Impact of the COVID-19 pandemic on the psychological aspects and mental health of elite soccer athletes: a systematic review

Introduction Investigation of the psychological impact on soccer athletes during the pandemic is essential given their unique challenges, including training disruptions and competition postponements. Understanding these effects will allow the development of specific strategies to preserve the mental health and performance of elite athletes, contributing to effective interventions with both short and long-term benefits. Objective To analyze the impact of the COVID-19 pandemic on the psychological aspects and mental health of elite soccer athletes. Method The review adhered to PRISMA criteria, and the study protocol was registered in the International Prospective Register of Systematic Reviews (CRD42022341545). Searches were conducted until July 2023 in databases including Cochrane, PsycINFO, PubMed, Scopus, SPORTDiscus, and Web of Science. Only original, peer-reviewed studies in English, Portuguese, or Spanish assessing the impact of the COVID-19 pandemic on the psychological aspects and mental health of elite soccer athletes were included. Results The search identified 1,055 records and 43 studies were included in this review between 2020 and 2023. In total, the sample included 16,321 soccer athletes of different age groups. Anxiety, depression, mood states, and mental well-being were the most investigated variables. Increased levels of anxiety, depression, and worsening mental well-being were observed in elite soccer athletes. Maintaining fitness during the pandemic showed positive results. Other variables, such as coping, resilience, and sleep quality monitoring, were less widely investigated. Evaluating methodological quality was considered regular for observational and experimental studies. Conclusion The study reveals a negative impact of the COVID-19 pandemic on elite soccer athletes, considering psychological aspects and their mental health, notably heightened anxiety and depression. Observational methods predominated, showing mood swings linked to individual characteristics and fitness maintenance efforts. Studies with better-designed methodological approaches and controlled experimental interventions are recommended in the future to mitigate the negative effects of the pandemic on soccer players. Systematic review registration https://www.crd.york.ac.uk/prospero/display_record.php?, identifier (CRD42022341545).


Introduction
In 2020, the COVID-19 pandemic impacted the world in all areas and caused unprecedented extreme damage to the world sports calendar, a fact that had not occurred since World War 2 (IOC, 2020).In the absence of vaccines and antiviral drugs, non-pharmaceutical interventions implemented in response to virus damage were the only options available to slow and moderate the spread of the virus through the population (Kenyon, 2020;Mann et al., 2020).In addition to quarantine and isolation procedures for those who have been exposed to or infected with COVID-19, social distancing is applied as a strategy to reduce the transmission of COVID-19, with the practice of confinement and social isolation being the most effective and widely used (Haug et al., 2020).
Such factors have led to the need to study the impact of the COVID-19 pandemic on the psychological aspects and mental health of athletes.In addition, the complex psychosocial situation of confinement has caused important changes and serious damage to the quality and quantity of training of athletes, and these factors have brought many uncertainties about the future of the sports environment (Andreato et al., 2020).Factors such as the abrupt change in their daily routine, the home confinement measures adopted, and uncertainty about the date of return to activities can lead athletes to experience conditions that affect their mental health, including external sources of distress, anxiety, mood swings, and other concerns and tensions (Evli et al., 2020;Jansen, 2021;Romdhani et al., 2022).
The systematic reduction in training caused losses in physical performance capacity, which meant a loss of competitiveness on the return to competition, generating a cascade of losses that still need to be better understood.In addition to the physical and technical damage, the psychological impact is of great concern to the athlete.Thus, sports science professionals and scientists are challenged to help athletes deal with some of these relevant aspects in times of a pandemic.As a consequence, several recent recommendations suggest minimizing the negative impacts of the COVID-19 pandemic on athletes in general (Andreato et al., 2020;Girardi et al., 2020;Farooq et al., 2021) and in soccer (Jia et al., 2022).Predominantly, the athletes had to deal with the frustration of their goals and changes in their usual training routines (Zinner et al., 2020;Leguizamo et al., 2021).
Soccer arouses great interest in the scientific community, and given its importance in sports sciences and other areas, it is currently the most investigated sport modality (Kirkendall, 2020).A challenging situation is to establish a procedure with implications for their wellbeing and mental health, while at the same time enabling increased performance (Leguizamo et al., 2021).It is known that psychological factors predispose athletes and that changes in sports performance are common and should be considered in sports development and preparation programs (Dönmez et al., 2022).Recent studies have shown implications of the COVID-19 pandemic, with a negative impact on mental status during the pandemic, including concerns about the sporting future, which caused increased anxiety and stress, as well as worsened sleep quality in athletes of various modalities (Håkansson et al., 2020;Mon-López et al., 2020;Jurecka et al., 2021).To date, there are no systematic reviews on whether psychological interventions and approaches were used and if they were effective during the pandemic.
In this sense, the current systematic review with a specific focus on soccer, aims to form a knowledge base, providing information from the evidence with approaches based on sports psychology and analyzing the trends in the evidence.A recent review investigated the effect of the COVID-19 pandemic and its implications on the mental and emotional health of athletes in a generic way (Jia et al., 2022).The authors reported that this phenomenon is complex and multifaceted, as the lack of social interactions with coaches and teammates, the absence of continuous access to training facilities and direct contact with professionals, and the lack of active use of healthy coping mechanisms resulted in worsening mental health of athletes in the COVID-19 era (Jia et al., 2022).However, no systematic review has been conducted on the implications of the COVID-19 pandemic on psychological and mental health aspects, considering the specificity of the sport and the characteristics of elite soccer players.
Psychosocial factors, including disturbances of attention and emotional balance, control of levels of arousal, anxiety, stress, daily annoyances, and other negative life events are predictive of the performance and mental health of soccer players.In this sense, it is imperative to verify whether interventions based on psychological approaches can reduce and mitigate the impacts of these factors on athletes during the pandemic.Based on empirical data, the analysis of the impact that the COVID-19 pandemic has on the psychological aspects and mental health of soccer athletes aims to promote a better understanding of this phenomenon and contribute to the development of guidelines based on evidence, so that clubs and soccer professionals can implement solutions and strategies to reduce the damages and preserve or even increase the performance of athletes in different dimensions in the sport.This will be particularly useful in helping to increase integrative approaches to athletes' performance and health.Thus, the present systematic review aims to analyze the impact of the COVID-19 pandemic on the psychological aspects and mental health of elite soccer athletes.

Methods
This is a systematic review of the literature that followed the criteria recommended by the PRISMA Declaration -Preferred 10. 3389/fpsyg.2023.1295652Frontiers in Psychology 03 frontiersin.org Reporting Items for Systematic Reviews and Meta-Analyses (Page et al., 2021) registered in the International Prospective Register of Systematic Reviews-PROSPERO (CRD42022341545).

Search strategy
The searches for articles were conducted in July 2023, in scientific journals indexed in the Cochrane, PsycINFO, PubMed, Scopus, SPORTDiscus, and Web of Science databases, with a search period from 1st January 2020 to July 11 2023, and the descriptors are presented in Table 1.
The search and selection procedures of the articles were carried out by two researchers (WC and AD'O) independently.Any disagreements were resolved by a third party (AA).

Eligibility criteria for studies
Only peer-reviewed studies were included, taking into account the following criteria: (i) the study was required to be related to the COVID-19 pandemic and present analyses of data from empirical investigations including soccer athletes in the context of training, competitive performance, injury treatment, as well as retired athletes or those who had left the sport; (ii) the article was required to be written in English, Spanish, or Portuguese, with full text available.Studies with only abstracts available were not included, due to the impossibility of performing a full analysis.
For this review, the eligibility criteria were based on the strategy -PECOS -Population, Exposure, Comparator, Outcome, and Study Design (Morgan et al., 2018; Table 2).

Study selection and data extraction
At this stage of the review, the Rayyan application, developed by the Qatar Computing Research Institute (Ouzzani et al., 2016), was used.The selection and extraction of data from the studies were carried out by two researchers (WC and AD'O) independently, and any disagreements were resolved by consensus discussion.
For the analysis and discussion of the results, the following data were extracted: characteristics of the sample (number of participants, sex, mean and age range, and competitive level of performance), instrument for evaluation of mental health variables and psychological aspects, type of study, research objective, year and language of publication, and main results.
For the analysis of Figure 1, we considered the dates of completion of the studies included in this review and the data of cumulative cases and deaths from COVID-19 according to the World Health Organization (2020).

Study quality assessment
The quality of the included studies was assessed using two toolsthe Quality Assessment Tool for Observational Cohort and Cross-Sectional Studies and the Quality Assessment Tool for Before-After   Study flowchart following PRISMA guidelines.
(Pre-Post) both from the National Institutes of Health (2021).Both tools include criteria that need to be met by the studies included in this review and at the end of the evaluation a score is assigned according to each criterion answered, for a "yes" answer, one point is added, and for "no, " "not applicable, " "not reported, " or "it is not possible to determine, " the value is assigned zero points.The Cohort and Cross-Sectional Studies tool -consists of an evaluation based on 14 criteria.A study-specific global score, ranging from zero to 14, was calculated by summing the scores of all criteria.
The tool for experimental studies (pre-post), contains 12 criteria, thus the overall score can vary from 0-12.A higher score indicates better quality of the study (National Institutes of Health, 2021).The evaluation was performed independently by two reviewers (WC and AD'O).Disagreements were resolved by consensus.When necessary, a third author (AA) was requested for the final opinion.The quality of the studies was not considered as an inclusion or exclusion criterion.Previous studies used these tools and demonstrated satisfactory applicability (Sarkies et al., 2017;Hayes et al., 2018).

Results
The search strategy identified 1,435 studies.After the duplicates were removed, 1,055 studies remained.Screening of abstracts identified 75 potentially eligible studies.A total of 43 original studies met the inclusion criteria (Figure 1 PRISMA flowchart).
Researchers from diverse nations have contributed to scientific insights regarding the impact of the pandemic on the psychological aspects and mental health of soccer athletes.Among the 43 studies included in this review, the primary authors represent a wide array of 10.3389/fpsyg.2023.1295652Frontiers in Psychology 05 frontiersin.orgcountries: Turkey, Brazil, Chile, Italy, Spain, China, Iran, Germany, Australia, Austria, Belgium, Denmark, Egypt, the United States, France, the Netherlands, the United Kingdom, Norway, Slovenia, Serbia, and Sweden.This international collaboration underscores the global effort to comprehensively understand the effects of the pandemic on elite soccer athletes.Some of the included studies (18/41.9%),did not report the country of origin of the athletes.Of the studies that reported the nationality, athletes of different nationalities were identified.Twenty studies (46.5%) included female and male athletes, 17 studies only male athletes, in three studies the athletes were only female (6.9%), and five studies did not report the sex of the participants.Most studies included adults and young people, representing 69.2% of the studies, except for two that included young athletes (mean age 12.6 years).Ten studies did not report the age of the participants.
Most studies included exclusively samples and data of soccer athletes (n = 34), and another nine studies included samples of soccer athletes with different sports modalities.
Regarding the study design, the majority were cross-sectional (42 of 43) and only one study design differs from the others, being non-randomized experimental.Seven studies presented a design with a longitudinal cross-sectional follow-up and three studies were crosssectional and comparative (Table 3).

Characteristics of the instruments used
Different instruments were used to assess soccer athletes during the pandemic.Of the 43 studies included in this review, only one study did not describe the instrument used (Smith, 2021) Among the instruments applied in the published studies 39 were identified and widely used in studies with athletes, and three instruments were developed exclusively for research during the pandemic.
Studies on elite soccer athletes that examine the psychological impacts of the COVID-19 pandemic have extensively utilized wellestablished assessment tools, reflecting a rigorous approach to understanding the nuances of mental health.Notably, instruments such as the State-Trait Anxiety Inventory (STAI) and Profile of Mood States (POMS) have been employed to gauge anxiety states, depression, and mood variations among athletes.Additionally, widely recognized scales, such as the Patient Health Questionnaire (PHQ-9), Generalized Anxiety Disorder 7 (GAD-7), and Beck Anxiety Inventory have been adopted to specifically assess depressive and anxious symptoms.
Researchers have also recognized the unique psychological challenges within the sports context, leading to the utilization of specialized assessments.The Competitive State Anxiety Inventory-2 Revised (CSAI-2R) and the Instrument to verify the basic psychological needs exemplify this tailored approach, aiming to capture the distinctive psychological nuances experienced by elite soccer athletes.
In pursuit of a holistic understanding of the pandemic's psychological impacts, some studies have taken a pioneering stance by developing customized instruments and employing novel methodologies.These include the creation of open-ended questions by the authors and the adaptation of questionnaires to meet the specific demands of the study.This adaptive strategy underscores the necessity for tools tailored to the unique circumstances of elite soccer athletes, offering a more nuanced comprehension of the psychological repercussions of the COVID-19 pandemic.

Athlete monitoring period during the COVID-19 pandemic
Most studies (29 out of 43) indicated the exact period of the pandemic in which the research was conducted.The majority of studies focused research on soccer athletes between March and June 2020 (23 out of 29), which is a period with a known high worldwide cumulative death rate of COVID-19, 540.267 cases.Five studies were conducted before this period (Figure 2).

Mood state
Eight studies (Mon-López et al., 2020;Aghababa et al., 2021;Han et al., 2021;Kesilmis et al., 2021;Villaseca-Vicuña et al., 2021;Wagemans et al., 2021;Montealegre-Mesa et al., 2023) assessed the mood swings of soccer athletes during the COVID-19 pandemic.Aghababa et al. (2021) found that due to the psychosocial situation of the COVID-19-related lockdown, the maintenance and execution of unique patterns of physical activity were not compensatory to the point of producing positive effects and changes in the mood states of soccer athletes (Aghababa et al., 2021).

Depression
Studies that analyzed depression in soccer players (13.64%), reported that during the emergency peak of the lockdown caused by the COVID-19 pandemic there was a significant increase in depression in elite soccer players, especially among those concerned about their future as players (Han et al., 2021;Leguizamo et al., 2021;Lima et al., 2021;Nassar et al., 2021;Dönmez et al., 2022).The mean values of the three dimensions of the coach-athlete relationship after lockdown are higher than before lockdown; blockage has different effects on proximity, commitment and complementarity at different ages; The relationship between the impact of lockdown on the coach-athlete relationship and the severity of the epidemic in each province is not significant.Mon-López et al.The results show a positive relationship between the average level of well-being and positive affect and intrapersonal variability over time.This indicates that resilience can be a protector for mental health.In addition, higher levels of anxiety trait were associated with higher levels of negative affect and greater variability over time.The mental health status of the athletes was better than the non-athletes, and the positive effect of the sport, which was made until the break due to the isolation period, continued on mental health.These findings show that physical activity and sports can help protect mental health.During the pandemic, there was no variation in the levels of symptoms of anxiety, stress, and depression in soccer athletes.The return to training, after the period of interruption of training, reduced the levels of somatic anxiety, cognitive anxiety, depression, stress, anxiety and self-confidence, but without significant differences.It was identified that athletes with more than 10 years of practice had a significant increase in confidence compared to athletes with less than 10 years of practice.The results indicated that college athletes at no risk for anxiety or depression used more Psychological Strategies (PE), while those at risk reported using debilitating strategies.Lack of emotional control in practice explained the greatest variation in predicting anxiety scores (29%) and depression (36%), while negative thinking in competition explained the greatest variation in anxiety (30%) and depression (35%) scores.The results are discussed in terms of athletes' familiarization with the variety of PE and its relevance to mitigating mental health risk triggers during the pandemic.(Continued)  Well-being NR/NR Hooper Scale "Well-being questionnaire" the soccer players investigated have average levels of trait-anxiety and a good level of general well-being, with a correlation between the two.
Although the current situation can be seen as threatening, the maintenance of working and active conditions for an athlete seems to be fundamental to feel a certain degree of control in the face of uncertainty, as well as coping strategies that allow a high sense of well-being.

Survey
The state of well-being in professional soccer players is altered in confinement in relation to competition, with significant changes in perceived fatigue, sleep quality, and level of stress and general well-being, which coincided with moderate to very large variation in these same variables, as well as the a percentage of change that was greater than the coefficient of variation between periods which could be an effect attributable to mandatory isolation. (Continued)

Sleep quality
The evaluation of the sleep quality of the athletes was investigated in four studies and significant changes were observed in the duration and quality of sleep of soccer athletes (Facer-Childs et al., 2021;Han et al., 2021).The effects of home training during lockdown brought positive results in the sleep of athletes (Keemss et al., 2022;Romdhani et al., 2023).

Other psychological outcomes
Studies were identified that investigated soccer athletes and other less frequent outcomes, such as coping, resilience, psychological distress, and fear caused by the pandemic (Jansen, 2021;Lima et al., 2021;Katanic et al., 2022;Kobal et al., 2022;Vitali et al., 2022).All health outcomes identified in the studies included in this review and their frequencies are shown in Figure 3.

Evaluation of the quality of studies
Tables 4, 5 present the general and specific classifications of the criteria on the evaluation of the quality of the studies (National Institutes of Health, 2021).The included observational studies scored an average of 7.00 (±2.26), ranging from 3 to 12. Based on this evaluation, the quality of the studies was generally considered regular (33 of 42), with 5 considered as of good methodological quality and four studies considered poor in the evaluation of quality.The agreement between the observers for all items was 85.6% (Table 4).
The majority of the observational studies (37 out of 42) did not report the exposure levels of study participants in relation to the results, some (26 out of 42) also reported no information on sample power or size because the analyses are exploratory in nature.It was also observed that only two studies of the 42 evaluated indicated the appropriate statistical procedures to minimize confounding factors.Well-conducted cohort studies control for multiple potential confounding factors.
The experimental study included in the review presented a score of nine, considered regular quality.In the current study, statistical tests were presented to provide p-values for pre-post changes.The study provided sufficient information about the intervention in a consistent manner regarding the study population, as well as making all the measures performed on the study participants available in a clear and reliable manner.On the other hand, the calculation of the sample size was not provided, nor were the people who evaluated the results blinded to the exposures/interventions of the participants in any of the studies.Outcome measures were evaluated before and after the intervention.The agreement between observers for all items was 86.5% (Table 5).

Overview and highlights
The present study aimed to analyze the impact of the COVID-19 pandemic on the psychological aspects and mental health of elite soccer athletes.Although a systematic review has recently been conducted including several sports modalities (Jurecka et al., 2021) to evaluate the effects of the pandemic on the physical activity, mental state, and quality of life of professional athletes, there is a need to deepen the searches and analyses, especially considering the most widely practiced and investigated modality in sports science (Kirkendall, 2020).
Regarding the nationality of the athletes investigated, 21 studies reported the origin of the athletes, who came from several different countries of the world.These data reveal the concern for the psychological aspects and mental health of soccer athletes in much of the world during the pandemic and related restrictions (de Souza et al., 2021;Kesilmis et al., 2021;Leguizamo et al., 2021;Keemss et al., 2022).
The current systematic review reports recent findings and summarizes the impact of the COVID-19 pandemic on soccer athletes, presenting rates of the main variables of psychological aspects and mental health measured during the pandemic and also showing a comprehensive approach in the selection of assessment tools for evaluating soccer athletes, emphasizing the importance of collecting not only overt symptoms but also sport-specific and individual factors experienced during the pandemic (Bernabe-Valero et al., 2021).The diverse array of instruments utilized contributes to richer understanding of the psychological impact of COVID-19 on elite soccer athletes, providing valuable insights for future research and interventions in sports science (Lee et al., 2023).This multifaceted approach not only enhances our understanding of the subject within the specific context of elite soccer but also holds significance for its potential applicability across diverse populations and nationalities (Richardson et al., 2022).The inclusion of various instruments in the study not only enriches the depth of the analysis, but also increases the possibility of applying the findings in future studies.
Studies with heterogeneous samples have been reported in previous reviews focusing on the general population.Even so, considering the population of soccer athletes, it is important to reduce the risks of selection bias by considering homogeneous samples (Crossley et al., 2020).

Impact of COVID-19 on psychological aspects in soccer athletes
Undoubtedly, the stress generated by the need to maintain physical condition prior to the pandemic caused imbalances in the stimulus-recovery relationship (Faude et al., 2014).Perceived stress is a critical factor in burnout among athletes and a moderate effect size was reported for the correlation of this variable with depression (Sarmento et al., 2021).A systematic review and meta-analysis prior to the pandemic synthesized, in an analytical and rigorous manner, data on psychological and hormonal changes induced by soccer matches.When psychophysiological stress was assessed after soccer   It cannot or cannot determine or cannot be determined or unreported (0); Yes (1); The quality of the studies was classified as poor (0-4 in 14 questions), regular (5-10 in 14 questions) or good (11-14 in 14 questions). 10.3389/fpsyg.2023.1295652 Frontiers in Psychology 16 frontiersin.orgmatches, cortisol changes were caused by alterations in cognitive anxiety, while testosterone changes were driven by alterations in mood state and social connection.In addition, it is highlighted that competitive levels should be considered as the main moderating variables of the relationship between soccer games and hormonal changes related to stress (Slimani et al., 2017).Understanding factors such as athletes' sleep quality, and other psychological variables, such as resilience and coping strategies is essential to develop effective management protocols that help soccer athletes maintain healthy sleep and, consequently, optimize their athletic performance (Bicalho et al., 2020;Madsen et al., 2021).Sleep quality has been less widely investigated relative to other psychological approaches, however it is important that athletes, coaches, and sports professionals work together to address these challenges and promote the overall health of athletes in contexts such as the COVID-19 pandemic (Nassar et al., 2021).

Impact of COVID-19 on the mental health of soccer athletes
A growing body of knowledge, analyzed here, indicates that anxiety and depression, as well as acute symptoms are usually mild or absent in this population.
Emerging evidence suggests that a considerable proportion of athletes may exhibit psychological alterations and persistent symptoms that can be potentially detrimental to performance and mental health (Bicalho et al., 2020;Ivarsson et al., 2021), which were not reversed with maintenance and training strategies outside the usual sports environment, suggesting that decisions to return to the game and training should be made with caution (Jansen, 2021).
In a previous review study, it was evidenced that the participation of soccer athletes at the male professional level could provide a certain protective effect for mental disorders or suicide (Morales et al., 2021).However, more research is needed with female athletes and other types of associated sports to corroborate the generalization about mental health aspects.
The evidence base on the mental health and well-being of elite athletes is limited by a dearth of high-quality systematic studies, including intervention trials.Based on current evidence, elite athletes appear to experience a broadly comparable risk of high-prevalence mental disorders relative to the general population.A higher risk for a mental health disorder may be experienced by elite athletes who are injured, approaching/in retirement, or experiencing performance difficulty.Although the importance of the mental health of the elite athlete is gaining greater attention, targeted and specific models of attention for the disorder have yet to be established for this group (Rice et al., 2016;Gouttebarge et al., 2022).

Strengths, innovations, and practical applications
The present study evaluated psychological aspects in the population of soccer athletes during the COVID-19 pandemic.Articles with this focus were collected from January 2020 to July 2023 and were systematically reviewed according to PRISMA guidelines.
The present review summarizes a robust body of evidence.From the results of the study, it seems appropriate to develop alternatives and support professional athletes during the COVID-19 pandemic.To improve indicators of mental health and overall athlete satisfaction and well-being during and after the pandemic, the development of guidelines related to the monitoring and control of aspects related to athletes' mental health is recommended.
In the context of soccer, teams of experts working with athletes should pay special attention to alterations in psychological aspects and mental state before and during situations, such as in pandemic times.In the future, more studies with interventions and/or protocols that already have a positive impact on athletes in different modalities, such as mindfulness, sleep hygiene, relaxation, for example, should be performed and applied to athletes, without, however, disregarding the methodological limitations of the study designs.In addition, further studies should minimize or exclude potential confounding factors that reduce certainties in the conclusions of studies on this topic.

Limitations
Although this systematic review provides a comprehensive overview of elite soccer, it has limitations.The articles reviewed in this study were mostly cross-sectional.It was not possible to analyze the prevalence and incidence of the psychological variables investigated, and it was not possible to perform a meta-analysis.Potential factors, such as age variability, competitive level, and athletes' experience may have hindered the strength of the association between psychological factors and mental health in the studies selected for this review.
Worsening psychological aspects were observed in most of the included studies, but this may not be causally related to COVID-19, given that most control parameters were not presented (e.g., uninfected athletes, infected athletes), including information on athletes with diagnoses of psychological problems prior to the pandemic, and lockdown.This review also reveals that the absence of control groups or baseline data (i.e., before lockdown) for the assessment of the pandemic phenomenon in the soccer universe are potentially confounding factors (e.g., previous psychological problems of the pandemic, state or trait of anxiety, for example).Inconsistent data or lack of clarity in some included studies are relevant limitations of the literature that should be addressed in future investigations.
Only published articles were included in the review, the gray literature was not included.In addition, the use of an electronic questionnaire as a research tool may have influenced the response bias and the systematic bias given the rigor in controlling the context during the evaluations.
Despite all the limitations presented, it should be taken into account that the understanding of every phenomenon related to the COVID-19 pandemic in the sports universe is still recent and despite this it was possible to gather the information in a rigorous way, as presented in this review.

Conclusion
The results demonstrate the negative impact of the COVID-19 pandemic on the psychological aspects and mental health of elite soccer athletes during the emergency phase of the pandemic in the year 2020.Because it is a recent topic, most studies used observational methods.Among the most commonly observed effects were increased levels of anxiety, depression, and worsening mental well-being in elite soccer athletes.Studies have shown important mood swings related to athletes' characteristics and maintaining fitness during the pandemic.For other variables, such as coping, resilience, and monitoring of sleep quality, although there are a reduced number of studies, positive results were shown for soccer athletes.Studies with better methodological designs with controlled experimental interventions are recommended in the future to mitigate the negative effects of the pandemic for this population of athletes.
It is crucial to acknowledge that athletes, especially soccer players, have faced unique challenges during the pandemic, such as disruptions in regular training, postponed competitions, and the need to adhere to strict health protocols.These adversities can have significant impacts on players' performance and well-being, both in the short and long term.
Therefore, we urge researchers to carefully consider the design of their studies, ensuring that their methodological approaches are robust and comprehensive.This includes collecting data from players before, during, and after the pandemic to properly assess the full impact of these unusual circumstances.
Furthermore, the implementation of controlled experimental interventions is essential to identify effective strategies to support players, such as tailored fitness programs, psychological support, and stress management techniques.These interventions can help mitigate the negative effects of the pandemic and promote the well-being of players.
the importance of cognitive-behavioral therapy for professional soccer teams.Its core is cognitive restructuring using the ABC (antecedents-behavior-consequences) modelEvli et al. (2020) Cross-athletes have a high state of anxiety due to uncertainty in a pandemic environment.It can be stated that this uncertainty increases the anxiety levels of these athletes, who practice the sport as a profession for reasons such as making money and keeping fit.Håkansson et al. have been linked to feeling worse during the COVID-19 pandemic and worrying about one's sporting future.Female athletes had a higher incidence of anxiety and depression symptoms.The fear of increased gambling during the crisis was not clearly demonstrated, but the risk in male athletes was common and associated with increased gambling during the pandemic.Li et al.
reduced sleep quality, duration and intensity of training.Mood states can affect sleep quality, sleep hours, and perceived exertion assessed.Emotional Intelligence is related to the training of behaviors in periods of isolation.The period of isolation did not affect men and women equally.Aghababa et al. psychosocial situation of COVID-19-related lockdown, it seemed very unlikely that unique patterns of physical activity could counterbalance possible impaired mood and behavior states.Balyan et al. nutrition were associated and are directly proportional.The nutritional habits of soccer players affect individuals.Soccer players who enjoy their life and feel psychologically happy produce effects on their nutrition and life satisfaction.Esteves et al. in anxiety state and anxiety trait, with higher results in men compared to women.Anxiety during the period of the COVID-19 pandemic impacted participants' self-perceived performance analysis.The importance of cognitive-behavioral therapy for professional soccer teams is highlighted.
unprecedented information about the effects of a lack of fans at soccer games during the COVID-19 pandemic on emotional behavior on the field.Without the external factor of the fans, players and staff acted more factually and got less excited.The evidence from this study indicates that the absence of fans has a substantial influence on the experience and behavior of players, staff, and referees.infection negatively affects the psychological states of soccer players.Among athletes who have been infected by COVID-19, it is recommended that these should be closely monitored, of life (QoL) score of the athletes worsened significantly and a significant negative correlation was found between the increase in body mass index (BMI) and QoL.There was a significant increase in BMI among athletes who did not exercise at home and a negative correlation with the change in QoL over the course of the blockade.The mothers' anxiety had a possible reflection on their children's weight gain.
12 athletes with citizenship roles during the pandemic, which collectively illustrate players promoting fan support and citizen public health compliance, well-being and life.The players also conveyed how they handled the pandemic with their athlete mindset and hopes for look promising about higher levels of physical activity in professional soccer players during home quarantine, stays at home can contribute to anxiety and depression.Maintaining regular physical activity and routine physical exercise in a safe home environment is one of the most important strategies for maintaining a healthy mental state.sport modified according to PMQ.The COVID-19 emergency period is associated with increased symptoms of anxiety and depression in professional soccer players, especially among those worried about their future as players.
observed in any physical and technical parameters between 4-5 and ≤ 3 substitutions (p > 0.05).In addition, 4-5 substitutions showed lower RPE (p < 0.001) and load RPE (p < 0.001), higher TQR (p = 0.008), and shorter time played by the player (p < 0.001), compared to ≤3.Thus, the new interim rule for replacements improved the balance between stress and recovery during the COVID-SM) problems in infected soccer players were associated with female players, participation in soccer at the lower level, performance concerns, and sleep problems.The evaluation of MS is indicated in infected athletes to assist in the detection and appropriate intervention.
skeletal muscle derived from tensiomyography, incidence of injuries, and selfassessment of the general well-being of elite soccer players.
not change between pre-and post-lockdown.The athletes rated the lockdown period as a positive event and felt better psychologically during the lockdown as they spent more time with family and friends.Although there were no differences in any of the variables that describe the muscle power of the lower limbs after the two-month blockade, the altered contractile properties of the muscles evaluated suggest suboptimal conditioning of the soccer players.profiles differentiate distinct groups of athletes in relation to anxiety, stress assessments, social support, and interpersonal coping.Evasive profiles were characterized less.Managing the COVID-19 situation may be more problematic for them than others in mitigating its negative psychological effects.Using a person-centered approach, the findings may inform the development of more appropriate care, support, and intervention for athletes, especially evasive ones, who have been characterized by less effective coping skills and resources.and female athletes showed higher perceived risk of COVID-19, while athletes with no experience with COVID-19 reported greater fear.Perceived risk (directly and via perceived safety of the training environment) and fear of COVID-19 were negatively associated with athletes' well-being and athletic readiness.reduction in physical activity levels, with 56% of participants reporting seven or more hours/week of moderate to vigorous physical activity, which decreased with age and changed according to geographic context.Perceived quality of life was lower in young people playing in non-elite clubs and in older girls; Coaches, more than official initiatives, were the main source of soccer exercises practiced at home.trained on average 5.4 ± 1.28 days a week and practiced 2.4 ± 0.64 h a day and in isolation 1.68 ± 0.79 h with training frequency of 1.4 times a day.Changes in mood states were inversely correlated with demand and training.There was a significant correlation between the time of previous daily training and in isolation and also with the weekly schedule during preventive isolation.Important changes in the mood states of soccer athletes were observed during the lockdown caused by the COVID-19 pandemic.Does not report age standard deviation: *; NR, Does not report; NA, Not applied; M, Male; F, Female.

FIGURE 2
FIGURE 2Timeline of the periods when the studies were developed and the monitoring of soccer athletes during the COVID-19 pandemic.Adapted fromRichardson et al. (2022).Cumulative case and death data are derived from the closest update provided by the World Health Organization (WHO, 2020) on the last day of each month.

FIGURE 3
FIGURE 3Frequencies of psychological and mental health variables investigated in the included studies (n = 43).

TABLE 1
Search strategy in electronic databases.
Corona Virus Disease 2019" OR "Novel Corona Virus" OR "2019-nCoV" OR coronavirus* OR corona-virus* OR covid OR "social isolation" OR quarantine OR confinement OR "home-based" OR "disease outbreaks" OR outbreak OR lockdown OR "social

TABLE 2
Inclusion and exclusion criteria of the studies selected for the review.

TABLE 3
Sample characteristics (number of athletes, sex, and age), study objectives and designs, athletes' competitive level, result variables, instruments, and main results.

TABLE 4
Evaluation of the quality of cross-sectional and longitudinal studies.

TABLE 5
Evaluation of the quality of the experimental study.cannot or cannot determine or cannot be determined or unreported (0); Yes (1); The quality of the studies was classified as poor (0-4 in 12 questions), regular (5-10 in 12 questions) or good (11-12 in 12 questions). It