"But I want to get fit"

I've been making the case for ten minutes for several chapters. There's a fair objection to all of it, and I owe you a direct answer.

"I'm not exercising only to lower my risk of dying in thirty years. I want to be fit. I want to run ten kilometres, or get stronger, or look different, or keep up with my kids. Ten minutes of walking isn't going to do that. If I settle for ten minutes I'm giving up on what I want."

Part of this is right. Ten minutes of brisk walking a day will not prepare you for a ten-kilometre race. It won't build much muscle. Fitness goals of that kind need training, which means sessions that are long enough and hard enough to push the body to adapt, done regularly for months. Arem's pooled study in chapter 3 found that benefits kept rising up to three to five times the recommended minimum. More is better, up to a high level. I'm not going to pretend that ten minutes is all anyone needs.

What I'd question is the idea that accepting ten minutes means settling for ten minutes. It helps to separate two things that exercise does.

The first is health. That means lower risk of heart disease and early death, better mood and better sleep. The research says most of that comes from modest amounts, and the first few minutes are the most valuable.

The second is performance. That means running further, lifting more and changing shape. It needs proper training, and the full session is the right tool for it.

The threshold habit gives you neither. By insisting on performance-grade sessions every time, and cancelling when they can't happen, you lose the health benefits on all the cancelled days. You also don't get the performance benefits, because one session a fortnight doesn't train anybody. You've kept the ambitious goal and given up the means of getting there.

So I'd treat ten minutes as the floor. The floor is the least you'll do on a day when you'd meant to exercise. There's no ceiling. On days when you have the block of time, do the full session. Train for the ten kilometres if that's what you want. Ten minutes is what happens on the other days, and its job is to make sure that no planned day is a zero.

I'd go further and say the floor helps the ambitious goal. Training depends on consistency over months. Most people don't fail at fitness goals because their sessions were too short. They fail because the sessions stopped. They missed a week, then restarted, then missed a fortnight, as chapter 8 described. A floor keeps the routine alive through the bad weeks, so that when a good week comes you're continuing and not starting again.

There's one more thing, and I have to be careful how I put it. Ten minutes often turns into more. Chapter 5 described how the beginning is the worst part. Once you're warm and moving, carrying on is easy, and you'll quite often find that the ten-minute walk has become twenty-five. That's a real and useful effect. But it only works if the deal is honest. If "ten minutes" is a trick you're playing on yourself, and you really expect thirty every time, then part of you will know that. The resistance at twenty to seven will be to thirty minutes, not ten. So the agreement has to be real. Ten minutes is enough, and you're allowed to stop. If you feel like going on, go on. If you don't, you've done what you set out to do, and the day isn't a zero.