According to the sources, the globular head of the myosin (thick) filament functions as an active ATPase enzyme . This enzymatic activity is essential for muscle contraction, as it allows the head to bind and hydrolyse ATP to provide the energy needed for cross-bridge formation with actin . Other proteins like troponin and tropomyosin are involved in muscle structure and regulation, such as masking active binding sites in a resting state, but they do not exhibit ATPase activity .