Oxygen consumption and substrate utilization during and after resistance exercises performed with different muscle mass

International Journal of Exercise Science 9(1): 77-88, 2016. This study investigated the energy expenditure (EE) and substrate utilization reflected by the respiratory-exchange ratio (RER) during and after resistance exercises performed with different muscle mass. Ten male volunteers (mean±SD; 26±4yr, 179±6cm, 77±8kg) performed multiple sets of the horizontal leg press (LP) and chest fly (CF) (5 sets of 10 repetitions with 15 repetition-maximum, 1-minute between-set intervals) in a counterbalanced design. Oxygen uptake and carbon dioxide production were measured during 40 minutes of resting; resistance exercise protocols (sets and intervals); 90 minutes of post-exercise recovery. Total fat and carbohydrate oxidation rates were calculated according to the non-protein respiratory quotient. Both exercise conditions elicited net excess post-exercise oxygen consumption (EPOC) of similar duration (approximately 40min). The EPOC magnitude at 40 minutes was greater after LP than after CF (7.36±1.10L vs. 4.73±0.99L; P\u3c0.001). The RER was higher in LP (1.30±0.04) than CF (1.16±0.05, P=0.0003) during exercise. During recovery the RER was similar in LP and CF (P\u3e0.05) and lower than pre-exercise (Pre-exercise=0.78±0.04 vs. CF40min=0.74±0.04; CF90min=0.68±0.02 and LP50min=0.73±0.06; LP90min=0.65±0.04, P\u3c0.05). However, fat oxidation after LP was greater than CF between 30-90 minutes of recovery (mean total fat oxidation: LP=10.9 g vs. CF=8.4 g; P\u3c0.01). The increases of EE and fat oxidation during post-exercise recovery were greater after multiple sets of resistance exercises performed with larger muscle mass than smaller muscle mass. This finding has practical implications for resistance training designed as part of weight management programs

Postexercise hypotension and related hemodynamic responses to cycling under heat stress in untrained men with elevated blood pressure

Purpose: To investigate the effect of heat stress on postexercise hypotension. Methods: Seven untrained men, aged 21–33 years, performed two cycling bouts at 60% of oxygen uptake reserve expending 300 kcal in environmental temperatures of 21 °C (TEMP) and 35 °C (HOT) in a randomized, counter-balanced order. Physiological responses were monitored for 10-min before and 60-min after each exercise bout, and after a non-exercise control session (CON). Blood pressure (BP) also was measured during the subsequent 21-h recovery period. Results: Compared to CON, systolic, and diastolic BPs were significantly reduced in HOT (Δ = − 8.3 ± 1.6 and − 9.7 ± 1.4 mmHg, P &lt; 0.01) and TEMP (Δ = − 4.9 ± 2.1 and − 4.5 ± 0.9 mmHg, P &lt; 0.05) during the first 60 min of postexercise recovery. Compared to TEMP, rectal temperature was 0.6 °C higher (P = 0.001), mean skin temperature was 1.8 °C higher (P = 0.013), and plasma volume (PV) was 2.6 percentage points lower (P = 0.005) in HOT. During the subsequent 21-h recovery period systolic BP was 4.2 mmHg lower in HOT compared to CON (P = 0.016) and 2.5 mmHg lower in HOT compared to TEMP (P = 0.039). Conclusion: Exercise in the heat increases the hypotensive effects of exercise for at least 22 h in untrained men with elevated blood pressure. Our findings indicate that augmented core and skin temperatures and decreased PV are the main hemodynamic mechanisms underlying a reduction in BP after exercise performed under heat stress.</p

Flexibilidade e esporte: uma revisão da literatura

A flexibilidade é um componente importante da aptidão física, podendo ser definida como a maior amplitude fisiológica de movimento para a execução de um gesto qualquer. Contudo, falta consenso científico quanto à sua importância relativa para a prática esportiva. O objetivo do estudo foi efetuar uma revisão da literatura especializada sobre as relações entre flexibilidade e esporte. Foram abordados os seguintes pontos: perfis de flexibilidade nas modalidades esportivas, influência na aprendizagem do esporte e relação com as lesões esportivas. Os resultados das pesquisas revelaram-se conflitantes para diferentes amostras em modalidades diversas. Em suma, o exame dos dados disponíveis indica que: a) parecem ser necessários níveis mínimos de flexibilidade para o desempenho esportivo, ainda que seja extremamente difícil determiná-los; b) padrões específicos de movimento acarretam manifestações particulares de flexibilidade, que são coerentes com as demandas da atividade. A associação da flexibilidade com o desempenho depende do esporte praticado. Assim, níveis altos de flexibilidade não são, necessariamente, os mais favoráveis em todas as modalidades esportivas; c) não é possível estabelecer com clareza a influência da flexibilidade na incidência de lesões no esporte. As lesões decorrem de fatores múltiplos, o que limita as possibilidades de isolamento do efeito independente da flexibilidade. Logo, a despeito do senso comum de que o treinamento da flexibilidade previne lesões, não se podem fazer afirmativas conclusivas neste sentidoFlexibility is a major component of physical fitness, being defined as the maximal physiological range of motion in a given movement. However, there is a lack of scientific consensus about its relative importance to sports practice. The purpose of the study was to review the literature about the relationship between flexibility and sports. Three points were focused: flexibility profiles in sports modalities, influence on sports learning and flexibility effects on sports injury. Research results report opposing findings from different samples and sport activities. In summary, available data suggest that: a) minimal flexibility levels seem to be necessary to sport performance, but they are extremely difficult to be determined; b) specific patterns of movement develop specific flexibility profiles, that are adequate to activity demands. The relationship of flexibility to performance is likely to be sport dependent. Therefore, high levels of flexibility are not the most favorable to all sport modalities; c) it’s not possible to discern with precision the influence of flexibility on injury in sports. Injury is an extremely multifactorial occurrence, and it’s very difficult to adjust flexibility effects for the unknown interactions between all the variables that can interfere on its rates. So, in spite of the ubiquitous notion that stretching prevents injury, no conclusive statements can be made in this sens

Are Self-selected Intervals as Effective as Fixed Intervals in Controlling Acute Responses in High-Intensity Interval Resistance Training?

International Journal of Exercise Science 16(4): 1205-1215, 2023. Physical conditioning programs often apply high-intensity resistance training (HIRT), but there is a lack of research investigating the effects of using fixed or self-selected resting intervals between exercises on the performance, relative intensity, and affective perception during this modality of training. This study compared fixed versus self-selected rest intervals in HIRT sessions on cardiorespiratory responses, number of repetitions, and enjoyment perception in trained young men. Sixteen trained males (27.1 ± 3.9 years; 56.6 ± 7.5 mL.kg-1.min-1) performed HIRT circuits with 30-s and self-selected recovery interval. The duration of resting intervals was longer in HIRT performed with fixed than self-selected intervals (14.04 ± 5.82 s; p \u3c 0.0001; ES = 3.2). Both sessions elicited similar relative HRR (79.4 ± 6.2 % vs. 81.6 ± 4.2 %; p = 0.14), VO2R (43.0 ± 12.2% vs. 47.7 ± 9.6%; p = 0.10), and enjoyment reflected by scores in the PACES questionnaire (107.9 ± 15.1 vs. 109.2 ± 12.8; p = 0.65). The total number of repetitions (403.4 ± 45.5 vs. 353.1 ± 27.4; p \u3c 0.01, ES = 1.3) and caloric expenditure (154.4 ± 28.6 kcal vs. 121.4 ± 21.6 kcal; p \u3c 0.001, ES = 0.13) were greater in HIRT performed with fixed vs. self-selected intervals. In conclusion, HIRT performed with fixed and self-selected rest intervals elicited similar relative intensity and enjoyment perception. However, the number of repetitions and caloric expenditure were greater in sessions performed with fixed 30-s

EFFECT OF CATHODAL TRANSCRANIAL DIRECT CURRENT STIMULATION OVER AN ANTAGONISTIC CO-ACTIVATION DURING AN ISOKINETIC PROTOCOL

The objective of this study was to evaluate the effects of cathodal transcranial direct current stimulation (t-DCS) over an antagonistic co-activation of lower limbs muscles during isokinetic exercise. We analyzed the results of isokinetic exercise for dominant leg knee’s extensors and flexors muscles during concentric-concentric protocol after cathodal and sham t-DCS. Seven healthy right-handed volunteers took part at the study. The cathodal current is an reducer of motor cortex excitability. Only three of the seven volunteers presented the expected behavior after t-DCS cathodal stimulation, in at least one phase. The findings of this study suggest that the effect of t-DCS cathodal on the muscular co-activation, remains unclear especially because the mechanisms underlying the stimulation of each cortical area are still unknown

Standardized MET value underestimates the energy cost of treadmill running in men

AbstractThe main purpose of the present study was to compare the reference metabolic equivalent (MET) value and observed resting oxygen uptake (VO2) for defining cardiorespiratory fitness (VO2max) and characterizing the energy cost of treadmill running. A heterogeneous cohort of 114 healthy men volunteered to participate. In Part 1 of the study, 114 men [mean±SD, age: 24±5 years; height: 177.1±7.9 cm; body mass: 75.0±10.0 kg] visited the laboratory twice for assessment of resting and maximal VO2 values to compare the reference MET value vs. observed resting VO2 and to investigate the association between resting VO2 and VO2max. In Part 2, 14 of the 114 men visited the laboratory once more to perform a 30-min bout of running at 8.0 km∙h−1/8.3 METs. The mean observed resting VO2 of 3.26 mL·kg−1·min−1 was lower than the reference MET value of 3.5 mL·kg−1·min−1 (P&lt;0.001). Resting and maximal VO2 values relative to total body mass and fat-free mass were positively correlated (R=0.71 and 0.60, respectively; P&lt;0.001). The maximal MET and energy cost of treadmill running were consequently underestimated when calculated using the reference MET value only for those with low VO2max (P=0.005 to P&lt;0.001). In conclusion, the reference MET value considerably overestimated observed resting VO2 in men with low VO2max, resulting in underestimations of the maximal MET, exercise intensity prescription, and the energy cost of running.</jats:p

The effects of a 12-week resistance training program on muscle strength of elderly women

O treinamento da força (TF) tem se revelado eficaz em idosos frágeis. Contudo, dúvidas persistem sobre a resposta ao treinamento em idosos com nível de independência funcional elevado. O objetivo do estudo foi observar os efeitos de 12 semanas de TF sobre a força muscular em mulheres idosas funcionalmente autônomas, mas sem experiência prévia com este tipo de treinamento. Trinta e cinco mulheres com 62 a 77 anos de idade passaram por anamnese e teste de esforço com ECG. Uma voluntária foi excluída por utilizar marcapasso, outras duas exibiram sinais de isquemia, seis não compareceram ao teste de esforço e sete abandonaram o TF por razões .diversas. A casuística contou com 19 indivíduos (idade = 69 ± 5 anos). Foram realizadas, duas vezes por semana durante 12 semanas, duas séries de 10 repetições máximas (RM) em exercícios para membros inferiores (“leg-press”) e superiores (supino reto). As médias semanais do volume de treinamento foram comparadas através de ANOVA para medidas repetidas (p &lt; 0,05). Os resultados indicaram tendência à melhoria da força durante o período observado, nos dois exercícios, da ordem de 58% para o “leg-press” e 61% para o supino. O ganho de força evoluiu rapidamente nas primeiras quatro semanas, tendendo a estabilizar-se nas semanas finais. Conclui-se que o TF pode apresentar resultados positivos em idosas com bom nível de independência funcional. A possibilidade destes ganhos ocorrerem em treinamentos de prazo mais longo, todavia, revela-se duvidosaResistance training (RT) seems to be effective in frail older subjects. However, there is less evidence on the responses of fully independent elders to RT programs. The purpose of this study was to observe the influence of a 12-week RT program on muscle strength of high functional elder women, but with no previous training experience. A group of 35 women with 62 to 77-years old was selected to perform a graded effort test and to answer an anamnesis, and 19 remained till the end of the RT program (age = 69 ± 5 years) one subject was excluded for using a pacemaker, two exhibited ischemia on the ECG, six did not show up to perform the effort test, and seven abandoned the program. RT consisted of two series of 10 maximal repetitions (RM), twice a week, in two exercises: double leg-press and chest-press. Mean results were recorded every week and compared by repeated measures ANOVA (p &lt; 0.05). The results indicated a improvement trend in both exercises, about 58% for the leg-press and 61% for the bench-press. Strength improvements took place mainly during the first four weeks of RT, with an slight stabilization tendency in the final weeks. Therefore, it seems that RT can bring about positive results in the strength of functional independent older women. However, further studies with sophisticated designs should be held to confirm these result

Assessment of Cardiorespiratory Fitness without Exercise in Elderly Men with Chronic Cardiovascular and Metabolic Diseases

Low cardiorespiratory (CRF) is associated with health problems in elderly people, especially cardiovascular and metabolic disease. However, physical limitations in this population frequently preclude the application of aerobic tests. We developed a model to estimate CRF without aerobic testing in older men with chronic cardiovascular and metabolic diseases. Subjects aged from 60 to 91 years were randomly assigned into validation (n = 67) and cross-validation (n = 29) groups. A hierarchical linear regression model included age, self-reported fitness, and handgrip strength normalized to body weight (R2 = 0.79; SEE = 1.1 METs). The PRESS (predicted residual sum of squares) statistics revealed minimal shrinkage in relation to the original model and that predicted by the model and actual CRF correlated well in the cross-validation group (r = 0.85). The area under curve (AUC) values suggested a good accuracy of the model to detect disability in the validation (0.876, 95% CI: 0.793–0.959) and cross-validation groups (0.826, 95% CI: 0.677–0.975). Our findings suggest that CRF can be reliably estimated without exercise test in unhealthy elderly men