With Simone Biles returning to action the Olympic gymnastics competition is assured of a dramatic conclusion on Tuesday as the American bids to end what has been a tumultuous Tokyo Games on a golden high.

Not seen in competition since last Tuesday when she abruptly dropped out of the team event after one vault, citing mental health issues, Biles will get one last shot at Tokyo gold when she competes in the balance beam final.

The second-of-three events on the final night of action at the Ariake Gymnastics Centre, all eyes are sure to be on Biles, who had looked set to return home to the United States with only a silver medal from the team event.

The 24-year-old came to Tokyo eyeing a record haul of six gold and ascending the throne as the greatest female Olympian of all-time across any sport but instead suffered a crisis of confidence that led to her withdrawing from the all-around and vault, uneven bars and floor finals.

Biles, winner of four gold medals at the 2016 Rio Olympics, explained later she was dealing with the "twisties" - where gymnasts are disoriented during their gravity-defying sequences.

While Biles is the reigning three-time world champion on the beam and 2016 Rio bronze medallists it is not considered her best apparatus.

But it does represent the least risk when it comes to skills that might be impacted by "the twisties".

A number of difficult acrobatic skills have to be performed on the beam but fast-paced tumbling and aerial twisting manoeuvres are limited on the apparatus.

If Biles were on top of her game she would be the clear favourite, as she would have been on every apparatus in every event in Tokyo, but questions about her fitness and state-of-mind hang in the air leaving the competition wide open.

China young guns 16-year-old Guan Chenchen and 18-year-old Tang Xijing, the 2018 Youth Olympics beam champion, are podium contenders as is another 16-year-old Vladislava Urazova, of the Russia Olympic Committee.

But the biggest threat Biles might face could come from within her own team with Sunisa Lee, who earlier snatched Biles's all-around crown, bidding for a fourth medal in her first Olympics.