The Truth About Cardio After 40

The pendulum swung too far. For decades cardio was prescribed as the cure for everything, and adults over 40 ran themselves into stress fractures, hormonal disruption, and joint pain chasing a fat-loss outcome that strength training would have delivered with less wear and tear.

The current evidence-based prescription is layered. Build a base of low-intensity zone-2 work — walking, easy cycling, swimming — for 150 to 200 minutes per week. Add one or two short, high-intensity sessions: hill sprints, bike intervals, or rowing. That's it.

Zone 2 builds mitochondrial density, which is the single best marker of metabolic and cardiovascular longevity we currently know how to measure. High-intensity work raises VO2 max, which independently predicts all-cause mortality more powerfully than smoking status.

Notice what's missing: the 90-minute grinding runs at moderate intensity. That zone — too hard to be easy, too easy to be hard — accumulates fatigue without proportionate adaptation. After 40, your hours are too precious to spend there.