It is advisable to start learning the long jump technique after some training in sprinting, which ensures the stability of the length of steps and the ability to develop a sufficiently high speed in the run-up.
Performing long jump movements with a low take-off speed is not difficult. Repulsion at high speed is very difficult. Therefore, teaching jumping technique should be closely related to special training aimed at developing the necessary physical qualities. Special exercises should primarily be aimed at developing high speed in the run-up and performing a strong and fast push.
What determines the distance of a jump?
In long jumps with a running start, the theoretical flight range of the jumper’s body depends on the value of the initial flight speed, the angle and height of the general center of gravity of the body. Air resistance slightly reduces flight range. In flight, the athlete can no longer influence the trajectory obtained as a result of the run-up and take-off.
Studies of jumping technique show that the initial flight speed, which for the best jumpers reaches 9.2-9.6 m/sec, is determined mainly by the take-off speed at the last step - 10.0-10.7 m/sec. When taking off, the jumper changes the direction of movement, creates an angle of departure (19--24°), providing the necessary jump height (50--75 cm) and flight range.
When pushing off, the jumper changes the direction of movement. As the results increase, the repulsion time decreases. This is explained by an increase in the speed of movement during the take-off, an increase in the angle of the leg, the angle of repulsion and a decrease in the amplitude of depreciation of the supporting leg. Changing the direction of body movement at high speed in conditions of reducing the time of interaction with the support requires significantly greater effort from the jumper in repulsion and is associated with a partial decrease in translational movement. Moreover, the decrease progresses with an increase in the departure angle of the o.c.t. body and jump height.
In the run-up - the ability to gain the highest speed in the last 2-4 steps and the ability to maintain the ability to take off.
In repulsion - the ability to change the movement of the body to a certain (within 20--22°) angle while maintaining the initial flight speed close to the take-off speed.
In flight - the need to continue running movements and prepare for landing.
In landing - the ability to carry it as far forward as possible and hold it as high as possible with the feet.
The nature of the movements - the amplitude and freedom of movement, the distribution of the magnitude and direction of efforts and their relationship in these phases - forms the basis of the general rhythm of the long jump.
Finding the best jump rhythm is the most important part of the teamwork between coach and athlete.
When improving your jump technique, you should focus on the average values of the take-off angle (20-- 22°). When the average values of the take-off angle are exceeded, the role of the initial flight speed increases, and at the same time the take-off speed (every 0.1 m/sec at the last take-off step gives 8-10 cm in the jump distance). And, conversely, the role of effort during take-off increases when the launch angle in jumps is below average values.
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Jumping Technique Basics
Jumping– these are exercises that require the predominant manifestation of speed-strength qualities in a short time, but with maximum neuromuscular effort. According to the type of motor activity, jumping belongs to the mixed nature of movements (cyclic - run-up and acyclic - flight). According to their tasks, jumps are divided into: a) vertical - jumps with overcoming a vertical obstacle - bars with the goal of jumping higher (high jumps and pole vaults); b) horizontal – jumping with the goal of jumping further (long jump and triple jump). Jumping is a type of exercise that promotes maximum development of speed and strength qualities, concentration of one’s efforts, and quick orientation in space.
With the help of jumping and jumping exercises, physical qualities such as strength, speed, agility and flexibility are effectively developed.
Athletics jumping is divided into two types: 1) jumping over vertical obstacles (high jump and pole vault) and 2) jumping over horizontal obstacles (long jump and triple jump).
The effectiveness of the jump is determined in the take-off phase, when the main factors for the effectiveness of the jump are created. These factors include: 1) the initial speed of the jumper’s body; 2) the angle of departure of the jumper’s body. The trajectory of the general center of mass of the body (GCM) in the flight phase depends on the nature of the take-off and the type of jump. Moreover, the triple jump has three flight phases, and the pole vault has support and unsupported parts of the flight phase.
Athletics jumps in their structure belong to a mixed type, i.e. There are both cyclic and acyclic elements of movement here.
As a holistic action, jumping can be divided into its component parts:
- run-up and preparation for take-off- this is an action performed from the beginning of the movement until the moment the pushing leg is placed at the place of repulsion;
- repulsion- this is an action performed from the moment the pushing leg is placed on the support until the moment it is lifted from the place of repulsion;
- flight- this is an action performed from the moment the pushing leg lifts off from the place of push-off until it comes into contact with the landing place;
- landing- this is an action performed from the moment of contact with the ground until the body’s movement completely stops.
Run-up and preparation for take-off. The four types of jump (high jump, long jump, triple jump, pole vault) have their own characteristics in the run-up, but also have certain common features. The main tasks of the run-up are to give the jumper's body the optimal run-up speed corresponding to the jump and to create optimal conditions for the take-off phase. In almost all types, jumps have a rectilinear form, except for the Fosbury flop high jump, where the last steps are performed in an arc.
The run-up has a cyclic structure of movement before the start of preparation for take-off, in which the running movements are somewhat different from the movements in the run-up. Running rhythm must be constant, i.e. it should not be changed from attempt to attempt.
Usually the run-up corresponds to the physical capabilities of the athlete that are observed in him at a given time. Naturally, with the improvement of physical functions, the run-up will change, the speed and number of steps will increase (up to a certain limit), but the rhythm of the run-up will not change. These changes are associated with two main physical qualities of the jumper, which should be developed in parallel - speed and strength.
The start of the run should be familiar, always the same. The jumper can begin the run either from a place, as if starting, or from the approach to the control mark for the start of the run. The jumper’s task in the run-up is not only to gain optimal speed, but also to precisely hit the place where he takes off with the starting leg, so the run-up, its rhythm and all movements must be constant.
Two options for takeoff can be distinguished: 1) uniformly accelerated takeoff and 2) takeoff while maintaining speed. Uniformly accelerated run - This is a type of run-up when the jumper gradually picks up speed, increasing it to optimal speed in the last steps of the run-up.
Running while maintaining speed – This is a type of run-up when the jumper almost immediately, in the first steps, gains optimal speed, maintains it throughout the entire run, increasing slightly at the end in the last steps. The use of one or another take-off run depends on the individual characteristics of the jumper.
The distinctive features of the last part of the run (preparation for take-off) depend on the type of jump. A common distinguishing feature is an increase in the take-off speed and movements of the body parts during this run-up segment, the so-called run-up.
In running long jumps and running triple jumps, in preparation for take-off, there is a slight decrease in the length of the last steps and an increase in their frequency.
In pole vaulting, in preparation for take-off, the pole moves forward and also increases the frequency of steps while simultaneously decreasing the length of the step.
In running high jumps, this stage depends on the style of the jump. In all styles of jumping that have a straight run-up (“step over”, “wave”, “roll”, “crossover”), preparation for take-off occurs in the last two steps, when the swing leg takes a longer step, thereby reducing the GCM, and the pushing leg takes a shorter, quick step, while the jumper’s shoulders are pulled back beyond the projection of the GCM. In the Fosbury Flop jump, preparation for take-off begins in the last four steps, performed in an arc with the body deviating away from the bar, where the last step is somewhat shorter and the frequency of steps increases.
It is very important to most effectively perform the technique of preparing for the take-off of the last part of the run. The take-off speed and the take-off speed are interconnected. It is necessary that between the last steps and take-off there is no stopping or slowing down of movements, no loss of speed. The faster and more efficiently the last part of the run is completed, the better the take-off will be performed.
Repulsion- the main phase of any jump. It lasts from the moment the pushing leg is placed on the support until the moment it is lifted from the support. In jumping, this phase is the shortest and at the same time the most important and active. From the point of view of biomechanics, repulsion can be defined as a change in the velocity vector of the jumper’s body when certain forces interact with the support. The repulsion phase can be divided into two parts: 1) creating and 2) creating.
The first part creates the conditions for changing the velocity vector, and the second implements these conditions, i.e. creates the jump itself, its result.
Push leg angle– this is one of the main factors determining the efficiency of converting horizontal speed to vertical . In all jumps, the leg is placed quickly, energetically and rigidly at the take-off point; at the moment the foot touches the support, it should be straightened at the knee joint. The approximate angle of placement of the pushing leg is determined along the longitudinal axis of the leg, connecting the place of placement and the GCM with the surface line. In high jumps it is the smallest, then, in ascending order, there are triple jumps and long jumps, the largest angle is in running pole vaults (Fig. 1).
Rice. 1. Comparative diagram of body positions at the moment
Placing the foot at the take-off point
The more you need to convert the horizontal speed to vertical, the smaller the angle of the leg placement (sharper), the leg is placed further from the projection of the GCM. The rigid and fast placement of a straightened pushing leg is also due to the fact that a straight leg can more easily bear a heavy load, especially since the pressure on the support in the first part of the take-off is several times higher than the jumper’s body weight. At the moment of setting, the leg muscles are tense, which contributes to elastic shock absorption and more effective stretching of the elastic components of the muscles with the subsequent release (in the second part) of the energy of elastic deformation to the jumper’s body. It is known from anatomy that tense muscles, when stretched, subsequently create greater muscle forces.
In the first part of the repulsion, there is an increase in the pressure forces on the support due to the horizontal speed and stopping movement of the pushing leg, the inertial forces of movements of the swing leg and arms; there is a decrease in GCM (the amount of decrease depends on the type of jump); stretching of tense muscles and ligaments that are involved in the subsequent part is performed.
In the second, creative part, due to an increase in the support reaction forces, a change in the velocity vector of the jumper’s body occurs; the pressure forces on the support decrease, closer to the end of the repulsion; stretched muscles and ligaments transfer their energy to the jumper’s body; the inertial forces of the movements of the swing leg and arms also take part in changing the vector of movement speed. All these factors create the initial speed of the jumper's body.
Departure angle– this is the angle formed by the vector of the initial speed of departure of the jumper’s body and the horizon (Fig. 2).
Rice. 2. Angles of repulsion and angles of departure of the GCM, depending
From the ratio of horizontal take-off speed and vertical
Take-off speeds in various jumps
At V=V 1 GCM height (A), at V>V 1 takeoff angle less (A 1 ), at V< V 1 takeoff angle greater (A 2 ).
It is formed at the moment of separation of the pushing leg from the place of repulsion. Approximately the take-off angle can be determined along the longitudinal axis of the push leg connecting the fulcrum and the central mass (special devices are used to accurately determine the take-off angle).
The main factors determining the effectiveness of jumps are the initial speed of the jumper's GCM take-off and the take-off angle.
Initial speed of the jumper is determined at the moment of separation of the pushing leg from the place of repulsion and depends on:
Horizontal take-off speed;
The magnitude of muscle effort at the moment of transferring horizontal speed to vertical;
The duration of these efforts;
The angle of setting the pushing leg.
When characterizing the magnitude of muscle effort at the moment of transferring part of the horizontal velocity to vertical, it is necessary to talk not about the pure magnitude of the effort, but about the force impulse, i.e. amount of effort per unit time. The greater the magnitude of muscle efforts and the shorter the time of their manifestation, the higher the force impulse, which characterizes the explosive power of the muscles. Thus, in order to improve results in jumping, it is necessary to develop not just the strength of the leg muscles, but explosive power, characterized by a force impulse. This feature is clearly expressed when comparing the take-off time in high jumps with the “flip” and “Fosbury” styles.
In the first style, the repulsion time is much longer than in the second, i.e. in the first case, force repulsion is observed, and in the second, high-speed (explosive) repulsion is observed. The results of high jumps in the second case are higher. If we look at the anatomical characteristics of these differences, we see that flip-flop style jumpers are larger, with more muscle mass in the legs, than Fosbury style jumpers, who are lean and have less muscle mass in the legs.
The take-off angle depends on the angle at which the pushing leg is placed and the amount of muscle effort at the moment of speed transfer, as discussed above.
Flight. This phase of the integral action of the jump is unsupported, except for the pole vault, where the flight is divided into two parts: support and unsupported.
It is necessary to immediately understand that in the flight phase the jumper will never be able to change the trajectory of the GCM, which is set in the repulsion phase, but will be able to change the positions of the body parts relative to the GCM. Why does a jumper perform various movements with his arms, legs, and change his body position in the air? Why study flying technique? The answers to these questions lie in the purpose of this jumping phase. In the high jump, the athlete, through his movements, creates optimal conditions for clearing the bar. In pole vaulting, the first support part is the creation of optimal conditions for bending and extending the pole (for the most effective use of its elastic properties). The second unsupported part involves creating optimal conditions for overcoming the bar. In long jumps, maintaining balance in flight and creating optimal conditions for landing. In the triple jump, maintaining balance and creating optimal conditions for subsequent take-off, and in the last jump, the goal is the same as in the long jump.
The trajectory of the GCM in flight cannot be changed, but the positions of the body parts relative to the GCM can be changed. So, in gymnastics, acrobatics, and diving, various rotations occur, but they are all performed around the GCM. It is known from the biomechanics of sports that changes in the positions of some parts of the jumper’s body cause diametrically opposite changes in other distal parts. For example, if you lower your arms, head, and shoulders when crossing the bar in the Fosbury high jump, this makes it easier to lift your legs; If you raise your arms up in a long jump, this action will cause your legs to drop, thereby shortening the length of the jump.
Consequently, by moving the body parts in flight, we can either create optimal flight conditions, or disrupt them and thereby reduce the effectiveness of the jump. And when the winner and prize-winners in jumping are separated by 1-2 cm, then rational and effective technique of movements in flight can play a decisive role.
Landing. Each jump ends with a landing phase. The purpose of any landing is, first of all, to create safe conditions for the athlete to prevent various injuries.
At the moment of landing, the jumper’s body experiences a strong shock effect, which falls not only on the body parts that are in direct contact with the landing site, but also on the distal, most distant parts from it. Internal organs are also subjected to the same impact, which can lead to various kinds of disruptions in their vital functions and diseases. It is necessary to reduce the harmful effects of this factor. There are two ways: the first is to improve the landing site; the second is mastering the optimal landing technique. The first way is reflected in high jumping and pole vaulting. At first, the athletes landed in sand, the level of which was raised above the take-off surface, but it was still a hard landing, and the athlete spent a lot of time learning how to land safely. Then came the age of foam rubber, and the landing site became much softer, results increased, a new type of high jump appeared (“Fosbury flop”), and fiberglass poles appeared. It became possible to spend more time on the jumps themselves, without thinking about the landing.
Annotation:
The purpose of the work is to theoretically substantiate optimal biomechanical characteristics in high jumps. A mathematical model has been developed to determine the influence on the height of the jump: the speed and angle of departure of the center of mass during repulsion, the position of the center of mass of the athlete’s body in the phases of repulsion and transition over the bar, the resistance force of the air environment, the influence of the moment of inertia of the body. The main technical mistakes of an athlete when performing exercises are highlighted. Biomechanical characteristics that increase the effectiveness of high jumps include: the speed of departure of the athlete’s center of mass (4.2-5.8 meters per second), the angle of departure of the center of mass of the body (50-58 degrees), the height of the departure of the center of mass of the body (0.85-1.15 meters). The directions for choosing the necessary biomechanical characteristics that an athlete is able to implement are shown. Recommendations are offered to improve the performance of high jumps.
Keywords:
biomechanical, trajectory, pose, athlete, jump, height.
Introduction.
An important component of increasing the efficiency of an athlete’s movements is the selection of optimal parameters that determine the success of performing technical actions. One of the leading positions in this movement is occupied by the biomechanical aspects of technique and the possibility of its modeling at all stages of an athlete’s training. In turn, the modeling process requires taking into account both the general patterns of movement technique construction and the individual characteristics of the athlete. This approach greatly contributes to the search for optimal parameters of the technique and its implementation at certain stages of the athlete’s training.
The theoretical basis for research on the biomechanical laws of sports movements is the work of N.A. Bernstein, V.M. Dyachkova, V.M. Zatsiorsky, A.N. Laputina, G. Dapena, P.A. Eisenman. The need for preliminary construction of models and subsequent selection of the most rational biomechanical parameters of an athlete’s movements is noted in the works of V.M. Adashevsky. , Ermakova S.S. , Chinko V.E. and others.
In this case, the search for the optimal combination of kinematic and dynamic parameters of an athlete’s jump, taking into account the natural transfer of mechanical energy from link to link, becomes important. This approach allows you to successfully influence the result of sports activity when performing a high jump. In this case, it is recommended to use mathematical models of movements, characteristics of the athlete's postures and movements.
Sports results in high jumps are largely determined by the rational biomechanical characteristics that an athlete is able to implement, namely: take-off speed, take-off speed, take-off angle of the athlete’s body center of mass, position of the athlete’s body center of mass in the take-off and transition phases over the bar.
At the same time, some of the positions stated above in relation to high jumps require clarification.
So Lazarev I.V. notes that determining the features of the fosbury-flop technique at the stage of developing sports skills, identifying the structure and mechanisms of repulsion, developing and using jump models in training is one of the pressing problems of technical training of high jumpers with a running start. The greatest influence on improving sports results in high jumps with a running start using the Fosbury flop method is exerted by kinematic (take-off height in the unsupported phase of the jump, take-off speed) and dynamic (repulsion impulse along the vertical component, average repulsion force along the vertical component, effort at the extreme) indicators .
Zaborsky G. A. believes that comparison of model characteristics of the motor optimum with real the reproducible structure of the jumper’s movement in take-off will allow him to identify such elements of his technical and speed-strength readiness, the correction and development of which will allow him to form an individually optimal take-off technique in jumps.
At the same time, there is still an urgent need for research in building jump models for modern conditions of competitive activity.
The research was carried out on the state budget topic M0501. “Development of innovative methods and methods for diagnosing leading types of preparedness of athletes of various qualifications and specializations” 2012-2013.
Purpose, tasks of the work, material and methods.
Goal of the work- theoretical substantiation of the main rational biomechanical characteristics in high jumps, as well as in drawing up recommendations for increasing the effectiveness of high jumps.
Job Objectives
- analysis of specialized literature,
- constructing a model to determine the influence on the height of the jump of the speed and angle of departure of the center of mass during take-off, the position of the center of mass of the athlete’s body in the phases of take-off and transition over the bar, the air resistance force, the influence of the moment of inertia of the body,
- drawing up recommendations for improving results in high jumps using the “Fosbury flop” method.
Subject of research there were biomechanical characteristics of the athlete that contribute to increasing the performance of high jumps.
Object of study- highly qualified athletes - high jumpers.
To solve problems, we used a special software package “KIDIM”, developed at the Department of Theoretical Mechanics of NTU “KhPI”.
Research results.
Sports results in high jumps are determined mainly by rational biomechanical characteristics that an athlete is able to implement, namely: take-off speed, and, consequently, the speed and angle of departure of the center of mass of the athlete’s body, the position of the center of mass of the athlete’s body in the push-off and transition phases over the bar. Therefore, there is an obvious need to conduct theoretical and practical research to implement all of the above biomechanical parameters in order to obtain maximum results in high jumps using the Fosbury flop method.
In this case, one should proceed from the following premises. The height of the jump is determined mainly by the biomechanical characteristics that the athlete is able to implement, namely:
- take-off speed,
- the speed of departure of the center of mass during repulsion,
- the angle of departure of the athlete’s center of mass during repulsion,
- the position of the center of mass of the athlete’s body in the phases of repulsion and crossing the bar.
The speed and angle of departure of the athlete's center of mass during take-off are the main biomechanical characteristics in high jumps.
The speed of the athlete's center of mass during repulsion is the resulting speed of the vertical and horizontal components of the athlete's repulsion speed.
For men - high-class masters, the horizontal take-off speed is 6.5 - 8 m/s, and the resulting speed of departure of the athlete's center of mass during repulsion is 4.5-5.4 m/s.
The height of the body's center of mass during take-off depends on anthropometric parameters and the method of jumping. When crossing the bar, the center of mass of the body, depending on the method of jumping, can be higher than the bar (flip) or lower using the Fosbury flop method.
The angle of departure of the athlete's center of mass during repulsion is selected as the most rational within 56 - 58 degrees to the horizon, taking into account the force of air resistance.
With a rational combination of these biomechanical parameters, the result of jumping using the Fosbury flop method is 2.2 - 2.4 m.
Let us consider, using the calculation scheme, the influence on the speed of repulsion, and, consequently, the take-off speed of the center of mass of the athlete’s body, the vertical, horizontal components of the speed and take-off angle of the center of mass of the athlete’s body (Fig. 1).
v 0 = v = g g + v v ,
Here V 0 is the initial speed of repulsion (takeoff) of the center of mass of the athlete’s body,
V r =V X - horizontal take-off speed of the body (horizontal component),
Vв=V Y - vertical component of the repulsion speed,
h C0 - height of the center of mass of the body during repulsion,
0 =? c - angle of departure of the athlete’s center of mass during repulsion
In projections onto the Cartesian axis of the absolute coordinate system, this equality has the form:
v 0=v r ; v 0 = v B ; v =v 0 cos?; v =v 0 sin?.
Expression of absolute initial departure speed
G - gravity, Mc - moment of air resistance forces, h C - current height of the body's center of mass, Rc - air resistance force.
Aerodynamic drag force Rc for bodies moving in air with density p, is equal to the vector sum R c = R n + R T lift - R =0.5c ?sV 2 and drag force R =0.5c?s V 2. When calculating these forces, the dimensionless drag coefficients (c n and c ? ) are determined experimentally depending on the shape of the body and its orientation in the environment. The value of S (midsection) is determined by the value of the projection of the cross-sectional area of the body onto a plane perpendicular to the axis of motion, V is the absolute speed of the body.
Rice. 1. Calculation scheme for determining the initial parameters during repulsion
Rice. 2. Calculation scheme for determining rational biomechanical characteristics in the flight phase
Fig.3. Graphic characteristics of the trajectory of the center of mass for various values of the initial departure speed
It is known that the density of air is ? = 1.3 kg/m3. It should be noted that a body in flight has a general case of motion. The angles of rotation of the body in anatomical planes change and, accordingly, the value of S changes. Determination of the variable values of the midsection S and the drag coefficient c require thorough additional research, therefore, when solving this problem, we will accept their average values.
It is also possible to determine the average values of the coefficient (To), standing at V 2 - the absolute speed of the body in a jump.
Without taking into account the lifting force, the magnitude of which is very small, we obtain the average values of the coefficient. k=0.5s? ?s
k=0-1 kg/m.
Then, R? =R c =kV 2.
Let's compose equations for the dynamics of plane-parallel motion in projections on the coordinate axes
Here m- body mass, X c ,Y c - correspond to the acceleration projections of the center of mass, P e x , P e y- projections of the resultant external forces acting on the body, J z- moment of inertia relative to the frontal axis, ? - corresponds to the angular acceleration when the body rotates around the frontal axis, M e z- the total moment of external resistance forces of the medium relative to the frontal axis.
When moving in a plane xAy, The system of equations can be written as follows:
The angle between the current velocity projections of the body's center of mass and the velocity vector.
Solving this problem requires integrating the differential equations of motion.
Let's consider the influence of the speed and angle of departure of the center of mass of the athlete's body, the position of the center of mass of the athlete's body in the repulsion phases, the moment of inertia relative to the frontal axis, taking into account the forces of air resistance.
The results of calculations using mathematical models and the resulting graphical characteristics show:
- different values of the moments of inertia of the body relative to the frontal axis during flight change the value of the angular velocity, and, consequently, change the values of the rotation numbers N, which, with rational postures, can contribute to faster rotations around the frontal axis when crossing the bar,
- for real flight speeds of the athlete’s body, the drag force of the environment for different midsections has little effect on the change in the result.
- to achieve high results, it is necessary to increase the horizontal take-off speed and, as a consequence, the initial take-off speed, the take-off angle of the body’s center of mass, the height of the body’s center of mass during repulsion with their rational combination.
The obtained calculated biomechanical characteristics of the high jump are model ones and will differ somewhat in practice.
In the studies of Lazarev I.V. the main indicators were identified that have the greatest impact on improving sports results in high jumps with a running start using the Fosbury flop method: A) kinematic indicators:
- take-off height in the unsupported phase of the jump 0.74 -0.98 m;
- take-off speed 0.55m/s; B) dynamic indicators:
- repulsion impulse along the vertical component 0.67 - 0.73;
- average repulsion force along the vertical component is 0.70 - 0.85;
- effort at the extreme is 0.62 - 0.84.
It was also found that the peculiarities of the formation of the intra-individual structure of the technique of qualified jumpers as the sports result increases are characterized by a purposeful change in the indicators of the take-off speed, the angle of placing the leg for take-off, the path of vertical movement of the general center of mass (o.c.m.) of the body in take-off, and the take-off angle o.c.m. bodies. When performing a push-off, attention should be paid to the nature of placing the leg on the support with subsequent, and not simultaneous, acceleration of the fly links. The take-off position of the leg should be performed with an active running movement from the hip. The jumper must plant his feet with a full foot, while the foot must be located along the line of the last take-off step.
In the work of G. A. Zaborsky, it was established that the convergence of the real characteristics of movement in repulsion with theoretically optimal values is achieved by increasing the angle of inclination of the center of mass above the support when entering repulsion under conditions of a constant take-off speed. At the same time, the share of braking actions of athletes in repulsion decreases, and the accelerated swing movements of the body parts directly in the repulsion phase are activated due to the transfer of the share of these movements from the depreciation phase to the repulsion phase.
Rice. 4. Graphical characteristics of the dependence of the trajectory of the center of mass for various values of the angles of departure of the center of mass of the body
Rice. 5. Graphic characteristics of the trajectory of the center of mass for various values of the height of the center of mass of the body during repulsion
conclusions
An analysis of specialized literature has shown that in order to ensure high results in high jumps, it is necessary to take into account a number of multi-connected factors that ensure the maximum flight height of the body.
Basically, the sports result in high jumps is determined by the biomechanical characteristics that the athlete is able to implement, namely: take-off speed, speed and angle of departure of the center of mass of the athlete’s body, repulsion height of the center of mass of the athlete’s body.
Biomechanical characteristics that increase the performance of high jumps include the following ranges:
- take-off speed of the athlete's center of mass - 4.2-5.8 m/s,
- departure angle of the center of mass of the body - 50 0 -58 0,
- the height of the body's center of mass is 0.85-1.15m.
It has been established that in order to achieve high results it is necessary to increase the horizontal take-off speed and, as a consequence, the initial take-off speed, the take-off angle of the body’s center of mass, the height of the body’s center of mass during repulsion with their rational combination.
Rice. 6. Graphical characteristics of the number of revolutions for various values of the moment of inertia relative to the front axis
Rice. 7. Graphic characteristics of the trajectory of the center of mass for various values of air resistance forces
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Athletics jumps are exercises with a mixed cyclic-acyclic structure. Mastering the technique of these exercises contains a number of transitional phases that connect its individual parts. The complexity of these phases is that they involve a switch in the coordination of movements with a change in their structure and a redistribution of speed and effort. Particularly difficult in terms of the nature of switching and technical implementation is the phase of transition from run-up to take-off. It contains the dynamic and technical foundations that determine the achievement of high sports results. Therefore, the main problem in all jumps is the technical solution of the motor problem - the effective use of the horizontal speed of movement of the jumper and the power of repulsion, i.e. the need to inform the athlete’s body of the highest initial speed of takeoff at an optimal angle.
By the nature of the manifestation of motor qualities, athletics jumps are classified as exercises with a predominant manifestation of speed-strength qualities, which are defined as the ability to demonstrate large amounts of force in the shortest period of time.
According to the direction of movement, athletics jumps are divided into horizontal and over vertical obstacles. Determining the most effective jumping technique is explained by the need to achieve the greatest height or length of the athlete’s flight.
The flight range and altitude of the body depend on the initial speed and angle of departure and are determined by the formulas:
S=(V 0 2 sin2a)/g, h=(V 0 2 sin2a)/2g
where S is the flight range of the OCMT; h - flight altitude of the center of gravity (without taking into account its height at the moment of repulsion and landing); V 0 - initial speed of departure of the center of gravity; a is the OCMT departure angle; g is the acceleration of free fall.
Rice. 1. Initial take-off speed in high and long jumps
In Fig. Figure 1 shows a graph for determining the initial take-off speed in jumps.
The initial take-off speed is determined by the horizontal (Vx) and vertical (Vy) components, which depend on the take-off speed, the angle of the foot for take-off, the magnitude of muscle efforts and the time of their action during take-off.
The departure angle is formed by the vector of the initial departure speed and the horizon line. As is known, the maximum flight range of a body at an angle to the horizon is achieved at an angle of departure equal to 45° (at any initial speed and without taking into account air resistance). However, when jumping from a running start, the jumper cannot transfer his body into flight at an angle of 45°, since this requires equality of the horizontal and vertical components. An analysis of modern long jump technology indicates the leading role of the initial flight speed, which is determined by the take-off speed. The optimal launch angle for long jumps is 18-21°. The maximum flight altitude of the body is achieved at a departure angle of 90° (at any initial speed and without taking into account air resistance). However, when jumping without a run-up, the magnitude of the manifestation of force in repulsion is much lower. In modern high jumps, the takeoff angle is 50-60°.
Thus, the main problem in all jumps is the technical solution of the motor problem, which consists in the effective use of the horizontal speed of movement of the jumper and the power of repulsion, i.e. the need to give the athlete’s body the highest initial speed of takeoff at an optimal angle.
The speed and direction of the wind have a certain influence on the flight distance. Records in the long jump and triple jump are recorded at a wind speed of no more than 2 m/s.
When describing the technique of athletics jumps, the following parts are distinguished: run-up, take-off, flight, landing.
The following tasks are solved during the take-off run:
- gain optimal horizontal speed;
- ensure the position of the torso for effective repulsion.
In the long jump, triple jump and pole vault, you must strive to achieve maximum controlled speed. Moreover, in the first two jumps in the last meters, the athlete’s take-off speed is about 11 m/s. The run-up is performed in a straight line, its length is 21 - 24 running steps (40 m). In high jumps, the run-up is performed in a straight line (stepping method) or in an arcuate manner (Fosbury method), the optimal speed for qualified athletes is 7.5 - 8 m/s; run-up length - 9-11 running steps.
The run-up has a cyclical structure until the start of preparation for take-off, when the jumper’s movements change somewhat. The rhythm of the run must be constant, that is, not change from attempt to attempt. When jumping, you always need to accurately hit the take-off point, so it is important to maintain a standard run-up under changing conditions (wind, different surfaces, air temperature, etc.).
Rice. 2. The relationship between the take-off angle (beta) and the take-off angle (a) in long jumps (a) and high jumps (b)
An important part of the run-up is the preparation for take-off, which occurs in the last steps of the run-up. During support on the swing leg, there is a slight decrease in the center of gravity, which is expressed in a slight increase in the angle of flexion of the leg at the knee joint in the support phase. The body takes a vertical position in the long jump and triple jump; in the high jump, it deviates slightly back to 10°. Between the last steps of the run and take-off there should be no stopping, slowing down of movements, or loss of speed.
Repulsion- the main part of the jump: here the problem is solved of informing the body of the maximum initial take-off speed and creating an optimal take-off angle.
Angular parameters characterizing repulsion, are presented in table. 1 and in Fig. 2. These include:
- setting angle- the angle between the axis of the pushing leg, drawn through the OCMT (conventionally, the base of the thigh bone) and the point of contact of the leg with the ground, and the horizontal;
- damping angle-ferri is the angle in the knee joint of the pushing leg at the moment of greatest flexion;
- repulsion angle- the angle between the axis of the pushing leg and the horizontal at the moment the leg lifts off the ground.
The leg is placed on the push-off quickly, almost straightened at the knee and hip joints, on top of the entire foot, the muscles should be tense. At the moment of setting up, the pushing leg experiences a load several times greater than the jumper’s body weight. In the first part of the push-off, the pressure on the support increases, the leg bends, and the muscles work in a yielding mode. In the second part of the push-off, extension of the pushing leg occurs at the hip and knee joints and plantar flexion at the ankle, the muscles work in an overcoming mode. Straightening the leg at the joints occurs in a certain sequence: first the hip joints begin to straighten, then the knee joints, and the push-off ends with plantar flexion of the ankle joint. Larger and slower muscles are involved in the work first, then smaller and faster ones. They start working sequentially and finish contracting simultaneously. Moreover, the shorter and faster the flexion and stretching of muscles in the depreciation phase (within optimal limits), the stronger and faster their contraction will be.
Table 1. Angular repulsion parameters
The work in repelling the fly links: the arms and the fly leg is of great importance. Together with body weight, they load the muscles of the pushing leg and thereby increase their tension and duration of contraction. As soon as the swing slows down, the load on the muscles of the pushing leg decreases sharply, which ensures a faster and more powerful end to their contraction. Swinging with straightened limbs requires greater muscle effort and is performed slower than with bent limbs, which is not beneficial for pushing off.
In long jumps, the torso takes a vertical position when taking off. In high jumps, at the moment of placing the pushing leg, it is slightly deflected back, no more than 10°, and at the moment of the end of the take-off it should be vertical, forming one line with the pushing leg.
Thus, the effectiveness of repulsion depends on a number of conditions: the magnitude of the muscular efforts of the pushing leg, the time of their manifestation, the amplitude, unity and simultaneity of swing efforts, volitional efforts and the ability to concentrate efforts on repulsion, coordination of movements.
Jumping flight is characterized by the parabolic shape of the jumper's GCMT trajectory. In flight, the jumper moves by inertia and under the influence of gravity; in the first half of the flight it rises at a uniform rate of speed, in the second half it falls at a uniform rate of acceleration. In flight, no internal forces of the jumper can change the trajectory of the GCMT movement. By movements in flight, the jumper can only change the location of body parts relative to the center of gravity. In this case, a change in the position of some parts of the body causes opposite changes in others.
Rice. 3. Vertical components of the result in high jumps
In high jumps in the flight phase, the problem of effective implementation of the gained take-off altitude is solved.
The result in high jumps consists of three main vertical components (Fig. 3):
h-1 is the height of the GCMT location at the moment of separation from the support; h-2 - vertical movement of the center body after separation from the support; h-3 - bar transition efficiency, the distance between the maximum take-off altitude (h-1 + h-2) and the bar.
- The value of h-1 is determined by the height of the jumper, the length of the legs, and the location of the fly links of the body at the moment the repulsion ends.
- The value of h-2 is determined by the initial speed and departure angle, as discussed in detail above.
- The value of h-3 depends on the location of individual parts of the jumper’s body relative to the center of gravity in flight. The desire to reduce this component was the driving force behind the evolution of high jump technique. Thus, the distance between the GCMT and the bar when jumping using the “stepping over” method is 10-15 cm. When jumping using the “Fosbury” method, this component is equal to 0 for some highly qualified athletes. Thus, the actions of a high jumper in flight have a direct impact on the result - overcoming planks at the highest possible height.
In horizontal jumps in the flight phase, the tasks of maintaining balance and taking a position (“tuck”) are solved for effective landing. Due to the elevation of the departure point of the GCTC above the point of its landing, the downward part of the flight path is steeper. To prevent forward rotation after take-off, the jumper must move the pelvis forward and slightly tilt the torso, slightly straighten the swing leg forward, and then lower it down.
The choice of the method of movement in flight is determined by the individual capabilities of the jumper. For beginners, the “legs bent” method is the most accessible; it helps you quickly master balance, lifting your legs, and holding your feet before landing.
Performing a tuck starts with moving your hips forward, raising your knees high and slightly bending your torso forward. The leader in this movement should be the lifting of the legs, and not the bending of the torso. Premature forward bending limits the ability to lift the knees and causes the legs to drop early. The arms should be slightly bent at the elbow joints and move forward, and then down and back. Lowering the arms can be attributed to compensatory movements, due to which the rest of the body rises up relative to the center of gravity, which allows you to land a little further. If the jumper raised his arms, this would cause the legs to drop and, accordingly, land early.
The role of landing in different jumps is not the same. So, in vertical jumps the main task is to ensure safety. When conducting classes and competitions, a landing site must be organized that meets the requirements of the competition.
Rice. 4. Horizontal components of the result in the long jump
In horizontal jumps (long jumps), proper preparation and execution of the landing can improve the result, which consists of three main horizontal components (Fig. 4):
- X-1 - the distance between the foot of the pushing leg and the projection of the center of gravity at the moment of completion of the push-off;
- X-2 - OCMT flight range;
- X-3 - the distance between the footprint closest to the place of repulsion on the sand and the projection of the center of gravity at the moment the feet touch the sand.
- The value of X-1 depends on the repulsion angle and is about 3.5% of the result.
- The X-2 value is determined by the initial speed and departure angle, as discussed in detail above, and accounts for about 88.5% of the result.
- The X-3 value depends on the efficiency of the jumper’s actions during landing and is about 8% of the result. The feet touch the sand somewhat closer than the flight path of the center of gravity. The tuck ends by straightening the legs and body while moving the pelvis forward. After touching the sand, the legs quickly bend at the knee joints, the pelvis moves forward. When the flight path is fully used, the jumper descends onto the buttocks behind the landing marks of the heels.
Landing safety in long jumps is ensured by landing at an angle to the plane of the sand, as well as by shock-absorbing flexion of the legs at the hip, knee and ankle joints with increasing muscle tension.
