Corresponding member of RAS, Dr.Biol., Professor N.A. Fudin¹
PhD S.Y. Klassina¹
PhD S.N. Pigareva¹
Dr.Med., Professor Y.E. Vagin^2
1P.K. Anokhin Research Institute of Normal Physiology, Moscow
²I.M. Sechenov First Moscow State Medical University, Moscow

 

Keywords: sports, submaximal exercise, hypoventilation training combined with physical exercises, physical working capacity, functional state .

 

Introduction. Hypoventilation breathing (HVB) during high-intensity physical practices is known to affect man's functional state and contribute to the improvement of his physical working capacity [6]. The hypoventilation training as part of the study was meant to form the bradypnea (slow breathing) pattern in the subjects [4]. We assume that the efficiency of HVB as a means of enhancing physical working capacity will increase in case the hypoventilation training is combined with physical exercises.

Objective of the study to analyze the combined effects of hypoventilation and high-intensity physical practices on the functional state and physical working capacity under submaximal exercise.

Methods and structure of the study. Sampled for the study purposes were 18 apparently healthy male volunteers aged 18-19 years doing sports on a regular basis. The sample was split up into 2 groups: Experimental (EG, n=12) and Reference (RG, n=6) Groups, with only the EG trained to master the modern hypoventilation techniques in combination with high-intensity physical practices.

The EG subjects were trained for 5 weeks, twice a week, for 60 minutes each [5]. First, the subjects were to hold their breath inhaling and do maximum squats, after which they had 15-minute HVB training. The HVB technique teaching process was based on the respiratory training focused on the formation of the slow breathing pattern in the subjects according to the system as follows: inhalation - 1.2 sec, exhalation - 1.5 sec, pause - 7-10 sec. After a 2-minute rest, the subjects were asked to perform maximum number of squats, and the 15-minute hypoventilation training on verbal instruction was carried out once again. On other days, the subjects were to continue developing the HVB technique independently, with inspiratory breath holds being performed 3 times a day.

The sample was subject to 2 homotypic pre- and post-experimental tests - high-intensity cycle ergometer (160 W) submaximal tests. The 1st test was carried out before the HVB training, the 2nd one - after the HBV training combined with physical exercises in the EG. During the study, the subjects were in the following functional states: "background" (2.5 min), "warm up - 60 W" (2 min); "exercise submaximal stress test" at the load power of 160 W and constant pedaling speed of 1 rps, "recovery" (6 min). The load testing duration was determined by the failure of the subjects to perform exercise further (Tsubmax, sec).

Exercise stress test was conducted using the cycle ergometer "Sports Art 5005". The electrocardiogram (ECG) and pneumogram-guided test was carried out by means of the digital ECG system "Poly-Spectrum-8" ("Neurosoft", Ivanovo, Russia). The pedaling speed was constant and amounted to 1 rps (the "SIGMA - bc-509" device was used with its sensor being attached to the cycle ergometer pedal). ECG was recorded in the I standard lead and "V5" lead. Based on the ECG data obtained in the background and during exercising, the following physiological parameters were estimated: heart rate (HR, bpm) and respiration rate (RR, 1/min), time of submaximal training (Tsubmax, sec). Also, by means of calculation we estimated the "physiological cost" (ρ,%) of submaximal training [2]. Under the "test load", the total EMG of the quadriceps muscle of the right thigh was recorded by means of the computer electromyography system ("Synapse" - "Neurotech", Taganrog, Russia). We analyzed the average EMG amplitude values (Aavg, mV) and the number of turns (EMG potentials range above 100 mV) [1]. ECG, pneumogram and EMG were registered in the background and during exercising in the last 30 sec. In addition, we registered the maximum inspiratory flow rate (sec) in the background and at the final stage of the experiment,.

Before the start of the experiment, all the subjects were informed in detail on the ongoing research and gave their written consent to participate. The experimental procedure was approved by the Ethics Committee of P.K. Anokhin Research Institute of Normal Physiology.

Results and discussion. Under the influence of high-intensity muscular load, the muscle's oxygen demand increases dramatically, which is accompanied by increasing hypoxia and a subsequent decrease in physical working capacity. In this regard, the problem of hypoxia tolerance in the subjects becomes particularly relevant and requires the use of various breathing exercises, such as hypoventilation training. Figure 1 illustrates the histograms of the inspiratory breath hold rates in the EG and RG subjects before and after the HVB training combined with physical exercises.

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Fig. 1. Mean values of inspiratory breath holds (sec) in Experimental (EG) and Reference (RG) Group subjects before (white columns) and after (shadow columns) HVB training combined with physical exercises.

 Legend: * – p<0.05 – significance of differences in EG and RG subjects before and after hypoventilation training combined with physical exercises

 

As seen from Figure 1, after the HVB training combined with physical exercises a significant increase was observed in the inspiratory breath hold rates (p<0.05) in the EG subjects, while in the RG ones, not trained to master the hypoventilation techniques, the breath hold rates remained at the baseline level. It follows that the EG subjects' hypoxia tolerance improved after the HVB training combined with physical exercises. It is hypoventilation breathing that can improve the individual's hypoxic resistance during exercise, since it modifies the physiological breathing mechanism, decreases the sensitivity of the respiratory center chemoreceptors and reflexogenous zones of peripheral vessels to high levels of CO2.

The table shows the mean time of submaximal training and "physiological cost" of such training before and after the HVB training combined with physical exercises.

 

Mean time of submaximal training to failure (Tsubmax, sec) and "physiological cost" (ρ,%) of such training in 1st (before HVB training combined with physical exercises) and 2nd (after HVB training combined with physical exercises) tests in Experimental (EG) and Reference (RG) Group subjects

Legend:  * – р<0.05 – significance level in 1st and 2nd tests; # – р<0.05 – intergroup significance level in 2nd test.

 It can be seen that the hypoventilation training combined with physical exercises doubled the physical working capacity of the EG subjects - from 165.1±25.6 to 307.3±52.0 sec (p<0.05), while that of the RG ones improved insignificantly. At the same time, this growth claimed high "physiological costs", and what is more, in the EG this indicator increased statistically significantly (p<0.05). Therefore, the HVB training combined with physical exercises contributed to a significant increase of the physical working capacity of the EG subjects, however, this growth claimed a significant increase in the "physiological cost" as well. The "physiological cost" in the RG slightly changed.

It would appear reasonable that one of the main reasons for failing to perform high-intensity physical exercise further is muscle fatigue. Figure 2 demonstrates the average EMG amplitude values.

 

Fig. 2 Average EMG amplitude values (Аavg, mV) in Experimental (EG) and Reference (RG) Group subjects in 1st (white columns) and 2nd (shadow columns) tests

 

As seen, as opposed to the 1st survey, during the 2nd one, the average EMG amplitude tended to decrease in both the EG and RG. Given that after the HVB training combined with physical exercises the EG subjects’ submaximal workout was almost twice as long as the RG ones, their Aavg shift was greater and amounted to (-26.3%) versus (-17.8%). There was a minor downward trend in the number of EMG turns in both of the groups.

It is known that fatigue develops due to decreased excitability of the cerebral cortex resulting from the long-lasting proprioceptive input that reduces the alpha-motor-neurons discharge frequency and thereby blocks the impulse reactions of the motor cortex. In case the level of fatigue is not that high and can still be volitionally overcome, the EMG Aavg and frequency, that characterize the motoneuron function, increase. However, "...extreme muscle fatigue leads to a decrease of the EMG amplitude and frequency" [3, p. 339]. As a result, the contractile force of muscles decreases (muscle effort decreases), though excitation at the spinal or neuromuscular synapses is not blocked [3]. In light of the foregoing, it can be assumed that a slowdown in the muscular effort when pedaling the cycle ergometer at the time of "failure" is due to the development of muscle fatigue. Therefore, after the HVB training combined with physical exercises, the EG subjects demonstrated an expressed trend for weakening of the muscular effort at the moment of "failure", with a moderate sagging of the alpha-motor-neurons discharge frequency, which is characteristic of the state of extreme fatigue. We believe this is due to the changes in the state of the cortical nerve centers and development of protective inhibition of the cerebral cortex.

Conclusion. The hypoventilation breathing technique in combination with the high-intensity physical practices was tested to improve the hypoxic tolerance rates in the Experimental Group as opposed to the Reference one. The HVB training combined with physical exercises doubled the physical working capacity albeit this growth claimed high "physiological costs". After the HVB training combined with physical exercises, the EG subjects demonstrated an expressed trend for weakening of the right-thigh quadriceps associated at the moment of "failure", associated with a moderate sagging of the alpha-motor-neurons discharge frequency, which is characteristic of the state of extreme fatigue. We believe this is due to the changes in the state of the cortical nerve centers and development of protective inhibition of the cerebral cortex.

 

References

1. Pryanishnikova O.A., Gorodnichev R.M., Gorodnicheva L.R. et al Sportivnaya elektroneyromiografiya [Sport electroneuromyography]. Teoriya i praktika fizicheskoy kultury, 2005, no. 9, pp. 6-11.

2. Ryzhikov G.V., Klassina S.Ya. Prostranstvenno-vremennaya struktura «kvanta» proizvodstvennoy deyatelnosti kontrolera i ego fiziologicheskoe obespechenie [Space-time structure of "quantum" of controller's professional activity and its physiological support]. Fiziologiya cheloveka [Human physiology], 1984, vol. 10, no. 1, pp. 144-152.

3. Fiziologiya myshechnoy deyatelnosti, truda i sporta. V serii: Rukovodstvo po fiziologii [Physiology of muscular activity, work and sport. In: Physiology guide]. Leningrad: Nauka publ., 1969, 585 p.

4. Fudin N.A. Fiziologicheskaya tselesoobraznost proizvolnoy regulyatsii dykhaniya u sportsmenov [Physiological feasibility of voluntary regulation of breathing in athletes]. Teoriya i praktika fiz. kultury, 1983, no. 2, pp. 21-22.

5. Fudin N.A., Sudakov K.V. [ed.] Gazovy gomeostazis (proizvolnoe formirovanie novogo stereotipa dykhaniya) [Gas homeostasis (voluntary formation of new breathing stereotype)]. Tula: Tula publ., 2004, 216 p.

6. Fudin N.A., Klassina S.Y., Vagin Y.E. Gipoventilyatsionnoe dykhanie kak sredstvo povysheniya fizicheskoy rabotosposobnosti cheloveka pri fizicheskoy rabote do otkaza [Effects of hypoventilation breathing on physical working capacity during exercise to failure]. Teoriya i praktika fiz. kultury, 2016, no. 12, pp. 55-57.

 

Corresponding author: klassina@mail.ru

 

Abstract

Objective of the study was to analyze the combined effects of hypoventilation and high-intensive physical practices on the physical working capacity under submaximal exercise. Sampled for the study purposes were 18 male volunteers tested by cycle ergometer tests till refusal. The sample was split up into an Experimental (EG, n=12) and Reference (RG, n=6) Groups, with only the EG trained to master the modern hypoventilation techniques in combination with the high-intensity physical practices. The sample was subject to the pre- and post-experimental high-intensity cycle ergometer (160 W) tests to find the resting and post-work functionality test data including: ECG; pneumograms; and EMG for the right thigh quadriceps. The submaximal exercise and pre- and post-test breath-holding test rates were measured in the tests. The study data and analysis demonstrate that the hypoventilation combined with physical practices doubles the physical working capacity albeit this growth claims high physiological costs. The post-work tests showed an expressed trend for weakening of the right-thigh quadriceps associated with a moderate sagging of the alpha-moto-neurons discharge frequency. We believe that the effect may be due to the central inhibition mechanisms triggered by excessive fatigue in the tests. The hypoventilation breathing technique in combination with the high-intensity physical practices was tested to improve the hypoxic tolerance rates.