"It's what I ride all the time, I love my single speed. The Whaka 100 is genuinely one of the toughest events and for me you sort of go into the pain cage. It's quite an alluring place to go to, that place where it hurts a bit," Day said.
Speaking the day after the event he said there were a few muscles that he was not used to being sore.
"It's a funny thing - some of the muscles in my fingers from gripping and braking, the back of my shoulder blades and neck, because on a single speed you have to work the handle bars all the time to get up hills. It's stuff you wouldn't use when running.
"On a bike it's hard work going up hills, and you're probably faster going up hills when you're running, but when you come down the other side you can sit there and roll, you that bit of reprieve to catch your breath again."
He said Rotorua residents were "incredibly spoilt" with the range of running and mountain biking trails available to them.
"I'm very proud of the beautiful, flowing trails we have in Rotorua. You sort of lose yourself in the landscape and you tend to forget that the pedals are going crazy beneath you or your running legs are working hard beneath you. You just get absorbed in the environment and that carries you a lot of the way through the event."
Day said he did not get as many opportunities to participate in events now that he was part of the team running them and the Whaka 100 was "really well organised".
"They always are, they do a great job and they're really professional. It's a pleasure to go to someone else's event. When I started off I was entering all sorts of events all the time, but once you're the organiser of these things you spend a lot of time on the finish lines hugging people and congratulating them.
"I had no doubt that I would finish the 100km on my single speed yesterday, but it's still a great sense of satisfaction when you do. It's a real challenge, there were a few times when I thought 'Why am I doing this?' Even though I was having a great day it's still hard work, so there's always a real sense of achievement.
"Physically you're capable, it's usually mentally, you have to decide if you really want it or not, it's very rewarding."
For his part in the challenge Farmer had agreed to train for and complete a 100km running event.
"I'm not looking forward to it," Farmer said. "But that was the challenge between the two of us. It was a pretty good effort doing it on a single speed, he was one of less than 10 people to actually go out there and do 100km on a single speed.
"He's pretty much done it with no training, just his running stuff, which is testament to his pedigree as well. It's awesome. With all the stuff they have going on, it's a big call to take the time out and do something like this."