The bulk of your cardio should feel almost too easy, and that ease is the point. Keep it at a conversational pace, often called zone 2, where you can talk in full sentences but not sing.
At that easy intensity, your body runs largely on fat and trains its aerobic machinery without draining you. Over weeks it builds more mitochondria and capillaries, the cellular engine and plumbing that raise your endurance and metabolic flexibility.
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The core idea is well established in exercise physiology, even if the branding oversells the precision. A base of easy aerobic training reliably improves fitness and metabolic health, while the exact heart-rate and lactate zones are approximate and individual.
Use the talk test rather than a gadget. If you can hold a conversation but would struggle to sing, you are in the range, and a rough guide is around sixty to seventy percent of your maximum heart rate.
The usual error is going too hard on easy days. Deliberately holding back feels counterintuitive, but that restraint is what lets you accumulate volume without burning out or getting hurt.
Aim for something like 150 minutes a week, in sessions of thirty to sixty minutes. Brisk walking, cycling, swimming, or an incline treadmill all count, whatever you will actually repeat.
This is the base, not the whole pyramid. Pair a foundation of easy zone 2 with one harder interval session a week, and you cover both ends of fitness rather than living in the exhausting middle.
For you, the easy pace is a feature. It is joint-friendly, sustainable across decades, and it improves the insulin sensitivity and stamina that everything else at sixty-five depends on.
Slow down to build the engine, then go hard once a week to raise its ceiling. On easy days, easy is the whole assignment, and easy is enough.
