This investigation examined differences in functional sit-to-stand power/velocity between cohorts of adults aged 18–97 years. This study included 264 healthy adults classified into four cohorts (18–40, C1; 60–69, C2; 70–79, C2; ≥ 80, C4). Participants completed the sit-to-stand task five times. Power and velocity were measured via the TENDO power analyzer. Absolute average power was maintained from C1–C3, but decreased (p < .01) in C4. Absolute peak power decreased between C1–C2 (p < .01), was similar between C2–C3, and decreased in C4 (p < .01). Relative (to body weight) average and peak power decreased between C1–C2 (p < .01), was similar between C2–C3, and decreased in C4 (p < .01). Average velocity was similar between C1 and C2, but decreased in C3 (p < .01) and C4 (p < .01), respectively. Peak velocity was significantly different between all cohorts (p < .01). Declines in functional power may plateau during the seventh and eighth decades, accelerating after 80 years.