Physiological and Somatic Principal Components Determining VO2max in the Annual Training Cycle of Endurance Athletes

purpose of the study was to assess the impact of training on the physiological variables achieved during the test effort in the macrocycle of road cyclists and their use in the maximal oxygen uptake (VO 2max) prediction at individual training stages in the VO 2max test. Nine well- trained male cyclists (age 25.6 5.2 years and body weight 72.4 7.35 kg) participated in the study and each phase of the macrocycle was followed by a time to exhaustion test (TTE) on the bicycle ergometer. The research showed that training loads signi cantly in uence the maximum power (PPO), ventilation (VE) in the preparatory period (T1), time of the test (TTmax) at the start of the competition period (T2), percentage of body fat in total body weight (%FAT) and skeletal muscle mass (MMS) during the competition period (T3). Of the 16 variables taken for the analysis

research showed that training loads signi cantly in uence the maximum power (PPO), ventilation (VE) in the preparatory period (T1), time of the test (TTmax) at the start of the competition period (T2), percentage of body fat in total body weight (%FAT) and skeletal muscle mass (MMS) during the competition period (T3). Of the 16 variables taken for the analysis of the principal components (PC), the regression model determined one principal variable responsible for VO 2max in the training macrocycle of cyclists, the relative value of maximum power (PPO RV) and the accompanying variables in individual periods: breathing frequency (BF), delta blood lactate concentration (DLA), body fat (FAT) and MMS. Determining PC in uencing the exercise capacity can be crucial in achieving the intended goals by athletes. Monitoring these indicators can help protect the health of professional athletes and provide guidelines in the training process, stimulate the body properly while protecting against overtraining. Keywords: endurance effort; cycling; training control; physical tness; VO 2max; physiological determinants 1. Introduction The purpose of controlling the effects of training loads during the preparatory season is to obtain information about the relationship between the size of the loads and the body's response to them, as well as the effectiveness of the training program. Adaptation to the effort is evidenced by the difference between the amount of training load and the fatigue process [1]. In various sports, physical performance largely depends on the integrated status of the various physiological mechanisms. The most important of them in uencing endurance in cyclists is high aerobic capacity during maximal exercise, as well as the ef ciency of the circulatory and respiratory systems [2]. The maximal oxygen uptake (VO2max) is a well-known marker of cardiorespiratory tness and is associated with good health outcomes [3]. In addition to the “protective” health effects attributed to cardiorespiratory tness [4], VO2max is also the primary determinant of endurance capacity, explaining about 20–60% of the variability in performance with different modes and distances, which can be achieved by athletes in combination with other determinants of maximum endurance capacity [5,6]. Int. J. Environ. Res. Public Health2022,19,

good health outcomes [3]. In addition to the “protective” health effects attributed to cardiorespiratory tness [4], VO2max is also the primary determinant of endurance capacity, explaining about 20–60% of the variability in performance with different modes and distances, which can be achieved by athletes in combination with other determinants of maximum endurance capacity [5,6]. Int. J. Environ. Res. Public Health2022,19, 3951.

Int. J. Environ. Res. Public Health2022,19, 3951 2 of 12 During the time to exhaustion test (TTE) in which VO2max is determined, changes in the values of variables such as power (PO), heart rate (HR), oxygen uptake-VO2, and time of the test (TTmax) are frequently assessed indicators [7]. Professional cyclists are character- ized by high physical ef ciency, over 60 mL/kg/min, and generating high PO-over 400 W during TTE [8]. During the preparation for the racing season, the speci c training goals at various stages of the macrocycle are differentiated, which implies the use of appropriate physiological control [1,9]. In monitoring the training of cyclists, physiological parameters such as VO2, HR, PO and their interrelationship as a result of cardiorespiratory tness were most often assessed. There is currently a lack of research that follows year-round training of professional athletes and identi es the principal components (PC) of the physiological and somatic group that affect the VO2max. The results of this monitoring method can be used by the training staff in assessing the effectiveness of training and exercise capacity. The study aimed to assess the impact of training on the physiological variables achieved during TTE in the macrocycle of road cyclists and their use in VO2max pre- diction at individual training stages. The hypothesis was that endurance training affects the VO2max in the macrocycle of this group, and the physiological (e.g., VO2max, VE, HR) and somatic variables (e.g., BMI—Body Mass Index; FAT—body fat mass) can be used in VO2max prediction at individual training stages. Determining PC in uencing exercise capacity and training can be of key importance in achieving goals by athletes. It can be used by coaches, physiologists and sports doctors during the preparation of competitors for the main starts and in the prevention of overtraining syndrome. 2. Materials and Methods 2.1. Participants Nine well-trained road cyclists participated in the study (the study recruited athletes from sports associations in Poland), with a minimum of 5 years of training experience and a VO2max of approx. 5.0 L/min (approx. 65 mL/kg/min), aged 25.6 5.2 years and body height 181.0 5.6 cm. Other

and in the prevention of overtraining syndrome. 2. Materials and Methods 2.1. Participants Nine well-trained road cyclists participated in the study (the study recruited athletes from sports associations in Poland), with a minimum of 5 years of training experience and a VO2max of approx. 5.0 L/min (approx. 65 mL/kg/min), aged 25.6 5.2 years and body height 181.0 5.6 cm. Other data are presented in Table. During the macrocycle, the athletes implemented an individual training program (prepared by a professional trainer) based on the concept of linear periodization. During the preparations, four TTE were performed on a bicycle ergometer: T0 (TRAN: after transition period—27–30 Novem- ber 2014 and 8–10 December 2014), T1 (PREP—preparatory period—2–5 February 2015), T2 (COMP I—start of competition period—14–16 April 2015), T3 (COMP II—during com- petition period—1–4 July 2015). The workload in hours was for the subsequent periods 157, 144, and 189, respectively. Training included developing endurance, strength and speed. Comprehensive, specialized and targeted workouts were performed that were typical of cycling. The participants signed informed consent about the procedures and possible injuries that could result from the study. The study was approved by the Local Bioethical Committee University Ethics Committee decision Nr. 2/2014 and conducted by the Declaration of Helsinki of the World Medical Association. Table 1. Somatic and functional variables in the annual training cycle of cyclists. Data are presented as mean standard deviation. Variables/Periods Test TRAN; T0 PREP; T1 COMP I; T2 COMP II; T3 BM (kg) 72.41 7.35 72.63 7.17 72.40 7.00 71.96 6.31 BMI (kg/m 2 ) 21.94 1.49 22.02 1.30 21.91 1.29 21.79 1.27 FAT (kg) 7.84 2.51 7.07 2.58 6.94 2.15 6.62 1.74 FAT (%) 10.73 2.78 9.58 3.04 9.50 2.53 9.17 2.13 * Abbreviations: TRAN—end of the transition period, T0 test; PREP—preparatory period, T1 test; COMP I—start of the competition period, T2 test; COMP II—during the competition period, T3 test; BM—body mass; BMI— Body Mass Index; FAT (kg)— current body fat mass; FAT (%)—the percentage of body fat in total body weight; * statistically signi cant differences about T0,p 0.05.

test; PREP—preparatory period, T1 test; COMP I—start of the competition period, T2 test; COMP II—during the competition period, T3 test; BM—body mass; BMI— Body Mass Index; FAT (kg)— current body fat mass; FAT (%)—the percentage of body fat in total body weight; * statistically signi cant differences about T0,p 0.05.

Int. J. Environ. Res. Public Health2022,19, 3951 3 of 12 The training loads in each stage of the study were individually recorded by the competitors using a heart rate monitor (Garmin, Olathe, KS, USA). The authors of the work did not participate in the planning and corrections of training tasks in PREP. Table shows the average training load in individual periods of the training macrocycle, taking into account the percentage of work in the zone of aerobic, mixed and anaerobic metabolic changes. The volume of training in hours in individual test stages and their intensity in individual exercise zones are presented in Table. Table 2. The monthly average values of training loads (volume and intensity, nature of effort, training strategies, nature of cycling training, aerobic and anaerobic training protocol). Training Period/Test Month Training Volume (h) Training Volume (km) Training Intensity (% of HRmax) Aerobic Aerobic– Anaerobic Zone Anaerobic Zone TRAN (T0) November 49.0 3.86 1183.0 82.70 94 4 2 PREP (T1) December 60.2 6.29 1564.3 116.26 90 6 4 January 47.3 5.05 1433.2 78.75 70 25 5 February 71.9 7.90 2001.6 244.02 65 27 8 March 72.1 8.09 2101.2 185.06 62 23 15 COMP I (T2) April 76.0 7.55 2158.0 103.51 60 20 20 May 61.9 3.08 2213.0 113.00 55 25 20 COMP II (T3) June 50.9 3.52 2097.6 117.48 50 25 25 Abbreviations: TRAN—end of the transition period, T0 test; PREP—preparatory period, T1 test; COMP I—start of the competition period, T2 test; COMP II—during the competition period, T3 test; HRmax—maximal heart rate. 2.2. VO2max Test and the Body Composition Measurement TTE was performed four times: in TRAN, PREP, COMP I and COMP II. Before the VO2max test, body height (cm) was assessed during the T0 stage, with an anthropometer accurate to 0.5 cm (Vitako & Vbody-Nutrition, Health & Sport EquipmentVitako Sp. z o.o., Poland, Warsaw). Then, before each test, the body weight (kg) was determined with an accuracy of 100 g. The body composition, BMI and percentage of body fat in total body weight (FAT%) were determined using the electrical impedance method using the In-Body 570 analyzer (In Body

accurate to 0.5 cm (Vitako & Vbody-Nutrition, Health & Sport EquipmentVitako Sp. z o.o., Poland, Warsaw). Then, before each test, the body weight (kg) was determined with an accuracy of 100 g. The body composition, BMI and percentage of body fat in total body weight (FAT%) were determined using the electrical impedance method using the In-Body 570 analyzer (In Body Ltd., Seoul, Korea). All VO2max tests were performed on the same ergometer (LODE Excalibur Sport, Lode BV, Groningen, The Netherlands), which was individually adapted to the rider. The ergometer was coupled to a gas analyzer- MetaLyzer-3B-R2 (CORTEX Biophysics GmbH, Leipzig, Germany). TTE was performed in similar environmental conditions—19–21 degrees of Celsius, 40–50% relative humidity, each time in the morning. Standard VO2max test was performed with an initial load of 40 W, then the load was increased by 40 W every 3 min until the cadence could not be maintained >70 rpm. During TTE, the following were recorded: HR with the Sport Tester RS 800 from Polar Inc., in combination with an air-gas analyzer (Polar Inc., Kempele, Finland). In ad- dition, the following were recorded: VO2max (mL/kg/min) and (L/min); absolute and relative values of maximum power—PPO (W) and PPORV(W/kg); maximum minute ventilation VEmax (L/min); index—PPO/VO2max; index VO2max/HRmax; maximum heart rate—HRmax; maximum test duration—TTmax (s); breathing frequency/respiratory rate—BF (1/min); respiratory exchange rate—RER (VCO2/VO2); volume CO2(VCO2); and increase in blood lactate concentration during exercise DLA (mmol/L). Fingertip capillary blood samples for LA assessment (Biosen C line Clinic, EKF-diagnostic GmbH, Barleben, Germany) were collected just before TTE (while standing), at the end of each exercise load (every 3 min), as well as 4–5 min after TTE (while seating). Number of blood lactate measurements during exercise depending on the time of TTE. In addition, somatic

Int. J. Environ. Res. Public Health2022,19, 3951 4 of 12 variables were recorded: body mass—BM (kg); %FAT; FAT (kg); BMI; skeletal muscle mass—MMS (kg); lean body mass—FFM (kg); and total body water content—TBW (L). The HRmax and VO2max values were de ned as the highest heart rate and oxygen uptake values obtained in TTE. The value of PPO was determined for the highest last load in the progressive test by the software of the MetaLyzer 3B-R2 gas analyzer (30 s). The lactate threshold (LT) was de ned as the intensity of exercise at which there was an increase in lactate concentration above baseline (the exercise intensity corresponding to a blood lactate concentration of 2.5 mmol L 1 ). The LT was determined by the D- max method. The anaerobic threshold (AT) was de ned as the exercise intensity above which blood lactate begins to rise sharply (the exercise intensity corresponding to a blood lactate concentration of 4 mmol L 1 ). It is de ned the same as the onset of blood lactate accumulation (OBLA). The individual anaerobic threshold (IAT), also de ned as the maximal lactate steady state, was explained as the maximal exercise intensity that can be continuous without a rise in the blood lactate concentration. The lactate in ection point was de ned as the exercise intensity at which the blood lactate concentration begins to increase signi cantly and was created by drawing tangents [10–12]. In addition, athletes were instructed to refrain from vigorous exercise on the day before TTE, and similar eating habits were maintained before each measurement. 2.3. Statistical Analysis Data are presented as average values and standard deviation (m SD). The normality of data distributions was tested using the Shapiro–Wilk W-test. For multiple compar- isons between the mean values of the physiological variables of the VO2max test and the somatic features, general linear models (GLMs) with repeated measurements for depen- dent groups using Bonferroni's post hoc analysis were used. The measurements were repeated against the variable “test” [(T0), (T1), (T2) and (T3)]. The physiological vari- ables and body composition (+/ D%), in the training

isons between the mean values of the physiological variables of the VO2max test and the somatic features, general linear models (GLMs) with repeated measurements for depen- dent groups using Bonferroni's post hoc analysis were used. The measurements were repeated against the variable “test” [(T0), (T1), (T2) and (T3)]. The physiological vari- ables and body composition (+/ D%), in the training macrocycle of cyclists with the base valuesT0, T1 T0,T2 T0 and T3 T0, were calculated according to the formula D% = (T1, T2, T3 T0)/T0 100. To reduce the data to a set of PC, principal component analysis (PCA) was used. Each PC contains a set of correlated variables. At the same time, PC are not correlated with each other. This causes each major component to provide separate information. Before performing PCA, the Pearson correlation matrix was visually inspected to determine the factorability of the data for PCA. The number of signi cant factors was determined by the Kaiser–Guttman criterion, which retains PC with eigen- values of 1.0 or greater. At a later stage of the analysis, multiple regression was used, during which for the estimation of VO2max at each stage of the study, independent vari- ables were components distinguished as a result of PCA. Statistical signi cance was set at p 0.05.Statistical calculations were performed using Statistica 13.3 (TIBCO Software Inc., Palo Alto, CA, USA) for MS Windows 10. 3. Results Table 2max test and the somatic variables of road cyclists in four periods of the training macrocycle. In the group of physiological variables only for PPO (W) and VEmax (L/min), there was a signi cant increase in the value in the T1 compared to T0 (436.7 31.45 vs. 404.3 33.67;p 0.05 and 180.3 24.11 vs. 163.7 17.81;p 0.01, respectively). In the group of somatic variables, a signi cant increase was noted in the T3 for MMS (kg) (37.4 3.53 vs. 36.5 3.61; p 0.05) and a decrease in FAT (%) (9.2 2.13 vs. 10.7 2.78;p 0.05). Figure 2max, PPO, VE, TTmax) and somatic variables (FAT and MMS) relative to the base level (T0), which react signi cantly to

respectively). In the group of somatic variables, a signi cant increase was noted in the T3 for MMS (kg) (37.4 3.53 vs. 36.5 3.61; p 0.05) and a decrease in FAT (%) (9.2 2.13 vs. 10.7 2.78;p 0.05). Figure 2max, PPO, VE, TTmax) and somatic variables (FAT and MMS) relative to the base level (T0), which react signi cantly to training loads in individual research periods. The highest increase (10.2%) is observed for VE (L/min) in T1 and FAT (%) (15.6%) in T3.

Int. J. Environ. Res. Public Health2022,19, 3951 5 of 12 Table 3. Selected physiological variables of the VO 2max test and body composition of road cyclists in four periods of the training macrocycle (T0, T1, T2, T3). Data are presented as mean standard deviation. Variable/Periods TRAN; T0 PREP; T1 COMP I; T2 COMP II; T3 Physiological variables of VO 2max test VO 2max (mL/kg/min) 65.8 3.87 69.6 4.10 68.7 4.60 69.7 1.58 PPO (W) 404.3 33.67 436.7 * 31.45 425.3 28.8 418 42.67 PPO RV(W/kg) 5.6 0.35 6.0 0.30 6.4 1.40 5.8 0.36 VEmax (L/min) 163.7 17.81 180.3 ** 24.11 174.2 17.96 171.3 20.88 BF (1/min) 54.4 9.31 56.7 8.51 54.2 10.48 55.0 6.09 HRmax (bpm) 192.6 6.23 192.2 8.58 191.2 6.46 188.8 8.80 RER (VCO 2/VO 2) 1.1 0.05 1.1 0.06 1.2 0.06 1.1 0.05 VCO 2(L/min) 5.2 0.40 5.6 0.53 5.5 0.56 5.5 0.55 Somatic variables BM (kg) 72.4 7.35 72.6 7.17 72.4 70 72.0 6.31 FAT (kg) 7.8 2.51 7.1 2.58 6.9 2.15 6.6 1.74 FAT (%) 10.7 2.78 9.6 3.04 9.5 2.53 9.2 * 2.13 BMI (kg/m 2 ) 21.9 1.49 22.0 1.3 21.9 1.29 21.8 1.27 MMS (kg) 36.5 3.61 37.3 3.31 36.8 3.19 37.4 * 3.53 FFM (kg) 64.6 6.12 65.7 5.47 64.8 5.34 69.7 1.58 Abbreviations: TRAN—end of the transition period, T0 test; PREP—preparatory period, T1 test; COMP I—start of the competition period, T2 test; COMP II—during the competition period, T3 test; VO2max—the maximal oxygen uptake; PPO—absolute value of maximum power; PPORV—the relative value of maximum power; VEmax—maximum minute ventilation; BF—breathing frequency; HRmax—maximal heart rate; RER—respiratory exchange rate; VCO2—volume CO2; BM—body mass; FAT (kg)— current body fat mass; FAT (%)—percentage of body fat in total body weight; BMI—body mass index; MMS—skeletal muscle mass; FFM—free fat mass; * signi cant differences from the baseline (T0); *p 0.05 and **p 0.01.Int. J. Environ. Res. Public Health 2022, 19, x FOR PEER REVIEW 5 of 13 Table 3. Selected physiological variables of the VO2max test and body composition of road cyclists in four periods of the training macrocycle (T0, T1, T2, T3). Data are presented as

This research evaluates training effects on VO2max in cyclists.