Figure 4.

Composite Bode plot showing the response of papillary muscle (three muscles of each type) to oscillations over the frequency range of 0.08–100 Hz. The upper panel shows that the phase becomes negative in human mutant mice (force lags length, indicating work producing) between frequencies of 0.9 and 2.6 Hz. The normal mouse papillary muscles have negative phase between frequencies of 0.3 and 0.5 Hz, with error bars too small to show. Human control mouse papillary muscles have a negative phase below frequencies of the normal mouse. The lower panel shows the mean calculated work per loop for the three muscle types. The peak work/cycle is produced between 0.3 and 0.4 Hz in the normal and control human muscle bundles. Work at this frequency is minimal in the mutant muscle bundles in which the peak work/cycle has been shifted to ≈1.3 Hz.