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The study was conducted in accordance with the Declaration of Helsinki. The study protocol was approved by the bioethical committee of the regional Chamber of Physicians and Dentists. The participants were informed of the purpose and course of the study, and provided their written consent to participate in the project. They also provided valid medical examination results, which was one of the inclusion criteria for participation in cardiac stress tests. The tests were performed under the constant supervision of a sports medicine physician. The sports event that the athletes were preparing for in the season was the XTERRA POLAND 2017 (1,500-m swimming, 36-km cycling, and 10-km mountain running). It constituted the XTERRA world championship qualifications. The competition was held in August 2017. The mean (range), dry-bulb temperature during the event equalled 31.2±3.1°C (25–33°C), the relative humidity was 69±8% (60–71%), and the dew point totalled 21±3°C (18–25°C). The swimming part was performed in a reservoir with the water temperature of 20±1°C. At this stage of the race, all the participants were equipped with wet suits. While cycling, the competitors participating in the observation used bicycles with carbon or aluminum frames. Prior to the start, participants were not given instructions as to at what pace they should run the race, nor were they recommended an amount of consumed liquids or products during the competition. The purpose was to avoid any influence of these factors on the final result of the competition. However, after the competition, each participant was asked to estimate the amount of liquids consumed at each nutritional point. The mean amount of liquid intake by the athletes equalled 0.7±0.3 L of water and 1.5±0.5 L of isotonic drinks. All measurements were integrated into the preparation cycle of the XTERRA competition, lasting 16 weeks. During the preparatory period, each participant trained for approximately 2–2.5 hours a day, 5–6 times a week. Within the 2 weeks preceding the start in the competition, the subjects did not take any medication. Evaluation of somatic and biochemical indicators: Body height (BH), body mass (BM), fat mass (FM) and lean body mass (LBM) were assessed in the anthropometric measurements. Body mass and composition were determined using bioelectrical impedance analysis (BIA) via the Jawon Medical body composition analyser, model IOI 353 (Korea), whereas body height was measured with the Martin type anthropometer (USA) to the nearest mm. Somatic and biochemical indicators were determined at the beginning of the preparatory period, i.e. 16 weeks prior to the start in the competition (baseline), approximately 2 hours before the XTERRA start (pre), immediately after completing the race (post 1h), 12 hours (post 12h) and 48 hours after the end of the race (post 48h). Somatic and biochemical measurements on the day of the competition were performed in specially prepared zones located near the start and finish lines. After completing the race, each subject left for somatic and biochemical measurements within 1–3 minutes. The participants were instructed to avoid consuming liquids after crossing the finish line until completion of the measurements. After the tests, the competitors were given water, isotonic drinks and a regenerative meal. The measurements before the start of the preparatory period, as well as 12 and 24 hours after the end of the competition, were carried out in the competition office. The material for biochemical tests comprised blood taken from the ulnar vein (7 mL). This was performed by a laboratory diagnostician in accordance with binding standards. The blood was collected into Vacutainer EDTA tubes. The following indicators were assessed for the blood: testosterone (EIA1559), cortisol (EIA-1887), c-reactive protein (EIA-1952), TNF-α (EIA-4641), myoglobin (EIA-3955), total protein (MBS2540455) and zonulin (201-12-5578). All the indicators were measured with the enzyme-linked immunosorbent assay test (ELISA), using the DRG-type microplatelet reader (E-Liza Mat 3000, Medical Instruments GmbH, Germany). The anabolic/catabolic balance indicator was determined on the basis of the following formula: testosterone/cortisol x100 [19]. Due to post-workout dehydration, the values of biochemical indicators determined on completion of the triathlon were corrected. The correction was performed by establishing%ΔPV using the appropriate formula:%ΔPV = -100x[(Bk-Bp)/(Bk)], where: Bp–baseline protein level determined prior to the exercise; Bk—endpoint protein level determined after exercise [20]. The Kraemer and Brown [21] formula was used to calculate the corrected values. Wsk = (%ΔPV.0.01.Wpo) + Wpo, where: Wsk−corrected value, Wpo−post-exercise value.
The physiological indicators were assessed at the beginning of the preparatory period (baseline). For the assessment of maximal oxygen uptake (VO2max) and the level of the second ventilatory threshold (VT2), a graded, treadmill test was applied (Saturn 250/100R, h/p/Cosmos, Germany). The effort started with a 4-minute warm-up at the speed of 8 km·h–1, with the surface inclination angle of 1°. Then, the running velocity was increased by 1.1 km·h–1 every 2 minutes. The test was carried out until refusal. In the course of the test, the following indicators were registered with an ergospirometer (Cortex MetaLyzer R3): respiratory ventilation per minute, percentage of carbon dioxide in exhaled air, oxygen uptake per minute, carbon dioxide output per minute, respiratory quotient and carbon dioxide respiratory equivalent. Heart rate (HR) during the test was measured with a sports watch (Suunto Ambit 4, Finland). For the determination of VT2, changes were analysed in respiratory indicators occurring along with the increase in work intensity. The criteria for VT2 assessment were the following: (a) the percentage of CO2 in the exhaled air reached its maximal value and then decreased; (b) the CO2 respiratory equivalent was at its minimal value and then increased; (c) when VT2 was exceeded, a non-linear, large increase in respiratory ventilation was observed [22, 23]. The highest registered quantity was considered the VO2max value.
Before the tests, the participating competitors underwent nutritional consultations in order to rationalise and standardise their diets. The dietary assumptions were developed in accordance with the qualitative recommendations for rational nutrition of athletes [24] and the quantitative recommendations for endurance sports competitors [25, 26]. Energy demand was set at the level of 3,500–5,000 kcal, carbohydrate supply of 6–10 g/kg body mass, protein supply of 1.2–1.7 g/kg body mass and fat supply of 1.0–1.5 g/kg body mass. The athletes were acquainted with the assumptions of the peri-workout nutrition strategy [27, 28]. They were instructed on the necessity to preserve the dietary model during the whole follow-up period (16 weeks), and to eliminate supplements that could influencebiochemical tests.
Characteristics of the studied competitors: The study involved 15 triathlon-training athletes, aged 32.8±3.1 years, with the average training experience of 10±4.2 years. The sports level of the participants corresponded to sports classes I and II (national-level competitors).
Methods of statistical analysis and presentation of results: The results of the study are presented as arithmetic means and standard deviations. The consistency of distribution of the evaluated indicators with normal distribution was checked using the Shapiro-Wilk test. Changes in somatic and physiological indices were evaluated with the Wilcoxon test. The relationships among the described variables were determined using Pearson’s linear correlation coefficient.Statistical analysis of the results was performed with the use of Statistica 10.0 for Windows by StatSoft.Differences among all the analysed indicators were assumed statistically significant at the level of p≤0.05.
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