Myosin ATPase activity is quite slow in the absence of actin. Once activated, all myosin heads hydrolyze ATP at the same rate. An actin binding site and an ATP binding site are present on opposite sides of the myosin head. The characteristics of the myosin heads in different muscle types results in vastly different force generation per head. Thin filaments occupy the central portion of a band of the sarcomere b.
Thin filaments contain the proteins troponin, tropomyosin, actin and titin.
Twitch tension depends upon both the force produced by the contractile proteins and upon the characteristics of the series elastic element. If the elastic elements are fully stretched twitch tension exceeds titanic tension. No force can be produced contrary to the direction of shortening. At rest, myosin retains ADP and Pi. When the crossbridge is activated, force is produced before the first ATP hydrolysis.