Looks like they are not using tires, either, probably some kind of spikes on the rear wheel?

= boredom injuries.

Still, pretty darn cool. Wisconsin is known for innovation/creativity during long winters.
1-We used to screw machine screws (hex end) into the knobbies of our dirt bike tires to ride on ice.
Only problem: when riding significantly below zero, the engine block tended to expand at different rates than other parts, i.e. seizure.

2-We would run a garden hose from the top of the silo (65') and let it run until we had a 3' icicle running up the silo, then we climbed it with pitons, etc.
Only problem: Silo's such as this are cement block, which is porous. A 65' 3 ft thick column of ice is, uh, heavy. Use your imagination. Angry father.

3-When the drift got to the eave of the barn, the gambrel roof was perfect to wet down until it froze, ride the toboggan off the top, down the barn into the yard.
Only problem: Barn roof was tin, with 1x4 spaced boards to nail the tin to. It dented. A lot. Angry father.

4-"Progressive Smear" on frozen ponds. Start with one person "it," and the crowd crosses the pond, avoiding a tackle; the "its" grow as more are tackled, last 1 wins.
Only problem: The nearest ER was 8 frozen miles away. Angry parents, several of them over the years.

5-"broomstick hockey" with rubber boots, no skates, tennis ball fora puck. Same ER problem as with the smear game.

My brother was one of those guys who mounted a small board and a sail to 3 skates and went on the lakes. Tremendous speeds, wicked "ice rash."