Physical performance starts easing around age 35

Strength, stamina and overall fitness typically begin tapering near age 35, according to a Swedish project that tracked participants for 47 years. Performance did not fall suddenly. The losses started gradually and picked up speed later in life, including among adults who stayed active.

Researchers repeatedly tested 427 women and men born in 1958, following them from age 16 through 63. The measurements covered oxygen-based fitness, the ability of muscles to keep working and the capacity to generate force quickly. Most endurance and aerobic scores topped out somewhere from age 26 through 36, while certain power measures crested sooner. At 63, average results were about 30 to 48 percent below their highest points. Men and women followed broadly comparable patterns of decline, although their individual abilities varied.

Activity still made a meaningful difference. People who took up exercise as adults improved their physical capacity by roughly 5 to 10 percent. Those active in adolescence also generally carried stronger performance into later years. A 2026 analysis of this same group connected stronger aerobic results at 34 and 52 with more flexible arteries at 63. Researchers now plan to study the biological processes behind the downturn and the reason movement can reduce, but not eliminate, performance losses.