Simone Biles, from Spring, TX, during the balance beam in the women's gymnastics US Olympic team trials at SAP Center, in San Jose, US, July 10, 2016. [Photo/Agencies]

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.

But the all-conquering gymnast, who has been immortalized in comic strips in his homeland and has an army of screaming teenybopper fans around the world, has his eyes firmly set on a medal he has yet to get his hands on - the Olympic men's team gold.

The collective strength of China means that since 1994, Chinese men have won 10 of 12 world championship team titles and three of the five Olympic golds up for grabs.

Japan, which captured five straight golds from 1960 to 1976, climbed to the top of the podium in Athens in 2004, but that was during the pre-Uchimura era.

Since his arrival on the world stage, Japan has had to make do with silver medals behind China in 2008 and 2012.

But having finally toppled China from its lofty perch at last year's world championships in Glasgow, Uchimura hopes he can now lead his band of Japanese brothers to Rio glory.

"All I can think about is how much I want team gold. That's everything," said Uchimura, who has won a record six consecutive all-around golds at the worlds.

Despite his diminutive 5-foot-5 frame, Uchimura is regarded as a gymnastics goliath as he has turned countless rivals into emotional wrecks in his never-ending search for perfection.

"A lot of foreign athletes say I perform like a machine. I take that as a compliment," said Uchimura, whose Olympic medal haul totals one gold and four silvers.

"To me, moves and performances that are mechanical are perfect. A robot can be more accurate and exact in movement than a human can every time."

While other gymnasts have won more medals and more golds, no one has dominated the sport or maintained their levels of excellence across six apparatus for as long as Uchimura.

In a grueling sport that seems to leave champions on the scrap heap faster than it takes Usain Bolt to run the 100 meters, Uchimura's gymnastics lifespan defies logic - but the 27-year-old is not the only one expected to break records in Rio.

American Biles, who was 11 years old when Uchimura picked up his first Olympic medal in 2008, has also been an unstoppable force after becoming the first woman to win a "three-peat" of all-around golds at the worlds.

"Everyone says that I'm an alien or a robot, but I think he (Uchimura) is," said the 19-year-old, who is the most successful female athlete at the worlds with a record haul of 10 gold medals.

"I think what Uchimura has done is very amazing and I don't think anyone could do what he does."

Yet she is now tipped to pull off a feat no woman has achieved for 20 years.

Since the event was introduced to the Olympic program in 1952, only three women have captured back-to-back world and Olympic all around titles: Larisa Latynina (1960), Ludmilla Tourischeva (1972) and Lilia Podkopayeva (1996).

So why does the 5-foot-3 dynamo think no one has done the double since 1996?

"I wasn't born earlier, so I had no say in that!" quipped Biles, who was born in 1997.

Biles and her American teammates - including Olympic all-around champion Gabby Douglas - are the overwhelming favorites to win a second successive gold having annihilated all before them since 2011.