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 30^o and 90^o 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 6^th and 39^th experimental sessions.

Results

The 6-s RD protocol induced larger gains in MVIC at 30^o of knee angle measurement than the 2-s RD protocol. Increases in MVIC at 90^o 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.

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.

A realização do sistema supersérie com diferentes segmentos corporais não impacta no volume e percepção subjetiva de esforço

O objetivo do estudo foi comparar os sistemas tradicional(TRAD) e supersérie (SS) quanto ao número de repetições (volume) e percepção subjetiva de esforço (PSE) nos exercícios supino e extensão de joelhos. Doze homens treinados realizaram de forma randomizada (medidas repetidas) os protocolos em sistemas TRAD e SS (4 séries com pausas de 2 minutos, intensidade de 10 repetições máximas). No sistema SS, cada série do exercício banco extensor foi realizada durante a pausa do exercício supino. Não houve diferença significativa no volume (TRAD supino - série 1: 16,1 ± 1,6; série 2: 10,9 ± 2,1; série 3: 7,8 ± 2,3; série 4: 7,0 ± 2,0; TRAD extensão de joelhos – série 1: 13,1 ± 2,5; série 2: 11,0 ± 2,0; série 3: 9,1 ± 1,7; série 4: 7,6 ± 1,6; SS supino – série 1: 16,3 ± 2,3; série 2: 10,9 ± 1,6; série 3: 7,8 ± 1,9; série 4: 6,1 ± 1,4; SS extensão de joelhos – série 1: 13,8 ± 1,8; série 2: 11,2 ± 1,6; série 3: 8,8 ± 1,7; série 4: 7,0 ± 1,7) e na PSE (TRAD supino - mediana série 1: 15,0; medianasérie 4: 19,5; TRAD extensão de joelhos - mediana série 1: 17,0; mediana série 4: 19,5; SS supino - mediana série 1: 16,5; mediana série 4: 20,0; SS extensão de joelhos - mediana série 1: 17,5; mediana série 4: 19,5) entre os protocolos. Verificou-se redução do volume e aumento da PSE no decorrer das séries em ambas situações experimentais. Considerando a similaridade dos resultados obtidos entre os sistemas SS e TRAD, aaplicação de SS torna-se uma alternativa eficiente para a redução do tempo de treinamento.

The effect of 10 weeks of strength training on the electromyographic response of quadriceps portions

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.