There are three types of muscular contractions: concentric, isometric, and eccentric. Concentric refers to the work or positive phase, in which the muscle shortens to pull the insertion towards the origin. This is typically the “up” part of an exercise, such as when you push the bar away from your chest in a bench press. Isometric refers to the neutral phase when the muscle length does not change and a position is held, such as in a plank, wall sit, or holding a barbell in the middle of a curl. Eccentric refers to the return or negative phase of an exercise, when you are lowering the weight back towards its starting position. This deceleration stage is one in which a great deal of strength is developed, and focusing on it can create boosts in overall force production.
This focus is achieved by performing Slow Negative Reps. Consider a typical lifting tempo to be 2-1-4, in which you move through the concentric phase for a two count, hold the weight at the top of the movement for a one count, and then return to weight to the start of the movement for a four count. If you simply double the eccentric phase—aiming for an eight count (or more, if you wish)—you will be building muscular strength as the control required during this phase to keep the weight from accelerating becomes the focus. Bodybuilders will often “cheat” near the end of a set, accepting assistance from a partner to help move the weight through the positive phase while letting themselves alone focus on the negative phase. That said, it is highly recommended to use a spotter at all times, especially when focusing on slow negative reps.
A great example of employing negative repetitions is with the push-up, especially for those individuals who can only complete a modified push-up in which their knees maintain contact with the floor. Starting at the top of a traditional push-up (knees off the floor), slowing lower yourself downward while counting backwards from 10, taking the full time of the countdown to move from the top position to the bottom position before pushing yourself back up. If you cannot get up from the bottom, that is okay; use your legs if necessary to climb back up to the top position, and lower yourself again. Not only will this improve strength in your chest, shoulders, and arm muscles, but it will get you closer to completing full push-ups than modified push-ups ever will!
Negative Reps training can be applied to any exercise, but it cannot be stressed enough how important a spotter is. In the above example with push-ups, there is no risk of dropping weight on yourself, but if you apply this method with free weights, a spotter is essential to ensure your own safety. Apply negative reps either at the end of your last set of an exercise or even as your lifting tempo throughout the set, and see your strength explode!