Human aging particularly after ∼70 years, is associated with declines in physical function and athletic performance, that are accelerated in part by age-associated declines in physical activity and exercise training. Because elite athletes maintain high levels of physical activity across the lifespan, older athletes (Masters) may present as a proxy for healthy human aging. Although longitudinal studies are most informative about human aging, there are substantial practical challenges to conducting longitudinally designed research. Masters athletic records and comparisons of performance across age groups can serve as a practical and unique probe to predict the trajectory of human function throughout the lifespan. While useful, the cross-sect...