Subsarcomeric resolution of myosin activity reveals cMyBP-C phosphorylation reduces SRX in the P- & C-zones, compensated for by an increase in the D-zone. Cy3-ATP turnover rates were calculated as an average across all zones of the sarcomere, as well as individually for the P-, C-, and D-zones. The Cy3-ATP turnover rates per zone were used to calculate the relative population amplitude of SRX myosin heads based on triple-exponential fits. Data were collected from untreated porcine myofibrils (N = 3 pigs, n = 3,638 events) or myofibrils treated with 62.5 U/μl of PKA (N = 3 pigs, n = 1,463 events). Data are shown as the mean and 95% CI errors. Significance was calculated using bootstrap analysis and indicated by *. Table 1 provides the values used in the graph. PKA phosphorylation affects the distribution of SRX and DRX in porcine myofibrils.