glutathione peroxidase (0.49±0.16 arbitrary units) in the livers of ovariectomized rats compared with the livers of unovariectomized animals (5.71±0.71 nmol/g tec, 100.14±10.99 nmol/g, and 1.09±0.54 arbitrary units, respectively). Moreover, resistance training for 10 weeks was not able to reduce the oxidative stress in the livers of ovariectomized rats and induced negative changes in the hepatic anti-oxidative/oxidative balance. CONCLUSION: Our findings indicate that the resistance training program used in this study was not able to attenuate the hepatic oxidative damage caused by ovariectomy and increased the hepatic oxidative stress.

Effects of ovariectomy and resistance training on oxidative stress markers in the rat liver

OBJECTIVE: The objective of this study was to assess the effects of resistance training on oxidative stress markers in the livers of ovariectomized rats. METHOD: Adult Sprague-Dawley rats were divided into the following four groups (n = 8 per group): sham-operated sedentary, ovariectomized sedentary, sham-operated resistance training, and ovariectomized resistance training. During the resistance training period, the animals climbed a 1.1-m vertical ladder with weights attached to their tails; the sessions were conducted 3 times per week, with 4-9 climbs and 8-12 dynamic movements per climb. The oxidative stress was assessed by measuring the levels of reduced glutathione and oxidized glutathione, the enzymatic activity of catalase and superoxide dismutase, lipid peroxidation, vitamin E concentrations, and the gene expression of glutathione peroxidase. RESULTS: The results showed significant reductions in the reduced glutathione/oxidized glutathione ratio (4.11±0.65 nmol/g tec), vitamin E concentration (55.36±11.11 nmol/g), and gene expression of glutathione peroxidase (0.49±0.16 arbitrary units) in the livers of ovariectomized rats compared with the livers of unovariectomized animals (5.71±0.71 nmol/g tec, 100.14±10.99 nmol/g, and 1.09±0.54 arbitrary units, respectively). Moreover, resistance training for 10 weeks was not able to reduce the oxidative stress in the livers of ovariectomized rats and induced negative changes in the hepatic anti-oxidative/oxidative balance. CONCLUSION: Our findings indicate that the resistance training program used in this study was not able to attenuate the hepatic oxidative damage caused by ovariectomy and increased the hepatic oxidative stress. .

Tolerância ao esforço em ratos com estenose aórtica e disfunção ventricular diastólica e/ou sistólica / Exercise tolerance in rats with aortic stenosis and ventricular diastolic and/or systolic dysfunction

FUNDAMENTO: A Tolerância ao Esforço Físico (TEF) é uma medida de condicionamento cardiorrespiratório. A capacidade aeróbica é reduzida na Insuficiência Cardíaca (IC), embora não haja dados disponíveis sobre esse parâmetro em animais com disfunção ventricular e sem sinais de IC. OBJETIVO: Avaliar a TEF em ratos com disfunção ventricular diastólica isolada ou associada com disfunção sistólica induzida pela Estenose da Aorta ascendente (EAo). MÉTODOS: Ratos Wistar machos jovens (20-30 dias de idade) foram divididos em Grupo Controle (GC, n = 11) e Grupo EAo (n = 12). Os animais foram avaliados em 6 e 18 semanas após a cirurgia para EAo. O teste ergométrico foi feito até a exaustão e foram avaliadas a velocidade da esteira e a concentração de lactato [LAC] no limiar de lactato, velocidade da esteira e [LAC] na exaustão, e tempo total do teste. RESULTADOS: Dados ecocardiográficos revelaram remodelação do átrio esquerdo e hipertrofia concêntrica ventricular esquerda em 6 e 18 semanas. A fração de encurtamento endocárdico mostrou-se maior no grupo EAo do que no GC em 6 e 18 semanas. A fração de encurtamento da parede média mostrou-se maior no grupo EAo do que no GC em 6 semanas. O índice cardíaco mostrou-se semelhante no GC e no grupo EAo em 6 e 18 semanas, tendo diminuído entre 6-18 semanas em ambos os grupos. A razão entre a onda E a onda A foi maior no GC do que no grupo EAo em ambos os períodos e não se alterou em ambos os grupos entre a semana 6 e a semana 18. Os parâmetros do teste de esforço na esteira foram semelhantes nos dois grupos tanto na semana 6 quanto na semana 18. CONCLUSÃO: Embora a EAo promova a disfunção diastólica isolada ou associada à disfunção sistólica, em 6 ou 18 semanas, ela não é suficiente para alterar a tolerância ao esforço físico.

BACKGROUND: Physical stress tolerance (ST) is a measurement of cardiorespiratory fitness. Aerobic capacity is reduced in heart failure (HF) although there is no data available on this parameter in animals with ventricular dysfunction and no signs of HF. OBJECTIVE: Evaluate ST in rats with ventricular diastolic dysfunction isolated or associated with systolic dysfunction induced by ascending aortic stenosis (AoS). METHODS: Young male Wistar rats (20-30 days old), divided in: control group (CG, n=11) and AoSG group, (n=12). Animals were assessed at 6 and 18 weeks after AoS surgery. Treadmill exercise test was until exhaustion and evaluated treadmill speed and lactate concentration [LAC] at lactate threshold, treadmill speed and [LAC] at exhaustion, and total testing time. RESULTS: Echocardiography data revealed remodeling of the left atrium and left ventricular concentric hypertrophy at 6 and 18 weeks. Endocardial fractional shortening was greater in AoSG than CG at 6 and 18 weeks. Midwall fractional shortening was greater in AoSG than in CG only 6 week. Cardiac index was similar in CG and AoSG at 6 and 18 weeks and decreased between from 6 to 18 weeks in both groups. The E wave to A wave ratio was greater in CG than in AoSG at both periods and did not change in both groups between week 6 and 18. Treadmill stress testing parameters were similar in both groups at 6 or 18 weeks. CONCLUSION: Although AoS promotes isolated diastolic dysfunction or associated with systolic dysfunction at 6 or 18 weeks, it is not sufficient to modify physical stress tolerance.

Exercise tolerance in rats with aortic stenosis and ventricular diastolic and/or systolic dysfunction.

BACKGROUND: Physical stress tolerance (ST) is a measurement of cardiorespiratory fitness. Aerobic capacity is reduced in heart failure (HF) although there is no data available on this parameter in animals with ventricular dysfunction and no signs of HF. OBJECTIVE: Evaluate ST in rats with ventricular diastolic dysfunction isolated or associated with systolic dysfunction induced by ascending aortic stenosis (AoS). METHODS: Young male Wistar rats (20-30 days old), divided in: control group (CG, n=11) and AoSG group, (n=12). Animals were assessed at 6 and 18 weeks after AoS surgery. Treadmill exercise test was until exhaustion and evaluated treadmill speed and lactate concentration [LAC] at lactate threshold, treadmill speed and [LAC] at exhaustion, and total testing time. RESULTS: Echocardiography data revealed remodeling of the left atrium and left ventricular concentric hypertrophy at 6 and 18 weeks. Endocardial fractional shortening was greater in AoSG than CG at 6 and 18 weeks. Midwall fractional shortening was greater in AoSG than in CG only 6 week. Cardiac index was similar in CG and AoSG at 6 and 18 weeks and decreased between from 6 to 18 weeks in both groups. The E wave to A wave ratio was greater in CG than in AoSG at both periods and did not change in both groups between week 6 and 18. Treadmill stress testing parameters were similar in both groups at 6 or 18 weeks. CONCLUSION: Although AoS promotes isolated diastolic dysfunction or associated with systolic dysfunction at 6 or 18 weeks, it is not sufficient to modify physical stress tolerance.

Effects of low-level laser therapy (808 nm) on isokinetic muscle performance of young women submitted to endurance training: a randomized controlled clinical trial.

Low-level laser therapy (LLLT) has shown efficacy in muscle bioenergetic activation and its effects could influence the mechanical performance of this tissue during physical exercise. This study tested whether endurance training associated with LLLT could increase human muscle performance in isokinetic dynamometry when compared to the same training without LLLT. The primary objective was to determine the fatigue index of the knee extensor muscles (FIext) and the secondary objective was to determine the total work of the knee extensor muscles (TWext). Included in the study were 45 clinically healthy women (21 ± 1.78 years old) who were randomly distributed into three groups: CG (control group), TG (training group) and TLG (training with LLLT group). The training for the TG and TLG groups involved cycle ergometer exercise with load applied to the ventilatory threshold (VT) for 9 consecutive weeks. Immediately after each training session, LLLT was applied to the femoral quadriceps muscle of both lower limbs of the TLG subjects using an infrared laser device (808 nm) with six 60-mW diodes with an energy of 0.6 J per diode and a total energy applied to each limb of 18 J. VT was determined by ergospirometry during an incremental exercise test and muscle performance was evaluated using an isokinetic dynamometer at 240°/s. Only the TLG showed a decrease in FIext in the nondominant lower limb (P = 0.016) and the dominant lower limb (P = 0.006). Both the TLG and the TG showed an increase in TWext in the nondominant lower limb (P < 0.001 and P = 0.011, respectively) and in the dominant lower limb (P < 0.000 and P < 0.000, respectively). The CG showed no reduction in FIext or TWext in either lower limb. The results suggest that an endurance training program combined with LLLT leads to a greater reduction in fatigue than an endurance training program without LLLT. This is relevant to everyone involved in sport and rehabilitation.

Metabolic and cardiac autonomic effects of high-intensity resistance training protocol in Wistar rats.

The aim of this study was to assess the effects of metabolic and autonomic nervous control on high-intensity resistance training (HRT) as determined by pancreatic glucose sensitivity (GS), insulin sensitivity (IS), blood lactate ([La]), and heart rate variability (HRV) in rats. Thirty male, albino Wistar rats (292 ± 20 g) were divided into 3 groups: sedentary control (SC), low-resistance training (LRT), and HRT. The animals in the HRT group were submitted to a high-resistance protocol with a progressively increasing load relative to body weight until exhaustion, whereas the LRT group performed the same exercise regimen with no load progression. The program was conducted 3 times per week for 8 weeks. The [La], parameters related to the functionality of pancreatic tissue, and HRV were measured. There was a significant increase in peak [La] only in the HRT group, but there was a reduction in [La] when corrected to the maximal load in both trained groups (LRT and HRT, p < 0.05). Both trained groups exhibited an increase in IS; however, compared with SC and LRT, HRT demonstrated a significantly higher GS posttraining (p < 0.05). With respect to HRV, the low-frequency (LF) band, in milliseconds squared, reduced in both trained groups, but the high-frequency band, in milliseconds squared and nu, increased, and the LF in nu, decreased only in the HRT group (p < 0.05). The HRT protocol produced significant and beneficial metabolic and cardiac autonomic adaptations. These results provide evidence for the positive benefits of HRT in counteracting metabolic and cardiovascular dysfunction.

Análise eletromiográfica dos músculos da coxa no exercício agachamento afundo até a exaustão / Thigh muscles electromyographic activity during lunge exercise to fatigue

O agachamento afundo possui um posicionamento dos membros inferiores diferencial em relação ao agachamento padrão, necessitando de maiores esclarecimentos acerca das participações dos músculos envolvidos. O objetivo foi analisar a atividade eletromiográfica dos músculos vastus lateralis (VL), vastus medialis (VM), bíceps femoris (BF) e semitendinosus (ST) durante a execução do agachamento afundo até à exaustão com o membro inferior posicionado frontalmente e posteriormente. Participaram do estudo nove mulheres ativas com média (DP) de idade de 22 (3,4) anos e massa corporal 60,3 (4,1) kg. O agachamento afundo foi dividido em duas etapas, diferindo apenas o posicionamento do membro inferior dominante (randomizado). Os sinais eletromiográficos foram captados utilizando um eletromiógrafo e analisados os valores "root mean square" (RMS) na fase concêntrica. Os resultados indicaram um aumento significativo do RMS em função do tempo para o membro inferior posicionado frontalmente e posteriormente (p< 0,001). No membro posicionado frontalmente, o aumento do RMS correspondeu a 50 por cento para o VL, 54 por cento para o VM e 48 por cento para o BF. O membro posicionado posteriormente apresentou um aumento de 75 por cento para o VL, 113 por cento para o VM, 62 por cento para o BF e 48 por cento para o ST. O RMS também foi significativamente maior no músculo VM em relação ao ST no membro inferior posicionado anteriormente (p = 0,03) e em relação ao ST e BF no membro inferior posicionado posteriormente (p = 0,02). Não ocorreu interação significativa entre o efeito do tempo e músculo na atividade eletromiográfica. O RMS normalizado não apresentou diferenças estatisticamente significativas no que se refere ao posicionamento do membro inferior dominante. A atividade muscular foi semelhante em ambos os posicionamentos do membro inferior, apresentando maior aumento de ativação dos músculos VL e VM em relação ao BF e ST.

The position of lower limbs during lunge is different from squat without clear understanding on differences in muscle activation. The objective was to compare the electromyographic activity of the vastus lateralis (VL), vastus medialis (VM), biceps femoris (BF) and semitendinosus (ST) during the execution of the lunge to exhaustion of the lower limb, changing position of the legs frontally and posteriorly. Nine active women participated of this study with a mean (SD) age of 22 (3.4) years and body mass 60.3 (4.1) kg. The lunge was divided in two phases, changing the forward leg (random order). The electromyographic signals were captured by an eletromyograph, and the root mean square (RMS) values were analyzed during the concentric phase. There was a significant increase of the RMS in time for the LL positioned frontally and posterior (p< 0,001). For the forward position, the increase of RMS was 50 percent for VL, 54 percent for VM and 48 percent for BF. The backward position had an increase of 75 percent for VL, 113 percent for VM, 62 percent for BF and 48 percent for ST. The RMS was significantly higher for VM than for ST the forward position (p = 0,03) and ST and BF for the backward position (p = 0,02). No interaction was observed between time and muscle in the electromyigraphic activity. The normalized RMS was not statistically different comparing the forward and backward position of the dominant leg. Muscle activity was similar in both positions of the LL, showing increased activation of the VM and VL muscles in relation to the BF and ST.

The measurement of lactate threshold in resistance exercise: a comparison of methods.

Resistance incremental tests (IT) make it possible to determine critical metabolic and cardiovascular changes, such as the lactate threshold (LT). Different methods are frequently used to improve the exactness of LT identification. The objective of the study was to identify LT by four different methods (visual inspection, log-log, algorithmic adjustment and QLac) during resistance exercise and to evaluate which methods present more precision. Twelve men performed a maximal IT on the leg press at relative intensities of 10%, 20%, 25%, 30%, 35%, 40%, 50%, 60%, 70%, 80% and 90% of 1RM with 1-min stages. During the 2-min interval between stages, capillary blood was collected for blood lactate analysis. LT was detected using each of the four methods. The intensity of LT by visual inspection method was 26·9 (5·2)% of 1RM, adjustment algorithmic method was 27·8 (3·6)% of 1RM, log-log method was 23·3 (3·5)% of 1RM and QLac method was 31·6 (9·8)% of 1RM, with significant difference only between log-log and QLac methods. Bland and Altman analysis shows better concordance for visual inspection versus adjustment algorithmic methods. The visual inspection, algorithmic and log-log methods detected the LT at the same intensity. The mathematical models, specially the algorithmic method, provide more precision.

Effects of 12-week overground walking training at ventilatory threshold velocity in type 2 diabetic women.

This study analyzed the effects of overground walking training at ventilatory threshold (VT) velocity on glycaemic control, body composition, physical fitness and lipid profile in DM2 women. Nineteen sedentary patients were randomly assigned to a control group (CG; n=10, 55.9±2.2 years) or a trained group (TG; n=9, 53.4±2.3 years). Both groups were subjected to anthropometric measures, a 12-h fasting blood sampling and a graded treadmill exercise test at baseline and after a 12-week period, during which TG followed a training program involving overground walking at VT velocity for 20-60min/session three times/week. Significant group×time interactions (P<0.05) in glycated hemoglobin (HbA1c), body mass, body mass index (BMI), peak oxygen uptake (VO(2peak)) and exercise duration were observed as effects of training exercise, whereas intervention did not induced significant changes (P>0.05) in fasting blood glucose, submaximal fitness parameters and lipid profile. Our results suggest that overground walking training at VT velocity improves long term glycaemic control, body composition and exercise capacity, attesting for the relevance of this parameter as an effective strategy for the exercise intensity prescription in DM2 population.

Effects of low level laser therapy (808 nm) on physical strength training in humans.

Recent studies have investigated whether low level laser therapy (LLLT) can optimize human muscle performance in physical exercise. This study tested the effect of LLLT on muscle performance in physical strength training in humans compared with strength training only. The study involved 36 men (20.8±2.2 years old), clinically healthy, with a beginner and/or moderate physical activity training pattern. The subjects were randomly distributed into three groups: TLG (training with LLLT), TG (training only) and CG (control). The training for TG and TLG subjects involved the leg-press exercise with a load equal to 80% of one repetition maximum (1RM) in the leg-press test over 12 consecutive weeks. The LLLT was applied to the quadriceps muscle of both lower limbs of the TLG subjects immediately after the end of each training session. Using an infrared laser device (808 nm) with six diodes of 60 mW each a total energy of 50.4 J of LLLT was administered over 140 s. Muscle strength was assessed using the 1RM leg-press test and the isokinetic dynamometer test. The muscle volume of the thigh of the dominant limb was assessed by thigh perimetry. The TLG subjects showed an increase of 55% in the 1RM leg-press test, which was significantly higher than the increases in the TG subjects (26%, P = 0.033) and in the CG subjects (0.27%, P < 0.001). The TLG was the only group to show an increase in muscle performance in the isokinetic dynamometry test compared with baseline. The increases in thigh perimeter in the TLG subjects and TG subjects were not significantly different (4.52% and 2.75%, respectively; P = 0.775). Strength training associated with LLLT can increase muscle performance compared with strength training only.

Cinética do consumo de oxigênio e tempo limite na vvo2max: comparação entre homens e mulheres / Oxygen uptake kinetics and threshold time at the vVO2max: tomparison between men and women

Foi investigada a influência do gênero no tempo limite (Tlim) e na cinética do VO2 durante corrida na velocidade associada ao VO2max (vVO2max) em nove homens e nove mulheres, todos adultos, jovens e sedentários, com idades entre 20 e 30 anos. Homens e mulheres realizaram dois testes em esteira rolante, sendo um teste incremental para determinar VO2max (42,66 ± 4,50 vs. 32,92 ± 6,03mL.kg-1.min-1) e vVO2max (13.2 ± 1.5 vs. 10,3 ± 2,0km.h-1), respectivamente. Um segundo teste com carga constante na vVO2max até a exaustão. O Tlim e a cinética do VO2 foram determinados. Não houve diferença significante entre homens e mulheres para constante de tempo (τ) (35,76 ± 21,03 vs. 36,5 ± 6,21s, respectivamente; P = 0,29); Tlim (308 ± 84,3 vs. 282,11 ± 57,19s, respectivamente; P = 0,68), tempo para atingir o VO2max (TAVO2max) (164,48 ± 96,73 vs. 167,88 ± 28,59s, respectivamente; P = 0,29), tempo para atingir o VO2max em percentual do Tlim ( por centoTlim) (50,24 ± 16,93 vs. 62,63 ± 16,60 por cento, respectivamente; P = 0,19), tempo mantido no VO2max (TMVO2max) (144,08 ± 42,55 vs. 114,23 ± 76,96s, respectivamente; P = 0,13). Estes resultados sugerem que a cinética do VO2 e o Tlim são similares entre homens e mulheres sedentários na vVO2max.

The aim of this study was to investigate the influence of gender on Tthre and VO2 response during running exercise performed at vVO2max. Therefore, eighteen untrained individuals (9 male and 9 female) with normal weight and aged between 20 - 30 years (VO2max = 42.66 ± 4.50 vs 32.92 ± 6.03 mL.kg-1.min-1 and vVO2max = 13.2 ± 1.5 vs 10.3 ± 2.0 km.h-1, for male and female, respectively) were assessed. Subjects performed two exercise tests on treadmill. First one was an incremental test to determine VO2max, velocity at VO2max (vVO2max) and second test was performed at steady velocity - vVO2max - until exhaustion. The threshold time (Tthre) and VO2 kinetics response was determined. No significant differences were observed between men and women for time constant (τ) (35.76 ± 21.03 vs 36.5 ± 6.21s, respectively; P = 0.29); Tthre (308 ± 84.3 vs 282.11 ± 57.19s, respectively; P = 0.68), time to achieve VO2max (TAVO2max) (164.48 ± 96.73 vs 167.88 ± 28.59s, respectively; P = 0.29), time to achieve VO2max in Tthre percentage ( percentTthre) (50.24 ± 16.93 vs 62.63 ± 16.60 percent, respectively; P = 0.19); time maintained at VO2max (TMVO2max) (144.08 ± 42.55 vs 114.23 ± 76.96s, respectively; P = 0.13). These results suggest that the VO2 kinetics response and Tthre is similar between untrained men and women at the vVO2max.