The purpose of this study was to investigate the influence of chronological age on muscular strength, power, endurance, and quality in recreationally active women 20 to 89 years of age. One hundred and fifty-two female volunteers completed the study requirements and were divided into five-year age intervals (20 to 24, 25 to 29, 30 to 34, etc.) to 75 to 79 years, with an additional group of 80 to 89 years. Apart from the two oldest groups, each five-year interval contained at least 10 female volunteers. The participants completed physical function assessments (grip strength and vertical jump) as well as comprehensive muscle function testing of the elbow extensors and flexors, the knee extensors and flexors, and the plantar and dorsiflexors. Muscle function testing consisted of measures of maximal isometric strength and isometric rate of torque development; maximal dynamic strength and the time to achieve peak output at 60 and 240 deg/s; components of maximal muscular power such as peak power, peak velocity, and time to peak power, and time to peak velocity during isotonic contractions at 1 Nm and 20, 40, and 60% of maximal isometric strength; dynamic muscular endurance testing at a slow and fast contraction velocity (60 and 240 deg/s); and muscle quality and specific power indices were determined among the isometric, isokinetic, and isotonic assessments made relative to body composition measures. Body composition was assessed using dual energy x-ray absorptiometry (DXA), in addition to site specific measures of muscle cross-sectional area and muscle density of the upper and lower leg via peripheral computed tomography (pQCT). Age-related changes in serum levels of myostatin and interleukin 6 (IL-6) and their relationships with the included muscle characteristics were assessed. Significant age group differences were observed among many of the parameters, with some of these observations being removed when accounting for muscle mass (muscle quality/specific power). Across the force output parameters, critical ages for the onset of rate of decline occurred in the following order: dynamic strength and muscular power, muscular endurance during 240 deg/s, isometric strength/muscle quality/specific power, and latest during the muscular endurance task at 60 deg/s. Further, critical ages were detected within younger age groups for the lower body parameters when compared to the upper body parameters. Muscle groups representing different fiber type composition did not appear to influence the onset of critical changes. Location of the muscle group tended to influence the magnitude of decline since groups located distally and groups located anteriorly displayed greater decreases with increasing age. Contraction velocity also influenced age-related changes with larger declines being observed during the faster contraction conditions. Myostatin and IL-6 were positively associated with age (both p<0.05), however their relationships with muscle mass and performance were diminished when controlling for age. In summary, the influence of age on muscle function is a question that must be further qualified as many factors, namely the muscle group, contraction type, and contraction velocity/intensity each play a role. Although serum myostatin and IL-6 displayed significant relationships with age, their limited relationships with muscle characteristics hinders their ability to serve as age- and muscle-related biomarkers.