Rob Ginnivan ran 13-miles on a treadmill Thursday while flying in a hot air balloon above Australia's capital.
The treadmill was powered by a small generator.
Ginnivan's an experienced runner, but the distance took him twice as long as normal to run because he could only take small steps on the treadmill.
He also said the basket tilted, so it felt like he was running uphill.
"Every time I took a step, the basket would sway from left to right so I kind of had this sea-type motion being in the air. It was quite bizarre and made it very difficult," Ginnivan said.
Ginnivan is trying to raise $95,000 for the Heart Foundation by running on land, at sea and in the air.
"The biggest issue was finding a day when we could fly for about three hours, which is quite unusual for a regular balloon ride," Ewan Roberts, the balloon pilot, said.