January Jones used to "lie" about training for 'X-Men: First Class'

She admitted: "My dad was a trainer, so in my 20s and 30s, I didn't work out, because he was always pushing my sisters, my mom, and me to exercise. We would rebel and not do it.

"It's not that I wasn't active. As kids, my two sisters were runners, I played tennis, and we all swam. But on a regular basis I wouldn't work out, ever.

"Even when I was filming 'X-Men' and they had trainers for all of us, I would lie and say I was exercising in my hotel room, when actually I was watching 'Friends' and having full tea service."

But after giving birth to her son Xander, now eight, the 'Spinning Out' actress wanted to be "stronger" and fitter and even though her body has completely changed, she's delighted with the results of her workout regime.

She added in an interview with Shape magazine: "After I had my son, Xander, I wanted to feel strong because my body had changed so much.

"As he got bigger and I was hauling around a 20- or 30-pound toddler, my lower back gave out and I saw my shoulders starting to curl and hunch. I wanted to do something for my posture and core strength.

"Two or three years ago I started doing barre classes, and after that I took regular private Pilates lessons.

"Then a friend told me about Lagree Pilates. I've been doing it two to four times a week for the past year now, and I've gained weight because I've put on muscle. I've gone up a size in clothes, but I feel like I look better naked."

And January is very motivated in her new class, even though it is difficult, because there are other women there to "push" her to stretch herself, unlike when she took the one-to-one classes.

She explained: "Lagree is quite difficult, but I've found that it's the only thing that really makes me feel stronger, and I'm loving it. The music is good and there's always a different routine, so it doesn't get boring.

"There are 10 of us in the class, and I like having women on both sides of me to push me.

"When I did the private Pilates lessons a couple of years ago, I just saw myself getting lazy with it because there wasn't that drive for competition. For me, that's what's motivating.

"If there's someone strong next to me, I definitely want to up my game. I find myself looking forward to it more than I've ever looked forward to a workout."