When the President of the United States jokes about his wife's "right to bare arms", you know critics have touched a nerve.

Michelle Obama may be a fashion icon, perhaps the most talked-about First Lady since Jackie Kennedy, but the sleeveless dresses and unashamed musculature of the First Lady break protocol practically laid down in the constitution.

For it is written, by self-styled wardrobe experts Trinny and Susannah no less, that women over the age of 40 who want to be taken seriously keep their arms - however toned - firmly under wraps.

Barack Obama's joke in front the US's political commentators at the weekend was a response to those quick to label Michelle Obama's style too informal and unseasonal, even if Mamie Eisenhower did set the benchmark by going sleeveless in her official White House photograph.

New York Times columnist Maureen Dowd wrote that "it is Michelle who looks as though she could easily wind up and punch out Rush Limbaugh, Bernie Madoff, and all the corporate creeps who ripped off America."

Tyler Brule, for the Financial Times, said: "Someone needs to tell Michelle Obama that there's a time and place for bare arms and it's not on an early spring evening at a rather important global conference in London."

Much has been made of Michelle Obama's statuesque 5'11" frame and her thrice-weekly fitness sessions. But when does arm muscle tone become more akin to Sigourney Weaver in Alien, Linda Hamilton in The Terminator or Serena Williams in full flight on the tennis court?

"Madonna has gone too far for me," says personal trainer Jenni Doogan, "but it's nice to have a bit of definition and a bit of shape.

"A lot of celebrities look fit and toned now rather than size zero. Most females now want to look like they do work out but not too much. It's about achieving that tiny bit of upper arm cutting in on their shoulder but not too muscly; just enough to say that they work out.

"It's definitely achievable if you're going to work hard at it."

To strike that balance between fashionable and fit, Ms Doogan recommends cardiovascular and resistance exercises to give the fat reduction and muscle tone required for Obama arms.

The group fitness instructor at LA Fitness gym in Milngavie advises using an arm cycle machine teamed with cross-trainer with arm movement and regular running for the cardio side, which, teamed with a healthy diet, will lead to fat loss.

The bicep, tricep and shoulders can be worked in exercises that can be performed at home. These include tricep dips off the seat of a chair using your body weight as resistance; dumbell curls to work the bicep by bringing weights up to shoulders by flexing arms at elbow; and lateral arm raises whereby hands are raised with straight arms to shoulder height, either at the side or front of the body.

Ms Doogan recommends performing two to three sets of 15-20 repetitions of each of these several times a week.

Shelley Boyle, owner of the Urban Beauty salon in Shawlands, Glasgow, is aware that women can hide a few tricks up their sleeves. Regular exfoliation and a little self-tan can help hide a multitude of arm sins.

She said: "I'm a huge fan of body brushing - you brush up the arms, which is amazing for improving the skin texture, getting the blood going and really improving the appearance of the arms.

"Remember plenty of moisturiser and a wee bit of fake tan will help to define the muscles. Really look after your arms. You can tell Michelle Obama is a woman who does."

Yet, limbering up stylishly for summer when your contacts book doesn't boast numbers for Kai Milla, Narciso Rodriguez, Michael Kors or Tracy Reese could be as simple as investing in the right underwear.

Therese Kearins, personal shopper at Debenhams in the Silverburn shopping centre, says: "When your bust is sitting where it should be, that can make your upper arm look slimmer.

"If you're busty, then a nice v-neck shape can draw attention away from your arms. When ladies get to their 70s they really don't like to show their arms and I think it's better to respect that, but 40 and 50 is still young. Just be confident and enjoy yourself."