The effect of heat stress on the running performance of professional soccer players during the Brazilian elite championship

The effect of heat stress on the running performance of professional soccer players during the Brazilian elite championship | Research Square window.SnipcartSettings = { analytics: { enabled: false } }; (function() { var accessVector = localStorage.getItem('access_vector') || ''; window.dataLayer = window.dataLayer || []; if (accessVector) { window.dataLayer.push({ user: { profile: { profileInfo: { snid: accessVector } } } }); } })(); (function(w,d,s,l,i){w[l]=w[l]||[];w[l].push({'gtm.start':new Date().getTime(),event:'gtm.js'});var f=d.getElementsByTagName(s)[0],j=d.createElement(s),dl=l!='dataLayer'?'&l='+l:'';j.async=true;j.src='https://www.googletagmanager.com/gtm.js?id='+i+dl;f.parentNode.insertBefore(j,f);})(window,document,'script','dataLayer','GTM-K279D39R'); Browse Preprints In Review Journals COVID-19 Preprints AJE Video Bytes Research Tools Research Promotion AJE Professional Editing AJE Rubriq About Preprint Platform In Review Editorial Policies Our Team Advisory Board Help Center Sign In Submit a Preprint Cite Share Download PDF Research Article The effect of heat stress on the running performance of professional soccer players during the Brazilian elite championship Diego Augusto, Fabrício Vasconcellos This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-4325069/v1 This work is licensed under a CC BY 4.0 License Status: Posted Version 1 posted You are reading this latest preprint version Abstract In recent years, climate phenomena, such as global warming, have represented a risk to players. Thus, studies involving outdoor sports and high temperatures have been conducted to show the influence on athletes' performance. However, this information requires greater clarity in the scientific community. The purpose of this study was to investigate the effects of heat stress on running performance in matches played during a Brazilian championship. Thirty matches were analyzed from 20 professional soccer players who belonged to the team in the state of Rio de Janeiro during the Brazilian elite championship (2019). To quantify running performance during soccer matches, players used GPS device units. Temperatures were classified by the Cluster method into three groups: high (35.9–29.5 C), moderate (26.4–21 C) and low (20.0–14.1 C). The 1-minute peak of acceleration and deceleration was greater in high temperature situations (p = 0.02–0.03). In matches with low temperatures, accelerations, decelerations, high-intensity running, and sprinting were greater (p = 0.01–0.02). Significant correlations, negative and low, for sprinting (r = − 0.23; p = 0.01), acceleration (r= -0.29; p = 0.001) and deceleration (r= -0.24; r = 0.007). The temperature influenced the running performance of soccer players. Soccer environmental conditions heat performance GPS Figures Figure 1 Figure 2 Introduce High temperatures are a concern in outdoor sports [ 1 , 2 ]. This problem has been assuming greater contours due to the phenomenon of global warming, representing a challenge for athletes, technical staff, and organizing entities [ 3 – 6 ]. In Brazil, it is common for matches to take place at times when temperatures are high (between 11 a.m. and 4 p.m.). In particular, the Brazilian men's soccer championship has a long duration (May to December), with matches in different seasons of the year and regions of the country. This may favor a variation in average temperatures throughout the competition [ 7 ]. Some research carried out in countries in the northern hemisphere and Brazil during the 2014 World Cup shows that high temperatures can reduce athletes' running performance during soccer matches[ 8 – 11 ]. For example, Ozgunen et al. (2010) demonstrated that semi-professional players from Turkey reduced the total distance covered in matches with high temperatures. Also, Coker et al. (2020) analyzed college players in the United States and observed an increase in distance at low intensity during matches in high temperatures. Nassis et al. (2015) observed, in the 2014 World Cup matches, that high temperatures during matches reduced the number of sprints performed by 5%. This reduction in performance is due to the increase in the perception of effort and physiological stress in athletes [ 12 , 13 ]. High thermal stress situations can cause cognitive ability changes in players [ 14 ] and technical actions [ 15 ]. In the case of Brazilian players, thermal stress is especially worrying because most of the year, the regions have high temperatures [ 7 ]. Therefore, temperature can be an essential factor to be monitored when considering the maintenance of match performance [ 16 ]. Despite this, our review effort indicated that studies on the relationships between high temperatures and running patterns during matches are scarce, considering the context of matches in national championships in Brazil. Given the above, research that evaluates players' performance in a real context, that is, during the matches played, is desirable. This is even more necessary for soccer players in Brazil due to the high stress usually present in the competitive season. However, there needs to be more investigations dedicated to these issues. In the context of Brazilian soccer, it was simply not possible to locate observational or experimental studies. Therefore, the present study aims to investigate the effects of heat stress on running performance in matches played during the Brazilian championship. It was hypothesized that running performance would be lower in matches played at higher-intensity actions, such as less high-intensity actions and sprints, in favor of lower-intensity activities. Methods Subjects Data were collected from 20 professional soccer players (25.7 ± 4.4 years; 181 ± 6.1 cm; 75.4 ± 7.8 kg) who belong to the team in the state of Rio de Janeiro during the Brazilian elite championship (2019). The players were classified according to their positions: central defenders (n = 4), wine defenders (n = 4), midfield (n = 8), attackers (n = 4). Only the matches in which the athletes completed at least 90 min of the match were analyzed. Goalkeepers were excluded. The players were monitored during 30 matches of the Brazilian elite championship, the matches were held between May and December. The championship was played by 20 teams and the matches were played in home and away during 38 rounds. This study was approved by the Ethics Committee of Hospital University Pedro Ernesto with opinion number (code 3.712.816). All procedures were carried out by the Resolution of the National Health Council and the Ethics Treaty of the Declaration of Helsinki (1996) for research with human participants. Environment temperature The ambient temperatures on the days and times of the matches were obtained by the meteorological station located closest to the stadium where they took place, based on data provided by the National Institute of Meteorology ( https://portal.inmet.gov.br/ ). After the matches, spreadsheets in CSV format were downloaded, and the temperature values at the beginning of the first and second half were collected in degrees Celsius; the highest temperature value was used. Temperatures were classified by the Cluster method into three groups: high (35.9–29.5 Cº; observations = 65), medium (26.4–21 Cº; observations = 50) and low (20.0–14.1 Cº; observations = 24). Running Variable To quantify running performance during soccer matches, players used 10Hz GPS device units (Viper pod, STATSports®, Belfast, United Kingdom) positioned on the trunk's upper part through a vest designed to reduce motion interference. According to the manufacturer's guidelines, the units were activated immediately before the pre-game warm-up. Players used the same GPS device in each match to avoid unit variation. The validity and reproducibility of this model were demonstrated by a previous study by [ 17 ]. After the matches, the geolocation data files from the GPS were exported using corporate software in spreadsheets in CVS format and transported to the Matlab environment (MathWorks® Inc., Natick, Massachusetts, USA). The geographic latitude and longitude coordinates were converted into Cartesian coordinates on the axes (x, y) and smoothed by a third-order digital filter (cutoff frequency 0.3 Hz). Based on these data different indices of physical performance were calculated, the total distances at different running intensities: total distance, moderate intensity (> 4m/s), high intensity (> 5.5m/s), sprinting (> 7m/s); high accelerations (> 2m/s²); high decelerations (> 2m/s²). The peak physical performance scenario during the game was determined using the moving average procedure in the time window (1 minute). The analyses started in the first minute of each half of the game, being interrupted at the end of each half. Peak values were determined based on each metric's most significant distance traveled (total distance, high-intensity running, high accelerations, high decelerations). Statistics analysis Data were described as mean and confidence interval (95%). The Kolmogorov-Smirnov test and Q-Q plot inspection verified data normality. Variables that did not show normality were corrected using log transformation. A mixed linear model was applied to compare the fixed effect of temperature (high temperature x medium temperature x low temperature), with 'Athlete ID' included as a random effect. In addition, multiple comparisons were adjusted using the Bonferroni method. Pearson correlations were calculated between the temperatures in each match and the running performance indicators; the classification of the correlations, very low (0 to 0.19), low (0.2 to 0.39), medium (0.4 to 0.59), high (0.6 to 0.79), very high (0.8 to 1). For variables with significant correlations, simple linear regression was performed. In all cases, statistical significance was set at p ≤ 0.05. The calculations were performed using the JASP 0.16.30 Software (Netherlands). Results Figure 1 shows the comparisons referring to distances at different intensities in different ambient temperature situations. A significant difference was observed for the distance variable in high-intensity sprinting with higher values for matches at low temperatures than high temperatures (p = 0.01; z=-3.051; p = 0.02; -2.648). Accelerations showed significant differences, with higher values for matches with low temperatures than high and medium temperatures (p = 0.001, z=-5.313; p = 4.541; z=-4.541). Decelerations also showed significant differences. Matches at low temperatures showed greater distances than matches at high and medium temperatures (p = 0.001; z=-4.672; p = 0.002; z=-3.432). The correlation between the performance variables and the ambient temperature values in degrees Celsius during the matches. Significant correlations, negative and low, for sprinting (r= -0.23; p = 0.01), acceleration (r = − 0.29; p = 0.001) and deceleration (r= -0.24; r = 0.007). The other variables did not show significant correlations (Table 2). Figure 2 shows the scatter plot with the relationship between the degrees Celsius during the matches and variables with significant correlations. In addition, the simple regression values showed that the temperature can negatively influence the variation, 5%, 8%, and 6% for running, acceleration, and deceleration, respectively. The results referring to the peak of 1 min, significant differences were observed for the peak of distance accelerating, and higher values in high-temperature situations were observed in comparison with the average temperatures (p = 0.02; z = 2.62). For the peak distance, decelerating also showed increases in matches with high temperatures x medium temperatures (p = 0.03; z = 2.55). For the other analyzed variables, no significant differences were found. These comparisons can be seen in Table 1. Discussion The present study aimed to investigate the effects of thermal stress on running performance in matches held in May and December in the professional championship of the A series. The main results of the study show: i) high temperatures positively influenced the peak distance in acceleration and deceleration 1 minute; ii) The total values of distance in high intensity, sprinting, acceleration and deceleration were reduced when the matches were performed in situations of high temperatures; iii) Low, negative and significant correlations were observed between ambient temperature and distance in sprinting, acceleration and deceleration; iv) The ambient temperature influenced between 5% and 8% of the runs during the matches of the Brazilian Serie A championship. Regarding running values at different intensities throughout the match, we observed a reduction in distance at high intensity, sprinting, acceleration, and deceleration in high-temperature matches. Considering the total distances covered during the matches, the results align with studies conducted with international soccer players [ 10 , 11 ]. As well as in other sports with similar physiological demands requesting high metabolic output, such as hockey [ 18 ]. For example, during the 2014 World Cup held in Brazil, it was observed that sprinting reduced (14%) and running at high intensity (8%) in matches held at high temperatures. High-intensity exercise under hot temperatures promotes different reactions in the body of high-performance athletes that favor a reduction in performance. Increases in internal temperature cause increased vascular and metabolic stress and decreased voluntary muscle contraction [ 2 , 19 , 20 ]. For example, in a study of Australian rules soccer players, researchers show that these athletes tolerated internal temperatures of up to 40.5°C when competing in hot environments [ 21 ]. In situations such as environmental stress, athletes are forced to modify their running patterns to maintain their ability to perform physical actions during matches. Low and negative correlations were demonstrated for sprinting distance, accelerations, and decelerations. These demands are actions that take place at maximum or submaximal intensity, whether in short spaces (accelerations and decelerations) or larger spaces (sprinting) [ 22 ]. Hot temperatures can benefit actions such as sprinting when performed only once, [ 23 ]. The improvement in the single sprint may be caused by better functioning of the anaerobic system and muscle activity. However, in situations of repeated effort, such as soccer matches, the ability to perform sprints over time is impaired, as in hot environments, they adjust the intensity of the runs over time. factors with an increase in core temperature, increased cardiovascular stress, elevation of the heart rate, and greater accumulation of metabolites, cause a reduction in performance [ 24 , 25 ]. Although in this research the correlations are considered low, this can represent considerable changes for high-performance athletes. The R² values indicated that accelerations, decelerations, and sprints are influenced between 8%, 6%, and 5%, respectively. Considering the sprints, the most important physical action of a match, due to its direct influence on the result, as it is related to the moments of goals [ 22 ]. Our findings corroborate other studies that also evaluated sprints during matches with high temperatures [ 10 , 26 ]. This negative influence of temperature on actions such as sprints, accelerations, and decelerations is related to increased metabolic stress caused by heat. It is known that only 25% of the metabolic cost is converted into mechanical work, while the 75% is dissipated in the form of heat [ 27 ]; in situations with high thermal stress, there is an energy gradient that needs to be used also to perform thermoregulation This is the primary mechanism used by athletes' bodies to balance the increase in skin temperature due to exposure to hot environments, this fact requires athletes to redirect blood circulation, which directly affects the energy transport necessary to exercise the physical demands of soccer. To our knowledge, this was the first study to analyze the effects of temperature on peak performance during soccer matches. Different studies have shown that peak moments are influenced by other contextual and positional variables [ 28 , 29 ]. Regarding the influence of temperature, we found that values are higher at high temperatures for distance in acceleration and deceleration compared to moderate temperatures. This may be associated with the fact that the peak metrics only happen in a specific minute of the match [ 29 , 30 ]. These moments of greater intensity mostly occur in the first part of the matches. The periods in which athletes have higher levels of muscular glycogen and lower accumulation of fatigue-derived metabolites [ 28 , 31 ]. Therefore, periods of greater intensity and not the volume of actions can be favored in matches with high temperatures. In summary, this study demonstrated that the ambient temperature influenced the performance of elite professional players in Brazil, precisely the actions at high intensity, sprinting, accelerations, and decelerations. This study has some positive points, such as practical applicability, allowing physical trainers and sports scientists to interpret the context of the match considering the environment. In addition, this information is recent considering the scenario of elite Brazilian soccer, which can help the entities that organize the matches carry out interventions to maintain the players' performance. However, the present study has some limitations. The temperature inside the stadium needed to be measured since the data collected were from the nearest meteorological station. In addition, the athletes' internal temperature was not monitored. Finally, only one team was analyzed. In this way, future research can be carried out measuring the temperature on the field of play and the internal temperature of the players, as well as including more teams. Conclusions In Brazil soccer matches are played in high temperatures. Considering the results of this study, showed that high temperatures above 29.9 Cº were observed to decrease running performance in Brazilian elite championship soccer players. Distance in acceleration, deceleration, and sprinting were influenced. Moreover, the temperature reduced the performance by 5 to 8% for actions such as accelerations, slowdowns, and sprinting. Results show that even elite players are affected by high temperatures during matches. In addition, these results may be of genuine practical interest to several organs, and changes can be made to maintain the intensity of the matches and the players' health. Declarations Author Contribution D.A was responsible for designing, collecting data and writing the manuscript.F.V reviewed the manuscript Financing This study was funded by FAPERJ, CNPQ, Post-Graduate and Research Sub-Rectory (SR-2), and the Post-Graduate Program in Exercise and Sport Sciences of Rio de Janeiro State University, Brazil. 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Frontiers in Sports and Active Living [Internet]. 2021 [cited 2022 Sep 3];3. Available from: https://www.frontiersin.org/articles/ 10.3389/fspor.2021.778813 Oliva-Lozano JM, Riboli A, Fortes V, Muyor JM. Monitoring physical match performance relative to peak locomotor demands: implications for training professional soccer players. Biol Sport. 2022;40(2):253–60. Ju W, Doran D, Hawkins R, Gómez-Díaz A, Martin-Garcia A, Ade J, et al. Contextualised peak periods of play in English Premier League matches. Biol Sport. 2021;39(4):973–83. Oliva-Lozano JM, Fortes V, Muyor JM. When and how do elite soccer players sprint in match play? A longitudinal study in a professional soccer league. Res Sports Med. 2023;31(1):1–12. Tables Tables 1 and 2 are available in the Supplementary Files section. Additional Declarations No competing interests reported. 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Also discoverable on Platform About Our Team In Review Editorial Policies Advisory Board Help Center Resources Author Services Accessibility API Access RSS feed Manage Cookie Preferences © Research Square 2026 | ISSN 2693-5015 (online) Privacy Policy Terms of Service Do Not Sell My Personal Information {"props":{"pageProps":{"initialData":{"identity":"rs-4325069","acceptedTermsAndConditions":true,"allowDirectSubmit":true,"archivedVersions":[],"articleType":"Research Article","associatedPublications":[],"authors":[{"id":297469641,"identity":"17ac064d-79e9-4671-b184-70be9d48d434","order_by":0,"name":"Diego Augusto","email":"","orcid":"","institution":"Rio de Janeiro State University","correspondingAuthor":false,"prefix":"","firstName":"Diego","middleName":"","lastName":"Augusto","suffix":""},{"id":297469644,"identity":"219cb272-3842-4575-9481-ba3c4fc40c02","order_by":1,"name":"Fabrício Vasconcellos","email":"data:image/png;base64,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","orcid":"","institution":"Rio de Janeiro State University","correspondingAuthor":true,"prefix":"","firstName":"Fabrício","middleName":"","lastName":"Vasconcellos","suffix":""}],"badges":[],"createdAt":"2024-04-25 15:22:43","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-4325069/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-4325069/v1","draftVersion":[],"editorialEvents":[],"editorialNote":"","failedWorkflow":false,"files":[{"id":55709419,"identity":"98a96a59-2fc5-4b15-bddb-47d258e601f9","added_by":"auto","created_at":"2024-05-02 05:56:38","extension":"png","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":107350,"visible":true,"origin":"","legend":"\u003cp\u003eSee image above for figure legend\u003c/p\u003e","description":"","filename":"Fig1.png","url":"https://assets-eu.researchsquare.com/files/rs-4325069/v1/a1d198c3b3be097fbf456cd3.png"},{"id":55709417,"identity":"91bfc8a2-0aff-4e23-9f14-0b4bc1610f90","added_by":"auto","created_at":"2024-05-02 05:56:37","extension":"png","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":334662,"visible":true,"origin":"","legend":"\u003cp\u003eSee image above for figure legend\u003c/p\u003e","description":"","filename":"Fig2.png","url":"https://assets-eu.researchsquare.com/files/rs-4325069/v1/0d23682e879cf58a1efb15ff.png"},{"id":56376816,"identity":"141b53f2-42a4-41c7-8fb9-8d3a337beb81","added_by":"auto","created_at":"2024-05-13 11:44:20","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":627793,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-4325069/v1/dc7269ba-6cb9-46e8-b1b8-9da603cdce10.pdf"}],"financialInterests":"No competing interests reported.","formattedTitle":"The effect of heat stress on the running performance of professional soccer players during the Brazilian elite championship","fulltext":[{"header":"Introduce","content":"\u003cp\u003eHigh temperatures are a concern in outdoor sports [\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e, \u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e]. This problem has been assuming greater contours due to the phenomenon of global warming, representing a challenge for athletes, technical staff, and organizing entities [\u003cspan additionalcitationids=\"CR4 CR5\" citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e]. In Brazil, it is common for matches to take place at times when temperatures are high (between 11 a.m. and 4 p.m.). In particular, the Brazilian men's soccer championship has a long duration (May to December), with matches in different seasons of the year and regions of the country. This may favor a variation in average temperatures throughout the competition [\u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eSome research carried out in countries in the northern hemisphere and Brazil during the 2014 World Cup shows that high temperatures can reduce athletes' running performance during soccer matches[\u003cspan additionalcitationids=\"CR9 CR10\" citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e11\u003c/span\u003e]. For example, Ozgunen et al. (2010) demonstrated that semi-professional players from Turkey reduced the total distance covered in matches with high temperatures. Also, Coker et al. (2020) analyzed college players in the United States and observed an increase in distance at low intensity during matches in high temperatures. Nassis et al. (2015) observed, in the 2014 World Cup matches, that high temperatures during matches reduced the number of sprints performed by 5%.\u003c/p\u003e \u003cp\u003eThis reduction in performance is due to the increase in the perception of effort and physiological stress in athletes [\u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e12\u003c/span\u003e, \u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e]. High thermal stress situations can cause cognitive ability changes in players [\u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e14\u003c/span\u003e] and technical actions [\u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e15\u003c/span\u003e]. In the case of Brazilian players, thermal stress is especially worrying because most of the year, the regions have high temperatures [\u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e]. Therefore, temperature can be an essential factor to be monitored when considering the maintenance of match performance [\u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e16\u003c/span\u003e]. Despite this, our review effort indicated that studies on the relationships between high temperatures and running patterns during matches are scarce, considering the context of matches in national championships in Brazil.\u003c/p\u003e \u003cp\u003eGiven the above, research that evaluates players' performance in a real context, that is, during the matches played, is desirable. This is even more necessary for soccer players in Brazil due to the high stress usually present in the competitive season. However, there needs to be more investigations dedicated to these issues. In the context of Brazilian soccer, it was simply not possible to locate observational or experimental studies. Therefore, the present study aims to investigate the effects of heat stress on running performance in matches played during the Brazilian championship. It was hypothesized that running performance would be lower in matches played at higher-intensity actions, such as less high-intensity actions and sprints, in favor of lower-intensity activities.\u003c/p\u003e"},{"header":"Methods","content":"\u003cdiv id=\"Sec3\" class=\"Section2\"\u003e \u003ch2\u003eSubjects\u003c/h2\u003e \u003cp\u003eData were collected from 20 professional soccer players (25.7\u0026thinsp;\u0026plusmn;\u0026thinsp;4.4 years; 181\u0026thinsp;\u0026plusmn;\u0026thinsp;6.1 cm; 75.4\u0026thinsp;\u0026plusmn;\u0026thinsp;7.8 kg) who belong to the team in the state of Rio de Janeiro during the Brazilian elite championship (2019). The players were classified according to their positions: central defenders (n\u0026thinsp;=\u0026thinsp;4), wine defenders (n\u0026thinsp;=\u0026thinsp;4), midfield (n\u0026thinsp;=\u0026thinsp;8), attackers (n\u0026thinsp;=\u0026thinsp;4). Only the matches in which the athletes completed at least 90 min of the match were analyzed. Goalkeepers were excluded.\u003c/p\u003e \u003cp\u003eThe players were monitored during 30 matches of the Brazilian elite championship, the matches were held between May and December. The championship was played by 20 teams and the matches were played in home and away during 38 rounds.\u003c/p\u003e \u003cp\u003eThis study was approved by the Ethics Committee of Hospital University Pedro Ernesto with opinion number (code 3.712.816). All procedures were carried out by the Resolution of the National Health Council and the Ethics Treaty of the Declaration of Helsinki (1996) for research with human participants.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec4\" class=\"Section2\"\u003e \u003ch2\u003eEnvironment temperature\u003c/h2\u003e \u003cp\u003eThe ambient temperatures on the days and times of the matches were obtained by the meteorological station located closest to the stadium where they took place, based on data provided by the National Institute of Meteorology (\u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://portal.inmet.gov.br/\u003c/span\u003e\u003cspan address=\"https://portal.inmet.gov.br/\" targettype=\"URL\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e). After the matches, spreadsheets in CSV format were downloaded, and the temperature values at the beginning of the first and second half were collected in degrees Celsius; the highest temperature value was used. Temperatures were classified by the Cluster method into three groups: high (35.9\u0026ndash;29.5 C\u0026ordm;; observations\u0026thinsp;=\u0026thinsp;65), medium (26.4\u0026ndash;21 C\u0026ordm;; observations\u0026thinsp;=\u0026thinsp;50) and low (20.0\u0026ndash;14.1 C\u0026ordm;; observations\u0026thinsp;=\u0026thinsp;24).\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec5\" class=\"Section2\"\u003e \u003ch2\u003eRunning Variable\u003c/h2\u003e \u003cp\u003eTo quantify running performance during soccer matches, players used 10Hz GPS device units (Viper pod, STATSports\u0026reg;, Belfast, United Kingdom) positioned on the trunk's upper part through a vest designed to reduce motion interference. According to the manufacturer's guidelines, the units were activated immediately before the pre-game warm-up. Players used the same GPS device in each match to avoid unit variation. The validity and reproducibility of this model were demonstrated by a previous study by [\u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e17\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eAfter the matches, the geolocation data files from the GPS were exported using corporate software in spreadsheets in CVS format and transported to the Matlab environment (MathWorks\u0026reg; Inc., Natick, Massachusetts, USA). The geographic latitude and longitude coordinates were converted into Cartesian coordinates on the axes (x, y) and smoothed by a third-order digital filter (cutoff frequency 0.3 Hz). Based on these data different indices of physical performance were calculated, the total distances at different running intensities: total distance, moderate intensity (\u0026gt;\u0026thinsp;4m/s), high intensity (\u0026gt;\u0026thinsp;5.5m/s), sprinting (\u0026gt;\u0026thinsp;7m/s); high accelerations (\u0026gt;\u0026thinsp;2m/s\u0026sup2;); high decelerations (\u0026gt;\u0026thinsp;2m/s\u0026sup2;).\u003c/p\u003e \u003cp\u003eThe peak physical performance scenario during the game was determined using the moving average procedure in the time window (1 minute). The analyses started in the first minute of each half of the game, being interrupted at the end of each half. Peak values were determined based on each metric's most significant distance traveled (total distance, high-intensity running, high accelerations, high decelerations).\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec6\" class=\"Section2\"\u003e \u003ch2\u003eStatistics analysis\u003c/h2\u003e \u003cp\u003eData were described as mean and confidence interval (95%). The Kolmogorov-Smirnov test and Q-Q plot inspection verified data normality. Variables that did not show normality were corrected using log transformation. A mixed linear model was applied to compare the fixed effect of temperature (high temperature x medium temperature x low temperature), with 'Athlete ID' included as a random effect. In addition, multiple comparisons were adjusted using the Bonferroni method. Pearson correlations were calculated between the temperatures in each match and the running performance indicators; the classification of the correlations, very low (0 to 0.19), low (0.2 to 0.39), medium (0.4 to 0.59), high (0.6 to 0.79), very high (0.8 to 1). For variables with significant correlations, simple linear regression was performed. In all cases, statistical significance was set at p\u0026thinsp;\u0026le;\u0026thinsp;0.05. The calculations were performed using the JASP 0.16.30 Software (Netherlands).\u003c/p\u003e \u003c/div\u003e"},{"header":"Results","content":"\u003cp\u003eFigure 1 shows the comparisons referring to distances at different intensities in different ambient temperature situations. A significant difference was observed for the distance variable in high-intensity sprinting with higher values for matches at low temperatures than high temperatures (p\u0026thinsp;=\u0026thinsp;0.01; z=-3.051; p\u0026thinsp;=\u0026thinsp;0.02; -2.648). Accelerations showed significant differences, with higher values for matches with low temperatures than high and medium temperatures (p\u0026thinsp;=\u0026thinsp;0.001, z=-5.313; p\u0026thinsp;=\u0026thinsp;4.541; z=-4.541). Decelerations also showed significant differences. Matches at low temperatures showed greater distances than matches at high and medium temperatures (p\u0026thinsp;=\u0026thinsp;0.001; z=-4.672; p\u0026thinsp;=\u0026thinsp;0.002; z=-3.432).\u003c/p\u003e\n\u003cp\u003eThe correlation between the performance variables and the ambient temperature values in degrees Celsius during the matches. Significant correlations, negative and low, for sprinting (r= -0.23; p\u0026thinsp;=\u0026thinsp;0.01), acceleration (r\u0026thinsp;=\u0026thinsp;\u0026minus;\u0026thinsp;0.29; p\u0026thinsp;=\u0026thinsp;0.001) and deceleration (r= -0.24; r\u0026thinsp;=\u0026thinsp;0.007). The other variables did not show significant correlations (Table\u0026nbsp;2). Figure\u0026nbsp;2 shows the scatter plot with the relationship between the degrees Celsius during the matches and variables with significant correlations. In addition, the simple regression values showed that the temperature can negatively influence the variation, 5%, 8%, and 6% for running, acceleration, and deceleration, respectively.\u003c/p\u003e\n\u003cp\u003eThe results referring to the peak of 1 min, significant differences were observed for the peak of distance accelerating, and higher values in high-temperature situations were observed in comparison with the average temperatures (p\u0026thinsp;=\u0026thinsp;0.02; z\u0026thinsp;=\u0026thinsp;2.62). For the peak distance, decelerating also showed increases in matches with high temperatures x medium temperatures (p\u0026thinsp;=\u0026thinsp;0.03; z\u0026thinsp;=\u0026thinsp;2.55). For the other analyzed variables, no significant differences were found. These comparisons can be seen in Table\u0026nbsp;1.\u003c/p\u003e"},{"header":"Discussion","content":"\u003cp\u003eThe present study aimed to investigate the effects of thermal stress on running performance in matches held in May and December in the professional championship of the A series. The main results of the study show: i) high temperatures positively influenced the peak distance in acceleration and deceleration 1 minute; ii) The total values of distance in high intensity, sprinting, acceleration and deceleration were reduced when the matches were performed in situations of high temperatures; iii) Low, negative and significant correlations were observed between ambient temperature and distance in sprinting, acceleration and deceleration; iv) The ambient temperature influenced between 5% and 8% of the runs during the matches of the Brazilian Serie A championship.\u003c/p\u003e \u003cp\u003eRegarding running values at different intensities throughout the match, we observed a reduction in distance at high intensity, sprinting, acceleration, and deceleration in high-temperature matches. Considering the total distances covered during the matches, the results align with studies conducted with international soccer players [\u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e, \u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e11\u003c/span\u003e]. As well as in other sports with similar physiological demands requesting high metabolic output, such as hockey [\u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e18\u003c/span\u003e]. For example, during the 2014 World Cup held in Brazil, it was observed that sprinting reduced (14%) and running at high intensity (8%) in matches held at high temperatures.\u003c/p\u003e \u003cp\u003eHigh-intensity exercise under hot temperatures promotes different reactions in the body of high-performance athletes that favor a reduction in performance. Increases in internal temperature cause increased vascular and metabolic stress and decreased voluntary muscle contraction [\u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e, \u003cspan citationid=\"CR19\" class=\"CitationRef\"\u003e19\u003c/span\u003e, \u003cspan citationid=\"CR20\" class=\"CitationRef\"\u003e20\u003c/span\u003e]. For example, in a study of Australian rules soccer players, researchers show that these athletes tolerated internal temperatures of up to 40.5\u0026deg;C when competing in hot environments [\u003cspan citationid=\"CR21\" class=\"CitationRef\"\u003e21\u003c/span\u003e]. In situations such as environmental stress, athletes are forced to modify their running patterns to maintain their ability to perform physical actions during matches.\u003c/p\u003e \u003cp\u003eLow and negative correlations were demonstrated for sprinting distance, accelerations, and decelerations. These demands are actions that take place at maximum or submaximal intensity, whether in short spaces (accelerations and decelerations) or larger spaces (sprinting) [\u003cspan citationid=\"CR22\" class=\"CitationRef\"\u003e22\u003c/span\u003e]. Hot temperatures can benefit actions such as sprinting when performed only once, [\u003cspan citationid=\"CR23\" class=\"CitationRef\"\u003e23\u003c/span\u003e]. The improvement in the single sprint may be caused by better functioning of the anaerobic system and muscle activity. However, in situations of repeated effort, such as soccer matches, the ability to perform sprints over time is impaired, as in hot environments, they adjust the intensity of the runs over time. factors with an increase in core temperature, increased cardiovascular stress, elevation of the heart rate, and greater accumulation of metabolites, cause a reduction in performance [\u003cspan citationid=\"CR24\" class=\"CitationRef\"\u003e24\u003c/span\u003e, \u003cspan citationid=\"CR25\" class=\"CitationRef\"\u003e25\u003c/span\u003e]. Although in this research the correlations are considered low, this can represent considerable changes for high-performance athletes.\u003c/p\u003e \u003cp\u003eThe R\u0026sup2; values indicated that accelerations, decelerations, and sprints are influenced between 8%, 6%, and 5%, respectively. Considering the sprints, the most important physical action of a match, due to its direct influence on the result, as it is related to the moments of goals [\u003cspan citationid=\"CR22\" class=\"CitationRef\"\u003e22\u003c/span\u003e]. Our findings corroborate other studies that also evaluated sprints during matches with high temperatures [\u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e, \u003cspan citationid=\"CR26\" class=\"CitationRef\"\u003e26\u003c/span\u003e]. This negative influence of temperature on actions such as sprints, accelerations, and decelerations is related to increased metabolic stress caused by heat. It is known that only 25% of the metabolic cost is converted into mechanical work, while the 75% is dissipated in the form of heat [\u003cspan citationid=\"CR27\" class=\"CitationRef\"\u003e27\u003c/span\u003e]; in situations with high thermal stress, there is an energy gradient that needs to be used also to perform thermoregulation This is the primary mechanism used by athletes' bodies to balance the increase in skin temperature due to exposure to hot environments, this fact requires athletes to redirect blood circulation, which directly affects the energy transport necessary to exercise the physical demands of soccer.\u003c/p\u003e \u003cp\u003eTo our knowledge, this was the first study to analyze the effects of temperature on peak performance during soccer matches. Different studies have shown that peak moments are influenced by other contextual and positional variables [\u003cspan citationid=\"CR28\" class=\"CitationRef\"\u003e28\u003c/span\u003e, \u003cspan citationid=\"CR29\" class=\"CitationRef\"\u003e29\u003c/span\u003e]. Regarding the influence of temperature, we found that values are higher at high temperatures for distance in acceleration and deceleration compared to moderate temperatures. This may be associated with the fact that the peak metrics only happen in a specific minute of the match [\u003cspan citationid=\"CR29\" class=\"CitationRef\"\u003e29\u003c/span\u003e, \u003cspan citationid=\"CR30\" class=\"CitationRef\"\u003e30\u003c/span\u003e]. These moments of greater intensity mostly occur in the first part of the matches. The periods in which athletes have higher levels of muscular glycogen and lower accumulation of fatigue-derived metabolites [\u003cspan citationid=\"CR28\" class=\"CitationRef\"\u003e28\u003c/span\u003e, \u003cspan citationid=\"CR31\" class=\"CitationRef\"\u003e31\u003c/span\u003e]. Therefore, periods of greater intensity and not the volume of actions can be favored in matches with high temperatures.\u003c/p\u003e \u003cp\u003eIn summary, this study demonstrated that the ambient temperature influenced the performance of elite professional players in Brazil, precisely the actions at high intensity, sprinting, accelerations, and decelerations. This study has some positive points, such as practical applicability, allowing physical trainers and sports scientists to interpret the context of the match considering the environment. In addition, this information is recent considering the scenario of elite Brazilian soccer, which can help the entities that organize the matches carry out interventions to maintain the players' performance. However, the present study has some limitations. The temperature inside the stadium needed to be measured since the data collected were from the nearest meteorological station. In addition, the athletes' internal temperature was not monitored. Finally, only one team was analyzed. In this way, future research can be carried out measuring the temperature on the field of play and the internal temperature of the players, as well as including more teams.\u003c/p\u003e"},{"header":"Conclusions","content":"\u003cp\u003eIn Brazil soccer matches are played in high temperatures. Considering the results of this study, showed that high temperatures above 29.9 C\u0026ordm; were observed to decrease running performance in Brazilian elite championship soccer players. Distance in acceleration, deceleration, and sprinting were influenced. Moreover, the temperature reduced the performance by 5 to 8% for actions such as accelerations, slowdowns, and sprinting. Results show that even elite players are affected by high temperatures during matches. In addition, these results may be of genuine practical interest to several organs, and changes can be made to maintain the intensity of the matches and the players' health.\u003c/p\u003e"},{"header":"Declarations","content":"\u003ch2\u003eAuthor Contribution\u003c/h2\u003e\u003cp\u003eD.A was responsible for designing, collecting data and writing the manuscript.F.V reviewed the manuscript\u003c/p\u003e\n\u003ch3\u003eFinancing\u003c/h3\u003e\n\u003cp\u003eThis study was funded by FAPERJ, CNPQ, Post-Graduate and Research Sub-Rectory (SR-2), and the Post-Graduate Program in Exercise and Sport Sciences of Rio de Janeiro State University, Brazil. This study was financed in part by Coordena\u0026ccedil;\u0026atilde;o de Aperfei\u0026ccedil;oamento de Pessoal de N\u0026iacute;vel Superior - Brasil (CAPES) - Finance Code 001.\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\u003cli\u003e\u003cspan\u003eAtwoli L, Baqui AH, Benfield T, Bosurgi R, Godlee F, Hancocks S, et al. Call for emergency action to limit global temperature increases, restore biodiversity, and protect health. Med J Aust. 2021;215(5):210\u0026ndash;2.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eP\u0026eacute;riard JD, Eijsvogels TMH, Daanen HAM. Exercise under heat stress: thermoregulation, hydration, performance implications, and mitigation strategies. Physiol Rev. 2021;101(4):1873\u0026ndash;979.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eChmura P, Konefał M, Andrzejewski M, Kosowski J, Rokita A, Chmura J. 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Res Sports Med. 2023;31(1):1\u0026ndash;12.\u003c/span\u003e\u003c/li\u003e\u003c/ol\u003e"},{"header":"Tables","content":"\u003cp\u003eTables 1 and 2 are available in the Supplementary Files section.\u003c/p\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":true,"highlight":"","institution":"","isAcceptedByJournal":false,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true},"keywords":"Soccer, environmental conditions, heat, performance, GPS","lastPublishedDoi":"10.21203/rs.3.rs-4325069/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-4325069/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003eIn recent years, climate phenomena, such as global warming, have represented a risk to players. Thus, studies involving outdoor sports and high temperatures have been conducted to show the influence on athletes' performance. However, this information requires greater clarity in the scientific community. The purpose of this study was to investigate the effects of heat stress on running performance in matches played during a Brazilian championship. Thirty matches were analyzed from 20 professional soccer players who belonged to the team in the state of Rio de Janeiro during the Brazilian elite championship (2019). To quantify running performance during soccer matches, players used GPS device units. Temperatures were classified by the Cluster method into three groups: high (35.9\u0026ndash;29.5 C), moderate (26.4\u0026ndash;21 C) and low (20.0\u0026ndash;14.1 C). The 1-minute peak of acceleration and deceleration was greater in high temperature situations (p\u0026thinsp;=\u0026thinsp;0.02\u0026ndash;0.03). In matches with low temperatures, accelerations, decelerations, high-intensity running, and sprinting were greater (p\u0026thinsp;=\u0026thinsp;0.01\u0026ndash;0.02). Significant correlations, negative and low, for sprinting (r\u0026thinsp;=\u0026thinsp;\u0026minus;\u0026thinsp;0.23; p\u0026thinsp;=\u0026thinsp;0.01), acceleration (r= -0.29; p\u0026thinsp;=\u0026thinsp;0.001) and deceleration (r= -0.24; r\u0026thinsp;=\u0026thinsp;0.007). The temperature influenced the running performance of soccer players.\u003c/p\u003e","manuscriptTitle":"The effect of heat stress on the running performance of professional soccer players during the Brazilian elite championship","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2024-05-02 05:56:32","doi":"10.21203/rs.3.rs-4325069/v1","editorialEvents":[{"type":"communityComments","content":0}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true}}],"origin":"","ownerIdentity":"01bcdc60-4654-48db-aea1-f85eee30b994","owner":[],"postedDate":"May 2nd, 2024","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"posted","subjectAreas":[],"tags":[],"updatedAt":"2024-05-13T11:36:10+00:00","versionOfRecord":[],"versionCreatedAt":"2024-05-02 05:56:32","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-4325069","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-4325069","identity":"rs-4325069","version":["v1"]},"buildId":"qtupq5eGEP_6zYnWcrvyt","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}