Подскажите, пожалуйста. Наткнулся на такой отрывок.

In a recent study, different types of muscular contractions were used in order to study responses of collagen synthesis. Both concentric and eccentric contractions[b][u] were performed in two different experimental groups. When performing eccentric contractions, the loading of both muscle and tendon was higher than with concentric contractions, whereas strain was not assumed to be different to a major degree in the two situations.

Речь идет о влиянии сокращений мышц на синтез коллагена (и рост сухожилий). Что это за упражнения? Насколько я понял, роясь в Интернете, "eccentric exercise" - это вроде бы упражнения с отягощениями, а насчет "concentric" что-то даже мыслей никаких нет.
Кто-нибудь знает, как это по-русски?

Виноват, немного не тот отрывок привел. Здесь сокращения (contractions), но дальше есть упражнения:

Although this suggests a potential coupling of signaling to the myofiber that involves activation of the collagen-rich tissue within the muscle, it has to be stated that performing even more heavy eccentric exercise in association with electrical stimulation can result in a marked degree of myofiber injury and this will cause an even more pronounced activation of the satellite cells.