A five-year study tracking 500 adults aged 70–77 found that exercise intensity matters enormously for preserving cardiorespiratory fitness as we age. Those who consistently did high-intensity training (HIT) saw far smaller declines in peak oxygen uptake (VO2 peak) compared to moderate-intensity exercisers. Men doing HIT declined only 3.1%, versus 7.7% for moderate exercisers. Remarkably, women doing HIT showed no significant decline at all, while moderate-intensity women declined 4.6%. The advantage of HIT over moderate training was roughly 1.3 mL/kg/min in both sexes at five years. Exploratory analyses also suggested that as people age, intensity becomes increasingly important — more so than total weekly exercise duration. This is meaningful because VO2 max is one of the strongest known predictors of longevity and overall health.
