For well over a hundred years, people have hopped on bicycles for transportation, recreation, competition, and more. In many parts of the world, spinning pedals moves goods and generates electricity. While usually attached to two wheels, pedal power takes many forms, adapting to a wide range of needs. Globally, over 100 million bicycles are produced every year - over 60% of them in China - easily doubling world production of automobiles. Efficient, clean, and cheap, pedal power in all its forms can solve modern problems with basic technology, and offers a health benefit to those cranking away. And it's hard to beat the simple joy of riding a bike. Gathered here are images of people around the world as we pedal for a reason, or just because. -- Lane Turner ( 49 photos total