Results showing pCa50 values (Ca2+ required for half maximal activation of tension) at pH 7.0 (left panel), 6.20 (middle panel), and the delta shift in pCa50 between pH 7.0 and 6.20 (right panel) in detergent permeabilized control myocytes (n=8), and myocytes expressing ssTnI (n=8), and ssTnIH132A (n=6) 5–6 days after gene transfer. Values are expressed as mean±SEM and the statistical comparisons shown in each panel demonstrate that the Ca2+ sensitivity at each pH was significantly different in myocytes expressing ssTnI versus controls (*<0.05 vs control by ANOVA). In myocytes expressing ssTnIH132A, the Ca2+ sensitivity at each pH also was significantly changed compared to ssTnI (p<0.001 vs ssTnI by ANOVA) and was comparable to results obtained in myocytes expressing cTnI.