Журнал наномедицины и нанотехнологий

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Force-Velocity Relation: Its Implications about Molecular Mechanism of Muscle Contraction

Sugi H and Chaen S

In 1938, Hill described the relation between force (P=load) and initial velocity of shortening (V) in contracting whole frog muscles as part of rectangular hyperbola: (P + a) V=b (Po – P), where Po is the maximum isometric force and a, b are constants. This equation indicates that muscle can regulate its energy output depending to the amount of load imposed on it. In 1954, H.E. Huxley and Hanson made a monumental discovery that muscle contraction results from relative sliding between actin and myosin filaments, providing structural basis to study and discuss mechanisms underlying the P-V relation. In 1957, A.F. Huxley has constructed a contraction model, in which muscle contraction characteristics including the P-V relation are explained in terms of attachment-detachment cycle between myosin heads extending from myosin filaments and the site in actin filaments. The Huxley contraction model stimulated the interest of muscle investigators to study the P-V relation using intact single muscle fibers with the following results: (1) the shape of P-V relation deviates from hyperbola at loads >~0.8 Po; (2) at the beginning of muscle shortening under lads