Dr. Med., Professor V.V. Dorofeikov¹
M.S. Smirnov²
PhD T.G. Nevzorova¹
PhD E.V. Shapot^1
1Lesgaft National State University of Physical Education, Sport and Health, St. Petersburg
²Saint Petersburg Research Institute, Saint Petersburg

Corresponding author: Vdorofeykov@ya.ru

Abstract

Objective of the study was to determine the effects of training loads on the blood level of muscle damage biomarkers, including cardiac biomarkers, in qualified male biathletes.

Methods and structure of the study. Subject to the study were 10 males aged 18-23 years (MS and CMS), height - 176.5±2.1 cm, body mass - 69.4±1.8 kg (Experimental Group (EG)). The Control Group was made of 10 male handball players aged 18-21 years and having the same sports skill level. The study was carried out at Kavgolovo Training Center and Medical Center of P.F. Lesgaft National State University of Physical Education, Sport and Health in two stages: preparatory (October-November 2018) and competitive (January-February 2019) periods of the one-year training cycle. The EG subjects were asked to ski using a freestyle technique for 120 minutes at a steady pace, with a heart rate of 140-160 bpm. The blood samples were taken from the vein on an empty stomach before and after training using the vacuum tubes with gel. The body response to physical loads was studied during the delayed recovery period, for which blood was collected 12-14 hours after training. The tests were conducted using the automatic analyzers Architect SR and Abbott (USA) reagents and control materials. The following biochemical indicators of the blood serum were assessed: total creatine phosphokinase (CK) activity, amount of cardiac isoform of creatine phosphokinase (CK-MB) by mass, levels of highly-sensitive troponin I (Tn), testosterone, creatinine, urea nitrogen, total cholesterol. The blood tests took less than 40 minutes.

Results and conclusion. The biochemical control using the high-tech methods for determining the blood levels of cardiac Tn, CK, urea nitrogen, and other laboratory blood readings helps coaches to determine the effects of training loads on the body of athletes in a timely and objective manner, adjust the training process, estimate the body’s adaptation to training loads, and detect cardiac and muscle disorders.

Keywords: biathlon, adaptation, heart, muscles, troponin I, creatine kinase.

Background. Modern sports impose specific requirements on the functional training of athletes. Changes in the body primarily affect the metabolites, which number regulated by enzymes [1, 4]. Most of the remaining proteins are located in the cells, and the release of these molecules (biomarkers) into the bloodstream indicates increased permeability of the cell membranes and/or cell death. Automated biochemical and immunochemical tests are gradually becoming part of the practical work of coaches and doctors in sports medicine, which, in turn, makes it possible to evaluate metabolic changes in the body of athletes and timely adjust the training process [1, 2].

Objective of the study was to determine the effects of training loads on the blood level of muscle damage biomarkers, including cardiac biomarkers, in qualified male biathletes.

Methods and structure of the study. Subject to the study were 10 males aged 18-23 years (MS and CMS), height - 176.5±2.1 cm, body mass - 69.4±1.8 kg (Experimental Group (EG)). The Control Group was made of 10 male handball players aged 18-21 years and having the same sports skill level. The study was carried out at Kavgolovo Training Center and Medical Center of P.F. Lesgaft National State University of Physical Education, Sport and Health in two stages: preparatory (October-November 2018) and competitive (January-February 2019) periods of the one-year training cycle. The EG subjects were asked to ski using a freestyle technique for 120 minutes at a steady pace, with a heart rate of 140-160 bpm. The blood samples were taken from the vein on an empty stomach before and after training using the vacuum tubes with gel. The body response to physical loads was studied during the delayed recovery period, for which blood was collected 12-14 hours after training. The tests were conducted using the automatic analyzers Architect SR and Abbott (USA) reagents and control materials. The following biochemical indicators of the blood serum were assessed: total creatine phosphokinase (CK) activity, amount of cardiac isoform of creatine phosphokinase (CK-MB) by mass, levels of highly-sensitive troponin I (Tn), testosterone, creatinine, urea nitrogen, total cholesterol. The blood tests took less than 40 minutes.

Results and discussion. At the first stage of the study, we assessed the athletes’ health status before the start of the competitive period after the day of rest; no athlete was found to be in the state of overtraining.

The educational experiment was designed to assess the degree of biomarker changes induced by the standardized training loads that lasted at least 90 minutes. During training, the average and maximum HR, duration (min) and distance (km) were recorded. The athletes themselves assessed their state of health after training using a 7-point scale (from 1 - very bad to 7 - excellent). The results obtained helped define model characteristics of training loads in the training process of biathletes. At the first stage, the training session lasted 114.0±3.8 min, the distance was 22.7±0.7 km, the average HR was 139.5±2.6 bpm, the maximum HR - 167.1±2.9 bpm. The pulsometry indicators indicated the aerobic nature of training loads. The subjective assessment of well-being showed that all athletes felt well.

The timing of blood collection after training is very important for the correct interpretation of the test results. Thus, patients are found to have an elevated Tn level within 12 hours after the onset of myocardial infarction, and the highest Tn level - within 12-14 hours. The biomarker level is then normalized within 7 days [2, 5]. The Tn blood level in the EG athletes was 15.1±5.9 ng/l. In two athletes, the troponin I level exceeded the limits of the normal range at the normal CK-MB level. It is believed that significant cardiac cell death occurs when the Tn level rises more than tenfold in relation to the upper limit of normal [5]. The CK-MB level in the athletes was 3.8±0.4 ng/ml and did not exceed the upper norm. The total CK activity in most biathletes, as before training, exceeded the normal values for healthy persons and was 284.6±42.3 u/l.

In assessing the biathletes’ myocardial contractile response to training loads, cardiac Tn showed greater sensitivity compared to the CK-MB level. Further study of the CK-MB dynamics was not helpful, and it was decided to remove the marker from further studies.

The competitive period started in December and lasted until the end of March. After a three-month training, the second phase of the study was carried out (January-February 2019). At this time, the biathletes trained and participated in national competitions; one athlete came down with mononucleosis and was excluded from the study. The subjects (n=9) were to ski using a freestyle technique in the evening. To standardize the physical loads, the training model characteristics were compared to the results obtained in October. The functional load on the body was similar to that in autumn; the subjective assessment of well-being during training did not differ from the data obtained at the first stage of the study. A correlation analysis using the Pearson criterion was carried out to assess the correlation between the sports results (10 km sprint event of biathlon) and myocardial damage biomarker level. There was a weak positive (r=0.49) correlation between the Tn level and the result of the race. Increased Th levels correlated with the decrease in the biathletes’ speed at the distance. No such correlation was found between the CK activity, other biochemical indicators, and net time in the sprint race. The majority of the athletes were in good fitness shape both in terms of the laboratory tests and the coach’s evaluation. The biathletes’ overexertion and overtraining due to a large number of competitions in the previous month were not observed. The changes in the biochemical indicators of the biathletes demonstrated the degree of adaptation of their body to the loads proposed within the training macro-cycle (3 months) (Fig. 1, a).

In the competitive period, the Tn level and CK activity decreased compared to the results obtained after training in November. In November, the level of Tn after physical loads in several athletes increased many times in a state of rest. At the second stage, the cardiac Tn level was normalized in all athletes, except Athlete 3,. It can be argued hence that from November to February, the Tn intensity was adequate for the athletes, their functional condition improved (Fig. 1, b).

Fig. 1. Level of laboratory markers of myocardial and muscle damage throughout training cycle, Tn, ng/l (a) and total CK activity d/l (b), see explanations in text

The decline in the total CK activity from the preparatory to the competitive periods indicated the adaptation of the athletes’ skeletal muscles. These typical changes in the CK activity are also noted in the work of I.L. Rybina [3].

To compare the effects of training loads on the level of muscle and myocardial damage biomarkers, the body reaction of the handball players was studied. The tests were conducted at the same time, the intensity and duration of the training loads did not differ significantly from those in the EG. The handball players (n=10) were characterized by the high activity of total CK at the first and second stages of the study (on average 598.2±130.7 u/l). The training effects of the situational sport discipline did not affect the cardiac Tn (in autumn, the next morning after training 2.9±0.7 ng/l, at the second stage - 3.4±1.3 ng/l). It can be assumed that the heart performance in this sport discipline determines the athletic result to a lesser extent. An abnormal increase in the total CK activity was detected in one handball player (21009 u/l) in spring. We believe that such a CK level was primarily due to his game position - a goalkeeper. As a result of massive muscle damage from the ball, the blood level of CK increased significantly.

Conclusion. The biochemical control using the high-tech methods for determining the blood levels of cardiac Tn, CK, urea nitrogen, and other laboratory blood readings helps coaches to determine the effects of training loads on the body of athletes in a timely and objective manner, adjust the training process, estimate the body’s adaptation to training loads, and detect cardiac and muscle disorders.

References

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