Dr.Biol., Professor  R.V. Tambovtseva
Russian State University of Physical Education, Sports, Youth and Tourism (SCOLIPE), Moscow

Keywords: fasting, energy supply, maximal oxygen consumption, lactate, oxygen consumption, carbon dioxide, heart rate, respiration rate.
       
Background. The national sport community gives a high priority to the efforts to find new ergogenic agents to improve the physical work efficiency and rehabilitation processes. Generally, however, the lack of such researches is expressed in the fact that researchers do not conduct an in-depth analysis of the bodily adaptation mechanisms triggered by the endogenous and exogenous factors. In this view, the works of N.A. Volkov [1-3] are considered unique due to the study of metabolic processes associated with energy conversion during muscular work and the possibility to significantly improve the bioenergy of muscular activity of athletes through targeted training and the use of ergogenic agents [1, 3]. In order to improve the bioenergy parameters that limit physical working capacity, a variety of ergogenic agents can be used in the practice of training of highly qualified athletes. The effects of fasting on physical working capacity and various functional indicators do not go unnoticed either [4, 7]. The scope of our multi-year research activity is related to the study of the effects of short- and long-term fasting on metabolic processes and indicators of mental and physical working capacity of athletes before and during physical activity, as well as during the rehabilitation period.
Objective of the study was to analyze variations of some bioenergy and physiological test rates obtained by the stepped work tests following a three-day fast.
Methods and structure of the study. Experiments under the study were run at the Muscular Activity Bioenergy Research Laboratory of the N.I. Volkov Sports Biochemistry and Bioenergy Department at Russian State University of Physical Education, Sports, Youth and Tourism. Sampled for the experiment were 7 martial artists who were tested by the stepped work test, with the oxygen (O2) and carbon dioxide (CO2) concentrations tested by CORTEX (Germany-based MetaLayser made) test system to produce the O2 consumption rate; CO2 exhale rate; respiratory ratio; ventilator equivalents of O2 consumption and CO2 exhale; heart rate tested by Polar (Finland made) heart rate monitor; and pre- and post-work (3/15min) lactate levels in the rehabilitation period tested by Doctor Lange Photometric system and standard tests.
Results and discussion. The stepped work test results showed that, on average, the subjects did not increase the test execution time (t=12 min) or average absolute work power (Wavg = 169.5 W). At the same time, due to the 6% decrease in the athletes’ body weight, the average relative work power increased from 2.11+0.18 W/kg to 2.25+0.25 W/kg, and the efficiency of work in terms of O2 consumption decreased insignificantly. After a three-day fast, the absolute maximum oxygen consumption (MOC) rate increased slightly by 1.5% (from 3.1083+0.07 to 3.1542+0.08 l), however, the relative MOC rate increased statistically significantly - by 8% (from 39+0.45 to 42+0.68 ml/min/kg). The reasons for the increase in the absolute MOC rate are ambiguous and may be caused by various factors. We assume that this could be due to the increased stroke volume, since the oxygen pulse (O2P) rate increased by 4% relative to the baseline (from 15.5+0.10 to 16.1+0.26 ml/beat) against the background of the decreased heart rate (HR) - from 201 to 196 bpm (2.5%). At the same time, the "oxygen" share in O2P acceleration increased by 1.5% (Table 1).

Table 1. Dynamics of energy parameters in athletes in stepped work test after three-day fast relative to baseline

It can be assumed that among the reasons for the growth of the absolute O2 consumption rate is a greater uncoupling effect on the oxidative processes in mitochondria with an increased amount of free fatty acids. A decrease in the respiration rate from 1.04 to 0.94, as opposed to the baseline, indicated a more intensive inclusion of fats in the energy supply of physical activity. In this case, the same values of La max (mmol/l) were registered during work in the initial state and during fasting, as well as the same rate of its accumulation.
Due to the reduced pulmonary ventilation - from 65+1.04 to 60+0.67 l/min (8%), VE/O2=26.2+0.45, as opposed to the baseline (VE/O2=27.3+0.63), became more economical with more rational O2 consumption: at the initial state, on average - 2.13 l/min; during fasting - 2.07 l/min, i.e. 3%.
It was found that under physical loads performed with the power of 40% of MOC or more, the production of ammonia (NH3) grew proportionally to the increase in the load intensity [6]. Numerous authors note that during physical activity performed against the background of depletion of glycogen stores in the muscles, the level of NH3 in the blood plasma increased significantly as opposed to the cases when these stores remained normal or excessive [2, 6]. There is a hypothesis in the literature that if the level of energy substrates in the body changes before exercise, then, during exercise, the amino acid metabolism changed as well. It is obvious that during muscular activity, when glycogen stores in the muscle tissue are depleted, the amino acid and NH3 exchange is apparently greatly affected by the increased level of branched-chain amino acids and free fatty acids. Such effects are not observed in case of excess carbohydrate intake [6]. Under physical loads, the hydrogen ion concentration increases. NH3 is produced when hydrogen ions bind, which gives some scientists reason to assume that this process is important for buffering [5]. After a 32-hour fast, cortisol stimulates gluconeogenesis. Cortisol accelerates the breakdown of proteins in the muscle and other tissues into amino acids, glucose precursors in gluconeogenesis.
The kidneys are capable of generating new bicarbonate ions. This process, apparently, can be associated with the release of protons together with NH3 leading to the formation of NH4+. Carbonic anhydrase contributes to the formation of hydrogen protons and HCO3- ions, which are secreted into the plasma of the peritubular capillaries. The excretion of protons from the body is carried out with the participation of glutamine, which is formed in the muscle tissue. After a three-day fast, the blood glutamate, as well as other glycogenic amino acids, increases. The enzyme glutaminase deaminates glutamine to form glutamate, after which glutamate is deaminated with the enzyme glutamate dehydrogenase. In both reactions, ammonia is formed, which diffuses into primary urine, where it binds to hydrogen ions to form ammonium ions and is subsequently excreted from the body with urine. With metabolic acidosis, the intensity of excretion of ammonium ions can be 10 times higher than its usual level. Indeed, during fasting, the average CO2 emission decreased from 2.35+0.36 to 2.08+0.21 l/min (by 11%) relative to the baseline. Apparently, this leads to decreased lung ventilation and VE/O2.
After the three-day fast, the subjects were tested with improved performance versus the pre-experimental test rates and improved efficiency associated with the growth of the relative MOC (by 8%) and anaerobic metabolism threshold. In the initial state, V’E l/min corresponded to OBLA (Onset of Blood Lactate Accumulation) at Point 17 - 8.5 min, and the point of intersection of the CO2 and O2 curves corresponded to Point 11 - 5.5 min. After fasting, V’E l/min corresponded to OBLA at Point 19 - 9.5 min. After fasting, the point of intersection of the СО2 and О2 curves corresponded to Point 16 - 8 min.
The point of intersection of the V’E curve was detected when load intensity was increased, which indicated the onset of respiratory compensation due to metabolic acidosis developing during work. The correlation between the ventilation and lactate thresholds during fasting enhanced, which was, apparently, associated with a significant depletion of intramuscular glycogen stores during exercise in a state of deficiency of energy substrates.
Conclusion. After the three-day fast, against the background of the decreased body weight, the athletes were tested with improved performance versus the pre-experimental test rates and improved efficiency associated with the growth of the relative MOC (by 8%) and anaerobic metabolism threshold. The VE/O2 rates, as opposed to the baseline, became more economical with more rational O2 consumption. It is hard to say unequivocally if a three-day fast is an effective ergogenic agent, despite the fact that some test rates improved. There is every indication of quite typical adaptive reactions of the body to the exogenous and endogenous factors and tendency of the body to maintain chemical homeostasis.

References

1. Breslav I.S., Volkov N.I., Tambovtseva R.V. Dykhanie i myshechnaya aktivnost cheloveka v sporte [Breathing and muscular activity in sport]. Moscow: Sovetskiy sport publ., 2013, 334 p.
2. Volkov N.I., Oleynikov V.I. Bioenergetika sporta [Sport biochemistry]. M.: Sovetskiy sport publ., 2011. 160 p.
3. Volkov N.I., Voytenko Yu.L., Tambovtseva R.V., Dyshko B.A. Problemy ergogennykh sredstv i metodov trenirovki v teorii i praktike sporta vysshih dostizheniy [Problems of Egogenous Methods and Techniques of Training in Theory and Practice of Elite Sport]. Teoriya i praktika fiz. kultury. 2013. no. 8. pp. 68-72.
4. Kustarev T.I. Vliyanie kratkovremennogo vozderzhaniya ot pischi na uroven razvitiya fizicheskih kachestv [Effect of short-term fasting on development of physical qualities]. PhD diss.. Malakhovka, 1999. 131 p.
5. Mohan R., Glisson M., Grinhaff P.L. Biokhimiya myishechnoy deyatelnosti i fizicheskoy trenirovki [Biochemistry of muscular activity and physical training]. Kiev: Olimpiyskaya literatura publ., 2001. 295 p.
6. Hargrivs M. Metabolizm v protsesse fizicheskoy deyatelnosti [Metabolism during physical activity]. Kiev: Olimpiyskaya literature publ., 1998. 285 p.

Corresponding author: ritta7@mail.ru

Abstract
The national sport community gives a high priority to the efforts to find new ergogenic agents to improve the physical work efficiency and rehabilitation processes. Objective of the study was to analyze variations of some bioenergy and physiological test rates obtained by the stepped work tests following a three-day fast. Experiments under the study were run at the Muscular Activity Bioenergy Research Laboratory of the N.I. Volkov Sports Biochemistry and Bioenergy Department at Russian State University of Physical Education, Sports, Youth and Tourism. Sampled for the experiment were 7 martial artists who were tested by the workload step test, with the oxygen consumption and exhaled carbon dioxide tested by CORTEX (Germany-based MetaLayser made) test system to produce the oxygen consumption rate; carbon dioxide exhale rate; respiratory ratio; ventilator equivalents of oxygen consumption and carbon dioxide exhale; heart rate tested by Polar (Finland made) heart rate monitor; and pre- and post- work (3/15min) lactate levels in the rehabilitation period tested by Doctor Lange Photometric system and standard tests. The study found the energy deficiency being of contradictory effects on the athletes’ energy supply systems. The athletes were tested with improved performance versus the pre-experimental test rates and improved efficiency associated with the growth of the relative oxygen consumption and anaerobic metabolism threshold.