Michelle Bridges shows first picture of baby Axel on magazine cover

Proud parents: Steve "Commando" Willis and Michelle Bridges. Photo: Don Arnold

• Michelle Bridges blasted as irresponsible

Michelle Bridges has shown off her newborn baby boy for the first time in public.

The fitness guru, 45, and her partner, Steve "Commando" Willis, 39, welcomed their first child together, Axel, on December 19 and Bridges is giving him his picture debut - on the cover of The Australian Women's Weekly.

Michelle Bridges shows off baby boy Axel for the first time. Photo: The Australian Women's Weekly

In the photo, she cradles the sleeping newborn to her cheek, while she glows in a royal blue dress with string straps that show off the fruits of her post-natal workouts. Axel was described as a "total delight" during the shoot.

In the February issue, the multimillion-dollar entrepreneur describes Axel as "the best thing I've ever done".

"I've got this mother instinct that people always talk about," she adds. "It's quite fierce and protective."

She is also set to open up about what life is like in their blended family alongside Willis' three children from two previous relationships, a health scare following birth that landed her back in hospital and how her body has changed.

Loving their front covers, the pair announced in July they were expecting Axel, in a magazine deal with Who magazine.

On Monday, The Biggest Loser trainer was criticised for her post-natal jogging workout, despite a disclaimer reminding people she is a professional with 30 years of training behind her.

Given that new mums are generally advised against running for three months after birth, the response to the post was unsurprising.

"If an individual decides to jog soon after giving birth, this is their choice," Women In Focus Physiotherapy posted to its Facebook page on Friday.

"However, as a public figure encouraging women who's [sic] body types, birth and fitness histories are unknown, to start jogging is quite frankly concerning. It could potentially cause a woman more harm than good in these early stages, especially to the pelvic floor and the ligaments that support the bladder, uterus and bowel."