Mechanical properties of control and MyBPC morphants. (A and B) Length–active force relationships (A) and active (a) and passive (p) force at optimal length (B) in skeletal muscles from 4–5-dpf control (open circles and bars) and MyBPC morphants (mybpc-1: triangles and hatched bars, mybpc-2b: black circles and bars). (C) Original recordings of single twitch contractions from a control (top) and an MyBPC-2B morphant (bottom). The initial rapid transient preceding the force development indicates the stimulation. (D) Summarized data for the latency (i.e., time between stimulus and onset of contraction) and half-time (t_1/2) for contraction and relaxation during single twitch (open bars: controls [n = 8], black bars: MyBPC-2B morphants [n = 7]). Statistical analysis: **, P < 0.01; ***, P < 0.001. Data are presented as mean ± SEM.