Shape and length of myosin heads and radial compressive forces in muscle

Irrespective of the exact shape and length of myosin heads, it is shown that radial compressive forces occur in contracting muscle, which tend to bring the myofilaments closer to each other. This is in contradiction with common observation: a muscle that shortens swells laterally. The presence of these forces is model-dependent and they appear only in the case of the traditional concepts of force generation. Here we present an overview and a historical account of the problem.