BIOMECHANICAL QUALITATIVE ANALYSIS OF KAYAK ROWING TECHNIQUE IN INITIAL TRAINING OF STUDENTS

Abstract

The educational policy of the Bulgarian education enables the teachers in secondary education to be carried out by choice in at least one obligatory educational field of educational content and one elective educational field of educational content. Our attention was drawn to the elective educational area "Rowing", introduced after 2019 in grades  8-12, 15-18 years old. For the convenience of teachers, we made a biomechanical qualitative analysis of the technique in the initial training in kayak style. By applying the analytical method for determining the center of gravity (CG), we determined the CG of the rowing-boat kinematic system, as a result of which, we determined the beomechanical expediency of the technique in the initial training in rowing style "kayak". Analysis of the spatial and spatial-temporal structures of rowing movements. Determining the main phases of work of the upper limbs, oars and torso. We used a cinematographic method in which a series of frames were made arranged in a cyclogram. The procedure for filming a kayak and a rower was organized in the sports hall "Dr. Stefan Mitov" of SWU "Neofit Rilski", Blagoevgrad. A 26 mp HUAWEI MATE 10 camera was used to capture the images. The graphics processing was done with PAINT 3D, Windows 10. The kayak is an "Ocean duo" model from RTM. The determination of CG by the analytical method is performed according to the following algorithm: 1) determination of partial centers of gravity (PCG) of the individual units of the kinematic chain of a certain sports posture (we worked on a photo); 2) according to external anatomical landmarks we plot the projections of the joint centers; 3) Connect the centers with straight lines - longitudinal axes; 4) measure the length of the longitudinal axis in mm for each segment separately and multiply it by the corresponding coefficient of the unit - (K) - shown in the figure as numerical values inscribed near the longitudinal axis. The resulting distance in mm is plotted from the proximal to the distal end along the longitudinal axis (from the inner to the body joint center to the outer) and we obtain the position of the Partial center of gravity; 5) after finding the PCG values in mm (X, Y) are measured on their coordinates. The data are recorded in a table, a value for X and Y is determined for each segment and plotted against a weighting factor of 0.07 head, 0.43 torso, etc. Multiply the values and get Δ X and Δ Y. Then add up all the values for X and Y. The values obtained are plotted on the graphic and the CG is localized. The CG data show that it is located below the base of the central sternum of the thorax, and in no rowing position does it extend beyond the body. For the initial study of rowing in such a kayak, in which the width of the board is greater and gives greater stability, it is important that the projection of the CG on the support area does not have large fluctuations in the anterior-posterior direction (sagittal plane) and lateral direction (frontal plane).The phase defining positions are catch, immersion, extraction, and release. After analyzing the kinematic chain rower-paddle-water mass, we found the following differences between the basic sports-competitive technique and the technique for initial training in students, basically they are due to size on the kayak (we used a tourist kayak).  Angle of enter in the water (^o) 36.5 compared to 48-50 with us; lateral angle of the paddle in the water phase (^o) 43.3 versus 50; water phase length (m) 1.09 versus 0.83; Distance of the blade path when extracting (m) 0.33 versus 0.40. (López & Ribas, 2011). To perform the correct technique of transferring the paddle, it is necessary to limit the movement of the center of the paddle in a virtual cube with a side of 40 cm, which is located at chest height and at a distance to the elbow joint of a raking hand. The basic rowing technique must be built after refining the kinematic parameters of the movement and building a basic motor control of the student.