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Why Do Muscles Feel Sore the Day After a Workout?

author image M. Gideon Hoyle
M. Gideon Hoyle is a writer living outside of Houston. Previously, he produced brochures and a wide variety of other materials for a nonprofit educational foundation. He now specializes in topics related to health, exercise and nutrition, publishing for various websites.
Why Do Muscles Feel Sore the Day After a Workout?
A runner expieriences soreness in his hamstring. Photo Credit Maridav/iStock/Getty Images

Muscle soreness is a general term that describes pain and discomfort in your muscle tissue. When you exercise, this type of soreness can develop a day or two later in the muscles you used during physical activity. While researchers once believed that post-exercise muscle soreness was caused by the buildup of a substance called lactic acid, they now believe that it results from physical damage to your muscle tissues.


Doctors commonly refer to soreness the day after a workout as delayed onset muscle soreness. While the exact cause of this soreness is unknown, current evidence indicates that it stems from the combined effects of factors such as bleeding in your muscle fibers, damage to specialized structures that hold your muscle fibers together and the release of certain chemicals into the spaces surrounding your muscle tissues. When these forms of damage occur, your body produces swelling and soreness as part of an inflammatory healing response that typically peaks within a couple of days and tapers off gradually.

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Degrees of Soreness

The extent of soreness you feel after working out depends largely on the ways in which you use your muscles, according to "Scientific American." If you attempt to lift more weight than your muscles can safely carry, the force on your muscles will cause them to lengthen rather than contract as they normally would. Movements of this type generate more muscle damage than movements that fall within your lifting capacity and allow your muscles to contract normally. In turn, increased muscle damage triggers greater amounts of post-exercise soreness.


Typically, DOMS symptoms disappear on their own within a week. You can ease the severity of existing muscle soreness in a variety of ways, including massaging or carefully stretching your affected muscles, avoiding any further stress on your affected muscles until soreness dissipates and performing low-intensity exercises such as casual walking to increase blood circulation to your sore muscles. You can also take nonsteroidal anti-inflammatory painkillers, including aspirin or ibuprofen, and follow the RICE protocol, which encourages rest, applications of ice or another cold source, use of compression bandages and elevation of your sore muscles above the level of your heart.


Lactic acid buildup produces short-term soreness that encourages you to end an exercise session and protects your muscles from serious damage. However, lactic acid production ends when you stop exercising. You can diminish or avoid the onset of DOMS by thoroughly stretching your muscles before and after any given exercise, warming up and cooling down properly when you exercise, introducing new workout routines gradually over time and avoiding abrupt changes to your exercise routine.

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