Filament compliance and tension transients in muscle

Huxley and Simmons (1971) proposed an explanation for some striking features in the transient tension response of a tetanized muscle fibre to sudden stretch or release. More recent work has shown that the stiffness of cross-bridges in skeletal muscle is an order of magnitude greater than appeared at that time. On the simplified treatment used in that paper, this would cause serious disagreement with the experimental observations. It is shown here analytically and by computer simulations that these discrepancies disappear when account is taken of (a) the range of positions of myosin molecules relative to attachment sites on the thin filament and (b) the recently-discovered compliance in the thin filaments.