Figure 7.

Probability distribution functions (PDFs) of sarcomere lengths pooled from nine tested animals in the relaxed-short (A), activated-short (B), relaxed-long (C), and activated-long (D) muscles. Two weighted Gaussian curves (red and green curves) were fitted to the PDFs. Sarcomere lengths in the relaxed muscles had a normal distribution and therefore had only one Gaussian curve with significant weight (A,C). For the activated-short muscles, the distribution of SLs became bimodal, with mean lengths of 2.12 and 2.64 μm (B). However, a similar switch to bimodality in SL distribution was not observed in the activated-long muscle, as the SL distribution became only slightly positively skewed (D). Note that the area under the PDF and the total area under the two weighted Gaussian curves are, respectively, equal to 1.