It was only Day 2 of their challenge to run 50km a day for 50 days, but the muscles of the two ultra-marathon runners were already sore even before they started.
Mr Lim Nghee Huat, 61 and Mr Yong Yuen Cheng, 43, felt slight stiffness in their muscles from the first day's running just 16 hours before.
Mr Lim, who is a Chinese current affairs editor at MediaCorp, also had a niggling pain in his toe.
But they pressed on and completed the 50km in 7 hours 5 minutes yesterday - slightly longer than the 6 hours and 13 minutes the day before.
The duo are attempting the feat to celebrate Singapore's 50th birthday and pay tribute to the resilience of the nation's pioneers.
"Seven hours is actually a good pace," said Mr Yong, who is a teacher at Hwa Chong Institution. "If we run too quickly, we may not be able to sustain the whole 50 days."
With another ultra-marathon runner Gerrard Lin, 31, the duo ran a route stretching from Marina Barrage to Changi Coastal Park yesterday.
Under the blazing midday sun, the runners struggled to get through a 10km stretch at Changi Coast Road that had no shade.
"It was really very, very hot," Mr Yong said.
Fortunately, they were supported by a crew who gave them iced energy drinks, wet towels and watermelon cubes. "They were really lifesavers, we wouldn't be able to do it without them," said Mr Lim.
His hawk-eyed wife, Deborah, cheered the runners on from the supplies car.
As they crossed yesterday's finish line, the runners broke into smiles. Mr Lim looked forward to a sports massage by his Chinese sinseh, while Mr Yong could not wait to soak his feet in cool water.
"The end of another 50km," Mr Yong said. "Tomorrow will be another mountain to climb."