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 researchers from the University of São
Paulo, Brazil, have taken the lab into the dojo to study the energy
requirements of the Japanese art of judo.
Three 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. 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,
muscles can rely on another type of anaerobic system: they use up
energy-storing compounds, called phosphagens, in muscular tissues.
The team outfitted judo practitioners with a portable physiology lab: a
mask attached to a device worn on the torso that analyzes gases in the
martial artist's breath and measures the pulse. Once the athletes were
hooked up, combat began. Metabolically, judo turned out to be a mix of
aerobic sports like running and anaerobic sports like weightlifting.
But the data revealed that phosphagen metabolism was crucial for
throwing people, and aerobic metabolism was also higher than expected.
The researchers say the findings should help judo teams train. By
knowing their energy expenditures, for example, martial artists can
better customize their diet.