Researchers define the role of energy systems in judo

Training methods used in nom-combat types of sports could help change the training and improve the physical aptitude of athletes in combat sports. This USP study was highlighted in Science.

By Elton Alisson

Agência FAPESP – Knowledge about how different energy systems in the human body contribute to the supply of energy that an athlete needs could help improve the training of athletes and increase their physical aptitude.

This type of evaluation is relatively easy to conduct with athletes such as cyclists and runners, whose repetitive and standardized movements during training can be reproduced in a laboratory on equipment such as ergometric bicycles and treadmills. But it is more complex to perform with athletes whose movements are unpredictable and depend on the action of their partners or opponents, in sports such as martial arts and team sports.

By using portable equipment that allows the athlete to move freely while connected to a computer by wires, researchers from the Universidade de São Paulo’s School of Physical Education and Sports (EEFE/USP) were able to define the contribution of different energy systems during judo training.

The results of the FAPESP-funded study were published in the Journal of Visualized Documents, an open-access journal that calls itself the “first scientific video journal”. They were also highlighted in Science magazine.

The researchers used a portable telemetric gas analyzer and blood samples tested for lactate levels to analyze the contribution of energy systems during the execution of arm, hip and leg techniques used to throw the opponent during a standing fight in judo. Twenty athletes with brown or black belts, who have practiced the sport for more than ten years and who participate in state and national competitions, were the subjects of the study.

The analyses showed that the contribution of the phosphagen systems  is crucial for athletes. These systems are in the substrata present in stretched in muscles and readily available to be degraded and to transfer energy for muscular contraction. The analyses further demonstrated that the participation of the aerobic system (which depends on the consumption of oxygen to convert food into energy) is greater than previously thought.

“If you have more knowledge about what happens to athletes when they perform certain actions during their sport, it’s possible to direct their training in the best way by making some physiological adjustments and creating a specific diet so that they may reach their desired goals,” said Emerson Franchini, a professor at EEFE/USP and coordinator of the project.

Franchini completed his doctorate with FAPESP funding. In addition to his work as a USP professor, he trains athletes from the Brazilian judo team. Among them are Leandro Guilheiro, Olympic medalist and holder of first place in the international ranking of fighters up to 81 kilos; Tiago Camilo, ranked seventh up to 90 kilos; and Rafael Silva, fourth worldwide in the over-100-kilo category.

Franchini explains that the human organism has three energy systems. One is oxidative (dependent on oxygen), and two are anaerobic (not dependent on oxygen)—the glycolytic and phosphagen systems—that convert food into energy.

“The physical actions performed during athletic training basically have the objective of improving the function of one or more of these systems, making it possible to increase the rhythm of energy transfer—so the athlete can perform more intense actions—or increase their saved energy—so he or she manages to maintain the intensity of exercise for a longer period, depending on the type of sport practiced,” he explained.

Franchini added that in the case of judo, a combination of two strategies is necessary because the techniques used during the fight are applied on an elevated level of physical intensity for a very short period of time.

“If the athlete manages to transfer energy more quickly in a judo fight, he can perform stronger movements and probably be more likely to execute a throw successfully,” said Franchini.

“On the other hand, in a competition where the athlete can have as many as six or seven five-minute fights in one day, not considering the possibility of postponement, it’s important that he also has a high capacity for maintaining the repetition of the exercise,” he said.

Other sports

According to Franchini, it is difficult to compare the calorie burning of a judo athlete with that in other sports because the energy used depends on the intensity of the exercise. To date, data on calorie burning during competition are rare.

However, compared with other martial arts, such as taekwondo, the estimates that the judo athletes expend more energy because of the duration of the fights and the intensity of the movements.

“In a judo fight, there are hold disputes all the time. Pulling and pushing against the opponent are frequent, and the pauses are shorter. In other sports, the athlete generally maintains an intermediate distance between himself and the opponent, and the movements are less intense,” Franchini noted.

One of the indicators used by the researchers to evaluate the intensity of the movements in martial arts fighting is the force/pause ratio. Whereas a taekwondo fight is characterized by periods of force averaging 8 to 10 seconds, with 60 seconds of less intense movements, judo athletes exert themselves for approximately 20 seconds, followed by 10-second intervals. “This also results in some differences in terms of energetic demand,” said Franchini.

According to the researchers, the model used by the USP group to evaluate the energy spent by judo athletes has now been used to estimate the contribution of energy systems in other sports.

Based on their evaluations, the scientists intend to make some physiological changes to the training of judo athletes and will compare this modified training method with the other training methods already adopted by athletes in their normal exercise routines.

“Based on a clearer understanding, it will be possible to develop more efficient training protocols than those that exist today for improving physical aptitude,” said Franchini.

The article “Determining the Contribution of Energy Systems During Exercise” by Franchini and others can be read and viewed in the Journal of Visualized Experiments at: www.jove.com/video/3413/determining-the-contribution-of-the-energy-systems-during-exercise?access=ybyomkk0.