Sliding filament theory can be best explained as

Sliding filament theory can be best explained as actin and myosin filaments do not shorten but rather slide pass each other. 

Mechanism of muscle contraction is best explained by the sliding filament theory which states that contraction of a muscle fibre takes place by the sliding of the thin filaments over the thick filaments. During shortening of the muscle, the ‘I’ bands get reduced, whereas the ‘A’ bands retain the length.