Some 35,000 people will be taking part in Earth Hour celebrations at the F1 Pit Building on Saturday next week - the largest turnout in the event's 10-year history in Singapore.
The event is led by green group World Wide Fund for Nature (WWF), which is tying up with the organisers of the Sundown Marathon this year.
Participants will be running for a cause this time and promoting environmental sustainability.
For instance, instead of liquid water in disposable cups, runners will be given water in jelly form at water points, in a bid to reduce waste. This feature, along with liquid water in reusable bottles, will be available in the 5KM Earth Hour Run.
The medals that runners receive at the run will also be different. Participants can bury the biodegradable medal in soil; it will then grow into basil plants.
Those interested can also purchase special race bibs to raise awareness about endangered wildlife species, such as Sumatran tigers and blue-throated macaws.
The bibs will contain facts about these animals, such as how there are just 371 Sumatran tigers and 250 blue-throated macaws left in the wild.
Mr Adrian Mok, managing director of race organiser HiVelocity, said that if the sustainability elements are successful, they could be incorporated into future races.
Runner Kyle Lek, 25, will be taking part in the March 25 event. Mr Lek, a management trainee in a manufacturing firm, said the environmental theme may not appeal to everyone.
"But by tying up with the Sundown Marathon, it gives the environmental cause a fitness spin, which could reach out to more people," said Mr Lek, who also tries to raise awareness about the environment in his own time.
He runs in rustic places in Singapore, such as Coney Island, and documents them on his Instagram account.
Last year, about 5,000 people took part in WWF's Earth Hour celebrations at The Float@Marina Bay.