Unicycle cranks vary in length to accommodate different unicycle wheel sizes, and different unicycling disciplines. Mountain unicycling is an adventure sport that consists of traversing rough terrain on a unicycle. Unicycles have also been used to create new sports such as unicycle hockey. In the following cutaway Adolf Hitler is shown juggling three fish while riding a unicycle. In January 2009 Focus Designs demonstrates electric unicycle to Segway inventor. When Jerry accidentally ends up riding the unicycle on the tightrope, the crowd hushes. Jerry's next assignment is to hand Nero, the tightrope walker, a unicycle. Participants run, bike, unicycle, carry kayaks, push shopping carts, or pull sleds. His personal hobbies/recreation included riding the ATV, snowmobiling, boating and riding his unicycle. The stimulus for this experiment was a brightly colored clown on a unicycle. His favorite hobbies at that time were sports, playing drums, baseball and riding his unicycle. A monowheel is a one-wheeled single-track vehicle similar to a unicycle. While in Oregon, he started performing on his unicycle under the name Jester Max. A unicycle is a vehicle that touches the ground with only one wheel. Unicycle handball uses a handball-sized ball.