Stephen is indisposed this week and has asked me to write his fitness column. He is feeling a little irked that people are not taking what he likes to see as his spiritual odyssey seriously: one colleague questioned his mental well-being when he admitted last time to feeling a kind of latent fascism; two friends thought the exercise kick was a substitute for a sex life; and the Guardian's editor said he was evidently having a mid-life crisis. If he wasn't depressed before, he certainly is now. He also took his liking for boxercise a little too far and did a few rounds in the ring: he now has a throbbing head, a tender nose and a bruised ego.
He wanted me to tell you what a model client he has been and how I see the role of the personal trainer. The former is broadly true: he's had his emotional ups and downs but most of the time has been committed and enthusiastic. After 10 weeks, he is in much better shape physically and is now able to do things that were unimaginable at the beginning. He went on a 40-minute run last week - further than he'd run for 20 years - and said he felt he could have run for another 40.
Exercising regularly is like anything: the better you become at it, the more you tend to enjoy it. Exercise will become a habit, and then a habit you don't want to do without. Sometimes it can become an obsession. I don't advocate this; my philosophy on exercise and nutrition is the same as that for life in general - moderation in all things. It's important not to be obsessed by weight loss or the way you look: it's how you feel that counts, and feeling good means a balanced diet and a sufficient amount of exercise.
You will feel the benefit almost as soon as you start training, but it could be a couple of months before you start to see a major change. Training makes you feel more self-confident and more alive. Some people don't realise that until they start doing it; they come purely for the weight loss or muscle gain, but I try to get away from that and emphasise the way you feel mentally as well as physically.
It's important to see clients regularly, say twice or three times a week. If you meet regularly, you are more at ease with each other and it's more productive. You can get to know people well, maybe even socialise with them, but you have to realise where to draw the line. I've never dated any of my clients and I'm keen to keep it that way.
The important thing is to remember the objectives you have set. Seeing a client mustn't just become an opportunity to chat and gossip, though there may be times when the client has had a really bad day and you have to be supportive and willing to talk. But you shouldn't get too close; you have to keep a lid on the relationship. It shouldn't go beyond professional boundaries.
Meeting a client for the first time is like a blind date. It's not someone you meet through a shared interest - most clients and trainers are at opposite ends of the spectrum in terms of age, income and status - but that's one of the interesting things. First appearances can be deceptive: sometimes I've disliked a client on first meeting but come to like them later. Problems only arise if the client thinks he knows it all or is not sufficiently committed, or if he looks down on you or treats you as a servant. It has to be a relationship of equals; after all, the gym is a great leveller.
I'd originally wanted to be a footballer and was an apprentice at Shrewsbury Town but that didn't work out (I was never quite quick enough) and I went to the US on a soccer scholarship. I'd always kept myself fit, and got interested in coaching and personal training over there. I like to think it's because I want to help people; anyone who is just doing it for himself is eventually going to be found out.
After finishing my degree in physical education I worked as a trainer in the US, before moving back to the UK two years ago. We lag behind the US in the acceptance of training: here it's viewed as a rich person's toy and some people are embarrassed to tell their friends they've got a trainer, but in the US it is much more accepted - go to Central Park and you will see 50 trainers at work. There are more training companies and training-based gyms, and there is more in-home training and group exercise.
It's important for a trainer not to have too many clients or to do too many sessions in a row. I try to treat each client as if they are my first of the day. That's hard to do when you are tired, but you have to remember why they're coming - they're coming for help and advice and they expect you to be on form. Sometimes it's hard: if I do eight people in a day it gets tough. You can burn out and feel yourself thinking, "I don't want to deal with these people any more"; some days you go home at night and you just can't bear to be nice to your friends and flatmates. Perhaps I should get a personal trainer too.
• Sam Jenkins is a trainer at Matt Roberts at One, 1 Aldwych, London WC2 (tel 0171-300 0600), where Stephen Moss is working out for three months.
