*Article* **Personality Determinants of Success in Men's Sports in the Light of the Big Five**

**Paweł Piepiora 1,\* and Zbigniew Piepiora <sup>2</sup>**


**Abstract:** The aim of the study is to describe personality profiles and determinants of success in sports in relation to the Big Five Personality Model. In order to achieve this aim, personality profiles of players from various sports disciplines was set against the personality profile of champions—players who are considerably successful in sports competitions. Subsequently, an attempt was made to determine which personality traits significantly determine belonging to the group of champions and therefore determine success in sport. The participants were men aged between 20 and 29 from the Polish population of sportsmen. A total of 1260 athletes were tested, out of whom 118 were qualified to the champions sample—those athletes had significant sports achievements. The research used the NEO-FFI Personality Questionnaire. Basic descriptive statistics, a series of Student's *t*-tests for independent samples using the bootstrapping method, as well as a logistic regression model were performed. In relation to other athletes, champions were characterized by a lower level of neuroticism and a higher level of extraversion, openness to experience, agreeableness, and conscientiousness. An important personality determinant was neuroticism: the lower the level of neuroticism, the greater the probability of an athlete being classified as a champion. There are differences between champions and other athletes in all personality dimensions in terms of the Big Five. Based on the result of the research, it can be stated that personality differences should be seen as a consequence of athletes' success, rather than as a reason for athletes' success, based on their age between 20 and 29.

**Keywords:** sport psychology; personality; neuroticism; champions

#### **1. Introduction**

A problem that has long been of interest to sports psychologists, coaches, and athletes alike concerns the determination of the personality traits of a champion [1,2]. This particular task would involve the identification of the athletes' personality traits which are essential to their success in sport [3,4].

For instance, Garland and Barry [5] carried out an experiment on American college athletes, varying in terms of physical fitness and sport level, to test the relationship between personality as measured by the 16-Factor Personality Questionnaire and their sports performance. It was shown that personality traits such as belief rigidity, extraversion, group dependence, and emotional stability were responsible in 29% for variations in physical fitness. Davis [6], in turn, tried to predict the success of professional hockey players by measuring their personality traits, but found no correlation. He believed that success was influenced by more important psychophysical factors.

In another study, Lerner and Locke [7] measured the willingness of American college athletes to compete in relation to their achievement motivation. To this end, they used the Sports Orientation Questionnaire, and measured their endurance by performing squats. Similarly, as in Garland and Barry [5], a relationship was found between personality and

**Citation:** Piepiora, P.; Piepiora, Z. Personality Determinants of Success in Men's Sports in the Light of the Big Five. *Int. J. Environ. Res. Public Health* **2021**, *18*, 6297. https://doi.org/ 10.3390/ijerph18126297

Academic Editors: Antonino Bianco, Carlos Marques da Silva, Manuel Gómez-López and Mário António Cardoso Marques

Received: 26 April 2021 Accepted: 7 June 2021 Published: 10 June 2021

**Publisher's Note:** MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affiliations.

**Copyright:** © 2021 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https:// creativecommons.org/licenses/by/ 4.0/).

success. Psychological factors such as goal setting and self-efficacy have been shown to validate the influence of personality on athletic performance.

In a cutting-edge experiment by Piedmont, Hill, and Blanco [8], four different Division 1 NCAA soccer teams were tested with the Big Five model. Coach ratings for several dimensions of player performance and actual game statistics were also collected. Regression analysis indicated that personality dimensions of neuroticism and conscientiousness explained about 23% of the coaches' variance ratings, while conscientiousness was the only predictor of actual game statistics, explaining about 8% of the variance.

A slightly different research was carried out by McKelvie, Lemieux, and Stout [9] on groups of university athletes (divided into contact and non-contact disciplines) and non-athletes, with the use of the Eysenck Personality Inventory. Extraversion did not differ significantly between athletes and non-athletes, nor between contact and non-contact sportsmen, but was higher for athletes in general compared to American academic standards. In the case of neuroticism, successful athletes scored significantly lower than unsuccessful athletes. As neither extraversion nor neuroticism results has changed over the four years of continuous research, one might conclude that people with higher extraversion and lower neuroticism are interested in academic sports.

In another study Anghel, Banica, and Ionescu [10] found out that personality traits of elite athletes were dependent and distinctive of the sports discipline they trained. The athletes were characterized by low neuroticism, high extraversion, and conscientiousness, but the intensity of individual personality traits depended on the trained sport discipline. This indicates the existence of a general personality profile of athletes, in which the strength of the acceleration of personality traits is determined by particular sports disciplines.

Mirzaei, Nikbakhsh, and Sharififar [11] made further attempts to investigate the relationship between personality traits and sports performance in the Big Five model. The research sample included more than 200 non-elite soccer players and futsal soccer players. It was shown that among the personality traits, only conscientiousness had a significant correlation with sports performance—conscientiousness alone was the only predictor of sports performance.

Then, Kim, Gardant, Bosselut, and Eys [12] conducted an experiment on a sample of team sports players and showed that low neuroticism, high extraversion, and conscientiousness all influence informal role-taking in a sports team, depending on the sports team. The same year, Steca, Baretta, Greco, D'Addario, and Monzani [13] examined more than 800 athletes and non-athletes with the use of the Big Five model. It was shown that the most successful athletes in their discipline had higher scores than the non-athletes in every dimension of the Big Five, except neuroticism, in which they scored lower. In contrast, less successful athletes outperformed the non-athletes only in extraversion and agreeableness. Athletes who were more successful in their competitive sports (champions) showed greater emotional stability (lower neuroticism), extraversion, openness to experience, agreeableness, and conscientiousness than less effective athletes. Moreover, individual athletes turned out to be more energetic and open-minded than team athletes. In another study, Piepiora and Witkowski [14] tried to generate psychological personality profiles of athletes performing individual and team disciplines, depending on the type of pressure exerted on the opponent in the starting situation. Differences were found in the scales of neuroticism and conscientiousness between sports disciplines in which pressure is exerted indirectly on the opponent, and disciplines in which the pressure exerted directly on the opponent. The study groups, with the exception of volleyball players and football players, differed from each other in terms of neuroticism scale, while the volleyball players showed less agreeableness and conscientiousness than other athletes.

Taking the above research and reflections as the starting point for the research problem formulation, it should be assumed that personality conditioning in sports champions in relation to the population of unsuccessful athletes, according to the Big Five model, focuses on lower neuroticism and higher extraversion, openness to experience, agreeableness, and conscientiousness [15,16]. However, there is ambiguity in relation to the type of sport, competing classes, or cultural affiliations. Personality traits are adequate to the specificity of the trained sports discipline, and its goals and challenges. The personality profiles of the athletes are at similar levels, but they are not identical. Among athletes, it is extremely difficult to distinguish and define the most favorable type of personality, as it is largely influenced by the trained sports discipline, and it determines the personal conditions of athletes [17–20]. Therefore, it was deemed necessary to verify which personality traits, and to what extent said traits, define sports champions and determine success in sports.

The research problem was an attempt at defining personality profile of sports champions and personality determinants of success in sport in the light of the Big Five factor model. In connection with the above, personality profiles of players from various sports disciplines in the areas of combat sports [21], individual sports [22], and team sports [23] were compared with the personality profile of champions [16]—players who are very successful in sports rivalry. Subsequently, attempts were made to determine which personality traits significantly determine belonging to the group of champions—and thus determine success in sport. For this purpose, the Big Five model was used, as it does not transgress the definition of personality traits understood as behavioral properties, showing interindividual variability and intra-individual temporal and situational permanence. They adopt a number of methodological assumptions that define the status of personality traits as "basic" dimensions of personality. The Big Five model defines the most general characteristics of behavior that are actual, invariant, universal, and biologically conditioned [24].

#### **2. Methodology**

#### *2.1. Participants*

The research was carried out between 1 October 2015 and 30 September 2019. The subjects of the study were men, intentionally, non-randomly selected from the Polish population of sportsmen. The criteria for the non-random, purposeful selection of respondents were: free will to participate in the study; senior age (between 20 and 29 years of age); at least the second or higher sports class; many years of sports experience—three years or more; a current competition license; and documented sports achievements at various levels of rivalry (national, continental, and world). A total of 1260 competitors were tested, 30 each from the following sports disciplines: alpine skiing, American football, archery, athletics—long runs, athletics—short runs, ballroom dancing, basketball, beach volleyball, biathlon, bodybuilding, Brazilian jiu-jitsu, break dance, canoeing, cycling, fitness, floorball, football, futsal, handball, horse riding, indoor volleyball, judo, ju-jitsu, kickboxing, kyokushin karate, mixed martial arts, mountaineering, Olympic karate, orienteering, Oyama karate, rugby, shidokan karate, shotokan karate, snowboarding, sport climbing, sport shooting, swimming, taekwondo, tennis, tobogganing, ultimate frisbee, and wrestling. Such a distribution of disciplines depended on the respondents' willingness to participate in the study. From the above population, 118 athletes were qualified to the sample of champions. Players with international sports successes were defined as champions. Therefore, the criterion for qualifying Polish players to the sample of champions was their 1st, 2nd, or 3rd place in international sports competitions. This includes medalists of the World Championship, the European Championship, the World Cup, the European Cup, the World Games 2017, and other ranked international tournaments in their sports disciplines. The following champions with significant sports achievements were identified: from alpine skiing (3), archery (5), ballroom dance (2), beach volleyball (2), biathlon (4), bodybuilding (4), Brazilian jiu jitsu (4), break dance (2), canoeing (2), cycling (2), equestrian (1), fitness (4), floorball (2), futsal (2), ju jitsu (5), judo (3), kickboxing (4), kyokushin karate (6), mixed martial arts (4), mountaineering (1), Olympic karate (1), orienteering (3), Oyama karate (4), shidokan karate (5), short (2) and long runners (8), shotokan karate (6), snowboard (3), sports climbing (3), swimming (3), taekwondo (5), target shooting (1), toboggan (3), volleyball (7), and wrestling (2). The other 1142 athletes were sportsmen with only national (Polish) sports successes. Only the best results of the respondents on the day of

the study were included in the study. The achievements of already tested players have not been updated.

#### *2.2. Method*

The NEO-FFI Personality Questionnaire was selected to examine the athletes' personality in terms of the Big Five factor model [25]. The selection criterion was justified by: the location of NEO-FFI in the theoretical model and relatively large methodological formalization compared to other approaches developed within the five-factor personality model; good psychometric characteristics; rich factual documentation of the measurement accuracy for the factors of the original version, which allows to assume that the inventory may be useful in scientific and practical research; and duration time acceptable for the athletes.

The items of the NEO-FFI Personality Questionnaire are formed by five scales measuring the factors of the Big Five model. They are marked with abbreviations of the first letters of the factors: neuroticism, extraversion, openness to experience, agreeableness, and conscientiousness. For the purposes of this study, the acronym NEOAC was adopted, i.e., the above-mentioned sequence of factors.

The NEO-FFI Personality Questionnaire is internally consistent. Its validity was demonstrated on the basis of research on the relationship between the results of the questionnaire and the assessments of the subjects made by observers, the heritability of the measured traits, and their correlation with other dimensions of personality and temperament. The factor validity was also verified. The results allow for a full description of the respondents' personality in the five-factor approach of the Big Five and forecasting their adaptation possibilities to the professional environment [24,25]. Moreover, the NEO-FFI assumes a maximum examination time of one hour. Such duration of the study was acceptable to athletes who expressed free will to participate.

#### *2.3. Data Analysis*

In order to verify the research problem, statistical analyses were performed using the IBM SPSS Statistics, version 25 (IBM Polska, Warsaw, Poland). Beforehand, basic descriptive statistics were calculated for each sports discipline included in the study. It was decided not to calculate normal distribution tests for each personality trait in each discipline due to the relatively small sample size and the multiple comparisons. Both of these factors could render the conclusions drawn from the results of such tests incorrect. For this reason, the so-called the rule of thumb was used for the analysis of skewness value. If the skewness value for a given variable ranged from −2 to 2, then it could be concluded that the distributions of these variables are not too asymmetric, which allows for the use of parametric tests. In the case of differently classified data comparisons, the skewness values for the compared groups were checked before the analysis. Each time, they fell within the accepted range. In order to solve the research problem, Student's *t*-tests for independent samples and a logistic regression model were performed. This model presents an exploratory analysis to see how individual personality traits will predict belonging to the champion group. It was necessary as *t*-tests only verify differences in a single dimension.

#### *2.4. Procedure*

All respondents consented to the processing of data related to their participation in the research by the researcher.

The project received a positive opinion (number 20/2019) of the Senate Committee on Ethics of Scientific Research at the University School of Physical Education in Wrocław.

#### **3. Results**

The sample of champions consisted of 118 men (9% of the respondents), and the sample of other athletes, 1142 men (91% of the respondents). In order to verify the research

of the effect.

**3. Results**

problem, a number of Student's *t*-tests were carried out for independent samples using the bootstrapping method, set at 10,000 samples and a 95% confidence interval. Five Student's *t*-tests were performed, and the statistical significance level for the analyses of variance was calculated as α = 0.01. The sample of champions consisted of 118 men (9% of the respondents), and the sample of other athletes, 1142 men (91% of the respondents). In order to verify the research problem, a number of Student's t-tests were carried out for independent samples using the bootstrapping method, set at 10,000 samples and a 95% confidence interval. Five Student's t-tests were performed, and the statistical significance level for the anal-

The project received a positive opinion (number 20/2019) of the Senate Committee on Ethics of Scientific Research at the University School of Physical Education in

*Int. J. Environ. Res. Public Health* **2021**, *18*, x FOR PEER REVIEW 5 of 10

The test results showed statistically significant differences in all personality traits from the Big Five model. In the case of neuroticism, a very strong difference effect persisted. A moderately strong effect was observed for extraversion and conscientiousness, and weak effects were observed for openness to experience and agreeableness. Sports champions were characterized by a lower level of neuroticism and a higher level of extraversion, openness to experience, agreeableness, and conscientiousness than the group of other athletes. The exact values of the performed tests are presented in Table 1. The samples are presented graphically in Figure 1. yses of variance was calculated as α = 0.01. The test results showed statistically significant differences in all personality traits from the Big Five model. In the case of neuroticism, a very strong difference effect persisted. A moderately strong effect was observed for extraversion and conscientiousness, and weak effects were observed for openness to experience and agreeableness. Sports champions were characterized by a lower level of neuroticism and a higher level of extraversion, openness to experience, agreeableness, and conscientiousness than the group of other athletes. The exact values of the performed tests are presented in Table 1. The

**Table 1.** Analysis of differences between champions and other athletes in the intensity of personality traits. samples are presented graphically in Figure 1.


\* correction for heterogeneity of variance; *t*—t statistic value; *p*—significance level; and Cohen's *d*—a measure of the size of the effect. \* correction for heterogeneity of variance; *t*—t statistic value; *p*—significance level; and Cohen's *d*—a measure of the size

**Figure 1.** Line graph of personality profiles; breakdown into champions and other athletes. **Figure 1.** Line graph of personality profiles; breakdown into champions and other athletes.

Finally, in order to verify the analyzed results, a logistic regression model was prepared where, based on personality traits, an attempt was made to classify the respondents into the group of sports champions and other athletes.

In the first step, all personality traits were introduced as predictors of the athletes' level. The null model was characterized by 90.6% correct classifications, which results from the ratio of the number of other athletes to all research subjects. The classification threshold, based on the ROC analysis, was set to 0.7. The model with five predictors was statistically

significant χ 2 (5) = 425.68; *p* < 0.001, and Nagelkerke's pseudo-R<sup>2</sup> was 0.62, which means that the proposed model explains about 62% of the variance. The Hosmer–Lemeshow goodness of fit test was statistically insignificant χ 2 (8) = 7.49; *p* = 0.485. The entire model correctly classified 94.3% of the observations. The analysis of the significance of the predictors in the discussed model showed that only neuroticism significantly predicted belonging to the champions group or to the other athletes group. For this reason, another model was created in which neuroticism was the only predictor. The second model was statistically significant χ 2 (1) = 423.02; *p* < 0.001, and Nagelkerke's pseudo-R<sup>2</sup> was 0.62. The goodness of fit test was again statistically insignificant χ 2 (7) = 13.44; *p* = 0.062. The overall percentage of correct classifications was also 94.3%. Pseudo-R<sup>2</sup> for one personality variable of logistic regression was 62% of the variance as other athletes are very different from the champions in their level of neuroticism. In the *t*-test analysis, the effect size was *d* = 1.81, which is a very high result. It is rarely seen, but apparently the two groups are quite different in this respect. The other personality measures did not contribute to the percentage of explained variance. Therefore, the second model, with the only predictor being the neuroticism measure, turned out to be as good as the model with five predictors. This means that neuroticism was the key personality trait that predicted the level of achievement among the tested athletes. A relationship was established in the developed model: the lower the level of neuroticism, the greater the probability of being classified as a sports champion. The relationship is presented in Table 2.



β—non-standardized Beta coefficient; β SE—standard error for the Beta coefficient; Wald's χ <sup>2</sup>—chi-square statistics for Wald test; eβ—odds ratio; and R2—statistics of model fit to data (R<sup>2</sup> <sup>×</sup> 100%—percentage of explained variance).

#### **4. Discussion**

The analyses showed statistically significant differences in all personality dimensions in the Big Five five-factor approach; namely: sports champions were characterized by a lower level of neuroticism and a higher level of extraversion, openness to experience, agreeableness, and conscientiousness than other athletes. This personality profile of sports champions confirmed earlier research reports [16,21–23,26], and at the same time negated the research of Mirzaei and colleagues [11], which suggested that only high conscientiousness correlated with sports results.

Whether the personality determinants of success in sport were formed solely in the course of many years of sports career, or already at the beginning of sports practice still remains an open question. Therefore, the opinion of respected scientists such as Allen [17–20], or Vealey [27] cannot be ruled out. Factors disrupting or supporting the development of a young athlete are created by his immediate environment. This, in turn, is expressed in self-esteem, which has a significant impact on the shaping of the personality and competences of talented players.

The logistic regression model analyzed the obtained results. On the basis of the fivefactor personality model, attempts were made to classify the researched population into the group of sports champions or the other athletes group. The research results have shown

that neuroticism was an important personality trait, allowing to classify athletes according to their level of sports achievements; the lower the level of neuroticism, the greater the probability of being classified as a sports champion. The numerous relationships found in the research between personality dimensions and athletes in various randomizations allow us to conclude that the results concerning neuroticism as a determinant of personality success in sport are highly probable and may be universal. The only predictor of sports results, and thus a personality determinant of success in sports, in terms of the Big Five, was neuroticism.

The dimension of neuroticism reflects emotionality in terms of experiencing negative emotions, i.e., emotional adaptation in relation to emotional imbalance. The sports champions were distinguished by very low neuroticism, thus it can be assumed that they were emotionally stable, calm, relaxed, and able to deal with stress without experiencing anxiety, tension, and irritation; whereas other athletes had a higher level of neuroticism compared to the champions. This means that their negative emotions influenced their adaptation to the environment. Neurotic people were prone to irrational ideas, and relatively inadequate to control their drives and cope with stress. This is due to the general excitability of the vegetative system. The reactions are too great in relation to the strength of the acting stimuli. Emotionally unstable competitors experience very strong pre-start conditions and can collapse in the face of important competitions. It can be expected that in difficult situations, their efficiency of perception, speed and accuracy of sensorimotor responses, efficiency of thinking processes, and the quality and effectiveness of action will deteriorate significantly. The dimension of neuroticism includes six formally distinguished components: anxiety, aggressive hostility, depression, impulsiveness, hypersensitivity, and excessive self-criticism. Therefore, champions may be distinguished from other sportsmen by low level of anxiety, which has a positive effect on motivation [6]; low aggressive hostility that triggers the state of start readiness, which translates into the control of arousal before and during the competition, and bravery understood as fighting until the very end [28]; low depressiveness that indicates an optimistic mood and a positive attitude [29]; low impulsiveness that crystallizes emotion control [30]; low hypersensitivity that gives good concentration of attention and the need for strong sensory impressions, as well as the ability to cope with failure and experience success [31]; and finally, low self-criticism that determines self-confidence and self-efficacy [32].

Taking the above into consideration, the greatest cognitive value of this paper is to prove that neuroticism is an important personality condition for success in sport. Therefore, one should adopt broad perspectives of analyses of neuroticism components as mental determinants of sports success. As there is no data regarding whether social factors influence the personality of the surveyed sportsmen, one should also pay attention to the role of the social environment of sportsmen. This knowledge may be useful in the detection and proper development of sports talents, modernization of sports training and better adaptation of athletes to the environment after the end of their career. It is also important to notice that sports activities shape the personality of players [1–4,33]. Therefore, the differences in personality shown in this study can be seen as a consequence of the athletes' success, rather than as a reason for athletes' success, based on their age between 20 and 29. Sports activity could be seen as a self-confidence generator. Under the influence of trainings, adepts start to improve in a given discipline, and this moderates their personalities. Athletes become convinced that they are the authors of their own fate and that they create their own lives. This is why the successes achieved by the players build strong personalities of athletes.

The obtained research results also provide a new argument about the health aspects of sports training (in the context of health through rational, long-term sports training) in personality development. There are few empirical studies on the relationship of motor, technical and tactical training, and the results of personality tests. Hence, the possibilities of a broader interpretation of research results from an interdisciplinary perspective are limited.

At this point, the strengths and limitations of the conducted cognitive experiment should be equally noted. The research sample was homogeneous in terms of ethnicity, gender, and the age range of 20–29 years. Athletes of other nationalities, women, and other age groups were not included. The research was conducted on a large group of respondents from sports disciplines popular in Poland. However, it was not possible to examine athletes from all sports disciplines trained in Poland. The group of champions included Polish athletes with international sports successes. Therefore, the obtained research results can only be applied to a specific population of athletes. Thus, the following conclusion can be drawn: a low level of neuroticism is a personality determinant of success in sport among Polish male athletes between the ages of 20 and 29. However, one must bear in mind that the personality determinants of success in sport in various disciplines are distinct. This is due to the specificity of sports competition in martial arts [21], individual [22], and team [23] sports, as well as different psychological requirements they place on competitors [1,33].

However, the general personality profile of athletes in terms of the Big Five is low neuroticism, high extraversion and conscientiousness, average openness to experience and agreeableness [4,17]. In comparison with the reports by Allen [20], it was noticed that low neuroticism also has a significant role in the personality differentiation of champions from the rest of the athletes. It has been proven that a low level of neuroticism may be a personality determinant of sport success among Polish athletes between the ages of 20 and 29, and its intensity depends on the sports discipline. It is therefore suggested that the coaches analyze the personality conditions of the players for sports competition, as these have a significant impact on the sports results. Hence, in sports theory, one should adopt broad perspectives of personality component analyzes as mental determinants of sports success.

#### **5. Conclusions**

There are differences between champions and other athletes in all personality dimensions in terms of the Big Five. Sports champions were characterized by a lower level of neuroticism and a higher level of extraversion, openness to experience, agreeableness, and conscientiousness in relation to other athletes. Analysis of the obtained data by the logistic regression model proved that only neuroticism was an important personality determinant predicting the level of achievement among the studied athletes: the lower the level of neuroticism, the greater the probability of classifying the athlete to the champion group. Champions are presumably balanced and usually resistant to stress. They are not very sensitive to various stressors. They have better attention span, and they do not panic in difficult situations. Their well-being is stable, and their emotional reactions are adequate to the stimuli. Therefore, sports development of athletes without the knowledge of the specific features and personality structure of various sports representatives may be an artificial and ineffective activity. It remains an open question whether the personalities of the champions were shaped only in the course of many years of their sports career, or whether they already distinguished champions at the beginning of their sports practice. Therefore, based on the result of the research, it can be argued that personality differences should be seen as a consequence of the athletes' success, rather than as a reason for the athletes' success, based on their age between 20 and 29.

**Author Contributions:** Conceptualization, P.P.; methodology, P.P.; software, P.P.; validation, P.P.; formal analysis, P.P.; investigation, P.P.; resources, P.P.; data curation, P.P.; writing—original draft preparation, P.P. and Z.P.; writing—review and editing, P.P. and Z.P.; visualization, P.P.; supervision, P.P.; project administration, P.P.; and funding acquisition, P.P. and Z.P. Both authors have read and agreed to the published version of the manuscript.

**Funding:** This research received no external funding.

**Institutional Review Board Statement:** The study was conducted according to the guidelines of the Declaration of Helsinki, and approved by the Senate Committee on Ethics of Scientific Research at the University School of Physical Education in Wrocław, approval no. 20/2019.

**Informed Consent Statement:** Informed consent was obtained from all subjects involved in the study.

**Data Availability Statement:** The authors confirm that the data supporting the findings of this study are available within the article.

**Acknowledgments:** Not applicable.

**Conflicts of Interest:** The authors declare no conflict of interest.

#### **References**


## *Article* **Sleep Quality in Chilean Professional Soccer Players**

**Carlos Jorquera-Aguilera <sup>1</sup> , Guillermo Barahona-Fuentes <sup>2</sup> , María José Pérez Peña <sup>3</sup> , María Mercedes Yeomans Cabrera <sup>4</sup> and Álvaro Huerta Ojeda 2,\***


**Abstract:** Recent research has shown that good sleep quality has a positive effect on physical performance. However, sleep quality in Chilean professional soccer players is unknown. The purpose of this study was to determine sleep quality in Chilean professional soccer players. It was a cross-sectional, explanatory study with observable variables. The sample consisted of 94 Chilean male soccer players belonging to four professional clubs. The main variable was the Sleep Quality Index, evaluated through the Pittsburgh questionnaire (Spanish version). After estimating sleep quality individually, the four professional soccer clubs' comparison was performed through a onefactor ANOVA. The Pearson test was used to relate the questionnaire variables; the significance level was *p* < 0.05. In the global analysis of the Pittsburgh Sleep Quality Index, a value of 4.75 ± 2.29 on a scale of 0–21 was observed, with no significant differences between the clubs evaluated (*p* > 0.05). Based on the results obtained, Chilean male professional soccer players present good sleep quality. However, the high values of "sleep latency" and "sleep disturbances" are indicators that should be worked on by the multidisciplinary team of each professional club. They should develop strategies to improve sleep hygiene, encourage good sleep, and fall asleep efficiently.

**Keywords:** sleep quality index; physical performance; professional soccer players

#### **1. Introduction**

Sleeping is a fundamental biological and physiological need of the human being. In fact, good sleep quality is a relevant factor for correct organic functioning; sleeping is regulated by the hypothalamus and cannot be omitted without experiencing harmful consequences for people [1] since, among other actions, it allows regulating and restoring psychological and physical functions [2]. Likewise, due to the brain's multiple electrical activities during sleep, sleeping is considered a state of dynamic consciousness [3,4]. Specifically, the brain activity developed during the hours of sleep modifies the organism's functioning; body temperature, specific hormone levels, blood pressure, and respiratory frequency might change [5]. Consequently, these organic changes, the product of brain activity during sleep, intervene in energy restoration processes, learning, memory, and cognition [1,6], favoring a state of recovery of people [7]. However, despite the existing evidence, a considerable number of people sleep fewer hours than necessary (sleep restriction) and have a low sleep quality [8].

Both the experience reported by patients [9] and scientific evidence [10] have established that people should sleep between 7 and 9 h a day for good sleep quality. On the contrary, generating a sleep restriction below the recommended time range (7 to 9 h) could generate a poor sleep quality [11], affecting the health of both common people [12,13] and

**Citation:** Jorquera-Aguilera, C.; Barahona-Fuentes, G.; Pérez Peña, M.J.; Yeomans Cabrera, M.M.; Huerta Ojeda, Á. Sleep Quality in Chilean Professional Soccer Players. *Int. J. Environ. Res. Public Health* **2021**, *18*, 5866. https://doi.org/10.3390/ ijerph18115866

Academic Editors: Manuel Gómez-López, Antonino Bianco and Carlos Marques da Silva

Received: 22 March 2021 Accepted: 28 April 2021 Published: 29 May 2021

**Publisher's Note:** MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affiliations.

**Copyright:** © 2021 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https:// creativecommons.org/licenses/by/ 4.0/).

elite athletes [14]. In recent years, it has been shown that poor sleep quality is associated with alterations in cognitive function, mood changes [15], endocrine system dysfunction [16], and depression of the immune system [17], among others [18]. Similarly, Spiegel et al. [19] showed that a four-hour daily sleep restriction for two consecutive nights reduced leptin levels and increased ghrelin levels in healthy adults; the researchers also associated these hormonal changes with an increase in hunger and appetite [19]. The latter could explain the modifications in body mass and overweight in people with sleep restrictions [20]. This background allows us to observe that sleep restriction, due to environmental factors, lifestyles, or diseases [21], affects the entire population [20,22–24].

There is evidence of deficiencies in the quality and quantity of sleep in elite athletes [14]. Specifically, Mah et al. [25] investigated the effects of sleep extension on sports performance, reaction time, mood, and daytime sleepiness in college basketball players, demonstrating that optimal sleep is probably beneficial for achieving maximum sports performance. Conversely, it has been established that poor sleep quality affects anxiety levels [26]; the latter condition is considered a negative emotion that decreases athletic performance [27], as it affects athletes' perception before a competition [26]. To mitigate sleep restrictions in elite athletes, generated by uncontrolled variables such as anxiety, and because high sleep quality is a critical component for sports performance [28], multidisciplinary teams have implemented sleep education and sleep hygiene methodologies [29–31]. However, before implementing sleep hygiene programs, sleep habits and sleep quality should be evaluated in different populations [32,33].

Sleep habits and sleep quality are well documented in the adult population [32] and some populations with special needs [20]. In this sense, and considering that elite athletes have been described as populations with special requirements and needs [34], sleep quality and hygiene have been a focus of attention [29–31]. Another critical factor within sleep hygiene, which has also been extensively studied, is the circadian cycle [35,36]; indeed, there is strong evidence linking disrupted sleep and circadian misalignment with weight gain, obesity, and adverse effects on individuals' metabolic health [35]. Therefore, as evidenced, adequate sleep at an appropriate time is essential for biological systems [36] and sports performance [28]. In this context, soccer is a social phenomenon that ranges from recreational to professional practice [37]. Likewise, there is evidence that soccer practice generates cardiovascular and metabolic benefits, helping to prevent diseases such as diabetes and hypertension [38]. Therefore, and considering that a large part of the population practices this sport, programs have been implemented to increase physical capacities [39], injury prevention [37] and good practices during rest periods [31]. Consequently, evaluating parameters such as sleep quality in athletes, specifically in Chilean professional soccer players, is a priority since good sleep hygiene ensures energy restoration, improves learning, memory, and cognition [1,6].

Despite the existing evidence and bearing in mind that many athletes present deficiencies in sleep quality and insomnia [40], studies in Chilean elite athletes are scarce [33]. In this context, only sleep quality, somnolence, and insomnia have been documented on Chilean elite Paralympic athletes [33]. Based on this background, and considering that sleep quality is a variable that conditions optimal sports performance [28], this study's main purpose was to determine sleep quality in Chilean professional soccer players. Secondary objectives were a) to quantify the number of sleep hours of Chilean professional soccer players; and b) to demonstrate, if there are, differences in sleep quality between different Chilean professional soccer clubs.

#### **2. Materials and Methods**

#### *2.1. Research Design*

Explanatory, cross-sectional research, with observable variables [41].

#### *2.2. Participants*

Ninety-four (94) Chilean male soccer players belonging to four professional clubs volunteered to participate in this study (*n* = 94; age = 25.6 ± 5.3). The evaluated clubs were Unión Española (*n* = 20), Deportes Antofagasta (*n* = 18), Palestino (*n* = 32), and Universidad de Chile (*n* = 24). The type of sampling was non-probabilistic by convenience. To be included in the study, participants had to be men, practice professional soccer for a minimum of four years, and train regularly between four to six times per week. The latter excluded participants with pathologies, musculoskeletal injuries, or a training frequency of fewer than four times a week. Before answering the questionnaires, and with all doubts resolved, the participants signed the informed consent form.

#### *2.3. Procedure*

After reading and signing the informed consent form, all participants were asked to answer the Spanish version [42] of the Pittsburgh Sleep Quality Index (PSQI) questionnaire [43]. Both the informed consent and the questionnaire were applied at the training site and before beginning any type of physical exercise.

#### *2.4. Materials*

PSQI. This questionnaire was created by Buysee et al. [44] and adapted to Spanish by Jiménez-Genchi et al. [42]. The instrument's objective is to self-assess the quality and subjective disturbance of sleep during a time interval of one month. Seven components assess this sleep quality: subjective sleep quality, sleep latency, sleep duration, sleep efficiency, sleep disturbances, the use of sleep medications, and daytime dysfunction [42]. Although the PSQI does not inquire about the specificity of the medication used to fall asleep, it is crucial to record them as psychiatric [45] and non-psychiatric medication qualitatively [46]. The questionnaire has two parts; the first consists of four items (each item with an open question): 1. During the past month, when have you usually gone to bed at night? 2. During the past month, how long (in minutes) has it usually taken you to fall asleep each night? 3. During the past month, when have you usually gotten up in the morning?, and 4. During the past month, how many hours of actual sleep did you get at night? The second part has six items with a total of 20 questions (each of these questions has four alternatives: 5. During the past month, how often have you had trouble sleeping because you... 6. During the past month, how would you rate your sleep quality overall? 7. During the past month, how often have you taken medicine (prescribed or "over the counter") to help you sleep? 8. During the past month, how often have you had trouble staying awake while driving, eating meals, or engaging in social activity? 9. During the past month, how much of a problem has it been for you to keep up enough enthusiasm to get things done? and 10. Do you have a bed partner or roommate? The participant must only answer up to item nine of the questionnaire since item 10, which consists of five questions, must be answered by the "bed partner." Only the self-assessed questions are included in the scoring. The 19 self-assessed items are combined for the scores for the seven "components." Each of them has a range of 0–3 points. In all cases, a score of "0" indicates no difficulty, while a score of "3" indicates severe difficulty. The scores of the seven components are then summed to obtain an "overall" score, with a point range 0–21, "0" indicating no difficulty, and "21" indicating severe difficulty in all areas [42]. It should be noted that, for this study, a score ≤5.0 was considered good sleep quality [47].

#### *2.5. Statistical Analysis*

The results obtained in the PSQI questionnaire are presented with their mean data and respective standard deviation (SD). The data were subjected to the Kolmogorov and Smirnov normality test. Comparison of the variables between the different professional soccer clubs was performed through a one-factor ANOVA. We used the Student's t-test to compare participants who scored ≤5.0 with those who scored over 5 points on the Pittsburgh questionnaire on the sleep variables. On the other hand, the effect size was

calculated using Cohen's d-test. The latter analysis considers an insignificant (d < 0.2), small (d = 0.2–0.6), moderate (d = 0.6–1.2), large (d = 1.2–2.0), or very large (d > 2.0) effect. To relate the different variables of the questionnaire, we used the Pearson test. This correlation coefficient was interpreted through classifications described by Mukaka [48], in which 0.9–1.0 corresponds to a very high correlation; 0.7–0.9 high correlation; 0.7–0.5 moderate correlation; 0.3–0.5 low correlation; and 0.0–0.3 very low correlation. Statistical analysis was performed with SPSS software. The significance level for all data was *p* < 0.05.

#### **3. Results**

The analysis showed that the 94 Chilean male professional soccer players sleep an average of 7.27 ± 0.92 h per day. In addition, it was observed that 53% sleep less than 7 h a day. Simultaneously, 45% of the soccer players responded that they take between 20 and 40 min to fall asleep, 19% take between 50 and 120 min to fall asleep, and 36% manage to fall asleep in less than 10 min. A relevant data within this analysis was the bedtime of the soccer players (this time corresponds to the sum of the time to fall asleep and the effective sleep time), reaching 8.20 ± 1.00 h. At the end of the analysis, it was also possible to observe a significant difference in bedtime between the different soccer clubs evaluated (*p* < 0.05). The data and their significance are reported in Table 1.



SD: standard deviation; min: minutes; \*: *p* < 0.05 between all groups.

According to the scores obtained in the PSQI questionnaire [42], it was observed that two of the seven components (component 2: sleep latency and component 5: sleep disturbances) had a value over one on a scale of 0–3. This observation was made in both analysis by clubs and as a whole. In the global analysis of the Pittsburgh Sleep Quality Index, it was observed a value of 4.75 ± 2.29 on the 0–21 scale and no significant differences between the clubs evaluated (*p* > 0.05). When comparing the soccer players who scored ≤5.0 with those who scored over five points on the Pittsburgh questionnaire in the sleep variables, we could observe significant differences in the time to fall asleep (*p* < 0.001) and in 6 of 7 components of the Pittsburgh questionnaire (*p* < 0.05). The data are reported in Tables 2 and 3.

Considering question 5 of the PSQI questionnaire, "During the past month, how often have you had trouble sleeping...?", it was observed that 62.8% of the participants reported difficulty falling asleep at some point during the last month. Simultaneously, 78.7% answered they woke up during the night or in the early morning, and 72.3% woke up to use the bathroom. The details of each of the responses to question 5 of the questionnaire are reported in Table 4.


**Table 2.** PSQI in Chilean male professional soccer players.

PSQI: Pittsburgh Sleep Quality Index; SD: Standard deviation.

**Table 3.** Comparison between male professional soccer players with scores ≤ 5.0 and above five on the Pittsburgh questionnaire.


SD: standard deviation; min: minutes; ES: effect size; \*: *p* < 0.05 between ≤5.0 and >5.0 group.

**Table 4.** Detail of responses to question 5 of the PSQI questionnaire.


PSQI: Pittsburgh Sleep Quality Index.

Pearson's test showed a high correlation between time to fall asleep and sleep latency (r = 0.79; *p* < 0.01), a high inverse correlation between participants self-reported effective sleep time and sleep duration (r = −0.72; *p* < 0.01), and a good inverse correlation between effective sleep time and overall PSQI score (r = −0.51; *p* < 0.01). The detail of all correlations is reported in Table 5.

**Table 5.** Correlations between time and effectiveness of sleep with the PSQI components in Chilean male professional soccer players.


PSQI: Pittsburgh Sleep Quality Index; C1: subjective sleep quality; C2: sleep latency; C3: sleep duration; C4: sleep efficiency; C5: sleep disturbances; C6: use of sleeping medication; C7: daytime disfunction; min: minutes; r: Pearson's correlation index; Sig. bil: significance (bilateral); \*: alpha < 0.05 (bilateral); \*\*: alfa < 0.01 (bilateral).

#### **4. Discussion**

Concerning the main objective of the study, to determine sleep quality in Chilean male professional soccer players, the Pittsburgh questionnaire analysis [42] yielded a value of 4.75 ± 2.29; this value is considered a good sleep quality [47]. In this sense, Swinbourne et al. [49] evaluated sleep quality in professional athletes; these researchers reported a 5.9 ± 2.6 in the Pittsburgh questionnaire and concluded that more than 50% of the evaluated athletes had poor sleep quality (≥5.0 points). In parallel, Khalladi et al. [50] evaluated the sleep characteristics of professional soccer players in the Qatar Stars League. The researchers reported a 68.5% prevalence of players with poor sleep quality (≥5.0 points), concluding that professional soccer players should be more aware of the importance of good sleep quality. It appears that the existing evidence on sleep quality in performance athletes shows worrying indicators [49], even more so in professional soccer players [50]. However, both the overall analysis and the present study showed good sleep quality in Chilean male professional soccer players when comparing the different professional soccer clubs (4.75 ± 2.29). In fact, there were no significant differences between the clubs evaluated (*p* > 0.05), and only one club exceeded five points in the Pittsburgh questionnaire [42].

A vital background to analyze is the hours of sleep reported by the present evaluated clubs (7.27 ± 0.92 h); this period is within the National Sleep Foundation's recommendations for young people (7–9 h) [10]. Apparently, without considering sleep quality, evidence shows that the amount of sleep hours reported by professional athletes is within the recommendations described above [31,49,50]. An example of this is the data reported by Swinbourne et al. [49]; the researchers evaluated the hours of sleep of 175 professional athletes from various disciplines, reporting an average of 7.9 ± 1.3 h of sleep per day. Likewise, Khalladi et al. [50] reported an average value of over 7.5 h of sleep in professional soccer players, while Caia et al. [31] reported that professional rugby players sleep an average of 7.28 ± 0.8 h per day. However, although evidence shows that elite athletes sleep the recommended number of hours [10], it has also been documented that athletes have sleep problems, identifying three factors that could alter sleep: (a) training, (b) travel, and (c) competition [14]. Consequently, correct sleep hygiene could guarantee positive changes in sleep behavior and a more restful rest [31], which could impact better performance in training and/or competition.

In the present study, when comparing the number of hours of sleep between male professional soccer players who scored ≤ 5.0 to those who scored over five points on the Pittsburgh questionnaire [42], there were no significant differences between these two groups of soccer players (*p* > 0.05). However, evidence shows a significant difference between those who score above and below five points—concerning the number of sleeping hours [50]. Despite this, there is still a lack of evidence to ensure that a score above five is associated with sleep outside the National Sleep Foundation's recommendations (7–9 h) [10]. When, the same comparison was made in the time to fall asleep, a significant difference was found between scores ≤ 5.0 and above 5 (*p* < 0.001). In this sense, Gupta et al. [14] developed a study that aimed to profile the objective and experienced sleep characteristics among elite athletes. They concluded that cognitive arousal before sleep appears as one of the mechanisms responsible for a longer time to fall asleep [14]; therefore, proper sleep hygiene education may lead to positive sleep behavior changes, which is likely to be beneficial in achieving peak athletic performance [31]. In the present study, regarding the overall PSQI score [42] and the comparison between soccer players with scores ≤5.0 and above five, no significant differences were found between the two groups (*p* > 0.05). However, a previous study showed significant differences in this index when purchasing participants with scores ≤ 5.0 and over five [50]. Despite this evidence, finding significant differences in these variables does not ensure causality since the results may be conditioned by sample size, group distribution, range, mean values, and standard deviations.

In parallel, a good inverse correlation between effective sleep time and the overall PSQI score was evident (r = −0.51; *p* < 0.01). However, due to the limited evidence relating sleep quality to athletic performance [28], it would be risky to attribute poor athletic performance to sleep deprivation and poor sleep quality. In this regard, Oliver et al. [51] evaluated whether a night of sleep deprivation impaired performance in a treadmill test. The researchers reported decreased performance with limited effect on running pace, and on cardiorespiratory and thermoregulatory function, but no effect on exercise perception. Similarly, Poussel et al. [52] evaluated the relationship between sleep strategies and performance during the 2013 North-Face Ultra-Trail du Mont-Blanc. At the end of the investigation, it was reported that runners who adopted a sleep management strategy based on more sleep time before the race completed the race faster (*p* = 0.02). Furthermore, the researchers reported that most finishers seemed to be aware of the importance of developing sleep management strategies. Contrarily, Blumert et al. [53] compared the effects of 24 h of sleep deprivation on weightlifting performance, concluding that 24 h of sleep deprivation does not affect weightlifting performance. Based on the evidence, when analyzing the effect of sleep deprivation on sports performance, there is a marked difference between strength and endurance sports. Apparently, in the latter sports discipline, sleep deprivation significantly affects sports performance [51,52]. A separate analysis is needed for team sports since most research is focused on the description of

sleep quality of athletes [31,49,50] and not on an association between good sleep quality and sports performance [25]. An example of this is the study by Mah et al. [25] who evaluated the effect of sleep length on reaction time, mood, and daytime sleepiness in college basketball players, concluding that optimal sleep is likely to be beneficial for peak athletic performance. Despite this, it is risky to claim that good sleep quality guarantees an athletic outcome in team sports.

Another critical component to consider is the high percentage of male soccer players who reported difficulty falling asleep at some point during the last month (>63%). This difficulty in falling asleep may be directly related to the sleep-wake cycle [54]; in this sense, it has been shown that an instantaneous interruption of sleep as a result of a response to a biological or physiological signal [55] can affect the circadian rhythm of athletes [56]. The latter corresponds to daily cycles that regulate the physiological functions of the organism [57]. Its alteration may contribute to an increased risk of diseases [58] and a decrease in sports performance [56]. Different studies have shown that circadian rhythms cause variations at the hormonal level, in gene expression and body temperature [57,59], directly influencing different components relevant to sports performance such as muscular strength [60], flexibility [59], aerobic endurance [61], and anaerobic power [62]. The sleepwake cycle is one of the most relevant circadian rhythms for athletes [54], indicating daily rest time [57]. This cycle can be negatively altered due to national or international travel [63], generating a decrease in sports performance due to fatigue and/or jet lag [64]. On the other hand, a score over five in the PSQI could indicate an altered circadian cycle [11]. Since the alteration of the circadian cycle could affect athletes' physical recovery [56], all the evaluated players should pay attention to it (especially players from Universidad de Chile, who as a whole obtained a score over five in the Pittsburgh questionnaire [42]). This alteration may develop health problems [58] and a decrease in sports performance [14,56].

There are several strategies to improve sleep quality of athletes. As a first measure is the use of electronic devices. An example of these are smartwatches; these devices allow monitoring and evaluating sleep quality efficiently and reliably [65,66]. Another strategy adopted by some athletes to improve sleep quality, and thus sports performance, is the increase of sleep time some nights before the competition [52]. Moreover, in the case of experiencing an acute period of sleep loss, it is suggested to focus more on psychological aspects (motivation) than on the sport's physiology [53]. Finally, the data obtained reinforces the need to educate professional soccer players and the multidisciplinary team on correct sleep hygiene [29–31].

#### *Limitations*

The results of our research show good sleep quality in Chilean male professional soccer players. However, the study did not have a control group to contrast the results with. There was only a qualitative comparison to the recommended values for good sleep quality and its analysis.

As a suggestion for future research and considering the specificity of the group evaluated, we recommend including stress and anxiety evaluations since these factors are mentioned as critical influencers on athletes' sleep quality and performance.

#### **5. Conclusions**

According to the results obtained, Chilean male professional soccer players have a good sleep quality. However, the high values of "sleep latency" and "sleep disturbances" are indicators that should be worked on by the multidisciplinary team of each professional club, generating strategies to improve sleep hygiene, encouraging good sleep, and efficient ways of falling asleep.

#### **6. Practical Applications**

Multidisciplinary teams working with elite athletes must cover all variables associated with sports performance. For this reason, assessing and improving sleep quality is

fundamental to ensure proper recovery between training sessions. Consequently, an easy way to monitor sleep quality is through the PSQI. However, to obtain high reliability rates in the application of this test, athletes must be familiarized with it. In this sense, and to increase the reliability of the test, we recommend that multidisciplinary teams regularly apply it to athletes. Finally, in assessing poor sleep quality, we suggest applying sleep hygiene programs to athletes, including a personalized study of the circadian cycle.

**Author Contributions:** C.J.-A. and Á.H.O.: conception, methodology, investigation, data curation, writing—original draft preparation, writing—review and editing. G.B.-F., M.J.P.P. and M.M.Y.C.: visualization and writing—review and editing. Á.H.O.: supervision and project administration. All authors have read and agreed to the published version of the manuscript.

**Funding:** This research received no external funding.

**Institutional Review Board Statement:** The Ethics Committee of Universidad Mayor approved the study and the informed consent. The study was conducted under the Declaration of Helsinki (WMA 2000, Bošnjak 2001, Tyebkhan 2003), establishing the fundamental ethical principles for research involving human subjects.

**Informed Consent Statement:** Informed consent was obtained from all subjects involved in the study.

**Data Availability Statement:** The data base of the study can be downloaded from the following link: https://figshare.com/articles/dataset/Basedate/14256491 (accessed on 29 April 2021).

**Conflicts of Interest:** The authors declare no conflict of interests.

#### **References**


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