Health Library / Training
This content is for education only and is not medical advice. I'm a fitness coach, not a physician. Talk to your doctor before starting any medication, hormone, supplement, or new exercise program, especially if you have a medical condition or take prescriptions.
There's a fitness number that tracks with how long people live better than almost anything else we measure, and hardly anyone over 45 knows theirs.
It's VO2 max — how much oxygen your body can actually use when you're working hard. When large groups of people have been tested and then followed for years, the ones with higher cardiorespiratory fitness die less, of basically everything. And the biggest jump isn't between the fit and the elite. It's between the bottom group and the one just above it.
Which is good news, because that's the cheapest improvement available. Going from doing nothing to doing something is where almost all the payoff sits.
Zone 2 has been talked about so much it's started to sound like a technique you need equipment to access. It isn't.
Zone 2 is the pace where you could hold a conversation, but you'd rather not be singing. You're working. You're breathing harder. You could keep going for an hour. If you can't get a full sentence out, you've gone too hard — which is the mistake nearly everyone makes, because it feels lazy.
On a heart rate monitor it lands roughly around 60 to 70 percent of your max, but the talk test gets you close enough and doesn't require you to know your true max, which most people estimate wrong anyway.
What it's doing: training the machinery in your muscle cells that burns fuel with oxygen. That's your aerobic base, it underpins everything else, and it improves at this pace specifically because you can accumulate enough time there. You cannot accumulate hours at a hard pace. That's the entire logic.
Two to three hours a week, in chunks you'll actually do. Walking uphill counts. A bike counts. Swimming counts. A brisk walk on flat ground may not be enough on its own if you're reasonably fit — you might need a hill or a pack.
Zone 2 builds the base. It doesn't do much for the top end, and the top end is the number that predicts things.
So once a week, something genuinely hard. Intervals — a few minutes near your limit, recover, repeat, a handful of times. Or hills. Or a rower. The specific tool matters far less than that you occasionally visit a place where talking is out of the question.
Once a week is enough. This is the part that's hard on recovery at our age, and a second hard session usually costs more than it returns.
Everything at one speed. The most common pattern I see: every session is moderately uncomfortable. Too hard to build a base, too easy to push the ceiling. You end up in the middle, which builds neither. Easy days easy, hard days hard.
Cardio instead of lifting. These do different jobs and you need both. Cardio won't hold your muscle. Lifting won't build your aerobic base. Run them alongside each other, ideally on different days or with the lifting first.
Nothing at all because of the knees. Almost always solvable. Bike, swim, row, incline walk, pool. I've had very few clients who couldn't find something, and none who couldn't find anything.
This matters more than the training advice. If during exertion you get:
Stop, and get checked. Not next month. Don't talk yourself into it being indigestion or being out of shape. Exertion is exactly when a heart problem announces itself, and being the guy who pushed through is not the story you want.
Also worth knowing: shortness of breath that's new and doesn't match the effort is the symptom people ignore longest, particularly women, whose heart symptoms more often show up as breathlessness or fatigue rather than the classic chest-clutching picture.
If you're starting from sedentary, over 45, or carrying any cardiovascular risk, get cleared first. Then go find a hill.
Last updated September 30, 2026