Abstract
tudy was to examine the association between cardiorespiratory and metabolic parameters and match running performance (MRP) in highly trained football players. The sample of participants consisted of 41 national-level football players (aged 23.20±3.40 years, body height 182.00±5.15 cm, and body mass 76.86±6.06 kg) from the Serbian Super league. For the purposes of this research, the following measurements were applied. A maximal multistage progres- sive treadmill test, with a direct measurement of maximal oxygen consumption (VO 2max) (using Fitmate MED, Cosmed, Rome, Italy) was conducted, alongside continuous heart rate monitoring. Capillary blood samples were taken from the hyperemic area using specific test strips, and, after sample collection, lactate concentration was immediately determined using a lactate analyzer. MRP variables were analyzed according to the BioIRC model of motion structure analysis, based on existing standards for profiling movement intensity. The results
MED, Cosmed, Rome, Italy) was conducted, alongside continuous heart rate monitoring. Capillary blood samples were taken from the hyperemic area using specific test strips, and, after sample collection, lactate concentration was immediately determined using a lactate analyzer. MRP variables were analyzed according to the BioIRC model of motion structure analysis, based on existing standards for profiling movement intensity. The results of multiple regression analysis indicated an association between cardiac parameters and total distance (R2 = 54.3%,p= 0.000), high-speed running (R2 = 46.4%,p= 0.000), and jogging (R2 = 33.6%,p= 0.004). Regression analysis revealed an association between cardiorespiratory parameters and total distance (R2 = 24.8%,p= 0.014), and high-speed running (R2 = 20%,p= 0.039). Meanwhile, no association was found between lactate concentration and running performance. The explanation for these regression analysis results is based on the observation that functional abilities represent significant potential for expressing movement performance, a crucial condition for success in football. Keywords:physical performance; cardiovascular endurance; lactate concentration; maximal heart rate; professional soccer players; running performance analysis; VO 2max 1. Introduction In recent years, the demands of modern football have changed, increasing significantly, and this trend certainly continues day after day [1]. Football, as a characteristic intermittent sport, requires players to execute multiple activities that require agility, strength, speed, balance, stability, flexibility, and endurance, implying that the physical conditioning of players is an extremely complex procedure [2]. In terms of training application, modern football and growing demands impose the need for the highest quality professional and scientific approach [3]. In competitive conditions of top-level football play, it is necessary to have high levels of functional abilities to adequately respond to the physical and tech- nical/tactical demands of the game, including the ability to perform a large number of Appl. Sci.2024,14, 3807.
Appl. Sci.2024,14, 3807 2 of 17 high-intensity movements, delay the onset of fatigue, and mitigate its impact on efficiency in the game [4,5]. Measurements in football show that both the aerobic and anaerobic pathways of metabolism make significant contributions to match performance [6]. During a football game, the aerobic energy system provides approximately 90% of the energy. In this regard, elite football players must have high aerobic endurance fitness to play for 90 min and recover between high-intensity sprints [7]. One of the best measures of cardiorespiratory fitness and endurance capacity performance is the maximal aerobic power, denoted by VO2max [8]. Generally speaking, maximal oxygen consumption (VO2max) represents the maximum work rate at which the body can absorb and use oxygen when engaging in maximal exercise. Given the demands of team sports, such as the ability to change direction during high-intensity running, the primary focus for players should be on endurance and metabolic conditioning [9]. Working muscle oxygen deficiency is thought to be a controlling factor in the metabolic alterations that lead to the depletion of muscle glycogen stores and the suppression of glycolytic enzyme activity. This is thought to be one of the main causes of the decline in efficiency and, consequently, the emergence of indicators of muscular tiredness [10]. The VO2max of elite soccer players is typically between 50 and 75 mL/kg/min, but different values higher than 70 mL/kg/min have been identified [11]. During competitive matches, professional players typically operate at approximately 80–90% of their maximum heart rate, which corresponds to approximately 75–80% of the VO2max [12]. Increasing VO2max is believed to enhance players’ tactical and technical per- formance by 7%. Additionally, this implies more efficient ball contacts and a greater number of longer sprints during a game, which increases the likelihood of scoring a goal [13]. It has been confirmed that leading football teams in the league have higher VO2max values compared to weaker teams [14]. Therefore, the efficiency of the cardiorespiratory system is considered one of the most crucial components of the physical readiness of football players [5]. The match running performance (MRP) of football players
which increases the likelihood of scoring a goal [13]. It has been confirmed that leading football teams in the league have higher VO2max values compared to weaker teams [14]. Therefore, the efficiency of the cardiorespiratory system is considered one of the most crucial components of the physical readiness of football players [5]. The match running performance (MRP) of football players has been the focus of researchers in recent years [15,16]. It has been established that, in professional football, players can cover total distances ranging from 9 to 14 km during matches, of which 5–15% are covered by high-intensity running [17]. Two important energy components determine energy expenditure in the game: the way players move and the way they control the ball. The energy expenditure of forward running is lower than that of backward and lateral running [18,19]. A football match’s progression is typically associated with a gradual decline in the speed of runs, a fall in the number of sprints, and a shortening of the distance covered at maximum speed, especially in the later part of the game [20]. The culprit of this decrease in speed and in the frequency of sprints has been identified as a sharp decrease in glycogen in the working muscles of the players as the match moves forward. This viewpoint is supported by an increase in the blood lactate of players in the latter stages of matches [21]. More rapid elimination of lactate from the blood as the game progresses is a significant concern because it determines, at least in part, how quickly an athlete will become fatigued [22]. Working muscle oxygen deficiency is thought to be a regulatory factor in the metabolic changes that cause the depletion of muscle glycogen resources and the inhibition of glycolytic enzyme activity. A greater lactate threshold indicates that a player can maintain greater average intensity in a task without lactate accumulation [21]. Anaerobic threshold (AT) and VO2max measurements are frequently used to assess aerobic fitness. It is important to note that players with higher values of VO2max during high-intensity activities achieve lower blood lactate concentrations compared to players
of glycolytic enzyme activity. A greater lactate threshold indicates that a player can maintain greater average intensity in a task without lactate accumulation [21]. Anaerobic threshold (AT) and VO2max measurements are frequently used to assess aerobic fitness. It is important to note that players with higher values of VO2max during high-intensity activities achieve lower blood lactate concentrations compared to players with lower VO2max values [23]. The majority of the published studies on the relationship between lactate threshold and endurance have shown a strong correlation, indicating that training-induced improvements in cardiorespiratory endurance are significantly associated with improvements in lactate threshold [24,25]. While outdoor tests can be used to indirectly evaluate both VO2max and AT, laboratory treadmill testing provides the most reliable
Appl. Sci.2024,14, 3807 3 of 17 measurement [26]. A previous study [26] has analyzed the correlation of cardiorespiratory fitness and team performance, player position, and physical characteristics. The mentioned study shows that cardiorespiratory fitness does not differentiate between age, weight, height, team performance, and player position, but VO2max varies with age, weight, height, and BMI [26]. The study also found a strong correlation between the physical requirements of player positions throughout a match and the aerobic capacity of players playing those positions, which should be considered in soccer training [13]. In addition, Doncaster et al. [27] reported that measures of ventilatory equivalent, a determinant of running economy, at all sub-maximal exercise intensities were inversely related to the volume and percentage of very-high-intensity activities. Today, it is known that coaches and sports scientists can tailor training plans based on well-defined physiological parameters such as VO2max, maximum heart rate, and blood lactate concentration [28]. Although recent studies have revealed an association between cardiorespiratory parameters and running performances, such as high-intensity running [29,30] and total distance covered [31], it should be emphasized that conflicting results have been obtained in the study by Metaxas et al. [32], where no association between VO2max and MRP was found. Therefore, these findings need to be verified. Regarding the association between lactate and MRP, only one study has shown an association between lactate levels and the total distance covered [33]. However, it is important to note that this study focused on young footballers. Additionally, a commonality among all mentioned studies is the limited number of observed parameters. Furthermore, there is a lack of studies that comprehensively assess the physiological parameters of players in a single sample. Therefore, there is a need for a study that will more thoroughly investigate this area. To the authors’ knowledge, this is the first study to report the effect of a wide set of variables, cardiorespiratory and metabolic parameters, on match running performance. More importantly, this study is the only one with a national-level sample of football players in the territory of Serbia. Hence, the purpose of this study was to determine the
investigate this area. To the authors’ knowledge, this is the first study to report the effect of a wide set of variables, cardiorespiratory and metabolic parameters, on match running performance. More importantly, this study is the only one with a national-level sample of football players in the territory of Serbia. Hence, the purpose of this study was to determine the association between cardiorespiratory and metabolic parameters and running performance in highly trained football players. In this regard, hypotheses have been formulated indicating that (i) thereis an association between cardiovascular and running performance; (ii) there is an association between cardiorespiratory parameters and running performance; and(iii) there is an association between metabolic parameters and running performance. This study will contribute to understanding the relationship between cardiorespiratory and metabolic parameters and running performance among highly trained football players in Serbia, and will determine which cardiovascular and metabolic parameters are associated with specific running speeds. 2. Materials and Methods 2.1. Participants The sample of participants in this cross-sectional study consisted of 41 elite football players (aged 23.20±3.40 years, with a body height of 182.00±5.15 cm, and a body mass of 76.86±6.06 kg; Table). All players were members of the Serbian Super League, which is the top-tier national football competition. That is, according to categorization, they are highly trained/national level athletes [34]. The criteria for inclusion in the study were players aged≥18 to≤35 years, with a training age of≥6 years, without a recent injury (>12 months) or any illness at that moment. Randomly, 4 teams out of 16 were selected from the league. Then, every other player was chosen through randomization. In the end, we selected 44 players to participate. Out of those, we gathered all the data for41 players. All participants voluntarily participated and were informed about the purpose, benefits, and risks of the study, and they all provided written consent to participate in the study. Additionally, all data have been anonymized to ensure the confidentiality of the players and teams. Therefore, all procedures conducted in the study involving human participants were in accordance with the Helsinki Declaration and were approved by the Ethics
were informed about the purpose, benefits, and risks of the study, and they all provided written consent to participate in the study. Additionally, all data have been anonymized to ensure the confidentiality of the players and teams. Therefore, all procedures conducted in the study involving human participants were in accordance with the Helsinki Declaration and were approved by the Ethics Committee
Appl. Sci.2024,14, 3807 4 of 17 of the Faculty of Medical Sciences, University of Kragujevac (decision number: 01-15731; date 29 December 2021). Table 1.Sample description. Mean SD Min Max Age 23.20 3.40 18.00 32.00 Body height (cm) 182.00 5.15 172.00 192.00 Body mass (kg) 76.86 6.06 63.00 88.00 2.2. Procedures The testing of football players was conducted in March 2022. Laboratory tests were performed in a room where the temperature was 20–23 ◦ C and the air humidity was 55–60%so that the microclimatic conditions corresponded to the recommended ones. All measurements were performed in the morning, at approximately the same time (11 a.m.). On the day of testing, participants did not train in the morning as they needed to be rested, and, afterwards, they resumed their daily obligations. A multistage progressive treadmill test was conducted. After warming up, they performed 3 min of running on a treadmill at a speed of 5 km/h; the speed and incline were determined to increase at precise time intervals. The criteria for stopping the test were the fulfillment of 2 out of 4 conditions: VO2max plateau reached (2 mL/kg/min); HR max reached; respiratory exchange coefficient (RER) > 1.2; the appearance of subjective complaints. The performance data of players’ running performance were collected using performance analysis software during official football matches. It should be emphasized that during the research, the participants did not have a break in training but rather continued with their daily routines. 2.3. Anthropometric Characteristics Anthropometric assessments were conducted following the guidelines of the Interna- tional Biological Program [35]. A Tefal 6010 scale (Rumilly, Haute-Savoie, France) was used to measure body mass, and the result was read from the scale’s display with an accuracy of 0.1 kg. Body height was measured using an anthropometer (GPM, Zurich, Switzerland), and the measurement result was read with an accuracy of 0.1 cm. 2.4. Cardiorespiratory Parameters For the purposes of this research, a maximum multistage progressive treadmill test was applied (Technogym Run Exciting 9000, Fairfield, NJ, USA). After positioning the subjects, a mask (Hans Rudolph, Kansas City, MO, USA) was secured with elastic straps to prevent
an anthropometer (GPM, Zurich, Switzerland), and the measurement result was read with an accuracy of 0.1 cm. 2.4. Cardiorespiratory Parameters For the purposes of this research, a maximum multistage progressive treadmill test was applied (Technogym Run Exciting 9000, Fairfield, NJ, USA). After positioning the subjects, a mask (Hans Rudolph, Kansas City, MO, USA) was secured with elastic straps to prevent air leakage, and the VO2max value was directly measured (Cosmed’s FitMate Med, Rome, Italy). After securing the mask, a heart rate monitor (Polar Pro Team System, Kempele, Finland) was placed with the strap positioned around the chest, just below the nipples, and fastened. The heart rate monitor was placed directly on bare skin to enable successful measurement with constant heart rate monitoring. Cardiovascular and respiratory parameter values were automatically recorded every 15 s. The subject walked and ran during the test at different intensities and on varying inclines. A standardized stepwise continuous test protocol was employed [36,37]. 2.5. Lactate Concentration To define lactate thresholds, capillary blood lactate levels (measured in mmol/L) were used at the end of each phase of the step-continuing test. Capillary blood samples were obtained from a hyperemic lobe using special test strips. After acquiring a sample, the lactate concentration was determined immediately using a lactate analyzer (Lactate Scout, EKF SensLab, Leipzig, Germany). The sensitivity and accuracy of lactate concentration measurement using the Lactate Scout analyzer (EKF SensLab, Leipzig, Germany) were scientifically validated [38]. Based on the obtained results, the metabolic efficiency index
Appl. Sci.2024,14, 3807 5 of 17 was calculated, which represents the ratio of blood lactate concentration at the 4th and 10th minutes of recovery. 2.6. Match Running Performance (MRP) For recording matches using the BioIRC Tracking Motion system (BioIRC, Kragujevac, Serbia), two identical Sony NEX-VG10 video cameras (Sony, Tokyo, Japan) were used, both in full-HD resolution, along with one high-speed control camera. The algorithmic part of the video-processing software for tracking the running performance (RP) of players was based on determining the similarity measure of the statistical color distribution of objects [39]. The software for analysis tracked player RP across the entire field, alternately analyzing video footage of each half of the field, depending on the current player’s activities. The analysis speed on the computer (with Intel(R) Core2Duo E6750@2.66 GHz, 2 GB RAM, Win7 32-bit; Intel, Santa Clara, CA, USA) was approximately 4 frames per second. Match videos were processed in multiple stages. For video file analysis purposes, the videos were compressed using the XVID codec in MOV format, with a frame rate of 30 frames per second. 2.7. Cardiovascular and Metabolic Variables The independent variables in this study can be categorized into three groups: cardiac parameters, parameters related to cardiovascular system efficiency, and lactate-related parameters. A total of eight cardiovascular variables were divided into two groups of four each. The first group included heart parameters such as maximum heart rate (HRmax), heart rate at the anaerobic threshold (HR AT), heart rate at the first minute of recovery (HR 1 ′ ), and heart rate at the second minute of recovery (HR 2 ′ ). The second group consisted of parameters associated with cardiovascular system efficiency, including maximum oxy- gen uptake (VO2max), running efficiency (VO2max/v), and cardiorespiratory efficiency (VO2max/HR). Lactate metabolism variables comprised lactate at 4 min (LA 4 ′ ), lactate at 10 min (LA 10 ′ ), metabolic recovery index (Index LA), and metabolic efficiency index (Index ME); Table. Table 2.Cardiovascular and metabolic variables. No. Variable Abbreviation 1. Maximum heart rate HRmax 2. Heart rate at the anaerobic threshold HR AT 3. Heart rate at the first minute
metabolism variables comprised lactate at 4 min (LA 4 ′ ), lactate at 10 min (LA 10 ′ ), metabolic recovery index (Index LA), and metabolic efficiency index (Index ME); Table. Table 2.Cardiovascular and metabolic variables. No. Variable Abbreviation 1. Maximum heart rate HRmax 2. Heart rate at the anaerobic threshold HR AT 3. Heart rate at the first minute of recovery HR 1 ′ 4. Heart rate at the second minute of recovery HR 2 ′ 5. Maximum oxygen uptake VO 2max 6. Running efficiency VO 2max/v 7. Cardiorespiratory efficiency VO 2max/HR 8. Lactate at 4 min LA 4 ′ 9. Lactate at 10 min LA 10 ′ 10. Metabolic recovery index Index LA 11. Metabolic efficiency index Index ME 2.8. MRP Variables The determination of MRP variables was conducted according to the BioIRC motion structure analysis model, based on existing standards for profiling movement intensities with respect to basic physical (movement speed) and physiological (physiological and biochemical changes at given speeds) parameters. Based on this model, five categories of movement intensity for players during the match were defined, and a sixth variable representing total player movement was calculated based on the measured variables [ The dependent variables were MRP variables including sums of movement (in me- ters) within specific speed ranges: walking (<8 km/h), jogging (8–15 km/h), running (15.1–19 km/h),high-speed running (19.1–23 km/h), sprinting (>23 km/h), and the total distance (total; Table).
Description
This study investigates the relationship between physiological parameters and running performance in elite football players.