Bounce
In a sporting sense, jumping power is a sub-function of speed . The goal of jumping is to get your body up into the air as far as possible by jumping off the ground quickly. There are many sports disciplines in which jumping power plays a very important role, e.g. B. in athletics: high jump , long jump , triple jump , pole vault . For this reason, the sport-specific jumping performance plays a decisive role in training control.
Physical basics of jumping power
The weight
Different forces act on the body for each jump. By far the most interesting force for jumping is weight. So if you want to jump, you have to counteract the weight. It ensures that people stay on earth and do not take off. For this reason the weight force is also called gravity.
In physics, weight is defined as follows:
- stands for the weight given in the unit Newton .
- stands for the mass, which is given in kilograms.
- stands for the amount of acceleration that affects people. It is given in the unit m / s²
Newton's third law
The law describes that an opposing counterforce acts on every force, with the same magnitude, so that both forces add up to 0.
In mathematics, this statement is defined as follows: F1 + F2 = 0 or F1 = - F2 For humans, this means that the weight force must counteract with the same force, i.e. upwards, in order not to be pressed onto the ground. This law has to be overcome when jumping.
The force plate
With the help of a force plate you can measure the vertical jumping force of a person.
The force plate has piezoelectric sensors between two wooden plates. The sensors react to pressure by building up an electrical field that can change the voltage. This tension is measurable and can then be defined as a force for various calculations. The higher the pressure on the sensors, the higher the change in voltage and the higher the force. The force plate can therefore determine the force that acts on a person when jumping. Since the height of the jump is also of great importance when jumping, you have to use the forces sensibly and calculate values with which you can do something.
Bounce
For humans, consider the example of “jumps from a standing position”. Man has to generate the potential energy when he has the mass and when jumping raises his center of gravity by the height . This energy comes mainly from the leg muscles. The height reached therefore provides information about the leg muscle strength required for this . To calculate it, you need the distance along which the force is exerted. The illustration opposite shows this route using a simple model of a leg.
The thighs are half as long as the legs of the first length. They form a right angle when jumping in the crouching position. As soon as the body moves from a crouched position to a stretched position, the Pythagorean theorem measures the so-called distance.
So the constant assumed muscle force acts on the route .
the relationship
.
The drop jump
With the help of the drop jump, the reactive jumping ability can be determined. The arms are at the hips during the jump and prevent impulse transmission. The extension of the ankle, knee and hip joints are extended after the forced deep dive and this initiates the jump. The stretching movement follows exclusively from the ankle. The goal is to reach the highest possible altitude.
Force-time curve
The force-time curve is illustrated below.
Since there is no contact with the ground when jumping in, the force-time curve starts from zero. The first contact with the ground occurs when point t 0 has been reached. The point t 1 initiates the interception of the energy in the jump. When landing, due to the increased entry, there is a greater force than when jumping from a standing position. This can be proven in mathematics. For this you need the formal for the falling speed:
v = √ (2 g h)
- h stands for the height from which you jump
- g stands for the acceleration due to gravity (9.81 m / s²)
If you have the impact speed, you can determine the magnitude of the braking acceleration. What plays a big role in this is how low you bend your knees. Suppose you bend your knees a meter. The deceleration we get on the formula: a brake = v 2 /2 * s
- V stands for the impact speed (before)
- S stands for the distance you bend your knees.
Finally, you need the most important formula to calculate the force that acts on a charge. F = m * a
- m stands for the mass. For example a drop jump jumper
- a stands for the previously calculated braking acceleration
Taking all values into account, the force formula looks like this: F = m · (2 · g · h) / 2 · s
From the point at which you exert your weight on the floor, the floor reaction force must be counteracted. This can be achieved by bending and stretching the legs in good time. This braking acceleration (A 2 ) lasts from t 1 - t 2 . The actual jump (A 3 ) only takes effect from t 2 , at which you have to apply more than your weight to the ground in order to leave the ground at time t 4 as a result of the high impulse . From a biomechanical perspective, it is defined using the third Newtonian axiom as follows:
- The following applies up to time t 2 : F actio > F reactio
- And from time t 2 the following applies: F reactio > F actio
The forced going deep immediately leads to tension in the jump muscles when you first hit the ground. For this reason, athletes with a high reactive force can achieve a greater initial strength than by simply going deep in the drop jump.
Three methods of jumping power measurement
A scientific method for measuring speed strength behavior is the jumping strength test. The jumping strength test consists of the Counter Movement Jump (CMJ) , Drop Jump (DJ) and Squat Jump (SJ) . With the help of these three components, the rapid strength behavior can be determined. The aim of these three components is to achieve the maximum possible jump height in a vertical straight jump. The hands are positioned on the pelvis to prevent the arm impulse from being transmitted. With a squat jump you jump from 90 ° knee and hip flexion without a backward movement. With the Counter Movement Jump you stand upright and make a quick start movement, up to a max. 90 ° knee angle, with a vertical jump through. With the drop jump, you release yourself from an elevation by swinging one leg forward and then jump as high as possible with brief contact with the ground. For this reason, standardized heights of fall are used, which are documented. With the drop jump, a short ground contact time is controlled in addition to the jump height, from which a so-called reactive force index can be determined. The jump height can be determined with the help of contact mats or a force plate. This is also documented. The jump height can also be determined from the jump or landing impulse. It should be noted that the determination of the jump height, especially when determining the flight time, is linked to the technically correct execution of the jumps.
The nervous system
The nervous system plays a crucial role in the maximum development of a jump. It is responsible for the tension a muscle can generate and how fast the contractions of the individual muscle fibers occur. The nervous system is also responsible for the formation and development of muscles. For this reason, prolonged physical activity has a major influence on how the CNS controls muscle formation and muscle building. If one examines the influence of sporting exercises on the leg muscle coordination during concentric jumps and vertical drop jumps, then a core of this investigation is motor versatility. An ability of an athlete that one possesses in one sport to transfer to another. From this it follows that long training in a certain sport can lead to the central nervous system programming the muscle coordination according to the requirements of this sport and, moreover, the learned ability-reflex pattern of the CNS seems to intervene hierarchically in the performance program of other tasks. This is only beneficial if you train convincingly in the sport and maximize the potential of the CNS to increase its training effects.
Jump types
Jumps from a standing position: Occur in sports such as rebounding in basketball, swimming (e.g. starting jump) or tennis (e.g. serving). What they have in common is that the body has little or no kinetic energy at the beginning of the jump movement, i.e. the athlete does not move.
Jumps from movement (one-legged and two-legged): When jumping from movement, the jumper reaches a greater height with both types of jump (one-legged and leg-legged). He uses the center of gravity speed of around 2 - 4 m / s (kinetic energy) for jumps with both legs and approx. 7 - 11 m / s for jumps with one leg. Such jumps can be seen, for example, in team sports such as volleyball in preparation for a smash hit.
See also
Individual evidence
- ↑ Goalie magazine. Retrieved November 14, 2015 .
- ↑ Aspects of jumping power and jumping power diagnostics with special consideration of the development in childhood and adolescence. Retrieved November 14, 2015 .
- ↑ Ulrich Göhner: Applied kinetics and biomechanics of sport. Tübingen 2008, ISBN 978-3-00-025535-9 , p. 86.
- ↑ Ulrich Göhner: Applied kinetics and biomechanics of sport. Tübingen 2008, ISBN 978-3-00-025535-9 , p. 88.
- ↑ M. Hillebrecht: Biomechanics in physical education. Retrieved December 14, 2015 .
- ↑ Bernd Rodewald, Hans Joachim Schlichting: Jumping, walking, running. (PDF) Retrieved November 19, 2015 .
- ↑ Drop Jump. Retrieved December 2, 2015 .
- ↑ Ulrich Göhner: Applied kinetics and biomechanics of sport. Tübingen 2008, ISBN 978-3-00-025535-9 , p. 89.
- ↑ Oliver Faude: Performance diagnostic test procedures in football methodical standards. In: German magazine for sports medicine. Retrieved December 20, 2015 .
- ↑ John Shepherd: Brain Instead of Muscles: CNS Training. In: Sports Psychology. Retrieved December 20, 2015 .
- ↑ Klaus Willimczik (Ed.): Biomechanics of Sports: Basics, Methods, Analyzes . Rowohlt, Reinbek near Hamburg 1989, ISBN 3-499-18601-2 .