Emphasizing eccentric actions is an excellent way to improve muscular strength and hypertrophy. The eccentric phase, or an eccentric action/movement is a controlled lengthening of a muscle as opposed to a controlled contraction, which is a concentric action. For example, take the bench press exercise: when I bring the bar from start position down toward my chest, I am performing eccentric action in my pectoralis and triceps. The movement is being driven by a controlled lengthening of the aforementioned muscles. Basically, an eccentric action is the negative work phase of any given movement such as the down phase of a squat, the arm extension phase of a cable row, or the lowering of a bicep curl.
Tremendous improvements in strength and hypertrophy can be made by increasing the resistance or time under tension for the eccentric phase. Studies have shown that a lifter can handle up to 20-60% greater loads in eccentric movements as compared with concentric (1). This can be used to a lifters advantage. Since varying exercise intensity is a great way to improve strength, the supra-maximal for eccentric movements can be added into a program to help increase muscle size and strength (2). Furthermore, adding emphasis to the eccentric phase of training may result in less neurological fatigue and central nervous system (CNS) exhaustion. Researchers have found that similar force loads result in lower levels of neural activation for the eccentric phase as opposed to the concentric (3). Thus either higher loads with similar neural fatigue levels can be used or similar loads with less fatigue if the eccentric phase is emphasized
There are a number of ways that we can utilize these eccentric training modes. The first and probably easiest is to simply exaggerate the duration of the eccentric phase by dragging it out for 4-6 seconds. Another way is to overload the resistance to a supra-maximal level and then control the negative phase. This would best be done with a spotter since it would be impossible to press a or squat out of a supra-maximal load. At the Rack, we have eccentric training hooks which detach from the bar at the bottom of a movement allowing extra resistance to be lifted in a safe manner.
In summary, if you want to see improvements in your size and strength while not overtaxing your nervous system, give extra focus to eccentric actions and reap the benefits.
Hollander DB, Kraemer RR, et. al. Maximal Eccentric and Concentric Strength Discrepancies Between Young Men and Women for Dynamic Resistance. Journal of Strength and Conditioning Exercise Research. 21: 34-40. 2007.
Colliander EB and Tesch PA. Effects of Eccentric and Concentric Musle Actions in Resistance Training. Acta Physiologica Scandinavia. 140: 31-39. 1990.
Seger JY and Thornstein A. Effects of Eccentric vs. Concentric Training of Thigh Muscle Strength and EMG. International Journal of Sports Medicine, 26: 45-52. 2005.