Quantitative Assessment of Myosin State Probabilities and Force Response in Striated Muscle

The macroscopic force generated by a muscle is the combined contribution of billions of motors comprised of actin-myosin crossbridges that individually interact following the laws of chemical dynamics. It is a complex system producing net mechanical work from chemical energies i.e. ATP hydrolysis. However, the exact hierarchy of chemical reactions is still predictive and widely varied. While the rate constants for several reactions is the same as in vitro conditions, it is challenging to calculate the straindependent rate constants. The only viable approach is to posit plausible values and simulate them to determine the force response under specific conditions. In this study, a computer model was generated in MATLAB to calculate the proportion of myosin in different acto-myosin states for isometric conditions using the parameters specified in the literature. The effect of power stroke length was also incorporated in the model which was not captured in previous models. Common misconceptions, assumptions, and shortcomings of the previous models were reviewed, including different mathematical approaches to muscle contraction.