Concentric vs. Eccentric Movement: What's the Difference?

When you're moving through a strength workout, it can be easy to zone out while completing rep after rep. But as it turns out—whether it's the down and up motion of a squat, or the lower and lift of a Pilates roll-up—each part of the exercise plays a distinct role. So while you absolutely get credit for showing up on your mat (seriously, great job!), understanding the different phases of your exercises can make a huge difference in your progress.

"In an exercise that involves a range of motion—not a static hold like a plank—the muscles undergo a shortening and lengthening phase," says fitness trainer BB Arrington, NASM-CPT. "The shortening phase is called the concentric phase, the lengthening or lowering phase is called the eccentric phase."

One of the best ways to picture concentric versus eccentric motion is to consider a biceps curl, says Arrington. "Lifting the weight up toward your shoulder is the concentric contraction, and lowering the weight back down to your side is the eccentric contraction."

In the concentric stage, your muscle is shortening, says Danielle Gray, NASM-CPT, and founder of Train Like a Gymnast. Some examples of this motion include pressing yourself off the ground during a pushup, standing up, and extending your arms overhead.

"While most people are focused on the concentric portion of an exercise, you can go the extra mile by being mindful in the eccentric phase and slowing this part down," says Arrington. Continuing with the biceps curl example, you may notice it's much easier to lower the weight than to lift it. "Because this part of the exercise is not as taxing, slowing down the rate at which you lower the weight is a way to increase the level of difficulty without any additional setup."

Eccentric movements are also thought to cause more muscle damage, says Gray, which is necessary for muscle building.

"Some people like to incorporate eccentric-only training," says Arrington, "or finish a set eccentrically, which is where they have a partner help lift the weight up and they lower the weight down with control."

For any type of resistance training, it's crucial to only lift what you can with correct form. "Oftentimes, I see gym-goers swinging the weights and using momentum so they 'lift more,'" says Gray. "This leads to joints being used incorrectly, which increases their potential for injury. Plus, she adds that lifting with proper form through the full range of motion will result in more even muscle damage and strength gains.

As for eccentric training specifically, it's imperative to engage your muscles as much as possible, says Arrington. "Oftentimes, when performing an eccentric movement, the client will do the minimum work possible to lower the weight, instead of contracting the muscle as much as possible to lower it down slowly and controlled."