E.V. Koshel'skaya, Ph.D.
A.V. Razuvanova, postgraduate student
O.S. Smerdova
National Research Tomsk Polytechnic University, Tomsk
L.V. Kapilevich, professor, Dr.Med.
D.Yu. Balanev, associate professor, Ph.D.
National Research Tomsk State University, Tomsk

Keywords: flight, landing, athletics, kinesiology, electromyography.

Motor actions during flight are some of the most difficult, in certain sports athletes have to deal with them all the time, and in many sports flight is the main position during exercise [2, 3]. In flight actions the essential psychological factor is readiness for safe landing, avoiding the loss of balance and falling [4, 6]. This factor often hampers the effective execution of an exercise.

The purpose of the research was to study the physiological and biomechanical characteristics of the landing phase of athletes of different skill levels when making a standing long jump.

Materials and methods. We examined a total of 30 men aged 17 to 24. They were divided into two groups according to the level of formation of their motor skills. The main group consisted of elite athletes - MS and CMS (16 people). The control group included students (14 people) who did not have any sports categories. To analyze the orientation of the body parts, their position in space and towards the support, the motion tracking method was used. The spatial movements of the body parts were registered using the camcorder Vision Research Phantom Miro eX2. The video was recorded at 100 frames per second. The findings were processed and analyzed using the program StarTraceTracker 1.1 VideoMotion®. The muscle bioelectric potentials were recorded using the electromyograph "FREE EMG".

Results and discussion. Figure 1A illustrates the dynamics of the head back-tilt angle when landing. The maximum angle value in the athletes from the control group was 210 degrees, and in those from the main group - 197 degrees. After which, the head posture of the jumpers from the control group remained unaltered, while in the athletes the angle reduces to 120 degrees at the moment of taking up the upright position.

The landing impact compensation occurs primarily in the knee joint, and the diagram of its angle changes (Figure 1B) is of similar dynamics in the subjects from both groups. However, the amplitude, and consequently the speed of joint movements are much higher in the main group. When landing, track and field athletes perform a deep knee-bend without fear of losing balance. While the subjects from the control group slow down and speed down the knee-bend, which leads to the intensification of mechanical loading on the locomotor system and traumatizing of the periosteum. Such way to maintain equilibrium is inefficient - body balance control is ensured by putting the center of mass of the body (CMB) to the vertical projection in the three-dimensional stability field or within the contour of the landing point. Moreover, closer CMB projection to the center of the three-dimensional field promotes steadier landing [4].

Fig. 1. Dynamics of the joint angles in the testees when performing standing long jumps.

А – head back-tilt angle, B – knee angle, C – hip angle.

Light line – main group. Dark line – control group.

The hip joint, being very close to the CMB, is already bent in the landing phase, and it keeps bending till the moment of shifting weight to the feet. Here, we can observe typical differences between the two examined groups (Fig. 4). The jumpers from the control group, securing safe landing, scarcely bend their hip joints from the very start of landing to the vertical position, keeping the angle value at 140 degrees. In the group of athletes the hip joint is already 70°-60° bent at the moment of contact with the support due to the legs being straightened ahead for the purpose of extension of the jump range. Athletes keep moving ahead in this position until they contact with the support, that is, they voluntary bring the CMB projection nearer to the landing area by bending their hip joints.

It is interesting to note that speed dynamics of the hip joint movements performed by the subjects from both groups is of similar nature (Figure 2). The main difference is in the amplitude of speed changes - in athletes it is much higher both vertically and horizontally. At the moment of contacting the support the horizontal velocity of the hip joint movement performed by an athlete equals to zero. The control group performed both horizontal and vertical movements at this moment, which led to a slip of the landing point.

Fig. 2. Speed dynamics of hip joint movements performed by subjects from the main (А) and control (B) groups.

Light line – horizontal velocity of the point. Dark line – vertical velocity of the point.

The detected diversity of movements of the body parts when landing is stipulated by the specifics of distribution of muscle activity (Fig. 3). Athletes engage the gastrocnemius muscle in a less degree, especially in the landing phase of the jump. The activity of the biceps femoris muscle is also of lower amplitude compared with the control group, so is the time of discharge. The rectus femoris activity is of higher amplitude in the group of athletes, however, it is of shorter duration. On the whole, in the landing phase athletes tend to have lower electrobiological activity of muscles and a more distinct accentuation of the peaks of their activity.

Fig. 3. Electrobiological activity of main muscle groups when making a standing long jump for an athlete from the main (А) and control (B) groups.

Conclusion. The findings suggest that technical skills are developed when performing standing long jumps thanks to the reorganization of the system of statokinetic reflexes of the athlete [1, 5]. Changes occur in the distribution of muscle tone in the flight phase, which leads to a change in the motion pattern in the cervical spine, as well as in the hip and knee joints. The result of such changes in athletes is the reduced horizontal component of the velocity of flight by the time of landing and putting the center of mass of the body to the support projection to ensure the equilibrium 

References

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