The 47-year SPAF study challenges standard aging models by revealing that aerobic capacity and muscular endurance actually peak in the mid-30s, nearly a decade after explosive power, which degrades first. This physiological decline follows a non-linear path: a slow drift of roughly 0.5% annually until the mid-50s, followed by a sharp acceleration to 2.5% loss per year, resulting in a total capacity reduction of 30-48% by age 63. Crucially, the variance in physical performance between subjects increased 25-fold between adolescence and late adulthood.