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What Causes Muscle Soreness?

What Causes Muscle Soreness?

By Justin Flexen

A day or two after a hard ride or HIIT workout, you’re not sure your achy, jelly legs will get you from the couch to the kitchen. Many fitness enthusiasts don’t mind a little muscle soreness following a tough workout—in fact they kind of consider it a badge of honor. Others prefer their workouts without the post-exercise pain.

But what actually causes muscle soreness?  And is it a good or bad thing?  

When you exercise you’re putting stress on the muscles, which causes microscopic tears to the muscle fiber. Soreness is essentially what you feel when these muscles are starting to repair themselves and recover. This breakdown and repair is how you get stronger over time. It could be from running, from cycling, or lifting weights.

A little bit of soreness isn’t a bad thing! It’s actually healthy because it means you’re stressing the muscles enough — i.e., challenging yourself appropriately — to break the muscle down. If you want to build up your strength or your endurance and get more fit, you have to push yourself a little bit.

Especially if you’re a beginner, it’s normal to feel that soreness. But it shouldn’t be debilitating at all. You never want to work out just to get sore because that’s when injury can happen.

How do I distinguish between being sore or injured?

The best way to think about it is that soreness, known as delayed onset muscle soreness (DOMS), normally occurs 24 to 48 hours after your workout and is more like a dull ache. With an injury you’ll usually feel it instantly, and the pain is sharper.  

Here’s an example: If I had a heavy chest day I’m going to feel a dull tightness throughout my chest. If I lie down I’m not going to feel the soreness until I start to move. Also, once I start to stretch, the soreness will start to dissipate.  Whereas if I pull a muscle in my chest I’m going to feel pain in that exact spot. It’s more isolated, and I’ll feel it even at rest.

The pain from an injury typically will last longer than a week, and may impinge on movement. That’s something to be very aware of: If you feel pain, stop. I never encourage anyone to work through an injury ever.

What are some ways to prevent, or at least lessen, post workout soreness?

First, you always want to give your body a full day, maybe two full days, to recover

I always suggest starting and ending each workout with a foam roll and a stretch. Those are the things most people overlook—they just want to do their workout and be done. Giving yourself 5 or 10 minutes to stretch out will reduce your risk of soreness by a lot.


When you’re warming up you want to keep your stretches dynamic, meaning they’re active movements. You want to hold a stretch for maybe 10 seconds max, and include a lot of dynamic movement. It’s not a static stretch that you hold for 30 seconds, we’ll get to that later. Dynamic movement will get your body ready for the work, and reduce your risk of soreness.

Foam rolling is also a great way to get into those muscle fibers and release any knots or any tension that you might be starting off with. You’re setting yourself up better and lowering your risk of injury if you foam roll first. There are a number of techniques, depending on the workout you’re doing. I like hitting the big muscle groups— your back, your quads, glutes, calves. That covers a lot of ground.

Once you’re done working out, after you’ve broken down those muscle fibers, then you want to do some static stretches where you’re holding  the stretch for 30 seconds or longer. This helps your muscles recover faster, and also improves flexibility and range of motion.

Cross-training and active recovery

Another way to prevent soreness is through active recovery — alternating tough workouts with yoga, stretch classes, even some light cardio like a leisurely 30-minute walk. Cross-training also helps prevent overuse injuries. Even on recovery days it’s good to move: if you’re sitting all day and not moving, that means there’s no blood flow getting to your muscles to help them recover. 


I really like warm Epsom salts baths to relax tight muscles. Cold showers can also help reduce muscle soreness. You could do a cold shower on a recovery day, or right after you work out—either one is fine. I like to do it after I work out—to me it feels really good, like a mini massage. I never thought I’d be doing that! It’s good, but intense—you have to build up to it, otherwise it will be a bit of a shock!

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