What's the best way to tug of war?

Tug-of-war is a sport in which both sides wrestle at one end of each rope, which belongs to the traditional sports in China. As early as the Spring and Autumn Period and the Warring States Period, there was a tug-of-war activity, but at that time it was not called tug-of-war, but called "strong hook" or "pulling hook", which later evolved into a popular "hook-making play" in Jingchu area.

Tug-of-war skills:

The modern tug-of-war sport is characterized by the fact that the two participants are of the same weight level and compete against each other by pulling tug-of-war ropes. The winner depends on which team pulls the opponent to the team first, and makes the mark on the tug-of-war rope exceed the set boundary. Therefore, tug-of-war coaches and players are concerned about how to produce better and sustained horizontal pulling force through training, posture change and rope position change, so that opponents can be pulled to our site to win.

1. Free body diagram of tug-of-war:

2. Folding, dumping moment and restoring moment:

Assuming that the fulcrum during tug-of-war is located at the pressure center of the foot, the following two conditions must be met if the body is to achieve balance: First, the resultant force is zero, that is, the gravity (Fcg) in Figure 1 is equal to the sum of the vertical reaction force (Gv) on the ground and the vertical component force (Pv) on the tug-of-war. Secondly, the closing moment is zero, that is, the dumping moment from the rope grip to the foot fulcrum is equal to the restoring moment from gravity to the foot fulcrum.

3. Friction:

In modern indoor tug-of-war, players wear special tug-of-war shoes that are beneficial to the competition. The most important point is that the special tug-of-war shoes have high friction coefficient, which can produce large friction under the same vertical action, which is more conducive to the stability and balance of posture; A well-trained first-class team pays great attention to the cleanliness of tug-of-war soles and tug-of-war channels, because the unclean surfaces of the two are one of the main reasons for the loss of friction coefficient. The smaller the angle between the center of gravity and the fulcrum of the foot and the ground, the largest horizontal component will be obtained, but the smaller the vertical component will be. If the friction caused by the vertical component is less than the pulling force of the other side, an unfavorable sliding phenomenon will occur. For example, when the angle between the center of gravity and the foot and the ground is large, the restoring moment is less than the dumping moment. Although it is not easy to slide, it is easy for the body to tilt forward due to the reduction of the restoring moment, which is also unfavorable to the competition.

4. resultant force:

according to the research data, it is found that if two players can each produce a horizontal pull of 8kg (KGW) and measure their total pull in series, the resultant force will be less than the sum of the horizontal pull of the two players of 16kg (KGW). The reason is that the resultant force will be consumed when two players pull in series, which is more obvious in the case of multiple players.

Therefore, the coach should pay attention to the factors of resultant force when arranging the position of players and guiding the direction of players' application. Only when the force is applied in a favorable direction and time point can it be beneficial to us. Otherwise, even with great muscle strength, it is meaningless if it cannot be combined with effective horizontal force at the same time pulse, and even another force will be generated to balance the excess force. Therefore, if the eight players in the competition can be consistent in the time of generating force, they can generate greater impulse (resultant force F× action time T) in a unit time, which will give the other side greater destructiveness.

5. Basic mechanics mode:

According to kinematics research, tug-of-war movement is a lever action type that operates through three groups of important joints of the body. One is the knee joint (β) with staring legs, and its optimal angle is between 11 degrees and 16 degrees; Secondly, the hip joint (γ) with trunk tension, the best angle is between 9 degrees and 12 degrees; The third is the included angle (α) between the foot fulcrum and the ground, and the optimal angle is between 4 degrees and 6 degrees.