Jessica Alba has hit the gym just six weeks after giving birth to her son Hayes.

The 'Sin City' star - who is also mother to daughters Honor, nine, and Haven, six, with husband Cash Warren - welcomed third child into the world on December 31, and on Monday (12.02.18), Jessica shared a selfie of her dripping in sweat with her personal trainer after doing an intense static cycling class.

She captioned the post: ''Got back in the saddle ish was hard. #6weekspostpartum thx @aaronhines @cyclehousela & @tracydawnhall 4 motivating me. (sic)''

The 36-year-old actress recently revealed she has been using her maternity leave to catch-up on her favourite box sets.

And it seems she has become addicted to Netflix comedy 'Grace and Frankie' whilst at home with her kids.

Jessica shared a picture of herself snuggled up to newborn on Instagram and wrote: ''Tuesdays/all the days w my Hayes #chillin watching @graceandfrankie-I'm on season 4 and I don't want it to end ? #bingewatching #graceandfrankie#lovethisshow #newbornmom (sic)''

The 36-year-old actress previously shared a picture of herself breastfeeding Hayes.

She wrote: ''Sitting at home- feeding baby boy having all the feels for @shanidardenthx for pampering me -really loved my facial- feeling glowy and hydrated (sic)''

Jessica and Cash are delighted to now have a boy in the family and big sisters Honor and Haven have already bonded with their little brother.

A source shared: ''Cash was rooting for a boy, and they are happy about their little miracle ... Jessica thinks that the process has been much easier so far because she has been a mom for years now.

''The girls are really excited to have a brother and already obsessed with him.''