When discussing muscle physiology, there are 3 types of contractions – concentric, isometric, and eccentric. Concentric contractions are when the muscle shortens in length, isometric contractions are when the muscle does not change length, and eccentric contractions are when a muscle lengthens. Eccentrics are also called negatives. These can be absolutely fantastic for muscle hypertrophy and strength as you are technically stronger when going from a shortened muscle length position to a lengthened position.
For instance, let’s say my 1 rep max is 405 pounds (15 years ago…). If I were to load up 425 on the bench press, I should be able to lower that weight down to my chest under control with a 3-5 second eccentric phase. Now there is a certain threshold in which the weight can become excessive, and it would just crash to my chest, but I should be able to handle 425 relatively well considering it is roughly 5% above my 1 rep max. Bench pressing like this is going to do a couple things. 1 – it’s going to cause more “tearing” of the muscle fibers on a microscopic level. The whole point of resistance training is tearing muscle fibers and allowing them to recover bigger and stronger. 2 – overloading helps you to adapt and get comfortable with such heavier loads from a nervous system standpoint. Eventually, this adaptation will carry over to the next time you attempt your normal 1 rep max. At this time, 405 should not feel like 405, it should almost feel lighter. 3 – using a slower cadence such as a 5 second eccentric will help identify weak points in the movement as well as help strengthen synergistic muscles and smaller stabilizer muscles. When you strengthen weak points, it’s going to make you stronger overall in the long run.
Now this is all well and good for some one trying to attempt a 1 rep max, but what about a patient that we are rehabilitating from an injury? Well, it works the same exact way. Very often, we find some form of muscular imbalance associated with an injury, if not, the main source of pain itself. Therefore, we must strengthen muscles that may be weak. To quote Dr. Kathy Dooley, “slow is smooth and smooth is fast”. So, using eccentrics are a phenomenal way to build some muscle strength following an injury, build some conditioning for specific movement patterns, or build some muscular endurance. Or if you just want to suffer while working out, do a few sets of exercises with a 5 second eccentric phase. You WILL BE SORE. Don’t say I didn’t warn you though.