What is the sliding filament theory and how is tropomyosin involved?

The sliding filament theory is the theory behind muscle contraction which involves the formation of actin- myosin cross bridges leading to the contraction of the muscle fibre. Tropomyosin is a protein found in actin based cytoskeletons

The sliding filament theory describes the mechanism that allows muscles to contract. According to this theory, myosin (a motor protein) binds to actin. The myosin then alters its configuration, resulting in a "stroke" that pulls on the actin filament and causes it to slide across the myosin filament. Calcium is required by two proteins, troponin and tropomyosin, that regulate muscle contraction by blocking the binding of myosin to filamentous actin. In a resting sarcomere, tropomyosin blocks the binding of myosin to actin.