mechanically and physiologically
Strength gains have been shown to be the result of numerous factors and conditions. These include neuromuscular potential (need source), the associated force production relationship of the agonist and antagonist muscles (Maynard & Ebben, 2003), muscle cross sectional area (Frontera, Meredith, O’Reilly, Knuttgen & Evans, 1988), orientation of fiber type (Terzis, Georgiadis, Vassiliadou & Manta, 2003), the mechanical leverage of tendon insertion and joint angles (need source), circulating hormone levels (Izquierdo, et. al., 2004), and ability to meet energy demands (need source).
As a result of training, neural adaptation and increasing cross sectional area via hypertrophy seem to account for the majority of the gains in strength capacity (Hakkinen, et. al., 2001).
Gender and age have shown to drastically effect the correlation between strength training and strength increases (Kent-Braun, Ng, Doyle & Towse, 2002).
Furthermore muscular endurance tests, particularly isometric, used to test strength across genders may be problematic as females seem to have a greater reliance on non-oxidative energy pathways than do males (Kent-Braun, et. al., 2002), and therefore do not experience the same degree of fatigue generated by low pH levels in the cytosol correlated with use of the oxidative energy pathways.