The calf muscles are an important source of shock absorption and propulsion during running gait (Hamner, Seth, Delp, 2010). They function primarily as plantar flexors (extension) of the ankle and are made up of the gastrocnemius, soleus and plantaris (sometimes).
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Strength testing standards currently involving using the calf raise test: a series of repeated single leg heel raises. A systematic review in 2009 (Herbert-Losier et al) demonstrated that the normal number of single leg calf raises that healthy individuals should be able to perform are 27 repetitions for men and 19 repetitions for women. 25 repetitions is a commonly used standard, although the literature varies as evident by the above systematic review.