It feels like being in prison, because it is like being in prison; and all over the world, people are asking: how do you stay fit when you’re confined to the house? This is assuming you don’t already have, or want to buy, a load of equipment. (Although if you do want something cheap and incredibly useful, get some resistance bands.)

You don’t need any stuff to get fit – no weights, no benches, definitely no fancy trainers. And you can aim high. Theoretically, you could wake up in four months’ time looking like a creature of myth, a man or woman who has been cursed with the upper body of a bullock. That may not be what you want, of course, and if you notice it happening, stop the calisthenics and concentrate on star jumps.

Press-ups are the thing nobody wants to talk about, because they’re such a fitness cliche. But everybody ought to do them, because they became a cliche for a reason – and you could do them in a large toilet cubicle. There are five types of press-up: regular; cross-over hand placement (this is genuinely impossible unless you are already very strong, but I only tried it twice); Hindu, where you start in a downward dog; handstand press-up (in your dreams); and one-armed press-up (in your other, marginally more frightening dreams). Start by trying five at a time. Given that you have a huge amount of time, you will soon be racking up 240 in a day. I say “you” advisedly; I’m certainly not. But I am working on it, because the sense of progress plays a huge part in staying sane. Even to go from five half-press-ups a day to five full ones brings more than a sense of personal achievement. It says that some things haven’t changed, one season will still follow another, practice still makes, if not perfect, at least substantially less inept. You might get frustrated, but you don’t get bored.

With pull-ups, you can switch from an overhand grip to underhand, you can stretch yourself by touching your chin to the bar, or going one-handed. If you don’t have a bar in your house, I’d recommend one, particularly if you like to row with your spouse about whether it has to be up all the damn time.

The classic small-space squat (it’s actually called the “prisoner squat”, at least by prisoners) is to push it slightly lower than a regular squat, so that your thighs are below parallel and your hands are clasped at the back of your neck for a warrior air. And there is the burpee, which is cardio not muscle-building, for when you are looking a bit Territorial Army.

Finally, the plank: toes and elbows and forearms on the floor, everything else off it, nice and straight and horizontal, a bit like, you know, a plank. This is extremely satisfying, since you can start at 30 seconds and work up in five-second increments every day. You will, if not see, then certainly feel the difference it has made to your abs within about a week.

What I learned

When you’re building up in small increments, you don’t need to build in so many rest days – just one a week.