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

Abstract

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.

Combination of Training to Failure and Non-Failure: An Unexplored Approach of Number of Repetitions, Rate of Perceived Exertion, Time Under Tension, Volume-Load, and Muscle Swelling in Trained Individuals

“…Consequently, fatigue accumulates across the sets, resulting in a decline in the number of repetitions and volume-load in each subsequent set. This significant reduction in repetitions performed until failure aligns with findings from other studies employing a two or even tree minutes rest period (35,36). Notably, fatigue accumulation triggers various physiological changes, including reductions in pH and energetic substrate availability (37).…”

Effect of Using Different Intensities in Resistance Training for Muscle Hypertrophy Gains—A Narrative Review

“…The analysis through magnetic resonance showed a significant increase in the CSA of the pectoralis major in all groups, especially in the group that trained 12RM. However, it was postulated that volume equalization could be ruled out with the level of hypertrophy, if there was a relationship with the type of fiber involved with the increase in CSA (41). Schoenfeld et al (55), verified the use of different intensities in the CSA of the muscles that make up the triceps surae (lateral gastrocnemius, medial gastrocnemius and soleus) in 30 healthy, untrained men.…”