Muscle Soreness, Explained


Muscle soreness after strenuous exercise is practically a given. Some exercisers seek it out, whereas others avoid it at all costs. No matter where you fall on the spectrum, you may be wondering what muscle soreness is, whether it’s good or bad and how to handle it.

You may have also heard the term “delayed onset muscle soreness,” which is commonly referred to as DOMS. This is the muscle soreness you experience 24–48 hours after exercise. When we talk about muscle soreness, we’re typically talking about DOMS.


Exercise of any kind acts as a stressor on your body. This stress isn’t necessarily a bad thing (we’ll get into bad stress later), but when the stress is new or more intense than usual, your body has to address it. Often, that response leads to muscle soreness.

Strength training, for example, breaks down the small proteins within your muscles, prompting your body to generate inflammatory proteins known as cytokines. “The inflammatory process does create some swelling locally at the muscular level, and that can sometimes lead to that feeling of tightness and soreness, along with the fact that the tissue itself is damaged,” says Heather Milton, MS, a certified strength and conditioning specialist and board-certified clinical exercise physiologist at NYU Langone’s Sports Performance Center.

Similarly, repetitive cardio exercises like running can create micro-tears, or breakage in muscle tissues, if you’re new to the sport, increase mileage or intensity or jump back into training after an extended break. “What we’re actually doing every time our foot lands is we’re trying to decelerate to keep our body from collapsing or you’re controlling the rate at which your muscles lengthen, and that’s actually when you create those micro-tears within the muscle tissues,” Milton explains.

Certain types of exercises can lead to greater post-workout soreness — namely, eccentric training.

Your muscles perform three different types of actions: eccentric, concentric and isometric. Eccentric refers to the lengthening phase of muscle contraction, or the lowering portion of an exercise. Think: Sitting back into a squat, uncurling your arm during a biceps curl or running downhill. Concentric refers to the shortening phase of muscle contraction, where you curl that dumbbell or stand up from a squat. Finally, isometric refers to holding a position, as when you hold a plank or wall-sit.

Eccentric training involves focusing on the lengthening phase of an exercise, either by performing that action at a slower pace, completing it with heavy weight, adding an explosive element (i.e., plyometric exercises) and/or performing it repeatedly (i.e., downhill skiing, downhill running).

One reason eccentric training creates greater muscle soreness is you have to control your descent, as opposed to letting gravity do all the work for you. This creates greater damage to fibers within your muscles, which leads to greater muscle soreness. “[During eccentric exercise] you’re trying to control the speed at which your muscle lengthens, and at that time, you’re tearing these cross-bridges, which are proteins that are attached to different protein fibers,” Milton explains.

The good news is your body is pretty smart; it adapts to the stresses of eccentric exercise so you’ll experience much less damage if you repeat the same workout a week later, according to a review in The Journal of Physiology.

Similarly, a study in Frontiers reveals it only takes one workout for your immune system to adapt so it’s better able to respond to your next bout of exercise.


On the one hand, muscle soreness following exercise is a good thing: “It means that you’ve created a stimulus at which your body is then going to adapt and become stronger,” Milton says.

On the other hand, it’s not a good idea to always be sore or to be so sore you can’t perform daily tasks without discomfort or pain. “If you’re having trouble going up and down stairs, or the soreness lasts longer than two days, that means you’ve definitely pushed your body more than the ideal amount to get the adaptation response,” Milton says.

So, what does an appropriate amount of soreness feel like? Well, first, it should only last about 24–48 hours, “and it should feel like, when you move a certain way, you remember that you did that workout yesterday,” Milton says.

Whether you’re sore or not, make sure you’re doing things to help your body recover between workouts. Your best recovery tools include sleep, hydration and nutrition. “The main recovery strategy we have is sleep, because that’s when we get the peak hormonal response from that exercise and the body repairs itself,” Milton says. According to a review in Sports Medicine, we experience the greatest boost in muscle protein synthesis during the dreamless non-REM sleep phase.

Also, pay attention to where you feel the soreness, as this will tell you if there’s something off with the way you’re performing the exercises. “If you’re doing a squat and all you feel is back soreness afterward, that’s a good indicator that you’re not utilizing the correct muscles, whether it’s because your muscles aren’t activating or your form is off in a way that’s causing you to use smaller muscle groups,” Milton says.


You may have heard people blame muscle soreness on a buildup of lactic acid, which is produced in your muscles during bouts of intense exercise. However, the lactic acid theory of muscle soreness was disproven back in the 1980s.

When lactic acid builds up in your muscles during exercise, it can create a feeling of discomfort, or even pain and make exercise challenging. When it comes to muscle soreness after exercise, however, lactic acid is blameless. “When we measure blood lactate levels, we can see that lactate does start to dissipate and become lower within 15–20 minutes following intense exercise, and that’s our body responding by utilizing lactate and putting it through different metabolic processes to buffer it and also use it for energy,” Milton explains.


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