To account for their observations, they suggested a ‘sliding-filament’ model in which myosin filaments run the length of the A-band and actin filaments slide into this band when muscle shortens.

Terrell L. Hill, George M. White, On the Sliding-Filament Model of Muscular Contraction, III. Kinetics of Cross-Bridge Fluctuations in Configuration, Proceedings of the National Academy of Sciences of ...