Fig. 1

Hill model. Hill (1938) [1] proposed that muscle consists of two basic elements: a contractile force producing element (CE), and an “elastic” element that is arranged “in series” (SE) with the contractile element. Hill (1938) [1] pointed out correctly that the series elastic element influences the contractile element’s length and rate of change in length (velocity) during dynamic contractions, and thus, affects the force producing capability of the contractile element