Does rest interval between unilateral exercise protocols influences on contralateral neuromuscular responses in untrained individuals?

INTRODUCTION: Effects on strength performance and muscle activation in the contralateral limb have been observed after training with the ipsilateral limb (IL). Cross fatigue effects in the contralateral limb (CL) can occur at intervals of up to 48 h after a training session performed with the ipsilateral limb. The objective of this study was to verify the effect of a training session in the ipsilateral limb, on the strength and activation of the muscles in the contralateral limb also submitted to the training protocol. METHODS: 10 untrained men (mean ± SD: age = 23.7 ± 4.9 years) performed unilateral knee extension with both limbs in equated protocols, in two conditions with different intervals between limbs - 20 min and 24 h. RESULTS: There were no differences in the comparison of the force produced between the pre x post interventions with the CL limb, as well as in the activation of the quadriceps during its performance. These results were similar for the two different intervals between the protocols. CONCLUSION: It was concluded that when the CL member performs the protocol after the IL, the responses in the CL depend mainly on the requirement imposed on the protocol performed by this member, without influence of the training protocol performed previously with the IL member.

Similar Inflammatory Adaptation in Women following 10 Weeks of Two Equalized Resistance Training with Different Muscle Action Duration.

This study is aimed at evaluating the profile of inflammatory markers and components of redox regulation in untrained women after 10 weeks of resistance training using equalized protocols but different muscle action duration (MAD). Twenty-two women underwent progressive resistance training exercising the knee extensor muscles for 10 weeks-3x/week, with 3-5 sets of 6 repetitions at 50% of the 1 repetition maximum strength test (1RM), with a rest of 180 s between the series, following the training protocol (i) 5 s of concentric muscle action for 1 s of eccentric muscle action (5C-1E) and (ii) 1 s of concentric muscle action for 5 s of eccentric muscle action (1C-5E). Quadriceps muscle hypertrophy maximum strength (1RM) and redox regulation/muscle damage/inflammatory markers (CAT, SOD, TBARS, FRAP, CH, LDH, CXCL8, and CCL2) were evaluated. Plasma markers were evaluated before and 30 minutes after the first and last training sessions. A similar gain in hypertrophy and maximum strength was observed in both groups. However, in the 5C-1E, a significant major effect was observed for SOD (F 1.19 = 10.480, p = 0.004) and a significant major time effect, with a reduction in the last training session, was observed for CXCL8 (F 1.37 = 27.440, p < 0.001). In conclusion, similar protocols of resistance training, with different MAD, produced similar inflammatory and adaptive responses to strength training. As the training load is progressive, the maintenance of this inflammatory and redox regulation profile suggests an adaptive response to the proposed strength training.

Resistance training intervention performed with different muscle action durations influences the maximal dynamic strength without promoting joint-angle specific strength gains.

The present study investigated the effect of 10-week matched (range of motion, volume, intensity, rest, and repetition duration) training protocols with varying muscle action duration (MAD) on maximal voluntary isometric contraction (MVIC) test at eight different knee angles and one-repetition maximum (1RM) test after in seated knee extensor machine. Forty women were allocated into one control and three training groups with varying MAD: 5C1E (5s concentric action [CON] and 1s eccentric action [ECC]), 3C3E (3s CON and 3s ECC), and 1C5E (1s CON and 5s ECC). All training groups (5C1E, 3C3E, and 1C5E) showed a greater relative response in 1RM performance than the control group (0.1 ± 3.5%, p ≤ 0.05). The 1C5E group presented greater relative increases in the 1RM performance (22.1 ± 11.6%) compared to 5C1E (13.6 ± 9.2%; p ≤ 0.05) and 3C3E (14.1 ± 5.5%, p ≤ 0.05) groups. The training groups increased the MVIC performance more than the control group (p ≤ 0.05), although there were no significant differences between the training groups. This study demonstrated that isoinertial resistance training protocols with shorter CON MAD showed greater maximum dynamic strength performance response than matched training protocols with other MAD configurations. However, the configuration of MAD did not induce angle-specificity to increase the maximum isometric strength.

Resistance training with different repetition duration to failure: effect on hypertrophy, strength and muscle activation.

BACKGROUND: This study investigated the effects of two 14-week resistance training protocols with different repetition duration (RD) performed to muscle failure (MF) on gains in strength and muscle hypertrophy as well as on normalized electromyographic (EMG) amplitude and force-angle relationships. METHODS: The left and right legs of ten untrained males were assigned to either one of the two protocols (2-s or 6-s RD) incorporating unilateral knee extension exercise. Both protocols were performed with 3-4 sets, 50-60% of the one-repetition maximum (1RM), and 3 min rest. Rectus femoris and vastus lateralis cross-sectional areas (CSA), maximal voluntary isometric contraction (MVIC) at 30o and 90o of knee flexion and 1RM performance were assessed before and after the training period. In addition, normalized EMG amplitude-angle and force-angle relationships were assessed in the 6th and 39th experimental sessions. RESULTS: The 6-s RD protocol induced larger gains in MVIC at 30o of knee angle measurement than the 2-s RD protocol. Increases in MVIC at 90o of knee angle, 1RM, rectus femoris and vastus lateralis CSA were not significant between the 2-s and 6-s RD protocols. Moreover, different normalized EMG amplitude-angle and force-angle values were detected between protocols over most of the angles analyzed. CONCLUSION: Performing longer RD could be a more appropriate strategy to provide greater gains in isometric maximal muscle strength at shortened knee positions. However, similar maximum dynamic strength and muscle hypertrophy gains would be provided by protocols with different RD.

Acute physiological responses with varying load or time under tension during a squat exercise: A randomized cross-over design.

OBJECTIVES: Despite advancements in resistance training (RT) methods, the acute metabolic and neuromuscular responses to time under tension (TUT) and load remains poorly understood. The aim of the present study was to investigate how TUT or resistance load impact muscular activation and blood lactate during an RT session. DESIGN: A randomized cross-over design. METHODS: Participants performed a squat exercise in three different conditions: baseline protocol (BPRO; three sets of eight repetitions with four second repetitions at 60% of 1RM) long duration protocol (LDPRO: six second repetitions) and high load protocol (HLPRO: 70% 1RM). RESULTS: Muscular activation of the vastus lateralis and biceps femoris, and blood lactate were assessed. Blood lactate was ∼19% and ∼26% higher after set one and three in LDPRO compared to BPRO (P≤0.011) and ∼17% higher for LDPRO compared to HLPRO (P=0.002). Additionally, blood lactate was ∼17% higher for HLPRO compared to BPRO after the third set of exercise (P=0.003). Vastus lateralis activation was ∼10% higher for HLPRO compared to BPRO and LDPRO for sets one and two. Biceps femoris activation was ∼17% higher for HLPRO compared to BPRO for set one (P= 0.023) while for set two HLPRO was greater than BPRO and LDPRO (∼19% and ∼14%, respectively; P≤0.007). CONCLUSIONS: Squatting with higher TUT caused a greater impact on the metabolic responses than lower TUT or higher loads, whereas an increase in training load resulted in greater muscle activation than higher TUT or lower training load.

Repetitions to failure increase pectoralis major activation with similar neuromuscular fatigue in trained men / Repetições até a falha aumentam a ativação do peitoral maior com similar fadiga neuromuscular em homens treinados

ABSTRACT Resistance training protocols performed to muscle failure (MF) have been employed in an attempt to maximize activation and neuromuscular fatigue. Therefore, the aim of this study was to compare the surface electromyography amplitude (EMGRMS) and frequency (EMGFREQ) of the pectoralis major between protocols performed to MF and non muscle failure (NMF). Seven trained men performed three sets at 60% of a repetition maximum, with a 3 min rest period and a 6s repetition duration. MF protocol was performing with maximum number of repetitions in all sets, while in NMF protocol subjects performed 6 repetitions in 3 sets. For data analysis two two-way repeated measures ANOVAs (Protocol x Repetition) were used and when necessary, Bonferroni post hoc was performed. The EMGRMS was higher in the protocol MF compare to NMF, but there was no difference in EMGFREQ between protocols. Although there were no significant differences in the frequency domain between protocols, perform repetitions to MF was a determining factor to generate higher amplitude of the electromyography signal. Thus, perform repetitions to MF could be considered an effective strategy to increase muscle activation in trained individuals, however, with similar neuromuscular fatigue.

RESUMO Protocolos de treinamento realizados até a falha muscular (FM) têm sido realizados na tentativa de maximizar a ativação e a fadiga neuromuscular. Portanto, o objetivo deste estudo foi comparar a amplitude do sinal eletromiografico (EMGRMS) e a frequência (EMGFREQ) do peitoral maior entre os protocolos realizados até a FM e sem falha muscular (SFM). Sete homens treinados realizaram três séries com 60% de uma repetição máxima, com um período de descanso de 3 min e uma duração da repetição de 6s. O protocolo FM foi realizado com o número máximo de repetições em todas as séries, enquanto no protocolo SFM os indivíduos realizaram 6 repetições em 3 séries. Para análise dos dados, foram utilizadas duas ANOVAs two-way com medidas repetidas (Protocolo x Repetição) e, quando necessário, foi realizado o post hoc de Bonferroni. Como resultado, a EMGRMS foi maior no protocolo FM comparado ao SFM, mas não houve diferença na EMGFREQ entre os protocolos. Embora não houvesse diferenças significativas no domínio da frequência entre os protocolos, a realização de repetições até a FM foi um fator determinante para gerar maior amplitude do sinal eletromiográfico. Assim, a realização de repetições até a FM pode ser considerada uma estratégia eficaz para aumentar a ativação muscular em indivíduos treinados, porém com fadiga neuromuscular semelhante.

Comparison of quadriceps muscle activation in exercises with different duration of concentric and eccentric contractions / Comparación de la activación muscular del cuádriceps en ejercicios con diferente duración de las contracciones concéntricas y excéntricas

AIM: The objective of the present study was to compare the amplitude of the electromyographic (EMG) signal of the quadriceps muscle portions vastus medialis (VM), vastus lateralis (VL) and rectus femoris (RF) and the activation ratio (VM/VL, VM/RF and VL/RF) in protocols with different durations of concentric and eccentric muscular actions. MATERIAL AND METHOD: Twelve female volunteers performed the knee extensor exercise with two different protocols [1s for concentric muscle action and 5s for eccentric muscle action (1:5); 5s of concentric muscle action and 1s of eccentric muscle action (5:1)] and 3 sets of 6 repetitions, 180s of pause between each sets and a intensity of 50% of 1RM. The root mean square of the amplitude of the normalized EMG signal was calculated for each repetition in each series. RESULTS: it was observed an increase in the activation of the VM and VL portions in equivalent repetitions of each series and for the VL portion, the 1: 5 protocol provided greater activation compared to the other protocol. No differences were found for muscles activation ratios VM/RF and VL/RF, being that for the VM/VL ratio there was only change at one repetition. CONCLUSION: The results suggest that the portions of the quadriceps muscle may present different EMG responses in similar protocols, but this fact may not interfere in the synergism between them. The reduced degrees of freedom of the knee extension exercise and the characteristics of the protocols adopted may be the elements that contributed to the limited alterations that occurred in the present study

OBJETIVO: El objetivo del presente estudio fue comparar la amplitud de la señal electromiográfica (EMG) de las porciones de músculo cuádriceps vasto medial (VM), vasto lateral (VL) y recto femoral (RF) y la relación de activación (VM/VL, VM/RF y VL/RF) en protocolos con diferentes duraciones de acciones musculares concéntricas y excéntricas. MATERIAL Y MÉTODO: Doce mujeres voluntarias realizaron el ejercicio extensor de rodilla con dos protocolos diferentes [1 s para la acción muscular concéntrica y 5 s para la acción muscular excéntrica (1: 5); 5s de acción muscular concéntrica y 1s de acción muscular excéntrica (5: 1)] y 3 series de 6 repeticiones, 180s de pausa entre cada serie y una intensidad del 50% de 1RM. La raíz media cuadrática de la amplitud de la señal electromiográfica normalizada se calculó para cada repetición en cada serie. RESULTADOS: se observó un aumento en la EMG de las porciones de VM y VL en repeticiones equivalentes de cada serie y para la porción de VL, el protocolo 1: 5 proporcionó una mayor activación en comparación con el otro protocolo. No se encontraron diferencias para las relaciones de activación de los músculos VM/RF y VL/RF, siendo que para la relación VM/VL solo hubo cambios en una repetición. CONCLUSIÓN: Los resultados sugieren que las partes del músculo del cuádriceps pueden presentar diferentes respuestas de EMG en protocolos similares, pero este hecho puede no interferir en el sinergismo entre ellos. Los grados reducidos de libertad del ejercicio de extensión de la rodilla y las características de los protocolos adoptados pueden ser los elementos que contribuyeron a las alteraciones limitadas que se produjeron en el presente estudio

The Effects of Altering the Concentric/Eccentric Phase Times on EMG Response, Lactate Accumulation and Work Completed When Training to Failure.

This study compared the electromyographic response, the blood lactate concentration (BLC), and the maximum number of repetitions (MNR) between protocols of different concentric/eccentric duration taken to muscle failure. This comparison may help to understand how different concentric/eccentric duration may influence performance and the central and metabolic responses in trained men. Seventeen strength-trained men performed two protocols in a counterbalanced design. Three sets of the Smith bench press exercise were performed to failure at 60% of the one-repetition maximum (1RM) using each protocol (4-s concentric/2-s eccentric [4 s: 2 s]; and 2-s concentric/4-s eccentric [2 s: 4 s]). The normalized root mean square (EMGRMS) and the mean frequency (EMGMF) of the electromyographic signals for the pectoralis major and the triceps brachii were compared in the first, middle, and last repetitions. The BLC was assessed at rest, during and after the test sessions. To compare the EMG and BLC, a 3-way ANOVA with repeated measures with a post hoc Tukey's test was used. To compare the MNR performed across the sets, an ANOVA-type rank test with the Dunn's post hoc test was used. The ANOVA indicated a greater EMGRMS for Protocol 4 s: 2 s in the pectoralis major and a lower EMGMF for Protocol 4 s: 2 s in the triceps brachii at the middle and last repetitions. Both protocols increased the EMGRMS and decreased the EMGMF across repetitions. Despite the results show different levels of activation and neuromuscular fatigue between protocols, the BLC and the MNR were similar.

The effect of 10 weeks of strength training on the electromyographic response of quadriceps portions / Efeito de 10 semanas de treinamento na resposta eletromiográfica das porções do quadríceps

Abstract This study investigate the effect of 10-week strenght training on the amplitude of the electromyographic (EMG) signal of vastus medialis, vastus lateralis and rectus Femoris. Twenty three untrained volunteers performed 3-5 sets (3 sets - weeks 1 and 2; 4 series - weeks 3 and 4; 5 series weeks 5 to 10) with 6 repetitions, intensity of 50% of 1 repetition maximum (1RM), 3 min rest between sets and 6 s repetition duration at the knee extensor exercise. One group (5:1) performed concentric action of 5 s and eccentric of 1 s and the other (3:3) performed concentric of 3 s and eccentric of 3 s. The VM, VL and RF EMG (RMS) activities were recorded in each repetition of the three series at the first training session and the first three series at the last session. The protocol 5:1 led to EMG reduction in all portions, with a greater number of repetitions presenting differences at the VL and RF. VM and RF presented similar results at Group 3:3. It was verified that all the differences occurred in the second half of the series. It was also verified differences in EMG ratios just in group 3:3 and only in VM/VL and VM/RF. These results suggest that the coordination was not affected when equivalent repetitions of series were compared. It was also suggested that these results were influenced by the reduced degrees of freedom of the exercise and the training load progression adopted.

Resumo Este estudo investigou o efeito de 10 semanas de treinamento de força na resposta eletromiográfica (EMG) do vasto medial, vasto lateral e reto femoral. 23 voluntárias executaram 3 a 5 séries de 6 repetições, intensidade de 50% de 1 repetição máxima (RM), 3 minutos de pausa entre as séries e duração da repetição de 6 s no exercício extensor de joelhos. Um grupo (5:1) realizou a duração da ação concêntrica em 5 s e excêntrica em 1s e outro grupo (3:3) realizou a concêntrica em 3s e a excêntrica em 3s. A atividades EMG (RMS) destas três porções do quadríceps foram registradas em cada repetição das 3 séries da primeira sessão de treinamento e nas três primeiras séries da última sessão. Os resultados mostraram diferenças na metade final das séries, sendo que no grupo 5:1 houve redução na EMG em todas as porções e o VL e o RF mostraram redução em um número maior de repetições. No grupo 3:3 o VM e o RF apresentaram redução. Para as relações de ativação entre as porções, diferenças foram identificadas apenas no grupo 3:3 nas relações VM/VL e VM/RF em um número reduzido de repetições. Estes resultados apontam que a coordenação entre as porções sofreu poucas alterações quando comparadas as repetições equivalentes de cada série. Sugere-se que os reduzidos graus de liberdade do movimento utilizado e a progressão da carga de treinamento tenham sido os fatores que conduziram a este resultado

Focus of attention and online demonstration effects on temporal error and muscle activation / Efeitos do foco de atenção e demonstração online no erro temporal e na ativação muscular

Abstract The purpose of the present study was to examine whether there would be performance differences between external and internal focus of attention conditions and an online demonstration condition, and if these differences would be observed at a neuromuscular level through EMG analysis, in addition to traditional outcome measures. We hypothesized that under the demonstration condition participants would perform better than under external and internal focus conditions. We also hypothesized that demonstration condition would show smaller EMG activity than external and internal focus conditions. Furthermore, we hope to replicate the benefits of external focus in relation to internal focus, both in outcome and product measures. Six male participants performed a bilateral leg extension under internal focus of attention, external focus of attention and online demonstration conditions. Muscular contractions goal times were set for concentric muscle action (4 seconds) and eccentric muscle action (2 seconds). An electrogoniometer was used to record muscular activation (production measures), and temporal error was used to observe performance (outcome measures). Results showed that online demonstration condition obtained better performance than external focus condition and a reduced muscular activation. However, differences between internal focus and the other experimental conditions were not found. These findings advance in the understanding mechanisms underpining the focus of attention, such as proposed by Constrained Action Hypothesis.

Resumo O objetivo do presente estudo foi avaliar as diferenças no desempenho entre as condições de foco de atenção externo e interno e uma condição de demonstração online. Adicionalmente, se essas diferenças seriam observadas em um nível neuromuscular por meio da análise EMG, além das medidas de resultados tradicionais. Foi levantada a hipótese que sob a condição de demonstração os participantes teriam um desempenho melhor do que sob as condições de foco externo e interno. Também foi levantado a hipótese que a condição de demonstração apresentaria menor atividade EMG do que as condições de foco externo e interno. Além disso, esperava-se corrobora os benefícios do foco externo em relação ao foco interno, tanto nas medidas de resultado quanto de produto. Seis participantes do sexo masculino realizaram uma extensão de perna bilateral nas condições: foco de atenção interno, foco de atenção externo e condições de demonstração online. Os tempos de meta de contrações musculares foram definidos para ação muscular concêntrica (4 segundos) e ação muscular excêntrica (2 segundos). Um eletrogoniômetro foi usado para registrar a ativação muscular (medidas de produção) e o erro temporal foi usado para observar o desempenho (medidas de resultado). Os resultados mostraram que a condição de demonstração online obteve melhor desempenho do que a condição de foco externo e uma ativação muscular reduzida. No entanto, não foram encontradas diferenças entre o foco interno e as outras condições experimentais. Esses achados avançam no entendimento dos mecanismos que sustentam o foco de atenção, como o proposto pela Constrained Action Hypothesis.

Effect of resistance exercise with different muscle action durations on lactate response / Efeito de protocolos de treinamento com diferentes durações das ações musculares na concentração de lactato sanguíneo

ABSTRACT The aim of this study was to compare the blood lactate concentration in strength training protocols with different muscle action durations in the bench press exercise. Seventeen volunteers performed three protocols with three sets of six repetitions at 60 % of 1RM, three- minute break between sets and different muscle action durations (2-4: 2s concentric and 4s eccentric; 3-3: 3s concentric and 3s eccentric; 4-2: 4s concentric and 2s eccentric). The analysis of blood lactate concentration considered the average values ​​per set in each protocol. The ANOVA two-way of the results showed that the main effect for protocol showed no significant difference between the three protocols (F = 0,75; p = 0,48; power = 0,48; η2 = 0,17), as the interaction among the factors (F = 1,68; p = 0,13; power = 0,09; η2= 0,62). However, there was significant main effect for set (F = 320,23; p = 0,0001; power = 1,00; η2= 0,95). Therefore, resistance training protocols equated with different muscle actions durations shows no differences in blood lactate response and, regardless of the protocol, its concentration increased throughout the three sets performed.

RESUMO O objetivo deste estudo foi comparar a concentração de lactato sanguíneo em protocolos de treinamento de força com diferentes durações das ações musculares no exercício supino. Dezessete voluntários executaram três protocolos com três séries de seis repetições a 60% de 1RM, pausa de três minutos entre as séries e diferentes durações das ações musculares (2-4: 2s concêntrica e 4s excêntrica; 3-3: 3s concêntrica e 3s excêntrica; 4-2: 4s concêntrica e 2s excêntrica). A análise da concentração de lactato sanguíneo considerou os valores médios por série em cada protocolo. Os resultados da ANOVA two-way mostraram que o efeito principal protocolo não apresentou diferença significante entre os três protocolos (F = 0,75; p = 0,48; poder = 0,48; η2 = 0,17), assim como para a interação entre os fatores (F = 1,68; p = 0,13; poder = 0,09; η2 = 0,62). Porém, houve diferença significante na concentração de lactato sanguíneo para o fator série (F = 320,23; p = 0,0001; poder = 1,00; η2 = 0,95). Portanto, protocolos de treinamento de força equiparados com durações das ações musculares distintas não apresentaram diferenças na resposta do lactato sanguíneo e, independentemente do protocolo, a concentração deste substrato aumentou ao longo das três séries realizadas.