What Causes Sore Muscles After Exercising?
Muscle Aches, Stiffness and Soreness Can Occur Days After a Workout
Mar 9, 2009
Ever wondered what causes the sensation of sore, stiff, aching muscles after a workout? Muscle soreness is an annoying problem, and can continue for several days after exercising. For people who are unaccustomed to exercise, muscle soreness can be a fairly daunting experience and may discourage them from exercising altogether.
It can be helpful to understand why muscles feel sore after exercise, and to know that it is usually nothing to worry about.
What is Muscle Soreness?
Muscle soreness is also called Delayed Onset Muscle Soreness (DOMS), or muscle fever. DOMS does not refer to 'the burn' that is sometimes felt during strenuous exercise; it is when the muscles begin to feel sore and stiff after exercise, typically between 24 and 48 hours later.
For example, if a person decides to go for a long run for the first time, he or she will probably experience aching leg muscles over the next few days, particularly the calf muscles, and this will be noticeable when walking.
What Causes Muscle Soreness and Stiffness?
It was once thought that a build up of lactic acid in the muscles during exercise causes muscle soreness, but now it is known this is not the case. Lactic acid is removed quickly after an exercise session and does not remain in muscle tissue for very long.
It is not clear exactly what causes delayed muscle soreness. One theory is that muscle soreness occurs because of microscopic tears in muscle fibres, and another is that it is due to tears in the tissue that connects the muscle rather than the muscle itself. Further possibilities include inflammation, changes in osmotic pressure, muscle spasms and a change in the way the muscle cells regulate calcium.
Muscles are distressed when they are made to perform actions they are not used to, such as working out harder than usual, taking up a new sport, or beginning a new workout programme. The greater the intensity of exercise that is performed, the greater the muscle soreness experienced afterwards.
Is Muscle Soreness Serious?
Muscle cells repair and regenerate themselves in the days that follow intense exercise, and they get stronger in preparation for performing the activity again. After this recovery process, the muscles function more efficiently and are more resistant to damage. This process is known as adaptation.
If a person is new to exercise, or takes up a sport for the first time, some degree of muscle soreness in the following few days is to be expected. Once the muscles become accustomed to an activity, they have a degree of protection and soreness is minimal.
It is important not to be put off continuing with an activity or workout if muscle soreness is experienced, for it is perfectly normal. It is a sign that the exercise has worked, the muscles are adapting and repairing themselves, and results are happening. There are many reasons to find the motivation to exercise regularly, such as to reduce the risk of coronary heart disease.
Even though muscle soreness can last for several days, it is not serious, does not need medical attention, and gradually goes away by itself. However, it is unwise to exercise with a serious injury.
Resources:
McArdle, W.D., Katch, K.I. and V.L. Katch. Exercise Physiology: Energy, Nutrition and Human Performance, 6th Ed. London: Lippincott Williams and Wilkins, 2006, 549-552
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