Dynamic and elastic stiffness of the semitendinosus muscle after knee joint immobilization in rats.docx

We clarified the maximum limit of the semitendinosus muscle
length in vivo was equivalent to 110% of slack length, which was taken as the limit of
the physiological range. To evaluate mechanical features representing muscle
stiffness within and beyond the limits of physiological muscle length,
quadratic functions were fitted separately to the dynamic and elastic
tension-strain curves at strains of 2.5%–10% Ls as the small
strain and at strains of 7.5%–20% Ls as the large strain.
The stiffness for small strains was then estimated by calculating the tangents
at strains of 5% and 7.5% Ls of the quadratic fit to four
points (strains of 2.5%, 5%, 7.5%, and 10%
Ls), while stiffness for large strains were similarly estimated from the
tangents for strains of 10% and 15% Ls of the quadratic fit to four
points (strains of 7.5%, 10%, 15%, and 20% Ls).