I did something terrible this weekend. One moment of madness; a rush of blood to the head. Something which lasted for a moment, but which I will regret for the rest of my life.

I joined a gym.

Yeah. I know.

Those of you who know me will be familiar with the fact that I avoid exercise like the plague. Instead, I prefer to fool myself: if I break into anything more than a walk as I ascend the stairs I convince myself that I’ve done the equivalent of an hour’s intensive workout, and that I’ve just burned 300 calories, or something. However, for five minutes on a humid Saturday afternoon, I felt myself drawn towards it, for one reason. When I’m playing football with my boys in a few years’ time, I don’t want to be one of those dads who lies spasming on the turf like a fish out of water after five minutes of activity. I don’t want to be one of those dads whose belly is so big when they stand at the loo to pee they’re not sure in which direction the stream is aimed. And so, rush, blood, you get the picture.

Yeah, someone like you, pork chop.

Following a pizza (which I figured would give me plenty of energy and probably a heart attack), I arrived at the gym on Monday evening clutching a moss green towel, a bottle of Evian and my Blackberry. After having a rather startled photo taken for membership purposes (either that or the receptionist fancied me), I was introduced to a short, buff chap named Mike, whose shaven head was the proud waxy peak of a body clad in a skin-tight shirt and clinging shorts. He thought I hadn’t clocked him looking me up and down, taking in my pale thighs wincing at the daylight, my short shorts, and my baggy Wigan Athletic football shirt with the number ’21′ emblazoned proudly on the back. But I had. I might be weak in body, but not in mind. Not until I’m old, that is, and can’t remember my own name or in which direction I’m facing.

Please don't sue me.

I say weak in body; it transpired during the initial assessment that my skeletal muscle stands at 39%, a full 2% higher than an average male of my age, height and weight. I literally have no idea where this muscle lies; it’s certainly not my upper body, that’s for sure. Whenever Jess nuzzles into my shoulder as we watch a film, she’s met with a cheekful of shoulder bone and little more. This mythical 39% could possibly be packed into my buttocks, which have been described as ‘pert and chiselled’ – by me, that is. We decided on a regime of cardio work and weights, carrying each out on alternate nights. Tonight would be simply a taster of all the equipment I would be using. “Easy…” I thought, as we stepped onto the gym floor, where the air was opaque with sweat, testosterone and terrible, terrible music.

Five minutes later, as I’m rowing like a Viking and staring at digital numbers that make no sense, I realise: I’ve made a big mistake.

Already Mike is telling me that he’s going to “push me”, as he boasts of doing an hour on the bike followed by a 10k run. I nod as I pull back on the chain, cursing him and myself in words that get no further than pursed lips. A few minutes later, and I’m on the cross-trainer.

“Just pretend you’re running.” urges Mike, and he’s beginning to get exasperated. Rightly so: for some unknown reason I cannot get the hang of this stupid machine. Instead of merely running, I find myself doing some kind of strange motion akin to trying to maintain balance on an icy puddle, my feet whipping back and forth like a couple of pendulums on ecstasy.

Mike gives up. “Bike next.” he states, curtly, and I dab my glistening forehead whilst hauling myself onto the saddle and beginning to pedal. This is more like it, I think, and begin to relax as my feet circle away.

“Uhh…let’s increase the resistance a bit.” Mike gesticulates towards the blinking display, which I regard in despair as I realise that out of a resistance scale of 1 to 12, with 12 being the most resistance, I’m cruising on a leisurely 1. He punches a few buttons, and suddenly I’m pedalling through clay, my thighs – or ‘quads’, as I later learned – beginning to burn. Mike tells me I need to be aiming for 80 somethings a minute (he doesn’t say ‘somethings’, I just can’t remember what the term is). I look at the display, noting poutedly that I’m currently on 50. I’m essentially doing the equivalent of cycling through the English countryside, enjoying the spring air, the sweet birdsong, and trying to avoid crazed gun-wielding madmen. I push up my speed to 80. It hurts. Mike tells me that in a roundabout way that if I do under 80 then I’m a little fairy girl.

It’s the treadmill next, the machine I’ve been dreading the most. I’m no runner; in fact, I’m only half decent at running if I’m either running towards or away from something. Still, I oblige, and follow Mike on legs that have lost all substance, with muscles that feel like they’re made of custard. To the observer I would have born a close resemblance to Bambi learning how to walk, or Fred Astaire in mid-flail.

The belt is cranked up to running pace, and I try my best to ignore the sweat dripping off my nose and pouring into my ears as I focus on some gangster music video being shown on a plasma screen – all bling, intelligible gesturing, sunglasses, and whatnot. It doesn’t work.

We’re on the weights next, which – thanks to my dumb luck – is in a room located at the top of a flight of stairs. Mike bounds up, taking two steps at a time. I stagger behind, clinging desperately onto the handrail like a pensioner who’s had his Zimmer frame snatched off him. I walk into the weights room, ignoring the fact that I am the very definition of white trash as walking muscles effortlessly pull chin-ups and dumbells around me. Fortunately, I find weights to be much easier than cardio; mostly down to the fact that I can completely lie about which weight is right for me. ”Ooh yeah, that burns just right.” I say, feigning straining as I lift the equivalent of a puppy.

The end is in sight, like a light at the end of a tunnel or a rousing crescendo in the closing stages of a mind-numbing opera. Mike compliments my quads as I flex on the tortuously-named ‘leg extension’ machine. I feel uneasy, but a strange sense of accomplishment at finally identifying just where that elusive 39% of muscle must be.

A few half hearted stretches later, and the session is over. I shake Mike’s hand limply and stagger to my car, spitting phlegm onto tarmac as I go. I somehow manage to punch out a text to Jess through tired thumbs. “Just finished,” it reads. “when I’m done crying I’ll drive home.”

Fortunately, the roads home are relatively straight. Any sharp or prolonged turns would surely have resulted in my stringy biceps capitulating, plunging the car into the nearest hedge via a few pedestrians enjoying an evening walk. Now, half an hour later, the pain is subsiding, and I can actually type this post with fingers attached to hands attached to arms that don’t flop lifelessly any more. That’s not to say I won’t wake up tomorrow in agony, and have to slide out of bed just to avoid using my legs.

Will I go back? Probably, for the sake of my health and my family. But let’s leave it a day or so first. I can still hear my muscles screaming.

They all hurt.