Concentric strength training just as effective as eccentric strength training
When you're doing strength training, the eccentric and the concentric parts of your reps are equally important, according to a meta-study published by scientist and trainer Brad Schoenfeld [Website].
Schoenfeld tracked down 15 studies in which participants had done exclusively concentric or exclusively eccentric strength training. He collated the results and re-analysed them.
Exclusively concentric strength training means you only use your muscles to lift the weights up, and then you let gravity to the work to lower them. Exclusively eccentric strength training is the opposite of this. A helper or a machine raises the weights for you and you use your muscles to lower the weights in a controlled fashion.
Doing only concentric training resulted in an average muscle growth of 6.8 percent; doing only eccentric training resulted in muscle growth of 10 percent. The difference between the effectiveness of each type of strength training was borderline significant - so not quite statistically significant.
"Given the modest effect size difference between exclusively eccentric and concentric training, it appears that eccentric-only training likely provides a small advantage over concentric-only training for promoting a hypertrophic response; notwithstanding, both contraction modes can promote significant muscular hypertrophy," wrote Schoenfeld.
"Further research is required to clarify whether the benefit of eccentric training is related to the higher forces produced and ultimately total work completed relative to concentric-only training."
"This means [...] that the eccentric phase is an important part of a rep when you're looking for maximal muscle growth," according to the Dutch website EigenKracht.nl. [eigenkracht.nl 10 Aug. 17] "A normal, classically performed rep includes a concentric and an eccentric phase."
"If you perform complete reps, you'll be fine. Briefly, the advice is: explosive lifting and controlled lowering. [...] Not doing the eccentric part of the rep by letting gravity do the heavy work is counterproductive."
"For example letting the barbell bounce on your chest when you're doing bench presses is not advisable. Not only is the risk of injury much higher, but your reps are at least 50 percent less effective."
J Strength Cond Res. 2017 Sep;31(9):2599-608.
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