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Fig. 4. A representative force-strain curve for a single pair of particles (middle
aponeurosis; Lo). Each point (x) is from a maximal tetanic
contraction via a different combination of ventral root filament
bundles. At the lowest recruitment levels used in this study (15-20% of
Po), the strains were typically more than 50% of the
strains attained at Po. This implies the existence of a
highly compliant toe region. The straight line is a tangent to the
force-strain curve at 75% of Po, and its slope is the
stiffness of the tissue at that point. Po for this muscle
was 1.58 N. Thus, it can be seen from the relationship between this tangent
line and the force-strain curve that the stiffness of the tissue did not vary
much above
30% of Po (0.5 N for this muscle).