On Tuesday, JoVE published a fascinating article on how energy is used during complex sports, such as judo and other martial arts. Previous research on exercise science has focused on sports that can be easily recreated in the lab, such as running and cycling, but these Brazilian scientists have found a completely unique way of studying more complex sports.

Science NOW picked up the story and did an excellent job of explaining how the researchers did it:

The Science of Judo

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.

Three different systems convert food to energy. During long periods of moderate exercise, aerobic metabolism does most of the work, using oxygen to turn sugar into energy, water, and CO₂. Running a marathon or cycling for 100 miles, therefore, is almost entirely aerobic.

For shorter, more intense exertion, or when the oxygen runs out, muscles can break down sugar anaerobically, although that system is far less efficient and produces muscle-burning lactic acid as a byproduct. Lastly, for very short bursts of energy, such as a 10-second sprint, muscles can rely on another type of anaerobic system: they use up energy-storing compounds, called phosphagens, in muscular tissues.