Fig. 1.

Dynamic mechanical properties of mature and aged patellar tendons. [A] The dynamic modulus (∣E*∣: the ratio of stress to strain measured in oscillatory applied displacement) at 6% strain for WT tendons at 150 and 570 days old. Aged tendons exhibited significantly decreased dynamic modulus revealing greater deformability at all frequencies. [B] Dynamic modulus at 1 Hz, shown at 4%, 6% and 8% strains. Results were consistent across all strains and frequencies (see Table 1, Supplemental Data S1). [C] Tangent of phase angle δ at 6% for WT tendons (δ: the angular gap between peaks of stress and strain sinusoids; tanδ: equal to ratio of dissipated force to stored force). Aged tendons had significantly higher phase angles demonstrating increased viscoelasticity and force dissipation. [D] Phase angle at 1 Hz, shown for 4%, 6% and 8% stains. Significance bars denote p≤0.05.