The combination of C1 and the MyBP-C motif is required to increase Ca²⁺ sensitivity of tension. (A) 10 μM mC2 (triangles; n = 4) had no effect on tension–pCa relationships relative to control (circles), whereas 5 μM C1m (squares; n = 6) significantly increased Ca²⁺ sensitivity of tension (ΔpCa₅₀ = 0.12 ± 0.04). (B) 10 μM C0C1 (triangles; n = 3) had no effect on tension–pCa relationships relative to control (circles), whereas 5 μM C0C1m (squares; n = 4) significantly increased Ca²⁺ sensitivity of tension (ΔpCa₅₀ = 0.27 ± 0.05).