Knowledge Base

Exercise-induced muscle damage

Muscle damage from physical loading 

Exercise damages muscles due to eccentric and concentric muscle loading. Exercise-induced muscle damage is greatest during eccentric contractions when muscles lengthen under tension, which commonly occurs during activities such as walking down stairs, running downhill or lowering heavy objects.

It frequently occurs after unaccustomed exercise, particularly if the exercise involves a large amount of eccentric (muscle lengthening) contractions. It can be split into two stages. In the first stage, the actual muscle damage occurs with physical activity; the second stage is connected to the development of the inflammatory reaction. After the symptoms of damage have subsided, the affected muscles need to rebuild. Delayed onset muscle soreness is typical for muscle damage. This delay interval is usually between 24 and 72 hours after training and is caused by the development of the inflammatory reaction in the damaged muscle.

Eccentric muscle stretching often leads to muscle damage from structural disturbance, causing an inflammatory response by the body, accompanied by swelling, increased temperature in that area, and temporary loss of muscle strength. The inflammatory reaction is necessary from the molecular point of view to initiate muscle regeneration. It should therefore not be suppressed synthetically, but if necessary only include food with anti-inflammatory effects in your diet (see above), and leave the muscles to properly regenerate prior to further training, to avoid serious damage. In exceptional cases, untrained individuals may end up with serious muscle damage (i.e. rhabdomyolysis), even leading to severe kidney damage. If you notice dark coloured urine after exercising, contact your doctor immediately.

Two phases of muscle damage 

The complex mechanisms associated with muscle damage can be simplified into two phases: initial phase or primary damage that occurs as a consequence of the mechanical work performed and a second phase that proliferates tissue damage through processes associated with the inflammation. 

Primary muscle damage 

Secondary muscle damage