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What are the causes of DOMS?

Delayed Onset Muscle Soreness (DOMS) is pain or discomfort that occurs as a result of muscle damage after intense exercise. DOMS can happen to anyone, but it is more likely to happen in people starting a new resistance exercise or programme with an emphasis on eccentric movements (running downhill, lowering weights etc.) and higher loads.  

During an eccentric contraction, the muscle must contract while also lengthening, and this is especially challenging to your muscle fibres. The way the muscle fibres are loaded during eccentric exercise makes them more vulnerable to muscle injury and DOMS.

What are the causes of DOMS? 

While the exact cause of DOMS is not fully understood, there are many theories. Experts believe that the most significant cause of DOMS is micro-trauma to the tiny fibres within our muscles. When you exercise, and muscles are required to work harder than they are used to or in a different way, it can cause microscopic damage to the muscle fibres.  

 Your body senses the damage, which stimulates pain receptors in the muscle and creates an inflammatory response, sending white blood cells and any extra fluid necessary for healing to the damaged muscle cells. This causes swelling, resulting in muscle pain, weakness and stiffness - the symptoms associated with DOMS.

Is lactic acid build up a cause of DOMS?

A common misconception is that lactic acid build up is the main cause of DOMS. Lactic acid is produced as a by-product by your body when oxygen stores are depleted. Although the presence of lactic acid does seem to be correlated with DOMS, as it is often present in the blood of people who are experiencing it, it is not actually the cause of DOMS. Lactic acid can cause acute muscle soreness during a workout, but it is usually cleared rapidly by the body within about an hour of finishing a workout. 

DOMS symptoms 

If DOMS is present, then it is usually fairly easy to notice during your normal day-to-day function. The main symptoms include:

  • Achy and sore muscles that are tender to touch

  • Muscle and joint stiffness

  • Decreased range of motion in nearby joints

  • Increased aching and soreness when the affected muscle is stretched

  • Temporary muscle weakness (due to decreased or impaired motor activation)


Having DOMS is usually a positive sign post exercise. It indicates that the muscle is healing into a stronger state than it was before the activity, and therefore the training was effective. Although DOMS is an indication of effective training that promotes muscle transformation to a stronger state, it is not something you should aim for. 

While resistance workouts will produce some muscle soreness, DOMS represents a level of soreness that is more extreme and requires more recovery. When someone is recovering from DOMS, muscle function is impaired during that time and performance may be inhibited. It can take 4-8 days to recover fully. During this recovery time it is best to train different muscle groups and less affected areas, and also give yourself positive rest time. Be sensible, listen to your body and by the end of the session you should feel better, not worse.