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Exercise induced muscle damage (EIMD) can be summarised by damage to a muscle fibre and the tissues within it (myofibril, sarcomere, z lines, t tubules, etc) and then the resulting inflammatory response to this (Morgan & Allen, 1999). Figure 1 shows the structure of skeletal muscle.

 

 

EIMD is generally the result of participation in unfamiliar exercise, prolonged endurance exercise or the most common with the most aggressive symptom levels is eccentric muscular contractions (Davies, 2010). An eccentric contraction is when a muscle lengthens or stretches under load. Lots of athletic movements contain an eccentric contraction so it is very common for athletes to regularly experience symptoms of EIMD, an example of some of these movements are:

 

  • Landing when running or jumping
  • Turning
  • Stopping
  • The downward movement in a squat or chin up
 
 

EIMD occurs predominately during eccentric contraction as the muscle tissue is put under much higher force demands than in concentric or isometric contractions, regularly exceeding 100% of maximal voluntary contraction force (Armstrong, Warren, & Warren, 1991) causing tissue damage. During these eccentric contractions the sarcomeres can be stretched much further apart than during concentric and isometric contraction, so far so that the actin and myosin filaments lose contact which also causes damage to the tissue (Proske & Morgan, 2001).

 

The inflammation that is induced by this damage then disrupts intracellular calcium ions leading to a loss of integrity in the sarcolemma cell membrane causing a leaking of intra cellular proteins like creatine kinase and myoglobin into the blood stream (Hortobágyi & Denahan, 1989; Peake, Nosaka, & Suzuki, 2005).

 
 

Figure 1

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