'Robots' Uchimura and Biles ready to roll

The world's best gymnasts are hoping the sweat and tears they've shed in training will provide them with the spark they need at the Olympics to pull the plug on two record-chasing champions who have been dubbed "robots".

Such has been the dominance of Japan's Kohei Uchimura and Simone Biles of the US over the four-year Olympic cycle that if they fail to win the all-around titles at the Rio Games it will be considered one of the biggest shocks witnessed in the sport.

After collecting every Olympic and world all-around title since taking silver at the 2008 Beijing Games, Kohei is favored to become the first man since compatriot Sawao Kato in 1972 to win successive Olympic all-around titles.