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17Technical errors in elite ski jumping: classification attempt
UDC 796.925
Postgraduate student R.Y. Shestopyorov1 PhD, Associate Professor S.A. Gorbunov1 PhD, Associate Professor S.S. Gorbunov1 1Tchaikovsky State Institute of Physical Culture, Tchaikovsky
Corresponding author: [email protected]
Abstract
Objective of the study was to analyze and classify technical execution errors in the modern elite ski jumping sport.
Methods and structure of the study. We have collected, for three competitive seasons, the formal training logs and competitive records of the World Ski Jumping Cup events to mine detailed data on the in-run speed, jump distance and technical execution errors. On the whole we have analyzed 863 jumps on different ramps for the three seasons, both in the winter and summer events (on artificial hills). The ski jumping data were produced by the relevant metering tools including speed sensors, video captures, Dartfish statistical processing system, and expert valuations.
Results and conclusion. We found none elite ski jumper immune to the jump phase execution errors in fact, with the in-run and landing phases by far leading in the numbers of errors.
We found no significant differences of the national elites in the in-run and take-off errors, with the latter clearly dominating in the error statistics.
Modern elite ski jumpers have developed multiple errors-correcting tools and skills - that may be trained by a range of special technical execution adjustment exercises. The error-correction skills will be mastered with due sensitivity to the technical error origin. The origin is often found in the poorly designed training systems.
Technical and distance scores in the modern elite ski jumping sport are highly sensitive to the technical errors in every jump phase. We found the Russian team's errors dominated by the cyclic (rollover) errors that snowball in the later jump phases. Efforts to eliminate such errors as early as possible will help seriously scale down the subsequent error rates and improve the techniques on the whole with the obvious benefits for the technical and distance scores.
Keywords: technique, ski jumping, phase structure, cyclic errors.
Background. Modern ski jumping sport is a technically difficult sport discipline that requires high-precision execution of every element in the relatively standard settings including the ground and aerial/air flow control phases. Presently the ski jumping sports elite gives a special priority to the take-off/ jump element [1, 4] deemed critical for the distance score. We believe, however, that the excessive focus on a single element appears too simplistic as it limits the causes and effects of the complex system exposed to multiple factors of influence [2, 4, 6].
When a goal of every elementary action in some
movement phase is attained in a harmonic manner, it guarantees a favorable setting for success of the next phase, albeit a single minor error may snowball in the subsequent phases [2]. This may be the key reason for the above excessive concentration on the take-off phase - since the skier immediately after enters the aerial phase with the posture set as close to the optimal as possible. No wonder that every minor take-off error may complicate the efforts to take the kinematically optimal aerial position and compromise execution of the next movement phases. Such errors are commonly referred to as the cyclic or rollover errors. An
error-free execution of every element in a harmonized sequence is deemed most beneficial for success, although almost never achievable in real practice, since any mechanical system of that kind is always exposed to multiple external factors of influence [6, 8]. The most beneficial option in this case is to learn to correct the cyclic errors in the bud to prevent their rollover to the next phases. As mentioned above, no one is immune to technical errors although every skilled ski jumper has to master the cyclic errors control/ mitigation techniques. This is the key reason why we see the ski jumping sport leaders now and then getting "out of the woods", even when the jump goes wrong in the early stage.
Objective of the study was to analyze and classify technical execution errors in the modern elite ski jumping sport.
Methods and structure of the study. We have collected, for three competitive seasons, the formal training logs and competitive records of the World Ski Jumping Cup events to mine detailed data on the in-run speed, jump distance and technical execution errors. On the whole we have analyzed 863 jumps on different ramps for the three seasons, both in the winter and summer events (on artificial hills). The ski jumping data were produced by the relevant metering tools including speed sensors, video captures, Dartfish sta-
tistical processing system, and expert valuations.
Results and discussion. We found none elite ski jumper immune to the jump phase execution errors in fact, with the in-run and landing phases by far leading in the numbers of errors: see Table 1 hereunder.
We found no significant differences of the national elites in the in-run and take-off errors, with the latter clearly dominating in the error statistics. Since the setting phase, the Russian ski jumping team is significantly different in the error rates from the other competitors: see Figure 1. Knowing that the jump scores are closely and negatively correlated with the error rates, we recommend special efforts being taken to control and mitigate the technical / cyclic errors otherwise there are no chances for success in the topranking international competitions.
Of special interest, as we believe, is the following consideration: the later is the error moment from the jump start, the higher is the error contribution to the jump score (mostly to the distance score), all other things being equal. For example, an in-run error may be corrected in the next phase, although a flight control error may virtually never be offset. Special efforts need to be taken in this context to scale down the most critical cyclic errors in the flight phase.
Cyclic errors made by the Russian ski jumping elite deserve special attention. These are the early-phase
Russia Norway Poland Austria Slovenia
In-run Take-off
Setting Flight Landing
In-run Take-off
Setting Flight Landing
Figure 1. Average technical errors classified by the jump phases and competing nations
Figure 2. Average cyclic errors classified by the jump phases and competing nations
Table 1. Average technical and cyclic execution errors in the summer Grand Prix events of the World Ski Jumping Cup, %
Jump phase Technical (cyclic) errors rates, %
Russia Norway Poland Austria Slovenia
In-run 9 7 9 8 8
Take-off 28 (9) 27 (7) 27 (8) 24 (8) 25 (8)
Setting-for-flight 26 (24) 18 (10) 17 (9) 17 (9) 19 (11)
Flight 19 (15) 15 (7) 12 (9) 14 (8) 15 (10)
Landing 12 (10) 10 (4) 8 (5) 10 (6) 9 (9)
Note: cyclic errors rates in brackets
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errors that snowball in the following phases: see Figure 2. It should be emphasized that the Russian elite makes largely the same cyclic errors in the take-off phase as the others, but virtually unsuccessful in the attempts to correct them, and let them roll over to the next phases. Polish and Austrian competitors, for instance, are much more successful in correcting the take-off errors later on. The take-off errors in the other teams were found fast offset in the setting phase - in contrast to the Russian team that is too tolerant and exposed, as we feel, to the cyclic errors.
Note that the Russian team leads in the cyclic errors as provided by the above Table in brackets. Moreover, 93% of the in-run errors in the team were tested to roll over to the take-off phase - versus only 46% and 44% (!) in the Austrian and Polish teams, respectively.
If we now compare Figures 1 and 2, it turns obvious that the Russian team's errors since the setting-for-flight phase are rooted in the earlier phases as the cyclic errors. This means that they should be scaled down as a matter of top priority to drastically improve the ski jumping technique and distance score. Typical setting execution errors include: short or excessive transverse twist; no synch in the skies setting for the flight; body mass center falling backwards; too aggressive ski attack angle; too early V-shaping of the skies; failures in keeping the right/ left feet horizontal; excessive setting (aerodynamic pose taking) time, etc. As a result, the jumper loses horizontal speed and fails to develop good lifting force - and no wonder that the setting execution errors seriously reduce the total score.
Modern elite ski jumpers have developed multiple errors-correcting tools and skills - that may be trained by a range of special technical execution adjustment exercises - including, e.g., stepped-difficulty, surprise/ novelty, re-sequencing and other practices. The error-correction skills will be mastered with due sensitivity to the technical error origin. The origin is often found in the poorly designed training systems. As a result, the athlete gets used to the specific kinematic cycle (movement sequence) with the relevant error-fixing muscular sensations, being confident that the movement is perfect. We found the present ski jumping sport leaders virtually immune to such growth errors - in contrast to the Russian elite. Therefore, we underline the need for the further trainings to be designed and updated with a top priority to the technical errors correction elements and skills to prevent them evolving into the cyclic errors.
We have omitted herein a range of random errors due to external/ unpredictable factors as they are less
controllable - in contrast to the "standard" common technical errors that need to be rooted out as early as possible in the trainings to prevent their evolution into the cyclic errors detrimental to competitive progress.
Conclusion. Technical and distance scores in the modern elite ski jumping sport are highly sensitive to the technical errors in every jump phase. We found the Russian team's errors dominated by the cyclic (rollover) errors that snowball in the later jump phases. Efforts to eliminate such errors as early as possible will help seriously scale down the subsequent error rates and improve the techniques on the whole with the obvious benefits for the technical and distance scores.
References
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https://en.wikipedia.org/wiki/Ski_ jumping#Techniques
Each jump is divided into four parts: in-run, takeoff (jump), flight, and landing. By using the V-style, firstly pioneered by Swedish ski jumper Jan Boklov in the mid-1980s,[12] modern skiers are able to exceed the distance of the take-off hill by about 10% compared to the previous technique with parallel skis.[citation needed] Previous techniques included the Kongs-berger technique, the Daescher technique and the Windisch technique.[12] Until the mid-1960s, the ski jumper came down the in-run of the hill with both arms pointing forwards. This changed when the Dascher technique was pioneered by Andre-
as Dascher in the 1950s, as a modification of the Kongsberger and Windisch techniques. A lesser-used technique as of 2017 is the H-style which is essentially a combination of the parallel and V-styles, in which the skis are spread very wide apart and held parallel in an "H" shape. It is prominently used by Domen Prevc.
Skiers are required to touch the ground in the Telemark landing style (Norwegian: telemarksned-slag), named after the Norwegian county of Telemark. This involves the landing with one foot in front of the other with knees slightly bent, mimicking the style of Telemark skiing. Failure to execute a Telemark landing leads to the deduction of style points, issued by the judges
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