Indonesian Olympic medallist Triyatno had a look of pained determination on his face as he hauled a 180 kilo barbell into the air -- no mean feat for a weightlifter fasting during the Islamic holy month of Ramadan.

The 28-year-old and fellow weightlifter Eko Yuli Irawan were Indonesia's only two medal winners at the last Olympics, clinching silver and bronze respectively, and the pressure is on as they gear up for Rio this summer.

But that has not stopped the athletes joining tens of millions of others in the world's most populous Muslim-majority country in forgoing food and drink during the daytime to mark Ramadan.

And they insist it has not affected their intensive preparations.

"I don't find it a heavy weight, it's not difficult," Triyatno said of juggling the competing demands of fasting and getting ready for the Olympics. "My training remains the same."

At a recent session at a gym in Jakarta's main stadium, the country's weightlifting team spent two hours grunting and groaning as they pumped iron under the watchful eyes of their coaches.

While most in Indonesia practise a moderate form of Islam, religion still plays a large role in many people's lives, and the training began with the team standing in a circle and saying a brief prayer.

Triyatno, who like many Indonesians goes by one name, claimed silver at the London 2012 Olympics in the -69kg class with a total of 333kg, while 26-year-old Irawan won bronze in the -62kg class, lifting a total of 317kg.

But the final medal tally of just two was Indonesia's worst at an Olympics for over 20 years, with the performance dragged down by a poor showing from the traditionally strong badminton players.

As the best performers in London, Indonesia's weightlifting team -- which consists of five men and two women -- are now carrying the country's hopes for success on their broad shoulders as they head into Rio.

- 'Warrior mentality' -
Triyatno and Irawan will face stiff competition from the likes of the Chinese and North Koreans, but they appeared relaxed at the recent training session.

And they insisted observing Ramadan would not get in the way of their preparations, with the men typically training four hours a day, five days a week.

"Praise be to God, up till now it has not affected me," Irawan told AFP of the fasting month.

"I am used to it, every time there is a championship, we must lose some weight so we must eat less anyway."

But he conceded that at times it was tough and thirst in particular was a challenge.

"It is a bit difficult to stay focused but we don't have to train hard every day, some days we just work on our technique," he said.

For his part, national team coach Dirja Wiharja did not believe the country's top medal hopes would be affected.

"Indonesian athletes have a warrior mentality, they will fight to give their best -- that is what a true champion is," he said.

The coach has made adjustments for training in Ramadan, Islam's holiest month when Muslims commemorate the divine revelations received by Prophet Mohammed.

For the pre-dawn breakfast that Muslims eat to set them up for a day of fasting, the weightlifters are given more supplements than usual and advised against eating unhealthy fried foods.

The training starts later, at 9:30 am instead of 9:00 am, to give them a little more rest.

Triyatno and Irawan had modest upbringings in the province of Lampung, on western Sumatra island, and stumbled into weightlifting almost by accident.

Irawan said he originally wanted to join his local football club but could not afford the monthly fee so took up weightlifting, which was free, while Triyatno was attracted by the prospect of getting to travel and staying in nice hotels.

But they quickly went on to compete at the national level and have never looked back.

After the Eid holiday at the start of July marking the end of Ramadan, the weightlifters will take part in a training camp in South Africa before heading to Rio.

While some have voiced concerns about the impact of fasting, others believe that such strong religious devotion could help Indonesia on the path to Olympic victory.

"If the faith is strong, we should do even better," said Aveenash Pandoo, a former South African national coach who is helping the Indonesians prepare for the Olympics.