Fig. 5.

Model of the shortening behavior from the unloaded length. (A) Four-element mathematical visco-elastic model of a contracting isolated muscle. The spring constant k₁ and dashpot constant η represent the visco-elastic behavior of the shortening part of the muscle, spring constant k₂ represents the lengthening muscle ends. The contractile force F_A was prescribed using the average measured force. (B) Fitted experimental data of the time-course of shortening in wildtype and MLPKO trabeculae. (C) Model of a normal (wildtype) and an MLPKO shortening time-course. The two curves were produced using values for k₁ taken directly from the passive stress–strain relationship. (D) Wormlike chain model of titin-based force in wildtype and knockout muscles, compared with the measured stress–strain relationship. For further details see text.