PhD A.I. Golovachev¹
Dr.Biol., PhD B.A. Dyshko²
PhD S.V. Shirokova^3
1All-Russian Scientific Research Institute of Physical Culture and Sports, Moscow
²LLC "Sport Technology" Sports Engineering Association, Moscow
³Moscow Secondary Special School of Olympic Reserve No. 2 Moscow City Department for the Physical Culture and Sport, Moscow

It should be reminded that oxygen consumption is a derivative of a complex display of the maximal lung ventilation (MLV) and oxygen consumption (O2CI) indices, where the former are indicative of the lung ventilation process and the latter – of the formation of the regulatory mechanisms of oxygen delivery and oxygen utilization in the working muscles [4-6].

Objective of the study was to identify the peculiarities of development of the respiratory system functional capacities in order to provide oxygen for the cross-country skiers’ body.

Methods and structure of the study. Sampled for the study were 11-28 year-old male cross-country skiers (n=696) with sport records of 3-20 years, with the skills ranging from the beginner level to the World Class Master of Sport (WCMS). The sample was tested by "Quinton" (USA) submaximal treadmill exercise, with the run speed varying from 2.0 m/s (7.2 km/h) to 3.0 m/s (10.8 km/h) depending on the age and skill level; with the treadmill floor fixed at 1 º; and the speed stepped up by 0.5 m/s (1.8 km/h) every 3 min. It should be emphasized that the choice of the incrementally increasing load to submaximal level was due to the fact that such loadings provide accurate information not only on the ultimate level of the system functioning, but also on the nature of dynamic processes when passing through various zones of the relative power (from moderate to submaximal) [1-3, 7].

The exhaled air parameters (allowing for the duration of the experiment) were analyzed using the "Beckman" gas analyzer (USA) (OM-11 for O2 and LB-2 for CO2) and automatic gas-analyzing complex Cortex MetaLyzer-3B (Germany) that was used to measure the percentage of O2 and CO2 in the exhaled air.

Along with the parameters of exhaled air, we recorded the subjects’ heart rate to analyze the cardiovascular system functioning. We used the "Polar Team System" heart rate monitors (Finland).

Results and discussion. The longitudinal study results enabled to characterize the growth of the studied parameters in the cross-country skiers at various stages of sport onthogenesis. The summarized data on the dynamics of absolute values are presented in the table, and the annual dynamics is illustrated in Figures 1 and 2.

It was found that maximal lung ventilation (MLV), which is indicative of the volume of air circulating through the lungs during external respiration, increased statistically significantly in the age period from 11-12 to 19-22 years - from 58.8±12.1 to 162.1±20.4 l/min (by 175.7%), and then leveled out and by the age of 25 reached its peak level - 164.9±21.9 l/min. After 25 years, there was a pronounced downward trend with the lowest level being registered at 28 years - 146.0±14.9 l/min (-11.5%; Fig. 1, upper diagram). The greatest annual increase in MLV was observed in the period of 11-12 to 13-14 years (Δ13-14-11-12=56.9 l/min; 96.8%; test=7.881; p<0.001) - the first half of puberty. Further on, the dynamics of growth of MLV was accompanied by the high (statistically significant) increment rates in the periods of 13–14 to 15–16 years (by 23.4%) and 15–16 to 17–18 years (by 10.0%), followed by the decrease in the annual growth rate at the age of 17-18 years, with the cessation of growth processes by the age of 19-22 years (Δ19-22-17-18=5.19 l/min; 3.3%; test=2.489; p<0.05), thus reaching its definitive values ​​(see Table 1). In the mature period 1 - from 23 to 28 years, the annual changes varied from -5.7 to 2.5%, and the absolute values ​​were not statistically significantly different (see table).

The age-specific dynamics of the oxygen consumption index (O2CI) was of a pronounced two-peak character with the statistically significant increase in the age period from 13–14 to 15–16 years, corresponding to the second half and end of puberty, as well as in the age period from 17–18 to 19-22 years, corresponding to the transition from adolescence to mature period 1 (see table). In general, in the age period of 11–12 to 19–22 years, the O2CI increased from 3.07±0.49 to 3.46±0.32% (by 12.7%), followed by the achievement of the first peak level at the age of 23 - 3.60±0.61% with the subsequent decrease to the level of 3.46±0.31% (-3.9%) at the age of 24. The age range from 25 to 28 years can be described as a period of the second increase in the absolute values ​​of the studied index and achievement of the peak level at the age of 28 years - 3.69±0.52% (Figure 2; lower diagram). The greatest annual increase in O2CI was observed in the age period from 11-12 to 13-14 years (Δ13-14–11-12=0.13%; 4.2%; test=0.685) and from 13-14 to 15-16 years (Δ15-16–13-14=0.11%; 3.4%; test=2.194; p<0.05) in the second half of puberty, followed by the decrease in the growth rates in the age period from 15-16 to 17- 18 years (Δ17-18–15-16=0.04%; 1.2%; test=1.074) and further increase in the growth rates by the age of 23 (4.0%). The second increase in the annual increment of O2CI was observed in the age period from 25 to 28 years and had an ever-increasing character with the peak level of 3.4% (Figure 2, upper diagram).