Associate Professor, Dr.Med. A.L. Pokhachevskiy¹
Professor, Dr.Med. M.M. Lapkin²
Dr.Med. S.V. Bulatetskiy³
Doctor of Laws A.A. Krymov¹
PhD А.V. Platonov⁴
PhD Y.М. Reksha¹
PhD A.B. Petrov⁵
(1) Academy of the FPS of Russia, Ryazan
(2) Ryazan State Medical University
(3) Ryazan Branch of Kikot Moscow University of the Ministry of Internal Affairs of Russia
(4) Vologda State University
(5) Lesgaft University, St. Petersburg

Keywords: heart beat lability, criteria, markers, loading tolerance, cardiac rhythmgram, maximal load test.

Maximal physical working capacity is an important subject matter in sports, as its achievement to a large extent determines the performance in competition. The need to study this quality to forecast survivability and as an objective health measure multiplies the research relevance [5].

Study of maximal physical exercise (PE) tolerance enables us to reveal its early markers and further accomplish a probabilistic forecast. The need to define them is determined by impracticality and sometimes by impossibility or inadmissibility of achievement of the maximal working capacity due to the training process circumstances or health conditions [3].

Goal of research was to study distribution of differences in successive cardio intervals (Dis) of the cardiac rhythmgram for the 1 to 3 minutes of load testing and their relation to the PE tolerance to reveal laws of its elaboration.

Methods and structure of the study. We examined a mixed population (68 persons) of apparently healthy senior school children and university students under 23 years old.

The maximal cycle ergometer test was performed of an individual record. The capacity W₁(Watt) of the first stage lasting three minutes is calculated based on the value of due basal metabolic rate (DBM) in kilocalories according to the formula W₁(W)=DBM × 0,1 (DBM is determined by a Harris-Benedict table) [1]. Further the load was incrementally increased every minute by 30 W by an individual maximal value, the pedalling speed reduced to 30 rpm, indicating the load end an the beginning of a recovery period lasting 7 minutes.

Load tests were performed before noon from 8 to 12 a.m. using an e-Bike bicycle ergometer (with the load range of 20–999 W). During the entire testing, the ECG system PolySpectr-12 (Neurosoft) recorded a digitized electrocardiogram, from which an array of R-R intervals was distinguished — a cardiac rhythmgram (CRG). Differences in successive RR-intervals, their distribution and also a PE tolerance measure — performance of the left ventricle (PLV), calculated according to the formula: (W / HR) × 100, where HR is the maximal heart rate at the peak of loading, W is the maximal load in Watts, are determined using Microsoft Excel. The research results were processed using a statistics package Statistica 6.0. In respect that the value distribution differed from the standard, the correlation analysis (Spearman) was applied.

Results and discussion. To study early markers of PE tolerance we suggested different heart rate (HR) variability criteria. In particular, we examined measures of pNN(%) 5, 10 and 15 ms [4]. pNN(%)x is a percent of pairs of cardio intervals (CI) with a difference of x milliseconds and more to the total number of CI in the array. It is known that this marker depends on HR. Newborn babies show a clinical value of pNN(%)15 and at relative physiological rest the value is determined as рNN(%)50 [2]. At that, empirical selection of these markers revealed the necessity of their scientific justification. To study the laws of HR variability and determine early markers of PE tolerance, we examined Dis in first (1, 2, 3) minutes of the load test.

The Dis of every minute had a bell substitute symmetrical shape with a blurred wave-shaped outline and bifurcated peak by the third minute (Fig.). Distribution dynamics from the first to the third minute manifested itself as narrowing of the base and growth of the central maximum. The pattern for the relation between PLV and Dis demonstrated substantial specifics as well (Table 1). In the first minute, a substantial inverse relation of studied measures corresponds to the range from -4 to 4 and is strengthened to the center, at that a null value of CI differences corresponds to a high relation level (-0.9). Further trend to the left and to the right of the central range is determined by the relation inversion with achievement of the relevance and growth of the interaction force from -10 (0.49) to the maximum of -13 (0.72), and from 11 (0.68), 14 (0.63) achieving the maximum to 15 (0.78). The following relation dynamics (to the left from -17 and to the right from 20) is characterized by a gradual decrease of the intensity and loss of relevancy.

In the second minute, the range of relevant inverse relations is reduced to the section from -3 to 3 (maximum of -2 (0.79)). At that, the range of positive values is conversely increasing: leftwards at the section from -6 to -17 (maximum of -11(0.78)) and rightwards from 8 to 18 (maximum of 10(0.75)) with a further (leftwards from -17 and rightwards from 18) gradual decrease of intensity.

In the third minute, at the persistent sequence of negative relations from -3 to 3 (with the maximum of -3 (-0,84)), the range of positive impacts is materially increasing from -5 to -17 (maximum of -12 (0.83)) and from 6 to 19 (maximum of 10 (0.79)). The following dynamics (to the left from -17 and to the right from 19) is characterized by a decrease in the intensity.

So, connection between variability of successive CI and PE tolerance is characterized by the following: firstly, expressed inverse relation with central, and in essence, minimal distribution values, secondly inversion and progressive dynamics of positive impacts in the context of CI differences increase regardless the sign of the resulted difference. The essence of the revealed phenomena is determined by a substantial physiological regularity that excludes the need to adapt to PE with the minimal variability of CI. At that, the necessity for a higher variability is regulated not by the maximal, but by the optimal value for such variability, which reveals in the intensification of the relation with achievement of the maximum within the difference range of 10–12 ms (regardless of the sign) with a further (more than 15 ms) drop in the intensity and loss of relevancy. Besides, increment of load time (by 2 and 3 min.) decreases a section of central negative relations and increases the range of peripheral positive relations. This regularity is explained with the same physiological base with the only difference that at increase of load time regulation priorities are to the greatest possible extent offset to the loading tolerance, limiting mechanisms that are not involved in the process or impede it.

Conclusions. The HR variability at early stages of adaptation to PE has its defining characteristics that determine its maximal tolerance.

Characteristic features of the interrelation of the PE tolerance are determined, firstly, by the presence of the central range of CI limiting the load tolerance, and two peripheral ranges (to the left and to the right) from the central one, CI of which realize the maximum of the tolerance. At that, the central range of values is narrowed from the 1 to the 3 minute of load, and peripheral ones are widened.

References

1. Mikhaylov V.M. Nagruzochnoe testirovanie pod kontrolem EKG: veloergometriya, tredmill-test, step-test, khodba [Stress Testing with ECG monitoring: cycle ergometry, treadmill test, step test, walking]. Ivanovo: Talka publ., 2008, 545 p.
2. Mikhaylov V.M., Kharlamova N.V., Belikova M.E. Pokazatel variabel'nosti serdechnogo ritma pNNx u novorozhdennykh [pNNx heart rate variability metric in newborns]. Funktsionalnaya diagnostika, 2006, no. 1, pp. 19-22.
3. Pavlov S.E., Pavlova T.N. Tekhnologiya podgotovki sportsmenov [Athletes' training technology]. Shchelkovo, 2011, 344 p.
4. Pokhachevskiy A.L., Petrov A.B. Dinamika izmenchivosti kardioritmogrammy pri nagruzochnom testirovanii [Heart rate variability dynamics during stress testing]. Sportivnaya meditsina: nauka i praktika, 2015, no. 4, pp. 41-45.

Corresponding author: sport_med@list.ru

Table 1. Correlative relationship of values for CI distribution and PLV

Fig. 1. CI distribution (red, yellow, green — 1, 2, 3 min. respectively)                 

Abstract

Rationale: dynamics of physical exercise (PE) tolerance is connected with elaboration of cross effects of adaptation that determine survivability and high training level. Goal was to study distribution of differences in successive cardio intervals (CI) of the cardiac rhythmgram for 1–3 minutes of load testing and their relation to the PE tolerance to reveal laws of its elaboration.

There was examined a mixed population (68 persons) of apparently healthy senior school children and university students. We performed maximal ergometry testing, results of which: Ras and performance of the left ventricle (PLV), calculated according to the formula: (W / HR) × 100, where HR is the heart rate at the peak of load, W is the maximal load in Watts, are analyzed using the correlation (Spearman) method. Distribution of differences of CI at early stages of adaptation to PE has its defining characteristics that determine its maximal tolerance. Specifics of interrelation of the PE tolerance maximum are determined, firstly, by the presence of the central range of CI (inverse relationship with PE tolerance) limiting the load tolerance and two peripheral ranges (to the left and to the right) from the central one, CI of which realize the maximum of the tolerance (direct relation to the tolerance). At that, the central range of values is narrowed from the 1 to the 3 minute of load, and peripheral ones are widened.