Research shows significantly greater hypertrophy when a weight is lowered at 4 seconds compared to 1 second. However, follow-up research shows that there are no differences in growth between 2 versus 4 second eccentric actions. When reconciling the literature, it can be speculated that in a 1 second eccentric action, you’re allowing gravity to do most of the work, not the muscles. Alternatively, taking 2 seconds on the eccentric forces the muscle to lower the weight; prolonging the duration of the eccentric action thus has no further benefit. Take home: You don’t need to count the timing of your eccentric actions; just make sure you lower slowly enough so that the muscles are doing the work, not gravity.

Keisuke Shibata, KauZuki TakiZawa, KaZunobu Nosaka, Masao MiZuno