The positive or concentric part of the movement is where your muscles contract, typically driving the weight up. The negative or eccentric part of the movement is where your muscles relax, lowering the weight back down. On a bicep curl, the concentric is when the bicep contracts, bringing the weight up from hanging by your hips to being by your chest. On any chest press movement, regardless of if you are laying on a bench or pushing up off the ground, the concentric pushes your arms out in front of you and the eccentric lowers them back down until your hands are by the sides of your chest.
While there are debates in the bodybuilding world about whether a full range of motion on each exercise is absolutely required to maximally stimulate hypertrophy, there is a lot less debate about the importance of the eccentric part of every movement. Studies have repeatedly shown that the stretched or lengthened position of a muscle while under load is the most hypertrophic part of a movement. That means that a greater hypertrophic yield will come from lowering the weights down than from pushing them back up. One study tested participants by weighted stretching alone, showing that calf muscles grew over time from just having stretched the calf muscle under weight.
Change how you think about a rep
We typically think of one rep as the one time we push the weight up. On a push up, we count “one” when we go from the ground to a plank position. On a squat, we count one when we go from squatting to fully erect. On a pullup, we go from hanging to bringing our chin up over the bar. Because fighting gravity by pushing or pulling a weight up is hard, we naturally think of that as the movement in an exercise.
Instead, think of the negative as the main part of the exercise. Count the eccentric as the rep rather than the concentric. A single rep should include bringing the weight down slowly and under control, and then bringing the weight up in an explosive movement to start your eccentric again. Don’t count your push up as “one” when you go up, instead count it when you slowly bring your chest back down to the ground. The intent of pushing yourself off the ground in a pushup changes from being the main part of the exercise to being the reset you perform before you start your negative again. This means that when you do a set, the last rep you complete should end on a slow and controlled negative (as if you were to do another rep) before you rerack the weights.
More commonly you see people simply drop their weights down when they complete the last concentric part of their rep on a set. Even worse, you often see people essentially let gravity take over and let the weights fall back down on every rep, even the first one. You need to milk the eccentric part of the movement on every rep to maximize the stimulus your muscles receive during the workout and you should do that by controlling the weight and slowly lowering it down.
Slow and controlled
Returning to pushups, when you lower your body towards the floor, your pecs and your triceps are getting stretched under weight. Remember, weighted stretching alone has been proven to stimulate hypertrophy and the eccentric part of the movement is the most hypertrophic part. As you lower yourself, the pecs and triceps have to release their muscular contraction while still holding weight up against gravity until they get to their maximally stretched position of the exercise when your chest is touching the floor without resting your bodyweight.
On every rep of every exercise, your eccentrics need to be slow and controlled. You need to milk the negative for all its got. Don’t let gravity take over and plop yourself or your weight down. You risk injury, especially with movements like squats, and you miss out on the most important part of every rep. Control the weight and focus on the weighted stretch as you lower in the negative. Take a one second pause at the bottom to allow your target muscle to experience its fully stretched position under weight before bringing the weight back up in a nice explosive concentric.
If you implement this technique, you will notice that your rep ranges get significantly reduced for the same weight you used to be able to do and if you want to do the same number of reps, you’ll have to lower your weight selection. If you could do 10 pushups of the more common variety where you quickly pump out reach rep while letting your body fall down under the pull of gravity, you will probably not be able to hit that 10th rep when you take the negative under control and lower yourself slowly.
This is a good thing. You were cheating before and missing out on a lot of gains. Having to lower your weights or your reps to incorporate this technique will increase your gains in comparison to sticking with heavier weights and looser form because the hypertrophic stimulus is significantly greater, even with lower weights, when you slow down the eccentric and focus on maximizing muscular loaded stretching. Remember that your intent in the gym is not to lift the heaviest weight that you can physically lift, but to maximally stimulate your muscles to grow. That means that you have to take a bit of a hit to your ego in order to get the gains.
This should be your new standard. Every rep should look the same and be done at the same tempo. When you track your reps week-to-week, you can then be certain that an increase of one rep is a legitimate increase of one rep - a rep that was hard, a rep that was controlled, a rep that was done with good technique - and your progressive overload goals will have been achieved.
P.S. “Can’t I just stretch and gain muscle?” You can, but let’s not fool ourselves. The study that showed calf growth due to weighted stretching was using extremely heavy weights and the calves were stretched for a very long time. Think painful. If you’re doing only stretching, you’re also missing out on a lot of gains. There’s a whole lot more hypertrophic stimulus to experience in the rest of that full range of motion for an exercise. The fact that weighted stretching is effective at growing muscle should simply inform us on how to maximize the stimulus we send to our body with every rep.