I used to gym. This won't surprise anyone who has seen me in person. My body works like a well-oiled machine, say, a typewriter from 1932. But I think some people assume writerly types avoid exercise, and I'm here to tell you it's just not true. Many of us flock to exercise and benefit greatly from watching it being done by other people.The gym was in a basement under the sports centre of the university I went to; a steaming, stinking, clanking, pain-filled hole where the weak were crushed. And that was just the university. The gym was pretty grim too.It was run by a pair of former bodybuilding champions who were identical twins. The only way you could tell them apart was from the tattoos on their necks, but you didn't want to stare too long in case they used you as dental floss.Come to think of it, not staring was a bit of a theme. That's the unspoken contract at hard-core gyms. Everyone is working on their bodies to turn them into extraordinary spectacles, but nobody is allowed to look at the work in progress.Some of it was hard to ignore, though. Most of the regulars had stretch marks on their biceps but one Nigerian law student had stretch marks that had their own stretch marks. His arms looked like two anacondas that had swallowed a kindergarten class.The anxiety of looking and not looking reached a peak every time he lay down on the bench and told his buddy to take it to the max. Twenty-kilogram weights were added to the bar like beads strung on a necklace. When they ran out of weights they bolted anvils to each end and then welded pianos to the anvils.Then the screaming started: yells of encouragement, howls of pain, roars of pure testosterone. How do you not look at all of that? And yet, if it all goes horrifically wrong, should you be watching?It's not every day you see a man lift a small house over his head. But it's also not every day you see a man explode in the most shame-making way imaginable. The word "prolapse" hung heavy in the air.I'm sorry to mention such horrible things, but that's the reality of exercise. The fitness industry shows us pictures of elves bounding along Alpine paths, but as I discovered that one time I ran for four minutes, exercise is horrifying, undignified and ultimately bloody. Exercise and you'll be thin, they tell us. Nonsense. The reason you get thin when you exercise is because you vomit uncontrollably and then you lose the will to live.Some people swear by personal trainers. I swear at personal trainers. For starters, they're very personal. "I've seen bigger calves on chickens. That's not a muscle, that's a mosquito bite. You're not sedentary, you're sedimentary." Also there's all that maths, where they try to calculate your Body Mass Index by multiplying the voluptuousness of your love-handles by the circumference of your nostrils, divided by the bum of the square of your other two sides.And don't get me started on all that biometric gibberish. I don't know what my resting heart rate is because I don't keep a stopwatch under my pillow. I mean, if you're measuring your heart rate, you're not resting, right? And if you are, it's not going to be your resting heart rate; it's going to be your "trying to stay as calm as possible but secretly worrying that you're getting an elevated reading because you're worrying about getting an elevated reading and now your pulse is speeding up and your personal trainer is going to tell you that you've got the heart of a cholesterol-clogged squirrel and you're not allowed to eat a single French fry for the rest of your life" rate.So why did I stop going to the gym? Well, unlike many of the regulars, I eventually graduated. But mainly I realised I didn't need to, because I had achieved peak muscle.Apparently most people who stop exercising do so because they get discouraged when they don't see the results they were hoping for. Not me. I discovered that my body responds incredibly well to weight training. Well, not my whole body; more my upper body. Upper left side. Really, just my left arm. OK, the only muscle that responds to exercise is my left bicep. But what a response. All I need to do is raise a teacup to my lips 10 times and the thing waxes Schwarzeneggerish.And at the end of the day, that's enough for me, because the end of the day is sunset, which means it will be dark soon and nobody will be able to see that there's only one functioning muscle.Right. Enough procrastination. It's time to go and work on that resting heart rate...