Development of Physical Fitness Through Simulation Exercises for Ski Racers Aged 13-14. Non-Randomized Quasi-Experimental Study

Introduction

The Olympic Games usually reflect the highest level of sport achievements of the country, where the number of gold medals won by Russian skiers has been decreasing during the last 20 years, a product of the little flexibility presented by the Russian training model according to modern standards [1]. In this context, the achievements of cross-country skiing today are so great that without systematic training from an early age, it is impossible to achieve high performance at adult ages, with the process of sports training in young ski racers entailing various determinants of athletic performance [2-4].

Currently, the periodization of sports training, following the traditional classical model, postulates three phases for the annual performance of the sport, the first being oriented towards the acquisition of skills and sports qualities (preparatory period), the second to the maintenance and expression of the physical and psychological changes generated (competitive period) and the last one directed to the generation of a controlled loss of physical condition to generate an optimal recovery to restart the sports cycle (transition period) [5-7].

In this sense, the preparatory period is considered the most important during the macrocycle in skiers since, at this stage, the foundations of athletic performance expressed in the competitive period are laid, where the role of physical qualities is fundamental for the development of physical fitness and sports technique reflected on the movement on skis, being the dosage of the workload in the preparatory period of a ski racer determinant for athletic performance [8-10]. In this context, the exact choice of exercises during training will largely establish the effectiveness of physical workloads in the long term, as simulation exercises characterized by replicating motor skills are a primordial link for the development and learning of coordinate structures and sports performance variables at both specific and global levels [11,12], where the imitation of alternate two-step ascents with or without poles in combination with flat runs and descents are widely recognized as alternate elements that allow the establishment of routes with variants on the pattern of specialized walking, walking, jumping and running simulation [13-16].

In the same way, simulation exercises are often used during the beginning of the preparatory period to achieve settlement of the technical elements of sport, since the low volume and intensity of the workloads allow the development of physical qualities and motor skills that are determinant during the absence of snow in the summer [13-16]. In this sense, the analysis of bibliographic sources has shown that in skiing, physical fitness is crucial to achieve sporting results, while when simulation exercises are used, there is a positive transfer of physical qualities by assimilation of the technical elements resulting from the nature of the activity and motor skills [11-15]. A problem can be seen around the training of skiers in sports schools, whose solution seems to be related to the implementation of a set of exercises that can improve the training process in sports schools.

For this reason, the aim of this study was to analyze the effects of simulation training tools on physical fitness in ski racers aged 13-14 years.

Method

Design

Quasi-experimental, non-randomized study based on the ''Transparent Reporting of Evaluations with Non-randomised Designs'' [17]. The informed consent and research protocol were approved by the Research Committee of Vyatka University (Russia), with children being authorized to participate by their parents or legal guardians by signing an informed consent form in accordance with the ethical standards set forth in the Declaration of Helsinki [18].

Participants

The study was conducted at a sports school in the village of Korshik (Kirov, Russia). The experiment involved only children (boys) aged 13-14 years, cross-country skiers, who formed a control group (n = 20) and an experimental group (n = 20). Eligibility criteria were as follows:

Inclusion criteria:

• Children aged 13-14 attend the Korshik Village Sports School (Russia).

• Children who practice cross-country skiing regularly at least three times a week.

Exclusion criteria:

• Children who did not agree to participate in the experiment if their parent or legal guardian did not sign the informed consent.

• Children who did not attend trainings or evaluations conducted in the classes taught at the Korshik Village Sports School (Russia).

• Children with acute or chronic illnesses that prevent them from participating in the experiment.

Intervention

The control group classes were conducted according to the usual training plan [19], while the experimental group was subjected to classes incorporating simulation exercises aimed at improving physical fitness in the preparatory period. These classes were conducted five days a week and in each class 20 or 90 minutes of the training session were allocated to the application of uniform and circular training methods. The intervention was divided into two stages:

From May to July 2022, the following simulation exercises were applied to develop endurance strength:

• Imitation of the hand movements of an alternating two-step run with a rubber buffer.

• Simulation of simultaneous hand movements in a single step with a rubber buffer.

• Simulation of simultaneous continuous running with a rubber buffer.

• Change the position of the legs with a load of 5 kg.

• Walking with resistance.

From August to November 2022, an emphasis was given to simulation exercises for the development of endurance and strength at high speed, including the following exercises:

• Jump on one leg, imitating the work of the hands, as in a two-step alternating run.

• Multiple jumps from foot to foot with strong and fast repulsion and flight.

• Simulation of jumping in a simultaneous one-step movement.

• Place the legs under the trunk and push with the supporting leg.

• Squat down on the supporting leg and push with the body moving sideways and forward.

• Simulation of the simultaneous movement of a step on the ground.

• Simulation of the simultaneous movement of two moving steps.

• Jumping: multiple jumps from one foot to the other, from side to side.

• Ski pole jumping simulation.

• Overcoming height through a jumping simulation with a two-step alternating movement with sticks.

The following methods were used to develop high-speed endurance:

• Variable method: 3-4 accelerations of 1 km. Climbs are overcome by a jumping imitation of a two-step alternating movement with sticks.

• Repeated method: repeated overcoming of climbs on different slopes by imitation of jumping with sticks.

• Repeated method: running 2-3 segments equal to 1/2 or 1/3 of the competitive distance with an intensity of 90-100% of maximum. Climbs are overcome by a jumping imitation of a two-step alternating movement with sticks. The rest between runs is at least 4-6 minutes.

Target

The aim of this work was to analyze the effects of simulation training tools on the physical condition of 13-14-year-old ski racers. For which, an alternative hypothesis that a set of simulation exercises applied contributes to improving the physical condition of 13-14-year-old skiers in the preparatory period was proposed.

Variables

Endurance strength was assessed using the pull-up and squat tests. The pull-up consisted of subjects being instructed to use an overhead grip with hands positioned slightly wider than shoulder-width apart, where each repetition would begin in a dead position (elbows extended, shoulders flexed and shoulder girdle elevated) with legs positioned behind the body, ankles crossed and knees bent. Once in the correct starting position, the subjects had to perform the concentric phase of the pull-up in an explosive manner, without swinging or kicking their legs. The concentric phase ended once the subject's chin passed the pull-up bar. Immediately after completing the concentric phase, subjects were instructed to perform the eccentric phase of lowering the body to the starting position at a comfortable speed, recording the maximum number of repetitions possible [20]. On the other hand, students were instructed to perform the maximum number of full squats for 1 minute, whose movement consisted of the subjects having to descend until the back of the thighs and calves made contact with each other or when the angle of the lumbar spine was equal to 0° [21].

Speed and endurance strength were assessed by the two-legged long jump test. This consisted of bending the knees while moving the arms forward and backward with a strong push, then jumping forward as far as possible, helping oneself with both arms and trying to land on the ground with feet together without losing balance to proceed to measure the distance performed [22].

The development of high-speed endurance was assessed by simulated 100-meter climbs and 500-meter run tests. The simulated 100-meter climb considered that standardized instructions were given for the 100-meter climb with 7 degrees of incline at the maximum possible speed to measure the time used in seconds [23]. The 500-meter run test considered that standardized instructions were given in the 500-meter run, where subjects were asked to run as fast as possible for 500 meters to measure the time in seconds [24].

Method of assignment

Each subject was assigned to an experimental group or to a control group in a non-probabilistic manner, this designation being made by pairing two groups of equivalent size. Thus, each group consisted of 20 children.

Unit of analysis

Groups of children were considered the lowest administrative unit used to evaluate the effects of the intervention. This consisted of a comparison of pull-ups, squats, long jump, simulated 100-meter, pull-up and a 500-meter sprint test.

Data analysis

The data were analyzed with IBM SPSS Statistics version 27.0 statistical software for the Windows operating system. The normality of the data distribution was determined with the Shapiro-Wilk test and the homogeneity of variances with the Levene test, the data being expressed through the descriptive data of central tendency and dispersion; mean and standard deviation. Differences between groups were determined with the Student's t-test for related samples, considering for all analyses the percentage frequency in addition to an alpha level of 0.05.

Results

Table 1 shows the analysis of the baseline data, which shows homogeneity between the control and experimental groups in the five indicators (p > 0.05).

Table 1. Baseline characteristics of the groups.

Table 2 shows the comparison of the physical fitness indicators of the control group before and after the intervention, where no statistically significant differences were observed in the five indicators (p > 0.05).

Table 2. Comparison of physical fitness indicators in the control group (n = 20).

Table 3 reports the comparison of the physical fitness indicators of the experimental group before and after the intervention, where statistically significant differences were observed in the five indicators (p < 0.05).

Table 3. Comparison of physical fitness indicators in the experimental group (n = 20).

Table 4 shows the comparison of the physical fitness indicators of the control group and the experimental group before and after the intervention, where statistically significant differences were observed in the five indicators (p < 0.05).

Table 4. Comparison of physical fitness indicators in the control group (n = 20) and experimental group (n = 20) post intervention.

Discussion

The simulation exercises incorporated in a sports training program for skiers aged 13 to 14 years produced significant improvements on the physical condition parameters, as expected by the planning methods and theory of sports training, since the program considered an adequate prescription of physical loads in terms of volume and intensity, in addition to an adequate duration for the generation of acute and chronic organic adaptations [8,11,25-27].

In this context, it is known that the behavior of coaches has always been oriented toward looking for ways to improve the training process, which is the multidisciplinary work key to obtaining improvements in athletic performance [11-14,23-28]. In general, we can observe that training proposals in skiing have been oriented toward the search for changes in standard training programs, emphasizing the specific training load together with the technical elements as fundamental links for injury prevention [4,29]. These data could indicate that, during a preparatory mesocycle in a traditional planning, improvements in physical qualities and sport biomechanics could be obtained through the incorporation of simulated exercises [5-8,30,31].

In this regard, the present work proposes to develop a series of simulation exercises aimed at improving physical fitness, with a set of simulated exercises oriented to the development of muscle strength fundamental for the modeling of body composition and the acquisition of oxygen consumption according to biological age and the needs of the sport [30-33]. Finally, these results suggest that a continuous pedagogical influence on athletes during the preparatory period should complement the search for positive results in the practical work in sports schools.

Conclusion

Simulation exercises incorporated into a sports training program for skiers aged 13 to 14 years can significantly improve the expression of basic physical qualities and, therefore, overall physical fitness and sports performance, being these results possibly attributed to the acute and chronic adaptations generated by the physical training load.

References

1. Batalov AG, Senatskaya VG, Shchukin AV. Competitive effectiveness in 50 km skiing marathon at winter Olympic Games and World Championships during the whole period of their organization (since 1924 till 2019). Russ J Phys Educ Sport [Internet]. 2020;15(2):9-14. doi: https://doi.org/10.14526/2070-4798-2020-15-2-9-16

2. Myakinchenko EB, Kriuchkov AS, Adodin NV, Feofilaktov V. The Annual Periodization of Training Volumes of International-Level Cross-Country Skiers and Biathletes. Int J Sports Physiol Perform [Internet]. 2020 Ago 19;15(8):1181-88. doi: https://doi.org/10.1123/ijspp.2019-0220

3. Philippe M, Ruedl G, Feltus G, Woldrich T, Burtscher M. How Frequent and why are Skiers and Snowboarders Falling? Sportverletz Sportschaden [Internet]. 2014;28(4):188-92. doi: https://doi.org/10.1055/s-0034-1366874

4. Meyers MC, Laurent CM Jr, Higgins RW, Skelly WA. Downhill Ski Injuries in Children and Adolescents. Sports Med [Internet]. 2007;37(6):485-99. doi: https://doi.org/10.2165/00007256-200737060-00003

5. American College of Sports Medicine. Progression Models in Resistance Training for Healthy Adults. Med Sci Sports Exerc [Internet]. 2009;41(3):687-708. doi: https://doi.org/10.1249/MSS.0b013e3181915670

6. Casado A, González-Mohíno F, González-Ravé JM, Foster C. Training Periodization, Methods, Intensity Distribution, and Volume in Highly Trained and Elite Distance Runners: A Systematic Review. Int J Sports Physiol Perform [Internet]. 2022;17(6):820-33. doi: https://doi.org/10.1123/ijspp.2021-0435

7. Issurin VB. New Horizons for the Methodology and Physiology of Training Periodization. Sports Med [Internet]. 2010;40(3):189-206. doi: https://doi.org/10.2165/11319770-000000000-00000

8. Vahtra E, Pind R, Mäestu E, Purge P, Kaasik P, Mäestu J. The Effect of Different Periodization and Modes of Concurrent Strength and Endurance Training on Double Poling Performance and Body Composition in Adolescent Cross-Country Skiers. Sports (Basel). 2022 Ene 20;10(2):1-10. doi: https://doi.org/10.3390/sports10020015

9. Karlsen T, Solli GS, Samdal ST, Sandbakk Ø. Intensity Control During Block-Periodized High-Intensity Training: Heart Rate and Lactate Concentration During Three Annual Seasons in World-Class Cross-Country Skiers. Front Sports Act Living [Internet]. 2020;2:1-9. doi: https://doi.org/10.3389/fspor.2020.549407

10. Grzebisz-Zatońska N, Grzywacz T, Waśkiewicz Z. The Influence of Endurance Training on the Lipid Profile, Body Mass Composition and Cardiovascular Efficiency in Middle-Aged Cross-Country Skiers. Int J Environ Res Public Health [Internet]. 2021 Oct 18;18(20):1-10. doi: https://doi.org/10.3390/ijerph182010928

11. Suzuki E, Ohya T, Ito R, Matsumoto T, Kitagawa K. Physiological Responses in Alpine Skiers during On-Snow Training Simulation in the Cold. Int J Sports Med [Internet]. 2014;35(5):392-98. doi: https://doi.org/10.1055/s-0033-1353146

12. Dutt-Mazumder A, Newell KM. Task experience influences coordinative structures and performance variables in learning a slalom ski-simulator task. Scand J Med Sci Sports [Internet]. 2018;28(5):1604-14. doi: https://doi.org/10.1111/sms.13063

13. Sollie O, Gløersen Ø, Gilgien M, Losnegard T. Differences in pacing pattern and sub-technique selection between young and adult competitive cross-country skiers. Scand J Med Sci Sports [Internet]. 2021;31(3):553-63. doi: https://doi.org/10.1111/sms.13887

14. Stöggl T, Ohtonen O, Takeda M, Miyamoto N, Snyder C, Lemmettylä T, Linnamo V, Lindinger SJ. Comparison of Exclusive Double Poling to Classic Techniques of Cross-country Skiing. Med Sci Sports Exerc [Internet]. 2019;51(4):760-72. doi: https://doi.org/10.1249/MSS.0000000000001840

15. McGawley K, Waerbeke CV, Westberg K-J, Andersson EP. Maximizing recovery time between knock-out races improves sprint cross-country skiing performance. J Sport Health Sci [Internet]. 2022;11(1):21-9. doi: https://doi.org/10.1016/j.jshs.2021.12.004

16. Mourot L, Fabre N, Andersson E, Willis SJ, Hébert-Losier K, Holmberg HC. Impact of the initial classic section during a simulated cross-country skiing skiathlon on the cardiopulmonary responses during the subsequent period of skate skiing. Appl Physiol Nutr Metab [Internet]. 2014;39(8):911-19. doi: https://doi.org/10.1139/apnm-2013-0550

17. Fuller T, Pearson M, Peters JL, Anderson R. Evaluating the impact and use of Transparent Reporting of Evaluations with Non-randomised Designs (TREND) reporting guidelines. BMJ Open [Internet]. 2012;2(6):1-11. doi: https://doi.org/10.1136/bmjopen-2012-002073

18. World Medical Association. World Medical Association Declaration of Helsinki: Ethical Principles for Medical Research Involving Human Subjects. JAMA [Internet]. 2013;310(20):2191-94. doi: https://doi.org/10.1001/jama.2013.281053

19. Gilgien M, Reid R, Raschner Ch, Supej M, Holmberg H-Ch. The Training of Olympic Alpine Ski Racers. Front Physiol [Internet]. 2018;9:1-7. doi: https://doi.org/10.3389/fphys.2018.01772

20. Beckham GK, Olmeda JJ, Flores AJ, Echeverry JA, Campos AF, Kim SB. Relationship Between Maximum Pull-up Repetitions and First Repetition Mean Concentric Velocity. J Strength Cond Res [Internet]. 2018;32(7):1831-37. doi: https://doi.org/10.1519/JSC.0000000000002431

21. Pallarés JG, Cava AM, Courel-Ibáñez J, González-Badillo JJ, Morán-Navarro R. Full squat produces greater neuromuscular and functional adaptations and lower pain than partial squats after prolonged resistance training. Eur J Sport Sci [Internet]. 2020;20(1):115-24. doi: https://doi.org/10.1080/17461391.2019.1612952

22. Simpson T, Cronin L, Ellison P, Carnegie E, Marchant D. A test of optimal theory on young adolescents' standing long jump performance and motivation. Hum Mov Sci [Internet]. 2020;72:102651. doi: https://doi.org/10.1016/j.humov.2020.102651

23. Ettema G, Braaten S, Danielsen J, Fjeld BE. Imitation jumps in ski jumping: Technical execution and relationship to performance level. J Sports Sci [Internet]. 2020;38(18):2155-60, doi: https://doi.org/10.1080/02640414.2020.1776913

24. Mazzoni G, Chiaranda G, Myers J, Sassone B, Pasanisi G, Mandini S, et al. 500-meter and 1000-meter moderate walks equally assess cardiorespiratory fitness in male outpatients with cardiovascular diseases. J Sports Med Phys Fitness [Internet]. 2018;58(9):1312-17. doi: https://doi.org/10.23736/S0022-4707.17.07525-9

25. Chaput JP, Willumsen J, Bull F, Chou R, Ekelund U, Firth J, et al. 2020 WHO guidelines on physical activity and sedentary behaviour for children and adolescents aged 5-17 years: summary of the evidence. Int J Behav Nutr Phys Act [Internet]. 2020;17(1):1-9. doi: https://doi.org/10.1186/s12966-020-01037-z

26. Faigenbaum AD, Kraemer WJ, Blimkie CJR, Jeffreys I, Micheli LJ, Nitka M, et al. Youth Resistance Training: Updated Position Statement Paper From the National Strength and Conditioning Association. J Strength Cond Res [Internet]. 2009;23(suppl 5):560-79. doi: https://doi.org/10.1519/JSC.0b013e31819df407

27. Okely AD, Ghersi D, Loughran SP, Cliff DP, Shilton T, Jones RA, et al. A collaborative approach to adopting/adapting guidelines. The Australian 24-hour movement guidelines for children (5-12 years) and young people (13-17 years): An integration of physical activity, sedentary behaviour, and sleep. Int J Behav Nutr Phys Act [Internet]. 2022;19(1):1-21. doi: https://doi.org/10.1186/s12966-021-01236-2

28. Mikkola J, Laaksonen M, Holmberg H-C, Vesterinen V, Nummela A. Determinants of a Simulated Cross-Country Skiing Sprint Competition using V2 Skating Technique on Roller Skis. J Strength Cond Res [Internet]. 2010 Apr;24(4):920-28. doi: https://doi.org/10.1519/JSC.0b013e3181cbaaaf

29. Ekeland A, Rødven A, Heir S. Injuries among children and adults in alpine skiing and snowboarding. J Sci Med Sport [Internet]. 2019;22(suppl 1):S3-S6. doi: https://doi.org/10.1016/j.jsams.2018.07.011

30. Lasshofer M, Seifert J, Wörndle A-M, Stöggl T. Physiological Responses and Predictors of Performance in a Simulated Competitive Ski Mountaineering Race. J Sports Sci Med [Internet]. 2021;20(2):250-57. doi: https://doi.org/10.52082/jssm.2021.250

31. Lee HT, Roh HL, Kim YS. Kinematic characteristics of the lower extremity during a simulated skiing exercise in healthy participants. J Phys Ther Sci [Internet]. 2016;28(2):626-31. doi: https://doi.org/10.1589/jpts.28.626

32. Castañeda-Babarro A, Etayo-Urtasun P, León-Guereño P. Effects of Strength Training on Cross-Country Skiing Performance: A Systematic Review. Int J Environ Res Public Health [Internet]. 2022;19(11):1-12. doi: https://doi.org/10.3390/ijerph19116522

33. Carlsson T, Wedholm L, Nilsson J, Carlsson M. The effects of strength training versus ski-ergometer training on double-poling capacity of elite junior cross-country skiers. Eur J Appl Physiol [Internet]. 2017;117(8):1523-32. doi: https://doi.org/10.1007/s00421-017-3621-1