This blog highlights a research paper published 25 years ago (Acta Physiol Scand 1990, 138, 263-271) entitled “Force and EMG signal patterns during repeated bouts of concentric or eccentric muscle actions” Drs. Tesch, Karolinska Institute and founder of nHANCE, and late Gary Dudley at NASA’s Kennedy Space Center. They had subjects perform 3 sets x 30 maximal either concentric (CON) or eccentric (ECC) actions using isokinetics (cinstant speed, no deceleration or acceleration). As expected there was marked muscle fatigue and force loss with CON actions, but and although force was much greater for ECC actions, there was NO fatigue whatsoever with ECC actions!
Why is this? As EMG activity increased with CON but not with ECC, the muscle failure in CON actions was clearly peripheral in origin. Thus, despite increased neural input, that was not sufficient to drive the muscle.
In case of ECC actions, it tells us that there are a large number of motor units that are not driving at full speed!
One of the most significant effects, of high-quality ECC training is ability to involve all motor units firing at their maximal frequency!
Then there will be fatigue noted even with ECC actions! A good sign!