To the problem of cross-bridge tension in steady muscle shortening and lengthening

TL;DR

This paper revisits the Huxley sliding filament model to better explain the force-velocity relationship in muscle contractions, proposing a new solution that aligns closely with empirical data using fewer parameters.

Contribution

A revised model of cross-bridge kinetics applying thermodynamics, providing a more accurate and parsimonious explanation of muscle force-velocity behavior during contraction.

Findings

The new model fits frog muscle tension-velocity data with only one adjustable parameter.

It reveals correlations between weakly and strongly bound cross-bridge states.

The approach simplifies understanding muscle mechanics compared to previous models.

Abstract

Despite the great success of the Huxley sliding filament model proposed half a century ago for actin-myosin linkages (cross-bridges), it fails to explain the force-velocity behavior of stretching skeletal muscles. Huxley's two-state kinetic equation for cross-bridge proportions is therefore reconsidered and a new solution to the problem of steady muscle eccentric and concentric contractions is reported. When the second law of statistical thermodynamics is applied to cross-bridge proportions, the weakly bound states appear to be correlated to the strongly bound states via structural and kinetic intrinsic muscle characteristics. The explicit force-velocity curve fits the empirical tension-velocity data on frog muscle shortening using only one adjustable parameter, while the Huxley model employed four parameters.