Ph.D., Professor V.A. Vishnevskiy¹
A. Istomin^{1                
1}Surgut State University, Khanty-Mansi Autonomous Region, Yugra

Keywords: overall endurance, special endurance, local endurance, sport accomplishments, junior cross country skiers

Introduction

It has been for a long time that the endurance development methodologies were based on the classical Maximum Oxygen Demand (MOD) theory designed on the assumption of this indicator being characteristic of the systems responsible for oxygen transportation to the working muscle groups. And it was largely due to this concept that the cross-country distance racing technique training systems have been dominated by regular, intermittent and interval racing models that quite often resulted in the cardio-respiratory systems being overstrained with the relevant negative impacts on the athletic performance. The situation, however, was changed in the late 20th century. First of all, a new peripheral MOD theory was developed that assumed that good oxygen supply to the working muscles is not enough as such for the reason that the muscles must be able to consume the oxygen supplied. Second, the MOD indicator was questioned as a perfect value of maximum aerobic capacity of the muscles because it was found that it is the oxygen consumption at the anaerobic threshold that is fairly indicative of the oxygen-consumption capacity of muscles.

In view of the above, a new hypothesis was offered that assumed that the high capacity of the energy-generation and contraction systems located directly in muscles and critical for local endurance gives the means to delay the onset of fatigue and reduce the loads on the “key factors” which may also contribute to fatigue when the relevant workloads are too intensive [3]. As far as the local endurance improvement problem is concerned, it should be mentioned that it still needs to be studied in more detail as the available studies are largely focused on the strength training or the so called “strength endurance” development aspects. At the same time, the role of local/ muscle group endurance in the cross country skiers’ training systems has been subject to growing interest in sport science [1, 4]. A few studies showed positive impacts of the local/ muscle group endurance development practices on the cardio-respiratory system of the 13-15 years old cross country ski racers [2]. It should be noted in this context, however, that the local endurance development problem will be considered much broader; and for every coach being able to design and manage the training process based on good knowledge and giving a due priority to the focused actions on the relevant muscle groups, he/she must be fully aware of the contributions of the overall and local muscular endurance factors to the individual athletic performance; and this was the reason for us to take this issue as a subject for the present study.

Objective of the study was to explore different types of endurance and their contributions to the athletic performance of the Class I-II junior (12-13 years old) cross country skiers.

Materials and methods

The study was performed in the period of February through April 2015. Subject to the study were the Class I-II junior cross country skiers aged 12-13 years from the Olympic Reserve Children’s and Youth Sport School “Cedar” in the city of Surgut.

The oxygen supply and consumption parameters were measured by the incremental cycle-ergometer tests (with starting load of 1.0 W/kg and load increments of 0.5 W/kg) using “Fitmate PRO” Hardware and Software System (HSS). Heart rate (HR) was metered using “Pollar” monitoring system during the whole test cycle. The test loads were increased by the above increments up to 85% of the maximum HR. Maximum oxygen demand per kilo of body weight was calculated using the submaximal testing method.

Special endurance of the athletes was rated by 5 x 500m snow skiing race tests with 5 minute rest breaks in between the races. The 500m distances were run at maximum possible speeds by the kick-double-pole variant of the classic stride. HR values were recorded after every 500m race. Local muscular endurance rates were measured by the push-ups on parallel bars up to muscle failure tests.

The subject athletes were basically rated based on the coaching team assessments and the practical sport accomplishments in competitions for the seasons of 2014-2015.

Results and discussion

The correlation analysis findings are given hereunder in Table 1. It should be mentioned that the only index (from among the set of the overall endurance indices) that was found to be in a reliable correlation with the athlete’s rating was the absolute oxygen demand index on the peak of cycle-ergometry test (with the HR coming to 85% of the maximum). In opinion of some authors, it is the oxygen demand at the anaerobic threshold that appears to provide a most objective indication of the aerobic capacity of muscle groups [3]. It is important to note that this indicator shows reliable correlation with age (r = 0.640, p < 0.05), body weight (r = 0.813, p< 0.01), MOC per kilo of body mass (r = 0.567, p< 0.05) and time of the 3^rd 500m race test (r = - 0.554, p< 0.05).

The local endurance indicators obtained by the push-ups on parallel bars up to failure tests were found to be in somewhat better correlation (r = - 0.683, p < 0.01) with the individual ratings of the subject athletes than the oxygen consumption indices. Furthermore, they were found being in good correlation with the 5 x 500m test race times (with variations from r = - 0.662 to – 0.748, p < 0.01) and the ratio of the HR after the 500m races to the 500m race times (with variations from r = 0.627 to 0.668, p< 0.05).

It was the special endurance (5 x 500m race) test that showed the closest correlations with the practical athletic accomplishments. The summarized race times, for instance, were found to be in strong correlations with not only the athletes’ ratings (r = 0.960, p< 0.01), but with sport classes (r = 0.583, p< 0.05); the HR after the 4^th and 5^th rounds of the special 500m race tests (r = - 0.789 and – 0.648, p < 0.01); the ratio of the HR after the 500m races to the 500m race times (with variations from r = - 0.953 to – 0.973, p< 0.01); and the local muscular endurance indices (r = - 0.717, p< 0.01).

The top rated athletes were found to perform the special tests at higher heart rates showing expressed correlations with both the 500m race times (with variations from r = - 0/733 to – 0.820, p < 0.01) and with the ratio of the HR after the 500m races to the 500m race times (with variations from r = 0.807 to 0.891, p< 0.01). Therefore, the HR value per 1 second of workload in the special tests was found to be higher for the 13-15 year old cross country skiers having the best practical sport accomplishments.

Table 1. Correlations of the 13-15 year old cross country skiers’ ratings with the overall/ special/ local muscular endurance indices

  The factor analysis using key component method with rotation of the correlation matrix about Varimax axis revealed the following three factors covering 86.8% of the dispersion. Factor 1 covering 65.6% of the dispersion includes a few variables such as the race times in the special 5 х 500m race tests with 5 minutes rest breaks; the HR after the 4^th and 5^th 500m races; the effort-to-results ratio for the 1^st to the 5^th test races; and the local muscular endurance rate estimated by push-ups on the parallel bars until failure test. This factor may be referred to as the special/ local endurance factor. Factor 2 with the factor weight of 14.6% (of the dispersion) includes: the maximum oxygen consumption per 1 kilo of body mass measured by submaximal testing; the oxygen consumption at the 85% of the maximum HR; and the oxygen consumption at the 85% of the maximum HR per 1 kilo of body mass. Let us call herein this factor the overall endurance factor. And the dominating variable of the last Factor 3 having the factor weight of 6.7% (of the dispersion) is the time (s) of the 5^th race to the time of the 1^st race ratio. Let us call herein this factor the special endurance factor.    

Conclusion

Results of the correlation analysis and factor analysis are indicative of the special and local endurance qualities being of particular importance for the sport accomplishments of the 13-15 years old cross country ski racers. The study results also demonstrate that the 5 x 500m race tests and the push-ups on the parallel bars until failure tests may be highly beneficial for assessments of athletic fitness levels in the training systems aimed at the highest sport accomplishments.

References

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Corresponding author: apokin_vv@mail.ru