M.N. Larionova¹
PhD V.S.Terekhin²
PhD, Associate Professor S.P. Mikhailovskiy^1
1St. Petersburg Mining University, St. Petersburg
²Lesgaft National State University of Physical Education, Sport and Health, St. Petersburg

Keywords: basic step in acrobatic rock-n-roll, kinematic rates, muscle electrical activity, model, dependability, authenticity.

Background. It is common for the modern acrobatic rock-n-roll community to execute the basic step in different manners/ versions since a standard for execution approved by the athletic and coaching communities is still lacking. The sport specialists tend to set the following requirements to the basic step: efficiency, safety and energy cost efficiency [1, 3, 5]. It should be noted, however, that coaches are still in need of reference points for the training systems – and they may be provided by a basic step model designed on analyses of the movement kinematics with muscular activity harmony/ efficiency profiles to effectively optimize the basic step mastering methods [2, 4, 6].
Objective of the study was to offer a basic step model for the modern acrobatic rock-n-roll based on the movement biomechans analysis. 
Methods and structure of the study. We used the following research methods: theoretical analysis and summaries of the reference literature; rules of competitions analysis; questionnaire survey of experts (n=62) in acrobatic rock-n-roll; competitive performance (n=180) analyses; and video capture analysis with classification of the basic step execution techniques supported by electromyographic tests. The study data were processed by standard mathematical tools to model an ideal basic step execution and test the model by experiment on a sample of 16 athletes. 
Results and discussion. Biomechanical test data were used to produce a basic step model as follows: (1) analyze the popular versions of the basic step technique in modern acrobatic rock-n-roll; (2) design a frame basic step model; (3) support it by an efficient modeling algorithm; (4) produce a basic step model; (5) test the model by an experiment; (6) process and analyze the experimental test data; and (7) analyze benefits of the basic step model for the modern acrobatic rock-n-roll.
Components of the biomechanical model at the primary modeling stage were shaped up on the assumption that the model is designed to mimic the target movement sequence; and that the right body side (lead leg side) biomechanics and the upper limbs movement sequences are virtually the same (having insignificant differences) for the basic step versions. This was the reason for the modeling process giving a special priority to the left (swing leg) side biomechanics. Furthermore, we estimated contribution of every basic step element to rank the elements in the following hierarchy/ sequence for the modeling algorithm: see Figure 1 hereunder.

Figure 1. Basic step modeling algorithm for acrobatic rock-n-roll
 

The basic step structure was found fairly consistent for the key versions. The angular specifications (indicative of the body element movement ranges, speed and acceleration for the same-pace movements) were found independent of the athletes’ anthropometric characteristics and other specifications; with the timing and accuracy of the movements (rated by the angular specifications) determined by the muscular action reciprocity. It is the optimal muscular action reciprocity that is critical for the performance quality i.e. plasticity, artistry and dance style.
The modeling algorithm was used to design the basic step model for the modern acrobatic rock-n-roll: see the Table hereunder. The resultant model was tested for compliance with the metrological dependability and accuracy criteria by a fact-finding educational experiment.

Table 1. Key components of the basic step model for acrobatic rock-n-roll
 

The experiment was designed to test, among other things, the basic step model data generation productivity and tolerance to the athlete’s performance and its ability to accurately simulate the subject process biomechanics. The test data showed the angular specifications of the hip, knee and ankle joints varying within the limited range in every test (V=1.89%-5.71%) that was interpreted as indicative of the basic step model high dependability for the key external parameters. In every attempt the model showed minimal deviations from the initial test rates regardless of the conditions and athlete’s physical fitness rate, with the right/ left leg movement accuracy tested virtually identical. A new test round after a significant rest break found the proposed basic step version being stable i.e. showing now significant differences with the previous test data (p>0,05).
Our analysis of the basic step model testing data showed low variation of the muscular reciprocity rates in 12 test rounds – that was interpreted as indicative of the high reproduction degree of the movement sequence and excellent harmony of the muscular control. A new test round after a significant rest break found the actual execution being fairly close to the model i.e. both the skills and the model was tested stable and dependable. The muscle action reciprocity rates showed insignificant differences across the test rounds (p>0.05). This means that the model basic step version is well memorized by the muscle memory, highly fatigue-tolerant and stable with time.
The basic step model testing experiment showed its benefits as verified by the sample progress in the technique mastering and execution in practice. Expert scores of 12 test rounds with the execution pace kept within the range required by the valid rules of competitions – were high enough, with the model basic step execution quality rated by 85% quality score on average. Version 2 of the basic step required 5 training sessions to attain the same quality level. Versions 4 and 5 of the basic steps claimed the same training time. And versions 3, 6 and 7 claimed the  longest mastering time (more than a month) to attain the same quality.
Conclusion. The basic step model test data showed a low variation of the execution quality rates for the basic step version 1 – regardless of the trainees’ skills – that means that the model version is highly accessible and easily trainable by the groups. The combined analytical toolkit applied in the study for the model efficiency testing purposes may be recommended for application in other gymnastic disciplines to reduce the injury rates and improve the competitive performance.

References

1. Gaverdovskiy Yu.K. Obuchenie sportivnym uprazhneniyam. Biomehanika, metodologiya, didaktika [Teaching sports exercises. Biomechanics, methodology, didactics]. Moscow: Fizkultura i sport publ., 2007, 930 p.
2. Gorodnichev R.M. Sportivnaya elektroneyromiografiya [Sports electroneuromyography]. Velikiye Luki: VLSAPC publ., 2005, 230 p.
3. Mamzin V.I., Mamzina M.V., Lalaeva E.Yu. Metodologiya vyyavleniya i primeneniya bazovykh gimnasticheskikh uprazhneniy [Basic gymnastic exercises identification and application methodology]. Aktualnye problemyi fiz. kultury i sporta [Actual problems physical education and sports]. Proc. reg. res.-pract. conf.. Volgograd, 1996, pp. 75-77.
4. Samsonova A.V., Komissarova E.N. Biomekhanika myshts [Muscle biomechanics]. Teaching aid. St. Petersburg, 2008, 127 p.
5. Terekhin V.S., Medvedeva E.N., Kryuchek E.S. et al.Teoriya i metodika akrobaticheskogo rok-n-rolla. Aktualnye problemy podgotovki sportsmenov [Theory and methods of acrobatic rock and roll. Actual problems of athletic training]. Study guide. Moscow: Sport publ., 2015, 80 p.
6. Khubbiev Sh.Z., Elmurzaev M.A. Novye podkhody k postroeniyu tekhnologii obucheniya dvigatelnym deystviyam [New Approaches to Construction of Technology of Teaching Motor Actions]. Teoriya i praktika fiz. kultury, 2014, no. 2, pp. 49-51.

Corresponding author: omelchenko2005@rambler.ru

Abstract
It is commonly acknowledged that basics of athletic mastery shall be laid fairly early, with the competitive accomplishments in the further sport career being largely dependent on how successful the beginner sport basics mastering process is. That is the reason why the sport community gives a high priority to the beginner training component in the coordination-intensive sport disciplines. Key mission of the beginner training is to form a technical framework for the model execution of the key elements. The study was designed to test a biomechanical analytical toolkit and produce a basic step model for the modern acrobatic rock-n-roll. 
The study methods included a theoretical analysis and summaries of the reference literature; rules of competitions analysis; questionnaire survey of experts (n=62) in acrobatic rock-n-roll; competitive performance (n=180) analyses; and the video capture analysis with classification of the basic step execution techniques supported by electromyographic tests. The study data were processed by standard mathematical tools to model an ideal basic step execution and test the model by an educational experiment.
The experimental data showed benefits of the basic step modeling tools as verified by a meaningful progress of the sample in the technique mastering and practical execution. The combined analytical toolkit applied in the study for the model efficiency testing purposes may be recommended for application in other gymnastic disciplines to reduce the injury rates and improve the competitive performance.