LONDON (Reuters) - Olympic 100 metres hurdles champion Sally Pearson finished seventh on her Diamond League return in Birmingham on Sunday (June 5) but vowed to be at her best for Rio after an agonising year recovering from injury.

"I'm not disappointed by today, it's not nice seeing a 13 seconds in front of your name but this is my first real race in just over a year now so I can't really complain," the Australian told BBC television.

"I wasn't running 100 per cent out there. That's not an excuse, it's just I wanted to be out there so badly so I was going to risk not getting a great position and a great time," said the 29-year-old.

American Keni Harrison won in a time of 12.46 seconds, with Pearson - whose personal best is 12.28 - crossing the line in 13.25.

The Australian had clocked 12.75 in a local meet on the Gold Coast last month, her first run-out since she shattered her wrist when she fell in a Diamond League meeting in Rome last June.

She had feared her lower left arm might have to be amputated after that injury, and an old Achilles problem further hampered her preparations for Rio, where she will be competing at her third Olympics.

Sunday marked a return to proper competitive action and she said she felt good, despite the odd niggle.

"It's just so nice to be back and being in a competitive environment. For me it's just taking one race at a time. I've got five in about two weeks so today is the first one of many," she added.

"We always go out onto the track wanting to win but some days it's just not our day. I'm going to make sure that I do everything that I can in my power to be at my best at the Olympics."