Any time you lift weights you break down fibers in your muscles. The resulting healing and recovery of these muscle cells leads to the increase in size and strength. The common hypotheses is that by increasing (to a certain extent) the breakdown of these fibers you are able to increase the size and strength of the muscle once it heals.
Eccentrics have been shown to increase the damage or “shear” to the muscles more so than any other phase of a movement. Therefore as long as they are done correctly eccentrics have the potential to drastically increase hypertrophy (muscle size gain) compared to other training methods.
How to Implement
There are multiple ways to incorporate eccentrics into your resistance program, but all involve making the descending portion of an exercise slow. Below are the two most common methods.
When you see the tempo of an exercise designated it will appear as “@####” Each number represents the number of seconds a portion of the exercise will take. The order is eccentric, hold, concentric, hold. Or you can think of it as down-pause at the bottom- up- pause at the top. Here’s a quick video to help clear it up.
If you were doing pull-ups with an eccentric focus you might see something like, @5011. This means you would take 1 second to pull your chin over the bar and hold at the top for 1 second. Then you would try make the descent last 5 seconds taking no time at the bottom to pause before the next rep.
Sometimes referred to as “negatives,” another method for building strength using eccentrics is to use more weight than you can actually lift. You can produce greater force when lowering something than lifting it. This allows you to control weights on the way down that you cannot actually press back up.
A simple exercise like the dumbbell curl is a great example of this. To focus on overloading the movement with an eccentric focus grab a pair of dumbbells that are too heavy for you to normally lift. Instead of lifting them with just your arms perform a clean to get the dumbbells up. Then control the weights on the way down taking 3-4 seconds. With this method you skip the concentric portion of the lift focusing solely on the down portion.
As you try these out in your training be careful to start with just a few reps and when overloading only use slightly more weight than your can normally lift. These methods can greatly increase the soreness you will experience afterwards if done incorrectly.
Be safe and have fun trying these out!