To address the effects of mechanical interactions between spatially distant but mechanically coupled segments of myocardial tissue we developed the simplest case model-the muscle duplex (Markhasin et al., PBMB, 2003).Muscle segments are mechanically connected and different sequences of muscle stimulation with varying time lags are applied for simulating excitation propagation throughout the myocardial tissue.Muscle segments can be either biological samples, computational models, or bio-computational hybrids (Protsenko et al., Am J Physiol, 2005).We considered combinations of "fast" and "slow" muscle samples that contract and relax relatively more or less rapidly to mimic differences in the mechanical activity observed in cardiomyocytes from different transmural ventricular layers, e.g.fast contracting subepicardial versus more slow subendocardial cells.