CRITICAL-REVIEW OF THE SWINGING CROSSBRIDGE THEORY AND OF THE CARDINAL ACTIVE-ROLE OF WATER IN MUSCLE-CONTRACTION

A critical analysis is presented of the experimental findings that led to the sliding filament model and to its offspring - the swinging (by rotating or tilting) crossbridge theory of muscle contraction (SCBT). Several principles that have been taken for granted implicitly and ex plicitly by the creators of these dogmas are discussed. The failure of numerous efforts to verify predictions of the SCBT, particularly the idea that the myosin molecules undergo a major conformational change, is critically reviewed. Analysis of various experimental data suggests that water may play an active role in muscular contraction. Examinati on of both the experiments that do not fulfill the expectations of the SCBT and the measurements of water liberation during the ''contractil e'' process suggests a new outlook according to which tension developm ent and movement are not due to major conformational changes but rathe r to restructuring of the hydration shells of actin and myosin.