Researcher G.G. Zakharov¹
Leading Researcher A.V. Voronov^2
1FSBI “Saint-Petersburg scientific-research institute for physical culture”, Saint-Petersburg
²FSBI “Federal Science Center for Physical Culture and Sport”, Moscow

Corresponding author: zaharov-grigori@mail.ru

Abstract

Objective of the study was to test and analyze the 15-17 year-olds’ technical skills in practical ski jumping competitions.

Methods and structure of the study. We sampled the 15-17 year-old ski jumping competitors (n=45) at the 2020 Student Sports Games in Tchaikovsky. The technical skills were captured by Sony HDR-CX650E camcorders fixed horizontally on tripods about 20m from and perpendicular to the jump line and rated at 50 frames per second. The camcorders were placed at the take-off and 6m/ 35m far downhill. The postural control and skiing symmetries was rated in the (1) in-run, (2) take-off and (3) flight phases from behind.

Results and Conclusion. The three phase (in-run, take-off and flight) kinematics was analyzed to rate the individual technical executions on the 102m long K-95 ramp in competitions. The jump techniques were analyzed on a more detailed basis in the leaders group.

The study data and analyses made it possible to rate the technical fitness of the 15-17 year-old ski jumpers for the 2020 Student Sports Games. The leaders group was tested with the postural controls in the in-run and mid-flight phases close to or matching with the technical execution standards. The take-off errors were due to the postural control asymmetries in the in-run and take-off phases in most of the sample, and we recommend the coaches giving a special priority to this technical element excelling aspects in the training systems. We also recommend the junior ski jumping training service quality being improved by regular camcorder tests with the postural control analyses and simulations to develop clear and symmetrical technical execution. Such tests and analyses are indispensable for the individual technical progress control with reference to the modern execution standards.

Keywords: ski jumping, junior ski jumpers, biomechanics, angle characteristics, aerodynamics.

Background. Junior ski jumpers are traditionally trained so as to master every technical element and jumping technique on the whole using simulators and practices on hills and snow bumps, with the basic skills mastered on special training tables and then on real competitive ramps and hills. Since the jumping skills schooling takes a long time, the beginner ski jumping technique training practices should be designed with a close reference to the best modern technical execution standards [2], with the more senior trainees’ skills and postural controls tested and corrected versus the phase-specific joint angle standards [3, 6] and aerodynamic flight indices [1]. It is very important for the ski jumping schools to design and manage the sports reserve training systems as recommended by the modern well-grounded theory and practice [4].

Objective of the study was to test and analyze the 15-17 year-olds’ technical skills in practical ski jumping competitions.

Methods and structure of the study. We sampled the 15-17 year-old ski jumping competitors (n=45) at the 2020 Student Sports Games in Tchaikovsky. The technical skills were captured by Sony HDR-CX650E camcorders fixed horizontally on tripods about 20m from and perpendicular to the jump line and rated at 50 frames per second. The camcorders were placed at the take-off and 6m/ 35m far downhill. The postural control and skiing symmetry was rated in the (1) in-run, (2) take-off and (3) flight phases from behind.

Results and discussion. The three phase (in-run, take-off and flight) kinematics was analyzed to rate the individual technical executions on the 102m long K-95 ramp in competitions. The jump techniques were analyzed on a more detailed basis in the leaders group (n=10). Given in Table 1 hereunder are the in-run postural control test data of the sample versus the technical execution standards [3, 6].

Table 1. The 15-17 year-olds in-run postural control test data versus the execution standard

*Note: angles rated to the ramp center line

The in-run phase postural control rates of the sample were found basically compliant with the standards, albeit the video captures shoot from behind found a few postural control asymmetries and ski control errors: see Figure hereunder. It may be pertinent to remind that the key goal of the in-run phase is to speed up as fast as possible and set into an optimal take-off position; with the parallel skiing on the whole track with minimal side friction plus the streamlined posture to minimize the air resistance for faster acceleration.

Figure 1. Postural control asymmetries and skiing errors in the in-run (1а), take-off (1b), flight start (1c) and mid-flight (1d) phases

In most cases, poor ‘body centering’ in the in-run phase appeared responsible for the further chain of errors (see Figure 1) including failures to control the total center of gravity in the take-off phase; deviations of the take-off jump line from the ramp center line; twists in the skier-ski system in the mid-flight phase etc. Our tests found 18 jumpers successful in skiing right in the middle of both tracks in every attempt; 5 jumpers failing at times doing that; 22 jumpers were tested with frequent skiing errors with the ski contacts with the track sides; and 24 and 21 jumpers were tested with serious and minor (respectively) in-run postural control asymmetries in the trunk and limb positions (see Figure 1a).

The take-off tests and analyses showed that, despite the joint angles being basically within the standard, the average take-off angles in both groups were above 90º - that is indicative of the ‘neutral position’ of the center of gravity on the edge in most of the sample. Such an execution of the key technical element fails to develop a due torque in the take-off point that facilitates taking the aerodynamically optimal configuration of the skier-ski system, i.e. the technical execution in this phase was tested inconsistent with the modern take-off standards. It should be noted that 30 out of 45 competitors were tested with the take-off postural control asymmetries, mostly with errors in the knees positioning and skiing track centering (Figure 1b); and 27 jumpers were tested with the flight startup asymmetries (Figure 1c).

The mid-flight postural control angles were rated 35m far from the table, i.e. in the mid-point of the landing slope of the K-95 ramp. The leading group was tested close to or within the standard at this point. The technical performance may be still improved by mobilizing the postural aerodynamics reserves to reduce the frontal air resistance by ‘more active’ and ski/ trunk controls so as to minimize the aerodynamic flight indices. The main group was tested with particularly low average aerodynamic flight indices = 0.55 and, hence, requires special mid-flight control improvement trainings.

Furthermore, only 3 and 22 athletes were tested with no or minor flight-control asymmetries, respectively. Most of the sample, including the leaders group, was tested with the limb/ trunk/ skis control asymmetries and/or twists in the skier-ski system, and/or deviations from the ramp center line (Figure 1d); with these errors seriously limiting the aerodynamic quality and aesthetic aspects of the flight phase [5, 6].

The landing phase analysis tested only 6 jumpers with the right Telemark landing (one foot in front) style;15 athletes were unsuccessful in their Telemark execution attempts; 13 jumpers landed with no Telemark whatsoever; and 11 landed in deep squatted (erroneous) positions penalized by the technical score deductions.

On the whole, the competitive scoring points recorded in protocols include the points for aesthetic/ artistic merits and technical execution of the in-run, flight and landing phases. The technical scores averaged 15.4 and 13.7 out of 20 for the leaders and main groups, respectively, that means the medium and low technical execution qualities.

Conclusion. The study data and analyses made it possible to rate the technical fitness of the 15-17 year-old ski jumpers for the 2020 Student Sports Games. The leaders group was tested with the postural controls in the in-run and mid-flight phases close to or matching with the technical execution standards. The take-off errors were due to the postural control asymmetries in the in-run and take-off phases in most of the sample, and we recommend the coaches giving a special priority to this technical element excelling aspects in the training systems. We also recommend the youth ski jumping training service quality being improved by regular camcorder tests with the postural control analyses and simulations to develop clear and symmetrical technical execution. Such tests and analyses are indispensable for the individual technical progress control with reference to the modern execution standards.

References

1. Zakharov G.G., Zlydnev A.A., Sergeev G.A. Biomechanical analysis of “contactless phase of repulsion” and the start of flight in modern ski jumping technique. Uchenye zapiski universiteta im. P.F. Lesgafta. 2016. No. 8 (138). pp. 61-66.
2. Zakharov G.G. Rating technical fitness in ski jumping in 15-17 year-old combined skiers. Innovative technologies in sports training, mass physical education and sport system. Proceedings national research- practical conference with international participation. Saint-Petersburg, 2019. pp. 59-64.
3. Sergeev G.A., Zlydnev A.A., Yakovleva A.A. Methodology for development of integrated target programs for training of regional combined teams of qualified athletes for four-year training cycle (case study of combined skiers of the Russian Federation). Study guide. Saint-Petersburg: Lesgaft National State University of Physical Education, Sport and Health publ., 2013. 132 p.
4. Buchner S. Technikleitfaden Skispringen. DSV Trainerschule. Planegg. 2015. 44 р.
5. Gneckow J. Entwicklungeines Anleitungsmaterialszur Vervollkommnung der Skisprungtechnikim Nachwuchstraining. DSV Trainerschule, Planegg. 2012. pp. 51-63.
6. Müller S., Kreibich S., Wiese G. Analyse der nationalen und internationalen Leistungsentwicklungim Skispringen. [Olympiaanalyse]. Available at: https://www.iat.uni-leipzig.de/datenbanken/iks/dsv-ssnk/ (date of request 28.02.2021).