Bruce Jenner wears a sports bra on motorcycle cruise while recovering from surgery amid gender transition

He is set to reveal the details of his transition into a woman during an interview with Diane Sawyer, airing this Friday.

And after reports Bruce Jenner has already undergone breast augmentation, the former Olympic athlete appeared to be wearing a supportive undergarment during an outing on Sunday.

As the 65-year-old hopped on his sleek Harley Davidson for a cruise around the Santa Monica mountains, the outline of his sports bra could clearly be seen under his black sweatshirt. 

On his way: Bruce Jenner - who is reported to have undergone breast augmentation last month - went for a spin on his motorcycle around the Santa Monica mountains on Sunday. The outline of his sports bra could be seen under his sweatshirt

He also wore jeans, Nike trainers and a black safety helmet while a dainty gold bracelet could be seen hanging on his left wrist.

RadarOnline reported that Bruce had gone under the knife last month.

'Bruce had silicone breast implants put in a few weeks ago,' Radar quoted an insider. 'He went with a smaller implant because he didn't want to look ridiculous.' 

'Recovery hasn't been that difficult, but Bruce has had to sleep in a recliner to help with the healing,' the source said.

'He’s not allowed to lift anything, and he has to wear a bra 24/7, but he’s expected to resume normal activities in the next six weeks.' 

Preparing for his moment in the spotlight: The 65-year-old is preparing for his big moment where he will reportedly reveal he's transitioning into a woman during an interview with Diane Sawyer airing on Friday

Speed demon: Bruce covered up with a black safety helmet but accessorised with a dainty gold bracelet on his wrist

'He has been emotional, but finally feels like this is the body he has meant to have,' they added. 

As well as growing out his brunette locks, Bruce has already undergone a laryngeal shave procedure to flatten out his Adam's Apple, and has reportedly had rhinoplasty to sculpt his nose into a more feminine shape. 

He has also been seen recently with painted nails and a fuller looking pout.

In a recent clip from his two-hour interview with Sawyer, the reality star - who has six biological children and four stepchildren - revealed his brood are his biggest priority, saying: 'I can't let myself hurt them. They're the only ones I'm concerned with.'

He is seen supported by his four oldest children Burt, 36, Casey, 34, Brandon, 33, and Brody, 31 who sit nearby as he chats with the ABC host.