Definition:
The sliding filament theory states that muscle contraction occurs due to the sliding of thin actin filaments over thick myosin filaments without any change in their length.
Explanation:
During contraction, myosin heads form cross-bridges with actin filaments and pull them inward toward the center of the sarcomere.
As a result:
• The sarcomere shortens
• Z-lines move closer
• I-band and H-zone reduce or disappear
• A-band remains constant
Final Answer:
Thus, muscle contraction is brought about by the sliding movement of actin over myosin filaments.