You crush your morning workout — running farther, lifting heavier or getting in one more round of that circuit. But that sweet satisfaction can quickly turn to regret the next morning when you’re too sore to swing your legs out of bed.

Many of us have experienced the burning, aching, jelly-leg feeling that begins hours, or even days, after exercise. But where does it come from and why does it always show up a couple days after certain workouts?

Any muscle soreness you feel 24 to 72 hours after exercise is called delayed onset muscle soreness, or DOMS, according to the American College of Sports Medicine (ACMS). This soreness doesn’t show up after all workouts — only when you do new or intense exercises to which your body isn’t accustomed. 


Those changes begin during exercise. Muscle contractions cause microscopic tears along the muscle and nearby connective tissues, according to ACMS. These tiny tears don’t directly cause the soreness. Rather, the pain is a side effect of the muscle repair process.

Soreness is a by-product of healing.

Once the muscle is damaged, inflammation ensues and electrolytes, such as calcium, begin to accumulate. The immune system also gets involved, according to a 2016 study in the journal Frontiers in Physiology, sending in immune cells called T-cells to infiltrate the sites of damage. Scientists still aren’t sure how these processes come together to cause pain and soreness, but it’s likely that they come together to trigger both healing and pain.

Moreover, despite what you may have heard, lactic acid buildup is not a cause of DOMS. Lactic acid, which is produced during the exercise as the muscle continues to break down glucose after all of the available oxygen has been used, doesn’t hang around in the body long enough after exercise to cause soreness, according to a 1983 study published in the journal The Physician and SportsMedicine. About 45 minutes after a workout, the study’s subjects’ lactic-acid levels were not elevated, but they still developed DOMS two days later. Although there is still some controversy surrounding the topic, most scientists, the American College of Sports Medicine included, consider the lactic acid theory to have been debunked.

What’s the limit?

Muscle soreness is a good sign that you’re making progress, so you can embrace the ache with some satisfaction. But that doesn’t mean it’s time to go and repeat the same workout. That’s because doing so could increase your risk of a more serious injury. The best thing you can do, is some light exercise. Very light — exercise can get blood flowing and help that muscle loosen.

Extreme muscle soreness is a different beast. Pain that lasts longer than a few days, or pain that is so severe that it prevents you from lifting a limb, may indicate a more serious type of muscle injury that can lead to kidney damage. If your soreness doesn’t improve, or if your urine turns a black tea-like color, that’s a red flag indicating that you need to see a doctor.

However, in most cases, DOMS is a sign that your body is adapting. The workout that caused you so much pain the first time around won’t leave you quite so sore next time — but don’t get too comfortable.

A little bit of soreness indicates progress,. If you’re not having any soreness — it may be time to switch gears.

Relieving muscle soreness

Muscle soreness is normal and rarely requires medical attention. In most cases, symptoms go away on their own within a few days. In the meantime, it is best to avoid putting too much strain on the injured muscles.

People sometimes recommend the following treatments to alleviate muscle soreness following exercise:

Massage: A qualified sports massage therapist or physiotherapist can provide massages for alleviating muscle soreness. Massages increase blood flow to the injured area, which may promote healing and help to relieve the pain.

Heat therapy: Taking a warm bath or applying heat pads can also stimulate blood flow to the injured muscles. Heat therapy tends to offer only temporary symptom relief.

Cold therapy: Cold packs or immersion in cold water can reduce inflammation and swelling in the muscles. Cold therapy is, therefore, useful as a longer-term treatment for muscle injuries.

Light exercise: Keeping the muscles active may help to reduce pain. It is important to keep the intensity light and avoid movements that put too much strain on injured muscles. Examples of light exercises include walking and gentle stretching.

Pain medication: Over-the-counter nonsteroidal anti-inflammatory drugs (NSAIDs) can help to reduce muscle inflammation and associated pain.

Contact your doctor or seek care if:

  • Your muscle soreness lasts for more than a week.
  • Your pain is unbearable and prevents you from moving.
  • Your pain gets worse with exercise.
  • Your pain causes dizziness or trouble breathing.
  • You notice redness, swelling, or warmth in the sore muscles.
  • The RICE treatment doesn’t work.
  • You feel pain in the joint, over the bones, or in the tendons.


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