Along with fellow residents and neighbours, Madam Aisah Mohamed Ismail pedalled her heart out yesterday, all for the sake of charity.

The 56-year-old pre-school teacher rode 4km on a stationary bicycle during the annual Ci Yuan Day, as part of a challenge that promised to donate a 1kg bag of brown rice to charity for every kilometre clocked.

"I like cycling, and this is for a really good cause," said Madam Aisah as she pedalled away, barely skipping a beat.

In total, the Ride for Charity challenge saw 2,000kg of brown rice given away equally to four charities - Awwa, the Salvation Army's Gracehaven home, the Metta Day Activity Centre for the Intellectually Disabled and the Ang Mo Kio-Hougang Community Development and Welfare Fund.

IT consultant Thilak Bhagavathi Kannu, 40, put in 4km. He said: "It's a very meaningful concept - you encourage people to exercise and give them a chance to do good at the same time."

The donated rice will be used in homes or institutions run by the charities, or distributed to needy families, said Ci Yuan Community Club. The cost of the rice will be borne by one of its sponsors.

Prime Minister Lee Hsien Loong kicked off the challenge yesterday, chalking up 3.26km on a stationary bike. Also along for the ride were fellow Ang Mo Kio GRC MPs Darryl David, Ang Hin Kee and Gan Thiam Poh, as well as Sengkang West MP Lam Pin Min.

Event organisers made an exception for PM Lee, declaring to cheers that 100kg of rice would be donated for every kilometre he racked up.

During his National Day Rally speech last month, Mr Lee had urged Singaporeans to choose healthier food options such as brown or mixed rice over white rice, as a way to combat diabetes.

Mr David said before the challenge: "It's so wonderful to see so many people here. Today we are celebrating a healthy lifestyle."

Ci Yuan is part of his division within Ang Mo Kio GRC. Ci Yuan Day is an annual event held to mark the opening of the community club two years ago. This year's event - which included mass dance workouts, a clay art station and a bouncy castle for children - was held at a community park in Hougang Avenue 8.

Yesterday, the site was also renamed Ci Yuan Harmony Park during a short ceremony. Formerly known as Punggol South Park, it got its new name from residents, who made their selection in an earlier vote. Other names on the ballot were Ci Yuan Pavilion Park and Ci Yuan Community Park.

WATCH THE VIDEO PM Lee cycles with residents str.sg/pmleecycles