"A short one is cheating"

This is the fifth reason, the one about standards, and I said I respected it most. You don't like token efforts. You'd rather do nothing and be honest about it than do ten minutes and pretend you've trained. A short session feels like a way of letting yourself off.

I'd like to take the standard at its word and see what it produces.

Suppose two people have the same busy life. The first holds to the full session. The plan is three sessions of forty-five minutes a week. In a good week all three happen. But most weeks aren't good. Let's say, and I'm being generous, that over a typical month the plan delivers one session a week on average. That's forty-five minutes a week. In a bad month, which for many people with this habit is most months, it delivers one session a fortnight or fewer. Call it twenty minutes a week, and for some stretches nothing at all.

The second person has no plan worth the name. They do ten minutes of brisk walking most days, say six days out of seven, because ten minutes nearly always fits. That's sixty minutes a week, every week, in good months and bad.

These figures are arithmetic on an example, and they aren't statistics about anyone. You can put in your own numbers from the exercise at the end of chapter 1. But for many readers the sum comes out the same way. The person with the high standard is doing less exercise than the person with the low one, often much less. Far from protecting the quality of their exercise, the standard is preventing most of it from happening.

Now go back to the curve in chapter 3. It's steepest at the bottom. The difference between nought and sixty minutes a week is where most of the benefit lies. The person doing ten minutes a day is standing on the good part of the curve all year round. The person waiting for full sessions spends long stretches at the bottom.

So which of them is cheating? I'd say it's closer to the truth that the high standard works as a respectable excuse, though I don't mean that as an accusation. Nobody chooses it for that reason. It feels like rigour. But judge a rule by what it produces, and a rule that says "do it properly or not at all" reliably produces not at all. It's like refusing to put five pounds into savings because you can't spare five hundred. Whatever you think of the principle, the account stays empty.

There's an identity question under this, and I'd like to answer it plainly. You might feel that people who exercise are a certain type. They have the kit and the routine and the hour carved out. If you do ten minutes in your work shoes you're not one of them. You're someone who walked round the block.

I'd turn that round. What makes someone "a person who exercises" is that they move their body on most days, year after year. The kit, the hour and the gym don't decide it. By that measure the ten-minutes-a-day person qualifies and the three-planned-sessions person mostly doesn't, however good their trainers are. If being that kind of person matters to you, regular short sessions will get you there sooner than full sessions that keep getting cancelled.

None of this means lowering your standards for the full session when you do one. It means having a second standard for the other days, and the second standard is that something beats nothing.