Why Your Muscles May Swell After a Workout and How to Fix It

Ice can help decrease swelling in muscles.
Image Credit: AndreyPopov/iStock/GettyImages

If you've ever begun a new weight-training program and then found it difficult to walk down stairs for the following few days, you're familiar with the uncomfortable side effects of muscle strengthening.

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Something else you might notice after a strength session is swollen muscles, which can lead to decreased range of motion, stiffness and overall discomfort.

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Why do your muscles swell after a workout? Exercising causes temporary inflammation and swelling as muscles fibers are broken down and rebuilt to increase strength.

Ahead, learn more about why your muscles are swollen after a workout and what to do about it.

Reasons Why Muscles Swell After a Workout

1. You're Lifting Weights Your Muscles Aren't Used To

If you notice your arms are swollen after an upper-body workout, for instance, this may have to do with starting a new routine or lifting heavier weights than you're used to.

When a muscle lifts loads that it is unaccustomed to, the stress causes tiny tears in its fibers. These tears are a natural part of building stronger muscles because when the damage is repaired, the muscle fibers are rebuilt stronger than before, according to University Hospitals.

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Almost immediately after exercise, white blood cells rush into the muscle to clear up the debris from the muscle damage, producing prostaglandins as a byproduct.

Prostaglandins is a hormone-like substance that causes pain and swelling, according to the Cleveland Clinic. Along with white blood cells, fluids carrying other nutrients and enzymes rush into the muscle to support the rebuilding process. The extra fluids packed into the muscle also cause swelling after a workout.

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2. Your Workout Includes Eccentric Muscle Contractions

A muscle contraction has two parts: the concentric or "positive" phase (i.e., the "up" phase of a biceps curl) and the eccentric or "negative" phase (i.e., the "down" phase of a biceps curl). Research, like this March 2017 review in the ‌Journal of Applied Physiology‌, has demonstrated that eccentric contractions cause the most muscle damage, pain and swelling; the muscle must lengthen as it contracts.

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So, if your biceps are swollen after doing an exercise like a biceps curl or your forearms are swollen after a wrist curl, it's completely normal.

Although weight training usually causes muscle soreness, the cumulative stress of eccentric contractions in weight-bearing endurance activities, such as running a marathon, can also cause muscle damage and swelling.

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3. You're Experiencing Delayed Onset Muscle Soreness

Swelling after exercise is a component of a condition called delayed-onset muscle soreness, or DOMS, according to the American College of Sports Medicine (ACSM).

In addition to swelling and soreness, DOMS can cause joint stiffness and temporary weakness in the affected muscles. How long do your muscles stay swollen after working out? In the case of DOMS, symptoms typically set in between 24 to 72 hours after your workout and subside after a few days, per the ACSM.

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Warning

A rare, but serious, medical condition called rhabdomyolysis can cause muscle swelling after working out. This condition occurs when muscles begin to rapidly break down, releasing the contents of muscle cells into the bloodstream, according to the Cleveland Clinic. In mild cases, a person might not have symptoms. However, in some cases, this is a life-threatening condition.

Rhabdomyolysis is most commonly caused by direct trauma to your muscle, but can also occur from overexerting your muscles. In addition to swelling, other signs and symptoms of this condition include muscle pain, weakness and tea-colored urine.

You might also experience nausea, vomiting, bruising, fever or confusion. Seek immediate medical attention if you suspect you have this condition to prevent permanent kidney damage from occurring.

To reduce your risk of rhabdomyolysis, drink plenty of fluids before you work out and during exercise and don't push yourself past your limits, according to the Cleveland Clinic.

Treatment for Muscle Swelling After a Workout

While you can't necessarily prevent sore, swollen muscles completely, there are a few ways to treat the above causes, according to the National Health Service (NHS):

  • Apply ice to your swollen muscles (for no more than 20 minutes at a time).
  • Massage your swollen muscles.
  • Lightly stretch your swollen muscles.

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Prioritizing active recovery (like walking, for instance), proper nutrition and sleep is also important in helping your body repair itself, according to the National Academy of Sports Medicine (NASM).

It's important to learn to tell the difference between swelling associated with recovery and swelling caused by injury. Acute, or sudden, injury — like a muscle tear, for instance — causes sharp pain during exercise and immediate swelling. Swelling from an injury like this is usually localized around a bone or joint.

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Chronic injuries may not cause appreciable swelling, but pain will be greater during exercise than in the following days. If you suspect injury, seek medical advice and use the PEACE and LOVE method to relieve the swelling:

  • ‌‌P‌‌rotection: Avoid movement to minimize bleeding and reduce the risk of aggravating the injury.
  • ‌‌E‌levation: Position your injury so it's higher than your heart to encourage interstitial fluid (the fluid found in the spaces around cells that carries oxygen and nutrients from the blood to the cells and removes waste products) to flow out of tissues.
  • ‌A‌void anti-inflammatories: Steer clear of anti-inflammatory medications, which may affect long-term tissue healing.
  • ‌‌C‌‌ompression: Apply pressure using tape or bandages to reduce swelling and tissue hemorrhage.
  • E‌‌ducation: Speak with your health care provider to learn more about your condition and how to properly manage it in the long term without overtreatment.
  • ‌L‌‌oad: So long as you're not experiencing significant pain, begin loading the injured area, which can encourage repair and remodeling and build tissue tolerance.
  • ‌O‌‌ptimism: Focus on feeling optimistic about your recovery, which can improve your prognosis.
  • ‌‌V‌ascularization: If possible, engage in cardio to increase blood flow to the injured area.
  • ‌‌E‌‌xercise: Try to exercise early on in recovery, which can help restore your mobility and strength.

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