Muscular power decreases with age, and lower-body power relates to overall functional fitness; however, functional lower-body power has not been evaluated in late-middle-aged (LMA) populations. Purpose:To evaluate average and peak lower-body functional power and velocity among sedentary (SED), recreationally active (RA), and masters athlete (MA) LMA adults.Methods:Participants were SED (n = 13, age = 59.3 ± 4.5 years), RA (n = 35, age = 59.6 ± 5.0 years), and MA (n = 26, age = 56.7 ± 5.4 years). Five sit-to-stand trials were completed to assess lower-body functional power. Average/peak power and velocity were calculated for each trial. Power was expressed relatively to account for participant body weight. Results:MA (13.44 ± 2.76 W/kg) had significantly (p < .01) greater peak power compared with SED (9.99 ± 2.70 W/ kg) and RA (9.93 ± 2.30 W/kg). Similar significant (p < .01) differences existed for peak velocity (SED = 1.02 ± 0.22 m/s, RA = 1.04 ± 0.22 m/s, MA = 1.25 ± 0.19 m/s). No differences existed for average power or velocity between groups.Conclusions:Maintaining a competitively active lifestyle results in greater lower-body functional power in LMA adults and may support longitudinal functionality.