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On the training ground of the No. 1 sprinting team.

Fixing his eyes on the training ground, Li Xue said, "I have read your resume. You graduated only three years ago and your major was sports training. You should have acquired some knowledge about sprint training, right?"

Dai Li nodded, "A little bit, but the knowledge we learned was very superficial."

"I know. I have participated in the compilation of many teaching materials about sprinting for universities. Honestly, those materials are now obsolete. We are now in the information era. All kinds of new technologies are emerging endlessly in various industries. The same can be said of the sports industry. As the saying goes, records are meant to be broken. Athletes, also, are becoming faster and stronger," Li Xue said.

Dai Li did not know what Li Xue meant by his words, so he kept nodding quietly and listened carefully.

Then Li Xue asked, "According to the knowledge you learned in university, sprinting puts a large emphasis on the push-off, right?"

"Yes. According to the textbook, the sprinter should stretch their hip, knee, and ankle joints as much as possible during their push-off to generate more force, which can give them more speed," Dai Li replied.

"Yes, I also believed that years ago. We believed that the best knee angle of the driving leg was 180⁰, so we included that in the textbooks as well. However, we no longer ask the athletes to stretch their legs out. The technique we aim for now is called the ’bent driving leg’ technique," Li Xue explained.

"The bent driving leg technique? Does that mean the driving leg is not stretched out completely?" Dai Li asked.

"Exactly. We used to believe that the backward leg-drive was the only driving force of the sprint; however, that theory overemphasized the resistance of the front leg; however, the driving effect of the back leg was even more overemphasized. The emergence of Gittell changed our opinion," Li Xue said.

This Gittell Li Xue spoke of was from Jamaica, which was the kingdom of sprinting. They had raised many world-class sprinting champions. Among those champions, Gittell was undoubtedly the best. Including the hurdles, he had already won nine gold medals in three Olympic Games. He had broken the world records for the 100m and 200m sprint many times. The world records he had set were unbreakable. Even without seeing Gittell in person, Da Li had already confirmed that the Gittell’s gifts had to be the highest level, S+. He was ruling this era of sprinting.

Li Xue continued, "The technique adopted by Gittell is the ’bent driving leg’ technique. The variation of the angle of his driving leg’s knee compared to his starting position of 90⁰ is very small; moreover, his center of gravity is very stable, which we have not even begun to understand. It is almost impossible to keep a stable center of gravity during violent push-off movements.

"Later, we found that we had overemphasized certain factors of the sprint, which should have actually been thought of as a whole. We overemphasized the resistance of the front leg, and the driving effect of the back leg, which resulted in disproportionate force between the anterior and posterior thigh muscles of the athlete. The force of the posterior muscles severely lags behind the force of the anterior muscles, so the application of force has to come closer to the projected center of gravity, which can ensure that the body’s center of gravity can be moved to the secondary position rapidly. However, it can also result in a longer secondary position and smaller strides."

Li Xue’s explanation would absolutely confuse the average person. But for Dai Li, it was like an enlightenment. Dai Li felt like his understanding of the sprint had been improved to a new level after just a simple explanation by Li Xue.

Li Xue continued his introduction, saying, "At the same time, our research also showed that the driving force of Gittell was not only the push-off, but also the front leg-swing of the legs. Our previous understanding had been that the push-off was the driving force and could create speed, and that the buffering was resistance, and could cause speed loss. Because of this, we kept emphasizing the importance of push-off strength, as well as the degree, direction, and speed of the stretch.

"When the ’bent driving leg’ technique was used in sprinting, the previous stretch theory vanished. Now, the only way to increase speed is to attach importance to the front leg-swing technique and enhance the combination of the front leg-swing and push-off. Therefore, the latest sprint technique the national team has been using is the coordination of the front leg-swing and push-off by prioritizing the front leg-swing, which is used to help the push-off.

"You should know that an athlete in a standing position can only perform the push-off. While the propulsive force is straight up, they cannot move their body forward. If the athlete bends their knee and swings their leg forward and upward, their center of gravity will move forward as well, which results in the forward inclination of the body. It is at that moment that the body’s balance can be maintained just by the back leg. Meanwhile, the front leg will generate a force on the ground in the downward and backward direction, which will push the body forward again to finish their stride. This is the basic principle of promoting the push-off with the front leg swing."

Dai Li nodded his head, "I got it. Basically, in our old training theories, the push-off was the driving force, while the front leg-swing was used only to control the direction of the forward motion. But now, we know that both the front leg-swing and the push-off are driving forces. The two of them are working together like a four-wheel drive vehicle, instead of a rear wheel drive vehicle."

"Well said! Your vehicle example is very fitting." Li Xue looked at Dai Li admiringly. His eyes had not deceived him; Dai Li was indeed a gifted coach.

Dai Li did not only have the Coaching System; he also had a gift, and was good at learning. He had always been hard-working. After his toughening experiences these last couple years, he had even acquired the ability to apply knowledge quickly, and not just recite the contents of a textbook like other college graduates.

Li Xue had not finished. He continued his introduction with a teacher-like tone, saying, "Sprinting is a complicated biomechanical activity composed of multiple actions. Humans are standing animals. Moving a relatively static object is easier than moving a relatively dynamic object; therefore, for sprinters, accelerating during the running start is fairly easy. Coupled with the increasing speed, because the acceleration time is much shorter, it is more difficult for people to keep enhancing the push-off effect. Meanwhile, as the speed is increased, athletes face greater air and brake resistance.

"The human body cannot be streamlined, so it is very difficult to tackle the problem of air resistance. With new technology, the Americans made some innovations to racing suits to lower the air resistance, such as tight-fitting sportswear made from nano-materials, which has been pursued and imitated around the world.

"However, ever since the emergence of Gittell, the Americans have realized that their little tricks are dwarfed compared to his absolute power. Wearing an ordinary vest and shorts, Gittell can still run faster than the Americans. So, a strong body and excellent technique are key points when it comes to improving performance.

"As for the brake resistance, the essence of reducing brake resistance is to lower the landing foot’s speed relative to the ground; the moment the landing foot touches the ground, the closer the person is to a speed of zero, which makes the effect stronger. The landing speed of athletes in our country is about 1.35m/s, which is 17% quicker than the speed of the American athletes. Because of this, it still needs our help for further improvement."

Once he finished, Li Xue pointed at the athlete who had just run over and asked, "Look at him; can you describe the advantages and disadvantages in the landing movement of his feet?"

Dai Li knew this would be the first question given by Li Xue, so he immediately began his observation carefully.