Why Aerobic Base Matters More Than High Intensity

High-intensity training comes up constantly in any search related to longevity. It's easy to come away thinking intensity is the main driver of VO2 Max and endurance gains. The Norwegian 4x4 workout, in particular, gets mentioned everywhere as a legitimate protocol, but it's also frequently misapplied, including by people who use it more often than their aerobic base can actually support.

What the Best Endurance Athletes in the World Actually Do

The best endurance athletes in the world are runners, skiers, and cyclists, and they all share one thing: an enormous amount of aerobic volume, accumulated week after week, year after year, for decades. High intensity is typically introduced once a race build begins; in the off-season, training is almost entirely aerobic. This is the group that posts VO2 Max numbers in the 70s and beyond (elite female athletes often run somewhat lower for physiological reasons, not because of training quality), along with a fat-burning capacity most of us can only aspire to. That capacity doesn't come from high intensity; it comes from years of aerobic volume, strength training, and steady progression. Intensity only becomes useful once that foundation already exists.

It's also worth noting how these athletes measure their hard efforts: almost never by heart rate. Heart rate responds to too many variables: sleep, stress, heat, hydration, to be a reliable moment-to-moment guide, so athletes train by watts and pace instead, since those are measurable and repeatable. A runner a few months from a race might run 10x800m at 2:30 with a 90-second walk recovery, paced rather than heart-rate-guided. They'll review the heart rate data afterward, but it isn't steering the effort in the moment.

Why Intensity Comes Last, Not First

This is why training should be sequenced deliberately. Aerobic volume, strength training, and functional movement form the base; intensity sits on top of that base, not underneath it. Skipping ahead to hard work before that foundation is built is the most common way people end up hurt, burned out, or stuck.

When and How to Add Intensity to Your Own Training

If you're testing your VO2 Max every six months, a good rule of thumb is to introduce high-intensity training about two months before your retest, which gives you 7 to 8 quality sessions to adapt to. It should also happen on the same equipment you'll be tested on; pushing hard on a bike won't translate to better performance on a steep treadmill incline.

For most people, that means working within the incline walking they're already doing. In the last 5 minutes of a 45-minute walk, increase both the incline and the speed rather than holding steady. As an example, if the walk has been at a 12% incline and 2.0–2.2 mph, those last five minutes can move up to a 15% incline and 2.4–2.8 mph. You're not chasing a heart rate or maxing out; you're teaching your body to handle a higher workload efficiently. One to two sessions a week, with that specific purpose in mind, is plenty. Hard for hard's sake is how people get hurt.

The 80/20 Rule, and Why We Lean Even Further

Aerobic volume should make up nearly all of your training. The standard recommendation across the endurance world is roughly an 80/20 split between low- and high-intensity work. Anecdotally, our BLU Members tend to do well with a ratio closer to 85/15, or even 90/10.

What matters most is raising your heart rate enough, often enough, to trigger the physiological adaptations that drive endurance, metabolic health, and brain health, without turning every session into something you have to grind through. Constant heavy breathing and exhaustion aren't a badge of honor; they're usually the first step toward overtraining, injury, or burnout. As coach Alan Couzens puts it: "Doing sporadic hard things is easy. Doing consistent, easy things is hard."

The Bottom Line

We can look at the healthiest populations on earth and observe one consistent thing: they move far more than anyone else. No structured intervals, no perfect heart rate prescriptions, just movement, built into ordinary life. The majority of your time should go toward intentionally moving as much as possible, simply to counter the sedentary nature of modern life. Once that low-hanging fruit is taken care of, structured workouts become the fun part, not the foundation. Don't let the constant stream of longevity advice about optimizing VO2 Max confuse that order.

Just. Move.

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