For Kayla Itsines, when it comes to staying in shape, you can never start too early. 

The fitness maven, 34, took to Instagram this week to share a sweet video celebrating her son Jax’s third birthday.

The video showed a very active and rambunctious toddler getting up to all sorts of adventurous activities.

He was also seen in the clip happily running on a treadmill, as doting mum Kayla stood behind the toddler, holding his hands.

The adorable video also showed Jax playing with big sister Arna, and being doted on by his father Jae Woodroffe.

The youngster also seemed unafraid of hard work, with the montage showing Jax dutifully mopping a gym floor.

For Kayla Itsines, when it comes to staying in shape, you can never start to early. (Pictured) 

The fitness influencer, 34, took took to Instagram to celebrate her son Jax’s third birthday, and shared a montage clip of the toddler that showed him training on a treadmill

‘Happy 3rd Birthday to my very well-behaved son JAXXXYYYYYBOOOYYYY WE LOVE YOU,’ Kayla captioned the post.

Followers flocked to the comments to swoon over the sweet video with many telling Kayla she had her work cut out for her with such a ball of energy for a son.

‘I’m out of breath watching this video compilation,’ one joked while another replied with: ‘I think I burned 200 calories from my heart racing with anxiety. 

‘I’m pretty sure I have the exact same footage of my 4yo boy.’

It was a sentiment not lost on Kayla who replied with: ‘Tell me about it.’

Another summed up the sentiment of many, adding: ‘He is 100% pure chaos and there is nothing better than seeing him love every second of life! Happy Birthday to Jaxy!’    

It comes after Kayla revealed how she handles family disputes between her young children.

Taking to Instagram in November, she revealed how she encouraged her daughter, Arna, six, to ‘stick up for herself’ after she had pushed her brother to the floor. 

The youngster also seemed unafraid of hard work, with the montage showing Jax dutifully mopping a gym floor

Kayla said her daughter had retaliated after she told her brother to stop shoving her around.

‘I got down to Jax’s level and looked at him dead in the eyes, and I said firmly and slowly: “She said stop. Listen the first time,”‘ Kayla said.

Kayla said that the squabble between the siblings had started because Jax was trying to take a toy from his sister.

‘…before I could do anything, Arna turned around and shoved him so hard he fell to the floor.  ‘He instantly looked at me shocked, looking at me for sympathy and started crying. 

Kayla and husband Jae Woodroffe, 34, tied the knot in December 2023.

The couple welcomed their first child together, Jax, in January 2023, with Kayla sharing custody of her daughter Arna, with her ex Tobi Pearce.