(see also "Several Insights into muscle contraction mechanism" part 1 and 2)

If the cross-bridge power stroke would be really the unique force generator in muscle, it could be effective only if the thin filaments were entirely stiff or permanently kept  rectilinear and parallel to the myofibril axis. Furthermore, it would be preferably that one cross-bridge never leaves (during its power stroke) the plane that contains both thin and thick interacting filaments. Otherwise, strange as it may appear, the result of the power stroke will not be the one expected,

but a complete surprise!


Furthermore, even if all three elements involved in this mechanical event (namely, the cross-bridge, the thick  filament from where it emerges and the thin filament with whom it interacts) would be permanently coplanar (a very unlikely situation), the sarcomere will not shorten, just because the thik filament will not crawl toward the sarcomere Z line (as the following animated gif tries to indulge us in illusion):



Instead, the only result will be the bent of a not rigid or not pre-stretched thin filament: