The deformations and twisting of the left ventricular (LV) wall, quantified by strain and torsion, provide insight into its regional and global contractile function. In this study, we investigated the influence of proteins entailing myocyte contractility and structural stability on ventricular biomechanics using mouse models with alterations in contractile proteins. The pattern and timing of LV strain and torsion in 2∼3 month mice that lack cardiac myosin binding protein-C (cMyBP-C-/-, n=6, cMyBP-C+/-, n=6), a thick filament-associated sarcomeric protein, and muscle LIM protein (MLP-/-, n=6), a cytoskeleton protein that is thought to be involved in transmission of mechanical stress, were evaluated against wild-type mice (n=6) in vivo using magnetic resonance imaging. Both cMyBP-C-/- and MLP-/- mice exhibited a severe depression in systolic function as indicated by decreased LV ejection fractions compared to wild-type mice. A significant reduction in LV torsion and principal strains E1 and E2, associated with radial wall thickening and circumferential shortening, respectively, were observed in cMyBP-C -/- and MLP-/- mice. Interestingly, reductions in LV torsion were also observed in heterozygous cMyBP-C null mice (cMyBP-C+/-). The time course of peak fiber torsion and strain appeared to be accelerated in cMyBP-C-/- mice, while peak strain development was slowed in MLP-/- mice. The lack of MyBP-C and MLP in the cardiac myocyte led to hypertrophic and dilated cardiomyopathy, respectively, and resulted in severe deficits in the overall contractile function of the heart. However, the pattern and time course of LV torsion and principal strain development appear to differ in these two models of heart failure, reflecting a contrast in the functional roles of cMyBP-C and MLP in the myocyte.