It's not often I turn to AC/DC for inspiration these days. I thought I'd left the Australian headbangers long behind: the scarf, the badges, the vinyl, locked away in a silver trunk in my attic with a few other dark and miserable secrets. In fact just thinking about them now makes me mildly embarrassed.

But lately I've been reading about motivational music and how it will help me run and while away the hours. Apparently, choosing the right type of music can pump up my energy levels, inspire me to greater efforts, to tap my toes in my running shoes. I'm not quite sure why, but I find myself turning to Highway to Hell. Five minutes before my jog I turn it on and turn it up. "She had the face of an angel smiling with sin, the body of Venus - with arms." Scary stuff - why did I ever like them? It's doing nothing for me.

I look at advice on a website: sportsmusic.com. For a pace leading to an eight- to 11-minute mile I need a tape at 155 beats per minute. It suggests the Bee Gees - Night Fever, Jive Talking, How Deep is Your Love. Are they serious? For a mile time of between six-and-a-half and eight minutes I need 169 beats: Queen's Crazy Little Thing Called Love, Eric Clapton's After Midnight. I leave for my gym and its mirrors and eight TVs.

I shouldn't be that depressed. Despite all the moans - and there are many - good things are happening to my body. Two months ago I would have broken into a sweat if I walked up the stairs, lungs burning, tears forming. Now I can skip up a flight two at a time.

The running itself is becoming easier. It takes about 30 minutes to get into my stride, but with my new best friend - the isotonic drink - I can keep going for nearly two hours without too much of a problem. My body is also changing: my chest is flattening slightly, rounding at the edges, becoming firmer. The stomach is still annoying me - stubbornly loose, not the washboard I'd dreamed of. But the legs are a different matter. They may not look pretty but they feel like iron pylons. I knock them with my knuckles and they sound solid. Music to my ears.