3. Results
The initial test conducted before the experiment showed that four subjects had average cardiac capacity, three subjects had below average cardiac capacity, and one subject had low cardiac capacity. According to data on aerobic capacity and muscle capacity at the HR of 180 beats/min, there were two subjects with below average indices and six subjects with low ones. Test results show that all athletes had low functional and physical fitness before the preparatory training period. Therefore, in all sports where endurance is the basis, cardiac capacity is one of the main limiting factors where endurance is a key success factor. Hence, low cardiac capacity indicates a low cardiac output, which entails a high increase in HR under small and medium loads. Since all the athletes had an average or low cardiac capacity, it was suggested to change the mesocysle I plan by increasing the share of aerobic distance training by 70% of the total training time (
Table 5 and
Table 6).
The coefficient of variation was calculated as the percentage ratio of standard deviation to the mean. The result characterizes sample uniformity and, therefore, uniformity in the status of the athletes.
Based on the data in
Table 1, we can observe that pre-experiment values differ within the sample: the relative aerobic capacity by 7.17%; the relative muscle capacity at a HR of 180 beats/min by 3.3%; and the relative potential capacity by 10.5%. These data indicate that participating athletes are comparable in fitness level. Hence, further research is feasible and data concerning the variation coefficients alongside mesocycles will be of value.
Test results obtained after mesocycle I have shown that the cardiac capacity increased in all the subjects due to high aerobic load. There were three young men with below average relative cardiac capacity, two subjects with average cardiac capacity, two subjects with below average cardiac capacity, and one subject with indices that remained low. The No. 3 athlete experienced an increase, but his relative cardiac capacity remained low, since he has the highest body weight. Therefore, cardiac output increase is a challenge that requires more preparation time. In light of the low cardiac capacity indices recorded in Nos. 2, 3, 5, and 8 subjects, the share of their aerobic load was planned to be 60% for the next mesocycle. At the same time, the share of aerobic load planned for the rest of subjects was 50%.
The relative aerobic capacity and the relative leg muscle capacity at the HR of 180 beats/min also increased during this mesocycle. There were three sportsmen with below average relative aerobic capacity while the remaining ones had low indices. Since the aerobic capacity resulted in not being high in all the subjects, the share of weight routine was increased by 25% and 30%. In the next mesocycle, the share of strength training of athletes, whose indices were low (below average), was planned to be 30% (25%) of the total training time. Higher cardiac capacity indices were recorded in Nos. 1, 4, 6, and 7 subjects. This allowed including the high-speed (8% of training time for Nos. 1, 4, and 7, and 5% for No. 6) and tempo (2% of training time for Nos. 1, 4, and 7) training into their programs (
Table 6 and
Table 7).
The coefficients of variation for relative aerobic capacity and relative muscle capacity at a HR of 180 beats/min increased compared with the pre-experiment values, reaching the point above 10%. This affected the homogeneity of the sample but does not make it unsuitable for comparison. The said raise that took place against the background of a decrease in potential capacity may be a result of different exercise styles that vary between sports schools and between individuals, depending on the time when they engaged in sports.
Test results obtained after the mesocycle I have shown that the relative cardiac capacity has increased in all subjects. However, this increase is not enough for deeper high-speed and tempo training, since the low relative cardiac capacity will be compensated by a high HR under these loads. This will have a negative effect on the recovery. Therefore, aerobic load was increased once again in the next three mesocycle. Boys with above average relative cardiac capacity spent 70% of training time performing the aerobic exercises, while the students with lower indices spent 80%.
The relative aerobic capacity has noticeably increased during the second mesocycle. According to the test results, there were three subjects with average indices, four subjects with the below average indices, and one subject with a low aerobic capacity. High load has positively affected the aerobic capacity growth in all the subjects. The next mesocycle contains only 20% of strength training due to low relative aerobic capacity indices and a positive combination of strength and long-term aerobic training.
The relative muscle capacity at the HR of 180 beats/min also increased in all the subjects at the end of the second mesocycle. In light of the high aerobic load, no high-speed or tempo training was planned to be included into the mesocysle III plan. The interval training was planned to be included (10% of the total training time) only into the programs designed for Nos. 1, 4, and 7 athletes with higher relative cardiac capacity (
Table 5 and
Table 8).
Data in
Table 8 (variation coefficients) show a progression of phenomena from the first mesocycle, which confirms the hypothesis that, with similar fitness level, differences in the training program between schools provoke sample heterogeneity and variation within the group.
Test results obtained after mesocycle I have shown that the cardiac capacity has increased in all the subjects. There were two students with the high relative cardiac capacity, five students with the above average indices, and one subject with the below average relative cardiac capacity. In general, all the high school boys, except for the No. 3 athlete, have reached a significant fitness level. Therefore, we have reduced their aerobic load in the next mesocycle—40% of the total training time. Since the No. 3 athlete had below average cardiac capacity, his aerobic load was increased by 90% of the total training time.
The relative aerobic capacity has increased in all the subjects, except for the No. 2 athlete, whose dynamics were rather negative due to high aerobic load. In the fourth mesocycle, the share of strength training was reduced to 10% for students with above average and average indices, and to 15% for two athletes with below average ones. The share of strength training for the No. 3 athlete was planned to also be 10% due to a large amount of aerobic load.
As for the relative leg muscle capacity at a HR of 180 beats/min recorded after the third mesocycle, positive dynamics were recorded only in those athletes who had less aerobic exercise and were included in the interval training program.
In light of a significant increase in the relative cardiac capacity in all the subjects, except for the No. 3 athlete, the mesocycle IV plan involved a share of interval (30%), high-speed (15%), and tempo (5%) training. Tempo training was included only into the programs designed for Nos. 1, 4, 6, 7, and 8 subjects. The No. 2 and 5 athletes spent more time on the weight routine (
Table 5 and
Table 9).
At the third mesocycle, the previously described trends progress, while the coefficient of variation for the relative potential capacity shows a significant decrease. Hence, with an increase in load, the relative potential capacity aligns between athletes in the series despite the difference in the exercise styles, which means that when interacting as a team in ski races, they all have chances to show similar, potentially best, results.
The EGM test conducted after the fourth mesocycle showed the following results: The relative aerobic capacity and the relative leg muscle capacity at a HR of 180 beats/min have increased markedly in all the subjects (except for the No. 3 athlete) due to high aerobic load (90%). This, in turn, had a negative effect on the maximum aerobic capacity of the leg muscles.
The relative cardiac capacity indices recorded after the fourth mesocycle turned to be lower in all the subjects, except for the No. 3 athlete. This decline is associated with deeper intervals, high-speed, and tempo training, followed by a high HR. Such training has led to a decrease in cardiac capacity through the cardiac output reduction, but affected the increase in cardiac muscle contraction. The latter indicates an increase in the HR at the AeT in all the subjects (
Table 10).
The fourth mesocycle saw further improvement in the uniformity of the sample (i.e., in terms of potential capacity), which proves that each individual athlete thrived to reach one’s own full potential during the exercise. Given that participating athletes are members of the same team, the proposed differentiated approach to training program creation will boost the efficiency of both individual skiers and the team without excessive loads, injuries, and potential diseases. Hence, a differentiated approach ensures the compliance of physical development programs for athletes with the principles of sustainability and lays the groundwork for the sustainable development of youth sports in general, with safety, healthcare, and long-term targets at the core.
4. Discussion
This research method allows assessing various functional capabilities of young male students without special difficulties and applying the results for making case-specific training programs. This research is relevant, as we have tested the cardiovascular system (muscle) capacity directly under the load. This allowed obtaining accurate information about each subject before the next mesocycle [
28].
In speed skiing, legs make a gradual contribution to the racing skier’s movement as the speed increases in a double poling manner in order to maintain the ability of the upper body muscles to react [
29]. The aerobic energy contribution of leg muscles is higher than aerobic energy contribution of the upper limb girdle [
30]. Hence, leg muscle testing is of considerable interest when it comes to speed skiing. This test provides more information about the cardiac capacity, since the MOC is limited by the ability of the cardiovascular system to deliver oxygen to the muscles [
31].
The initial study has shown that the majority of subjects have low and average cardiac capacity indices, since the load was reduced during the recovery stage of training (six weeks) before testing. Accordingly, the cardiac capacity decreased. Low estimates can also indicate poor cardiac development. The most favorable and intensive cardiac output growth was recorded earlier in 16–18-years-old skiers [
32]. Based on these indicators and test data, we have increased the aerobic load for each specific case. This allowed us to increase the cardiac capacity in 16 training weeks. Large studies have revealed that athletes participating in long-distance races have a low risk of heart ischemia [
33], since they are racing if their HR is low. The latter factor contributes to a cardiac output increase. High cardiac output is compensated by the stroke volume. This has a less negative effect on the cardiac muscle under intensive loads. Therefore, cardiac capacity increase will allow for gradually increasing the high-speed and tempo load without much harm to the cardiac muscle.
Some researchers note that endurance training divided into block periods has an excellent effect on several endurance and performance indicators compared to the traditional one [
34,
35]. Such block-like division is associated with a high concentration of training means and methods applied while developing particular physical quality at a certain stage of training. Our research is also partly based on a block training system. In our case, however, it is combined with a differentiated approach and test estimates obtained for each mesocycle. This allowed increasing the cardiac capacity in each specific case.
Traditional high-intensity training provides a limited performance improvement among highly skilled racers, and often leads to overload [
36]. The high-intensity loads of racing skiers were planned starting from their specific results. The problem was approached carefully.
A significant amount of high-intensity load improves the neuromuscular status and anaerobic muscle strength, and increases the cardiac muscle contraction power without much harm to the body only in highly qualified and enduring athletes [
37]. Test results obtained after the fourth mesocycle has shown that leg muscle capacity has increased significantly at the HR of 180 beats/min as the load increased. This indicates a complex increase in the cardiac capacity and the anaerobic metabolism threshold of the leg muscles. However, a higher amount of high-speed and tempo intervals applicable at this stage has led to a slight decrease in relative potential capacity and to an increase in the cardiac muscle activity at the aerobic metabolism threshold. This also reflects the cardiovascular system capacity.
To assess and distribute the intensity load in the training of trained young skiers, we measured the HR at the anaerobic metabolism threshold and the MOC at the maximum HR to assess and distribute the load while training the racing skiers that had an appropriate fitness level. We have also used the HR at the AeT figure to control the fixed load during the training.
In the course of examining the 16–18 years old skiers, the cardiovascular system response to the highly-intensive block interval training within the framework of a polarized microcycle was analyzed. The study showed that well-trained racing skiers can complete nine workouts with high intensity during a week without harming one’s health [
38]. In our case, a small amount of high-speed interval load was applied in specific cases during mesocycle 2, since not all of the subjects had suitable cardiac capacity for high-intensity loads. In the fourth mesocycle, high-speed, interval, and tempo training time was significantly increased for all the subjects, except for one skier, since his functional capabilities were low at that time. At these stages, high-intensity training loads were alternated in a wave manner to exclude over-training.
In the case of 17–18 years old skiers, studies have shown that prolonged intensive (5–10 min) aerobic training courses taken twice a week (40–45 min in total) improve the endurance and oxygen uptake at the anaerobic metabolism threshold, but not the short intervals with greater intensity [
39]. This can be explained by the fact that a prolonged intense aerobic load allows putting the high-threshold muscle fibers to work, as well as increasing their oxygen consumption.
The anaerobic capacity often changes at the critical intensity limit during the cycle. Thus, we can assess the athlete’s fitness level [
40].
In block training studies, there is also a strong increase in the athlete’s strength [
41,
42]. In the case of 16–18-year-old skiers, the study has showed that strength training, whose share has been increased during these 10 weeks, increases the strength of the upper body girdle [
43]. In our study, we have determined the aerobic capacity of the leg muscles, which indicates the power development of slow muscle fibers. The case-specific combination of weight routine and aerobic distance training has allowed a significant increase in the aerobic strength of the leg muscles in high school boys, engaged in speed skiing.
A further differentiated approach toward the physical training of young racing skiers, based on the leg muscle test data, will allow for improving their performance more effectively at different stages, as well as monitoring the response of their cardiovascular systems to the load. This research should also start from the upper body strength test conducted by means of the EGM for the purpose of designing a fitness program.
4.1. Limitations
This research has some limitations. The overall assessment of an athlete’s functional readiness requires a randomized controlled study with long-term follow-up. Many modern studies are based on an individual approach with a small number of subjects [
44,
45,
46,
47]. In our case, the fitness level should be controlled with regard to the received test data on a daily basis.
4.2. Ethical Approval
This research has been approved by the ethical review board of the authors’ affiliated institutions. Participants and their legal representatives gave informed written consent to participate in the study.