Additional single myofibril parameter results. Single myofibrils were isolated from the hearts of sham control (open bars) and AOB (closed bars), mounted in the experimental apparatus by two glass probes, and subsequently underwent Ca²⁺ activation/relaxation cycles by means of a rapid solution change. Myofibrils were activated either at ∼50% maximum (pCa = 5.7), or at saturating Ca²⁺ (pCa = 4.0). n = 5 hearts per group, up to 30 myofibrils were studied per cohort, SL 2.2 μm, 15°C. Subsequently, multiple muscle data were averaged to derive a single average datum per heart. Data were analyzed by two-way ANOVA. (A) Steady-state myofibril force development (Force): P = 0.035 Ca²⁺ impact, P = 0.075 AOB impact. (B) Ca²⁺ activation kinetics (K_act): P = 0.0001 Ca²⁺ effect, P = 0.553 AOB impact. (C) Linear relaxation rate (K_lin), P = 0.003 Ca²⁺ impact, P = 0.110 AOB impact. (D) Exponential relaxation rate (K_exp), P = 0.241 Ca²⁺ impact, P = 0.304 AOB impact). !, P = 0.05 pCa 4.0 vs. pCa 5.7.