Muscular contractions can be broken down into different segments. There is the concentric muscle action, the shortening of the muscle by reducing the distance between the two ends of the muscle; the eccentric muscle action, the lengthening of the muscle by increasing the distance between the two ends of the muscle (If incorporating plyometrics there’s also the amortization phase which is the isometric period between the eccentric and concentric movement). Most general movements in the gym have both a concentric and eccentric component to their movements, but understanding how to better utilize the eccentric portion of the lift can tremendously impact your muscular growth and improve your strength. Mechanical tension and high motor unit recruitment are two important factors that are necessary to improve muscular hypertrophy and strength. Muscles possess both active and passive elements that respond differently to mechanical tension, which, in turn, cause different levels of motor unit recruitment. The active elements include contractile units like actin and myosin filaments, these bind together during concentric movements, and the passive elements include sarcomeres and connective tissue that surround the contractile elements, these stretch during eccentric movements.
When you create a concentric action, the motor units controlling muscles activate to bind the actin and myosin filaments. This creates a bulging of the muscle and, eventually, leads to increase in muscle diameter. During the eccentric movement, the contractile elements unbind and the passive elements of the muscle will stretch, which leads to increases in muscle length. This is why eccentric training has become a staple in flexibility training because your ultimate goal is to increase the capacity for the muscle to lengthen. The combination of the active and passive elements allows you to utilize more weight during eccentrics than you can generally use for concentric actions, research has shown this to be 100-120% of 1RM. This sounds amazing right? But how should you incorporate them into your training?
The table below will outline some of the methods you can use to implement eccentric training into your workouts. Utilizing time under tension, your goal is to control the lowering portion of the movement, but always maximum effort during the concentric. Voluntarily slowing the concentric portion of the movement reduces the high threshold motor unit activation and ultimately hinders hypertrophy and force production. You want to rest at least 60 seconds between sets (will vary depending on the intensity), this will allow for adequate recovery before the next bout of work.
Eccentrics have use further than these scenarios that I outlined, especially in the realms of flexibility and physical therapy, but these are great ways to incorporate them. They are a prominent phase of every muscular contraction and have a great deal of carry over into other training avenues. It is important to remember that utilizing slow eccentrics are effective because of the combination of active and passive units. If you attempt to use slow concentrics, you will not activate the necessary muscle fibers to elicit hypertrophy/improvements. If you’ve been feeling as though you have plateaued in your training or progress, utilizing eccentrics can greatly benefit you in your continued development.
