Your muscles contract in 3 different ways—here’s why that matters when you work out

When you take a muscle through the full range of motion, it goes through three phases of muscle contraction: eccentric, isometric, and concentric. Placing more attention on one phase can yield different results, it all depends on what you’re training for.

For starters, what does any of that mean? Blink Fitness program manager Phil Timmons explains that eccentric is when your muscle is lengthening, concentric when the muscle is shortening, and isometric is when the muscle is contracting without moving (like when you’re in barre and shaking while holding at the bottom of a plié).

“You can perform all of these in one exercise, such as an arm curl or bicep curl,” Timmons says. “As you are curling the weight up and bending the elbow it is a concentric movement. While holding the curl at the top with elbow bent for several seconds it’s isometric and while lowering the weight back down and straitening your arm it’s eccentric.”

You always want to train first eccentrically, then isometrically, and finally, concentrically.

Rondel King, MS, exercise physiologist at the NYU Langone Sports Performance Center, explains that to safely build strength in a move (whether you’re just starting off or looking to increase the weight your lifting) you always want to train first eccentrically, then isometrically, and finally, concentrically. In this order, King says you’ll protect your joints and learn to accept force efficiently, transition that force efficiently, and then be explosive. You’ll inevitably move through all of these phases— what King wants you to do is switch up the amount of time you spend in certain phases.

Imagine you’re squatting. As you sit low your hamstrings are lengthening, or, contracting eccentrically. This is the part you want to work first.

“For instance, if you’re doing a goblet squat, you can count six seconds from top to bottom,” King says. “So what you’re doing, you’re essentially training those muscles to accept the high level of load for an extended period of time, as you descend into that squat at a six second count from the top to the bottom. So you’re working on controlling that weight eccentrically.”

Learn to accept force efficiently, transition that force efficiently, and then be explosive.

This may seem counterintuitive. The hard part is never going down, it’s coming up. But, when working eccentrically, King says you’re building the strength and control needed to execute the concentric phase (standing back up).  It’s during this phase that you damage the muscle, which is actually a good thing, King explains.

“It actually causes micro tears,” King says. “Essentially, you can develop more, bigger muscle fibers because of that damage.”

However, because of the damage you’re doing, Timmons adds that working this phase can cause more soreness.

Next, comes the isometric phase. King refers to this as the transition phase between eccentric and concentric, where the muscle isn’t lengthening, nor shortening. He says you want this phase to be quick and efficient. Continuing with our squat example, you can train this phase pausing at any point in the range of motion.

“It will essentially, get your neuromuscular system used to being or used to that particular zone,” King says.

Timmons adds that working in this phase also leads more to sculpting your muscle than growing your muscle.

Once you’ve got those phases down, you can move on to the concentric phase. King explains that this is where you work on your explosiveness.

“You would descend into that position, and then you go through an isometric phase as quickly as you can as soon as you get to the bottom of your squat, and then you can explode out of that position,” King says. “So you’re working on more of the contractility of the muscle and the generating a lot of force.

Eliminating the eccentric phase, just training power, may lead to less soreness.

When you see someone performing just the pick up, or concentric phase, of a deadlift, and then drop the weight down, it’s because they’re just training concentrically. King explains that because they’re eliminating the eccentric phase, they’re just training power, which he says may lead to less soreness. If the muscles know how to work the eccentric and isometric, he says this a fine way to train if power is your goal, but, you should never over work in once phase.

Timmons says that mixing up the tempo through the different phases can also help when you’re hitting plateaus in your results. Both Timmons and King say working through all three of these contractions is key

“You never want to train one fitness quality, or one muscle contraction quality, excessively,” King says. “You work on that quality to make your transition from eccentric to isometric to concentric, as efficient as you can, and it will overall make you a healthier athlete and a healthier person overall.”

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