Final answer:
Actin and myosin are the two protein filaments that slide over each other during a muscle contraction.
Step-by-step explanation:
The two protein filaments that slide over each other during a muscle contraction in the sliding filament theory are actin and myosin. Actin is a thin protein filament that slides over the thick myosin filament to produce muscle contraction. This process is driven by the binding of myosin to actin, forming cross-bridges that generate filament movement.