Mechanics of intramuscular aponeurosis when operating at different muscle lengths and forces

The aponeurosis of human muscles represents a significant proportion of the elastic tissues in series with the muscle. However, the aponeurosis should not be considered a simple spring, as is often assumpted in biomechanical models (e.g. Hill-type muscle models). Recent evidence for the effects of force and muscle length on the strains experienced by aponeurosis will be critically analysed to describe the potential functional importance of the aponeurosis and how it may enhance muscle versatility.