Martial arts are exhausting, as anyone who's traded a few punches, kicks, or throws can attest. But where exactly does the energy come from? Every form of exercise uses a different combination of the body's metabolic systems for energy. Cyclical sports such as running and cycling are relatively easy to replicate with exercise machines in a laboratory, but that's harder to do with more unpredictable sports such as martial arts. So a team of Brazilian researchers have taken the lab into the dojo to study the energy requirements of the Japanese art of judo.
