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What Causes Sore Muscles?

Muscles Sore? These Experts Explain Why It Hurts to Walk Up Stairs After a Tough Workout

Woman weightlifting

Sore muscles are happy muscles because it's usually a sign of progress! It means you've challenged yourself or worked muscle groups you don't normally work. This happened to me last night with a new yoga practice. Though I'm good at balance because of my gymnastics days, I'm still not used to holding crow pose, and my forearms and shoulders are currently sore with a capital S. If you're not sure exactly why you have these familiar aches, you're not alone. We asked some experts to break it down for us.

What Causes Sore Muscles?

Any burning sensation we feel in our muscles while we work out is likely due to the pH changes in those muscles during high-intensity exercise, Tedd Keating, PhD, associate professor of kinesiology at Manhattan College, explained. This is temporary. Delayed onset muscle soreness, or DOMS, is the soreness you feel a day or two after your workout. NASM-certified personal trainer and head coach at Ladder Stan Dutton told POPSUGAR that, oftentimes, muscle soreness is a result of lifting more weight or doing more reps than usual. "Exercise helps us develop nerves, and when we do something new, muscles can secrete substances that accelerate nerve growth. Basically, soreness can also be thought of as 'nerve-growing pains,'" he said.

Dr. Keating broke down the science behind DOMS. "Generally speaking, as with many other types of injury, the culprit is microtears within the muscle that lead to a gradual inflammatory process over the first 24 to 48 hours after a hard workout," he said. Typically, eccentric contractions or movements cause this damage. "When we lower the body under control, like in a squat or a deadlift, the muscle is lengthening as it's contracting, which puts a unique stress on the muscle," he explained. The longer we contract or lengthen the muscle, the more it's under stress and the more it works. Any new stress, like additional weight, reps, or range of motion, can all also contribute to soreness, Dr. Keating said.

Can I Work Out With Sore Muscles?

Yes! If you're doing something new, you should expect muscle soreness, Dr. Keating said. It's nothing to be afraid of, but you should definitely take measures to recover and give yourself time to rest (check out some essential recovery methods you can try after your workouts). If you're exercising on sore muscles, he recommended shifting the emphasis to different muscle groups that may not be so sore (like doing more upper body if your legs feel extra heavy from Spin class the day before). Plus, sticking with a workout that made you sore will eventually become easier. This is what Dr. Keating called the "repeated bout effect."

"A common misconception is that soreness is necessary for your workouts to be effective, but it's quite the opposite," Dutton further explained. "We exercise so that our bodies will adapt by getting stronger, leaner, and so our nerves grow into our work load. In other words, if you want to be less sore, focus on staying consistent with your training, and as your body adapts, you'll notice the difference in your ability to recover."

When to See a Doctor

Dutton stressed the importance of knowing the difference between soreness and pain. Being sore is uncomfortable and can sometimes last for a few days, he explained. It can even make daily tasks difficult. Pain, though, lasts longer and is "more acute." If you're in pain, see a physical therapist or doctor who can help you recover quickly, he said.

If soreness doesn't get better after 72 hours, it might be worth following up with a medical professional, Dr. Keating advised, explaining that in more severe cases, rapid breakdown of skeletal muscle tissue, or rhabdomyolysis, can occur. Muscle pain accompanied by a "cola-colored urine" may indicate rhabdomyolysis and can lead to kidney failure if left untreated, he noted. This is when you should seek immediate medical attention.

Image Source: Getty / svetikd
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