A Weekly Pause to Move You Forward
Last week I wrote about blood sugar. One of the levers I mentioned: aerobic fitness. Skeletal muscle clears glucose. Cardiorespiratory fitness improves insulin sensitivity, so the layers connect.
Before I get into it, a quick check. Do any of these sound familiar?
You used to train, then life intervened. An injury, a move, a new job, a baby, more responsibilities. The cardio is often the first thing to go. Or you never stopped, but your fitness doesn't seem to move. The same effort feels the same as it did two years ago. You're breathing harder than you think you should be at a pace that used to feel easy. You finish a session feeling like you worked, but you couldn't tell someone what you were actually building. You get to the end of a long day, and there's nothing left, not for the evening, not for the people in it.
These aren't signs you need to train more or start over. They’re often signs that the aerobic engine hasn't been built the way you think it has.
The reframe: this isn't a fitness metric
VO2 max measures the maximum rate at which your body can deliver and use oxygen during exercise. Most people think of it as an athlete's number. A thing triathletes track. It is. It's also one of the strongest predictors of all-cause mortality in the medical literature. Stronger, in large studies, than smoking, diabetes, or heart disease.
A large study following more than 122,000 patients found that going from low to below-average cardiorespiratory fitness reduced all-cause mortality risk by roughly 50%. The gap between sedentary and merely average fitness is larger than the gap between average and elite, so get moving!
This isn't a performance metric. It's a longevity metric wearing performance clothing.
The longevity argument isn't even the most immediate one. VO2 max declines roughly 10% per decade after 30, accelerating after 50. A number that feels adequate at 40 becomes a limitation at 50 and a genuine constraint at 60. The hike that feels easy now, the one you want to do with your kids or your partner or just because you want to still be doing hard things at 65, gets harder every year the baseline stays where it is.
The question isn't whether decline is coming. It is. The question is what baseline you're declining from. Building now, while the training response is still strong, is the highest-return window you have. Trained individuals decline at roughly half the rate of sedentary ones. The work you do now doesn't just raise the baseline. It flattens the curve.
And unlike most longevity markers, it responds directly to training. You can move it. Most people just don't know how.
I want to keep up with my son as long as I can, so I want to flatten the curve.