Move Like Your Time Depends on It

I almost didn't include an exercise chapter. Everybody knows exercise is good for you. Everybody has been told to move more. Adding another voice to the chorus felt like exactly the kind of advice this book is supposed to transcend.

But the research on exercise and temporal experience is too important to skip, because it reframes why exercise matters in a way I hadn't seen before.

The standard case for exercise goes like this: it's good for your heart, your weight, your mood, your longevity. True, all of it. Peter Attia calls exercise the most potent "pro-longevity drug" we have, and the evidence backs him. But all of those benefits are about quantity of life. More years. Less disease. Better biomarkers.

The temporal case is different. Exercise isn't just about living longer. It's about making the years you live feel longer.

Here's the chain. Cardiovascular fitness enhances cerebral blood flow. More blood to the brain means more oxygen and nutrients reaching the prefrontal cortex and temporal regions, which are precisely the areas responsible for attention, working memory, and temporal cognition. Studies show that higher cardiorespiratory fitness is associated with reduced loss of grey and white matter in these regions. You're literally preserving the brain hardware that processes time.

Better attention and working memory mean richer moment-to-moment encoding. Richer encoding means denser memory. Denser memory means retrospective time expands. A year lived with a brain that's well-supplied with blood and oxygen feels like a longer year than one lived with a brain running on reduced supply.

There's also the mitochondrial angle. After forty, mitochondrial function naturally declines. Mitochondria produce ATP, the energy currency of every cell, including neurons. As production drops, so does the energy available for neural processing. The result is subtle but pervasive: slightly less sharp attention, slightly less vivid perception, slightly less capacity for the kind of deep engagement that produces thick time.

Exercise is one of the most reliable ways to reverse this decline. Endurance training triggers mitochondrial biogenesis, the creation of new mitochondria. Resistance training preserves and builds the muscle tissue where much of this production happens. The combination doesn't just make you stronger and fitter. It increases the cellular energy available to your brain, which directly supports the kind of processing that makes time feel real.

And then there's the temporal experience of exercise itself. A hard workout compresses prospective time: you're so focused on the effort that the minutes fly. But it massively enriches retrospective time. The brain encodes exercise sessions with high detail because they involve significant physiological arousal, sensory intensity, and deviation from baseline states. A morning run is, neurally speaking, an oddball stimulus. It's different enough from sitting at a desk that the brain flags it as noteworthy.

Research on fitness and cognition in midlife adds another dimension. A study published in the Journal of the American Heart Association found that cardiovascular fitness improvements may provide proportionally larger cognitive benefits in older age than in youth. The midlife brain responds to exercise more dramatically than the younger brain, possibly because there's more room for improvement in the supply-constrained system.

This means that if you're forty-seven and haven't been exercising regularly, the potential upside is greater, not smaller, than it was at twenty-five. The brain that's been running on reduced blood flow has more to gain from improved supply.

Now, the intervention problem. I know from experience that "exercise more" is the kind of advice that sounds obvious and proves difficult. It's another thing on the list. It takes time, energy, planning, and equipment. It competes with sleep, work, family, and rest.

So let me be specific about what the research actually requires.

The cognitive and temporal benefits emerge from cardiovascular exercise at moderate intensity, performed consistently. Thirty minutes, three to five times per week. That can be walking at a pace that raises your heart rate, cycling, swimming, or running. It doesn't need to be heroic. It needs to be consistent.

The most reliable way to make it consistent, in my experience, is to attach it to something structural. I recently moved to a walkable neighbourhood. The school run is now a walk. The coffee run is a walk. The commute to anywhere in the city centre is a walk. I didn't add exercise to my schedule. I restructured my life so that movement happens inside activities I was already doing.

This is architecture, not discipline. And it works precisely because it doesn't require a daily decision. The movement is built into the day.

If walking isn't enough to raise your heart rate, add intensity to what you're already doing. Walk hills. Walk fast. Carry something. The point isn't to train for a marathon. The point is to get blood flowing to the brain regions that process your experience of being alive.

Because exercise isn't just adding years to your life. It's adding life to your years. And the difference is the difference between a long existence and a thick one.