The influence of transcranial direct current stimulation (tDCS) upon maximal strength performance in exercises recruiting large muscle mass has not been established in healthy populations. The purpose of this study was to investigate whether anodal tDCS was able to increase the performance during maximal strength exercise (MSEX) in healthy subjects. Fourteen volunteers (age: 26 ± 4 yrs) performed two MSEX after anodal or sham tDCS (2mA; 20min prior MSEX), involving knee extensors and flexors in concentric isokinetic muscle actions of the dominant limb (3 sets of 10 repetitions). The electrical muscle activity (sEMG) of four recruited muscles was recorded during MSEX. Anodal tDCS was not able to improve force production (i.e., total work and peak torque), fatigue resistance, or electromyographic activity during MSEX when compared to sham condition. In conclusion, anodal tDCS applied upon the contralateral motor cortex was not capable of increasing the strength performance of knee extensors and flexors in young healthy subjects.Resumo-"ETCC sobre o córtex motor não aumenta o desempenho de força em sujeitos saudáveis." A influência da estimulação transcraniana por corrente contínua (ETCC) sobre o desempenho da força muscular em exercícios que recrutam grandes massas musculares ainda não foi estabelecido em populações saudáveis. O objetivo desse estudo foi investigar se a ETCC anódica seria capaz de aumentar o desempenho durante exercício máximo de força (EMF) em sujeitos saudáveis. Catorze voluntários (idade: 26 ± 4 anos) executaram dois EMF com aplicação prévia da ETCC anódica ou placebo (2mA; 20 mim), envolvendo músculos flexores e extensores do joelho dominante em ação concêntrica isocinética (3 séries de 10 repetições). A atividade elétrica muscular (sEMG) de quatro músculos recrutados foi registrada durante o EMF. A ETCC anódica não foi capaz de melhorar a produção de força (trabalho total e pico de torque), resistência à fadiga ou atividade eletromiográfica durante o EMF, quando comparada à condição placebo. Em conclusão, a ETCC anódica aplicada sobre o córtex motor contralateral não foi capaz de aumentar o desempenho de força de flexores e extensores de joelho em jovens saudáveis. Palavras-chave: neurociência, ETCC, neuromodulação, fadiga e reabilitação motoraResumen-"tDCS en motor corteza no aumenta el rendimiento de fuerza en sujetos sanos." La influencia de estimulación transcraneal de corriente directa (tDCS) en ejercicios de fuerza muscular de rendimiento que reclutan grandes masas musculares no se ha establecido en la población sana. El objetivo de este estudio fue investigar si la ETCC anódica podría mejorar el rendimiento durante el ejercicio máximo de la fuerza (EMF) en sujetos sanos. Catorce voluntarios (26 ± 4 años de edad) realizaron dos EMF con la aplicación previa de ETCC anódica y placebo (2 mA, 20 i) la participación de los flexores y extensores de la rodilla dominante en acción concéntrica (3 series de 10 repeticiones). La actividad eléctrica muscular (sEMG) en cuatro músculos reclutados se r...

Post-stroke patients usually exhibit reduced peak muscular torque (PT) and/or force steadiness during submaximal exercise. Brain stimulation techniques have been proposed to improve neural plasticity and help to restore motor performance in post-stroke patients. The present study compared the effects of bihemispheric motor cortex transcranial direct current stimulation (tDCS) on PT and force steadiness during maximal and submaximal resistance exercise performed by post-stroke patients vs. healthy controls. A double-blind randomized crossover controlled trial (identification number: TCTR20151112001; URL: http://www.clinicaltrials.in.th/) was conducted involving nine healthy and 10 post-stroke hemiparetic individuals who received either tDCS (2 mA) or sham stimulus upon the motor cortex for 20 min. PT and force steadiness (reflected by the coefficient of variation (CV) of muscular torque) were assessed during unilateral knee extension and flexion at maximal and submaximal workloads (1 set of 3 repetitions at 100% PT and 2 sets of 10 repetitions at 50% PT, respectively). No significant change in PT was observed in post-stroke and healthy subjects. Force steadiness during knee extension (~25–35%, P < 0.001) and flexion (~22–33%, P < 0.001) improved after tDCS compared to the sham condition in post-stroke patients, but improved only during knee extension (~13–27%, P < 0.001) in healthy controls. These results suggest that tDCS may improve force steadiness, but not PT in post-stroke hemiparetic patients, which might be relevant in the context of motor rehabilitation programs.

This study compared acute responses of systolic and diastolic blood pressure (SBP/DBP), cardiac output (Q), heart rate (HR), stroke volume (SV), total peripheral resistance (TPR) and rate of perceived exertion (RPE) during resistance exercise performed continuously and discontinuously. Hemodynamic responses and RPE were assessed in the last of 4 sets of 12 repetitions of the knee extension with load corresponding to 70% of 12 repetition maximum, performed continuously (C) or discontinuously, with pauses of 5 s (D5) or 10 s (D10) interspersed in the middle of sets. The increase in SBP was higher for D10 (34.0±8.4%) and D5 (34.1±13.2%) vs. C (19.8±10.3%; P<0.001), while no difference was detected for DBP. Q (P=0.03) and SV (P=0.02) were higher, but HR was lower (P=0.04) in discontinuous vs. continuous. TPR remained stable during continuous, but significant decreases occurred during the pauses in the discontinuous protocols (P<0.001). The BP was higher in discontinuous than in continuous protocols, but the RPE was attenuated in discontinuous compared to continuous exercise. In conclusion, hemodynamic responses were exacerbated during resistance exercise performed discontinuously, but the perceived exertion was lowered.

No abstract

Prior research about the effects of the amount of exercised muscle mass upon cardiovascular responses (CVR) has neglected a potential bias related to total exercise and concentric/eccentric duration. Autonomic responses and perceived exertion (RPE) were compared in resistance exercises performed with larger and smaller muscle mass and matched for total exercise and concentric/eccentric duration. Twelve men performed 4 sets of 12 repetitions of unilateral (UNI) and bilateral (BIL) knee extensions at 70% of 12RM. Increases in CVR were always greater at the last set of BIL over UNI, as were SBP (35% vs. 23%), DBP (36% vs. 23%), HR (40% vs. 26%), RRP (90% vs 53%) and CO (55% vs 39%). No difference between protocols was found for autonomic modulation before and after exercise, but BIL induced significantly greater changes than UNI from baseline for R-R intervals (-13% vs. -7%), SDNN (-38% vs. -17%) and rMSSD (-41% vs. -21%). The rate of perceived exertion in the last set was higher in BIL than UNI (7.6±0.5 vs. 6.6±1.4 OMNI-RES; P<0.05) and did not correlate with any CVR. Thus, CVR were greater in resistance exercise performed with larger than smaller muscle mass. This information is relevant for patients with high cardiovascular risk.

Volume 12, número 4, outubro-dezembro/2013 99 ResumoEvidências indicam que reduções crônicas na pressão arterial (PA) provocadas por exercício físico dependem, em grande medida, da capacidade de se induzir após cada sessão de treinamento o fenômeno da hipotensão pós-exercício (HPE). A presente revisão descreve artigos sobre contribuição do exercício aeróbio, de força e concorrente para a HPE, bem como apresenta possíveis mecanismos fisiológicos envolvidos. A ocorrência de HPE após diferentes tipos de exercício parece ser bem-aceita, tanto em indivíduos normotensos, quanto hipertensos. Contudo, a dose ótima de exercício aeróbio (ex.: relação entre intensidade, duração, modo de exercício e forma de execução) e de força (ex.: relação entre intensidade, volume e massa muscular envolvida) para maximizá-la permanece incerta. Dúvidas também persistem em relação aos diversos mecanismos fisiológicos envolvidos na HPE, que parecem ser diferentes no exercício aeróbio e de força. Destacam-se os mecanismos centrais e locais associados, respectivamente, à diminuição do débito cardíaco (DC) e resistência vascular periférica (RVP). Nesse sentido, os mecanismos envolvidos na HPE após o exercício aeróbio associar-se-iam tanto a fatores centrais (ex.: diminuição da atividade nervosa simpática), quanto a fatores periféricos (ex.: vasodilatação sustentada pela liberação de óxido nítrico, prostaglandinas e receptores da histamina). Na força, a HPE parece relacionarse, principalmente, com a diminuição do DC e a queda do volume sistólico, em resposta à menor perfusão miocárdica ocasionada pela maior compressão sequencial dos vasos. Descritores: Pressão arterial; Fisiologia cardiovascular; Exercício; Promoção da saúde. AbstractEvidence indicates that chronic reduction in blood pressure (BP) due to physical exercise depends on the acute decrease in BP after a training bout, phenomenon referred as post-

It has been proposed that fatigue during strength exercise is negatively influenced by prior proprioceptive neuromuscular facilitation (PNF) stretching. However, it is possible that the effects of PNF on muscle endurance are affected by stretching duration. This study investigated the influence of PNF on the number of repetitions of the leg curl exercise performed with multiple sets and submaximal load. Nineteen men (age 25 ± 1 years, weight 75.8 ± 4.2 kg, height 178.1 ± 3.8 cm, 10-repetition maximum [RM] 78.3 ± 6.9 kg) performed 4 sets of leg curl with 10RM load with and without previous PNF (3 sets of hip flexion either with knees extended or flexed, duration ~2.5 minutes). The total number of repetitions decreased along sets in both situations (38.6% in control and 41.0% in PNF sessions, p < 0.001). However, no difference between control and PNF was detected for the number of repetitions in each set (first set, p = 0.330; second set, p = 0.072; third set, p = 0.061; fourth set, p = 0.150). In conclusion, the number of repetitions performed in multiple sets of the leg curl was not decreased by prior PNF stretching. Therefore, it appears that a moderate level of PNF could be used before resistance exercise with a minimal negative effect.

Bernardes, WL, Montenegro, RA, Monteiro, WD, de Almeida Freire, R, Massaferri, R, and Farinatti, P. Optimizing a treadmill ramp protocol to evaluate aerobic capacity of hemiparetic poststroke patients. J Strength Cond Res 32(3): 876-884, 2018-A correct assessment of cardiopulmonary capacity is important for aerobic training within motor rehabilitation of poststroke hemiparetic patients (PSHPs). However, specific cardiopulmonary exercise testing (CPET) for these patients are scarce. We proposed adaptations in a protocol originally developed for PSHPs by Ovando et al. (CPET1). We hypothesized that our adapted protocol (CPET2) would improve the original test, by preventing early fatigue and increasing patients' peak performance. Eleven PSHPs (52 ± 14 years, 10 men) performed both protocols. CPET2 integrated changes in final speed (100-120% vs. 140% maximal speed in 10-m walking test), treadmill inclination (final inclination of 5 vs. 10%), and estimated test duration (10 vs. 8 minutes) to smooth the rate of workload increment of CPET1. Peak oxygen uptake (V[Combining Dot Above]O2peak) (20.3 ± 6.1 vs. 18.6 ± 5.0 ml·kg·min; p = 0.04), V[Combining Dot Above]O2 at gas exchange transition (V[Combining Dot Above]O2-GET) (11.5 ± 2.9 vs. 9.8 ± 2.0 ml·kg·min; p = 0.04), and time to exhaustion (10 ± 3 vs. 6 ± 2 minutes; p < 0.001) were higher in CPET2 than in CPET1. Slopes and intercepts of regressions describing relationships between V[Combining Dot Above]O2 vs. workload, heart rate vs. workload, and V[Combining Dot Above]O2 vs. heart rate were similar between CPETs. However, standard errors of estimates obtained for regressions between heart rate vs. workload (3.0 ± 1.3 vs. 3.8 ± 1.0 b·min; p = 0.004) and V[Combining Dot Above]O2 vs. heart rate (6.0 ± 2.1 vs. 4.8 ± 2.4 ml·kg·min; p = 0.05) were lower in CPET2 than in CPET1. In conclusion, the present adaptations in Ovando's CPET protocol increased exercise tolerance of PSHPs, eliciting higher V[Combining Dot Above]O2peak and V[Combining Dot Above]O2-GET, preventing earlier fatigue, and providing better physiological relationships along submaximal workloads.