Behind the weird and wonderful world of bodybuilding

We knock the door but there's no reply. Dammit, this leaves us no choice.

We push down the handle, pop our head around the door and are immediately hit with a tidal wave of fake tan.

Spluttering through the mist, we venture into the tiny changing room: it's hot, stuffy and there's an energy in the air.

Everywhere we look, there's huge, hulking men painting themselves with a tan so dark it rivals creosote. Others are getting in some last-minute push-ups (that'd be the grunting) and some are scoffing energy bars and rice cakes.

Many of the bodybuilders are here with assistants, who are busy with miniature paint rollers and words of encouragement, and there's a mix of accents from around the country.

"You alright?," asks Martin Hall, a mountain of a man whose biceps are bigger than our body. "You look a bit lost."

After reassuring him we're not some mad muscle-hungry stalker, the 56-year-old (yes, really) tells us what it takes to get competition ready.

The personal trainer from Chesterfield is in the Over-50s category of today's National Amateur Body-Builders' Association England 2013 contest.

"It's a seven-days-a-week, 24-hours-a-day discipline," he says. "But I've been doing this for more than 20 years and I actually love the strict discipline of it all. It's like a full-time job. The diet is extremely tough and rigid, it's not for the faint-hearted – there's a lot of chicken!"

"I have no dairy and no sugar in the run-up to a competition," adds mum-of-four-boys Amanda Renshaw. "I'll get through 5kg of chicken easily, it's just protein all the way. That's hard, very hard, just eating the same thing over and over again.

"I've been training since I was 15 but I've only just started competing. I've always loved fitness and I've always had a strong physique but then I met Martin and he trained me up to competition standard and now I've really got into it.

"I've been preparing for this for nine months. I work out every single day, up to three times a day. I looking forward to getting even stronger and going on to bigger and bigger shows."

With that, the barber lifts up her vest to show us her abs. They're incredible. We vow to join a gym immediately. If not sooner.

But what's the atmosphere like backstage on show day?

"It's fantastic. I'm nervous and excited all at the same time. But it's very competitive. We're all friendly but we keep ourselves to ourselves, I'm not going to tell them any of my tips or training regime."

And, as a normal working mother, what's the reaction on the street to her muscles?

"Some people think it's too much but I love it," says Amanda, also from Chesterfield. "I really like that strong, healthy look. Besides, it comes in useful looking like this and having four boys – they don't mess with me."

At this point, one of the organisers comes in and calls the over-50s to the stage. The door and walls get covered with tan as the giants squeeze through and file out.

Weekend runs around to the front Brierley Hill Civic Hall so we can watch the action unfold. NABBA honorary life president Jim Charles has already warned us he runs a tight ship and likes to move through the many categories as swiftly as possible.

Inside, the lights are down but the stage lit up, a single podium placed in the middle.

Each bodybuilder comes on individually and performs a selection of poses to their own choice of music. Most go for drum and bass but, bizarrely, the odd bit of Ellie Goulding is thrown in too.

After that, it's a group line-up and the judges ask to see specific muscle combinations, before asking the competitors to pull their "most muscular" pose. They then retire from the stage and wait for the verdict. It's an exhausting process. The competitors summon up every ounce of strength within them to hold the gruelling poses.

We're told backstage how draining the process can be and that some entrants are known to be physically sick, such is the exertion. It's the women's turn next and we soon find ourselves back in another fake-tan filled dressing room. This time though, there's sparkles. Sparkles everywhere you turn.

There's stunning bejewelled bikinis, glittering high heels and shimmering false eyelashes and lip gloss.

Like the men, the women are getting in their last-minute preparations. One boyfriend is spray-tanning his girlfriend on the stairs, another girl is putting her make-up on with a shower cap atop her head and others are using resistance bands to pump up or scoffing power bars or Jaffa Cakes.

Kelsey Yung is in the Miss Toned category.

Dressed in a tiny pink bikini with mirrored detailing, the 30-year-old dancer and personal trainer has travelled from Barrow for the show.

"I've been competing since last year and I love getting out there on the stage. I get nervous at this point when I'm backstage and waiting to go on but once I'm out there, I love it.

"The reaction I get from people is always positive and I've got a lot of personal training work from my physique – I'm my own walking advert.

"I've been getting show ready for the past four weeks, I can get away with that and eating a teensy bit more than the others because I do so much cardio on a day-to-day basis.

"On show day, it takes a good two-and-a-half hours to get ready. There's the hair, the make-up, the tan – it's hard work. And the changing rooms are always boiling too so that never helps.

There's never any windows and when you're putting your tan on, you get absolutely roasting."

It's time to run back downstairs now for the junior section. Waiting on the stairs is tipped-for-the-top Sergio Lima from Essington's Saxon Gym. Born in Portugal, living in Wolverhampton, Sergio's being cheered on by fellow gym member Ryan Alexander, who assures us he's "out of shape" despite looking like Bane from Batman.

Now, when it comes to the juniors, don't let the name fool you - these are still big boys.

"I've been in the gym since I was 12 years old," says 18-year-old Luke Howard from Hartlepool.

"I've been bodybuilding for two years and the dedication you have to put in is unbelievable. I train six days a week."

Luke won Mr North Britain U17 last year and has his sights set on as many titles as possible. But, being just 18, does he ever feel like he's missing out on a normal teenage life?

"All my mates go out drinking and I can't do that. But, to be honest, I'm not bothered. I won't tell a lie though, the food does bother me. I do miss my food. Every time I walk past a pizza shop I'm like, 'oh my God'.

"It's a good lifestyle though – I'd encourage anyone to give it a go. It keeps you healthy and it's fun to be with your mates down the gym.

More people my age should give it a go."

Again, another call from the organisers comes in at this point, and the lads make their way to the stage.

With so many categories, the contest runs well into the evening but the hundreds in the audience remain in fine voice throughout.

Weekend however are shattered. Probably all that running up and down stairs.

With all this exercise who needs the gym, eh?

And then Kelsey walks past. And we're straight on the phone to the trainer.

Elizabeth Joyce