Roughly 5,000 riders pedaled across Massachusetts as part of the Pan Mass Challenge on Saturday, reaching the halfway mark of Bourne, where two-day riders will rest up overnight at the Mass. Maritime Academy.

About 3,000 volunteers were scattered across Massachusetts for the weekend, ensuring the riders had what they needed to make the trek and raise money for cancer research.

“The riders are the ones that make this happen, they’re the ones that get the donations. The amount of money that they have to raise is absolutely unbelievable,” Somerville’s John Wysocki said. “But on the day it’s really about the volunteers.”

Some of the riders will need to stop at the medical tent in Bourne, where volunteer doctors and nurses make sure they receive the care they require to finish the ride.

“I joined because my best friend, who’s also a patient of mine, passed away from colon cancer,” Dr. Richard Shuman said. “I wanted to give back. This is just one way we can do that.”

Volunteers are vital to the PMC. Even after the last rider pulls into Provincetown, they will still be hard at work.

Make a donation, 100-percent of which funds cancer research, by visiting PMC.org.