She's 50, fit and many would say fabulous. So why's she still dressing like a 25-year-old? Glen Humphries thinks it's time Madonna grew up.By now everyone should know Madonna has turned 50.You could hardly have missed it. There were reams of coverage about her impending half-century and most of it was sickeningly sycophantic from people trying to delude themselves that their darling Maddy is something more than an embarrassing has-been who is really far too old to be carrying on like she does.Now that she's 50 it would be nice if she acted her age. But she's not going to. Instead she's reverted to that sexy image she had more than 20 years ago.Back then it worked. But now? Now that bumping and grinding makes her look like a mum who's had too much to drink at her son's 21st and is trying to dirty dance with his friends. I don't even like Madonna and I'm embarrassed for her when I see her carrying on like that.Madonna's defenders have claimed she is showing that a woman can turn 50 and still be sexy. What she's doing, they babble, is redefining what a 50-year-old woman should look like and how she should act. But what she's doing is trying to act like she's still 25. That's not redefining, that's regressing.By all means, 50-year-olds can still be sexy - but surely that's not achieved by trying to dress like someone half their age. The message she's sending is that the only way a middle-aged woman can look sexy is to dress like her daughter.The image is there to be seen on the cover of her latest album, Hard Candy. Hard Candy? Hard-faced, more like it. Sporting a skimpy outfit and thigh-high boots, her facial expressions are supposed to appear sexy but actually look like those old women you see at a pub that bring to mind the phrase "mutton dressed as lamb". Perhaps the main difference between Mads and them is that her mutton is more gym-honed.It's part of Madonna's desperate struggle for relevance in a world where young popsters have long overtaken her. And it shows she's a one-trick pony; instead of focusing on the music, she just sexes up her image again. Once Madonna did have the music to match her habit of shocking people. Now, all she's got is the shock.For mine, Madonna's quest for relevance began when she pashed Britney Spears and Christina Aguilera at the MTV Music Awards in 2003. Madonna's American Life album had been released that year and tanked so she decided to get attention by piggybacking on the young stars that had, essentially, made her largely obsolete.It was supposed to be shocking but it was actually tiresome. Just Madonna yet again screaming "look at me!"That piggybacking is something she's continued, co-opting today's hip performers and producers like Timbaland, The Neptunes and Justin Timberlake to gain some relevance.By and large, it doesn't work. All it does it remind us how out of date she is. And old too. In the video for Four Minutes, her duet with Timberlake, she dances alongside the young star. Timberlake dances rings around her; moving all over the place while she struggles to match even half his moves. It's as though her ageing body simply can't do what his can.This is even more pronounced in the video for Hung Up which features plenty of young dancers busting some very acrobatic moves. And where is Madonna while they're doing this? She's in a dance studio wearing leg warmers, a revealing leotard and heels, tottering around like an old lady doing jazzercise. I'm sure this wasn't a deliberate ploy by Madonna but the contrast between her and the good dancers couldn't have been more stark.Late in the video, when she actually leaves the dance studio and meets up with the hot dancers, they're no longer pulling off those insane moves. Instead, they have to restrain themselves, limited to copying whatever dance steps Madonna's creaking body can still handle.Now that Madonna is 50, I just hope she chooses to take early retirement. And gets some dignity.