Sleep and musculoskeletal complaints among elite athletes of Santa Catarina*

BACKGROUND AND OBJECTIVES : There are many physio-logical processes going on during sleep which are important for physical and emotional balance and especially for motor function, essential for athletes’ performance. This study aimed at investigating associations between sleep duration and quality and musculoskeletal complaints among elite athletes of the state of Santa Catarina. METHODS : Four hundred and fifty-two athletes from various sports have been investigated on issues related to sleep (duration, quality) and musculoskeletal complaints in body parts through the Pittsburgh Sleep Quality Index and the Nordic Musculoskeletal Questionnaire, respectively. The association between sleep and muscle pain was analyzed by Spearman’s correlation of “number of painful body parts” and “Pittsburgh Sleep Quality Index scores”. RESULTS : Mean age of athletes was 21.16 years (5.82), being 61.1% females and 38% with poor sleep quality and association between the amount of nighttime awakenings with nocturnal pain (p <0.001). There has been high prevalence of musculoskeletal pain, more evident on knees, shoulders, ankle/feet and low back. The number of painful parts was correlated (r=0.216) with higher Pittsburgh Sleep Quality Index scores (p<0.001). CONCLUSION : Athletes had high prevalence of poor sleep quality and musculoskeletal pain complaints, especially on knee, shoulders, back and ankle/feet. The correlation between poor sleep quality and pain was more evident as the number of affec-ted body parts increased. Athletes with poorer sleep quality had more pain as compared to those with sleep duration changes, suggesting that musculoskeletal complaints are associated to athletes’ sleep quality rather than to sleep duration.


INTRODUCTION
Human beings should remain sleeping for most of the day, at least one third of it.Sleep is one of the most vital physiological functions for life and is related to several fundamental events for the maintenance of health [1][2][3] .Within this context, studies describe physiological mechanisms which relate sleep to major issues of life, such as energy restoration 4,5 , maintenance of immune system function 6 , neuronal plasticity promotion 7 and growth hormone secretion 8 .Sleep is also fundamental for athletes' good motor performance, especially considering the necessary recovery after hours of training [9][10][11][12][13] .Authors [14][15][16][17] state in their studies that restorative and good quality sleep is in fact critical for athletes considering sports demands such as remaining alert during training and competitions.It is known that elite sports should not be a priori considered synonym to health 18,19 , considering the negative events that training, aiming at sports performance, may bring to athletes, with emphasis to constantly living with pain.Studies on motor performance show high prevalence of pain, such as the study by Dore & Guerra 20 with professional ballet dancers, which has identified general prevalence of 70.2% of moderate and severe pain reaching 85.8% in the lumbar region.So, it is necessary to more thoroughly understand possible variables which might prevent common pain among sportsmen and, in this sense, Atkinson & Davenne 21 , and Halson 13 state that adequate sleep improves athletes' general health status, decreasing the risk for injuries and pain.Discussion about relations between sleep and pain is recent and needs to be deepened.Several authors discuss possible physiological mechanisms relating sleep to pain, considering, for example, that secretion of substances such as ghrelin would be involved with sensitivity to pain [22][23][24][25] .It is observed that scientific studies support the relevance of sleep for sports performance and for the success of athletic competitions.However, it is possible to identify major scientific knowledge gaps about the sleep of athletes when associated to pain.One should also emphasize the lack of studies investigating the sleep-wake cycle in Brazilian athletes.This study aimed at investigating associations between sleep duration and quality and musculoskeletal pain complaints in elite athletes of the state of Santa Catarina, Brazil.

METHODS
This study population was made up of athletes of different modalities, enrolled in the largest multisport competition of the state of Santa Catarina, Brazil, in which participate elite athletes of the state.Participate in this competition athletes of different Santa Catarina regions, after three eliminatory competitive stages (municipal, microregional and regional).Considering the population of athletes of the latest competition (4,720) and for the sample to be representative, minimum number of athletes indicated by means of Rodrigues equation 26 was 356 athletes, for a sample error of 5%.Athletes from different state regions, represented by delegations with the highest number of enrolled modalities were invited to be part of the sample.After authorization of official agencies promoting the competition, delegations with the highest number of enrolled modalities were invited to participate in data collection.Questionnaires were anonymously answered by athletes agreeing to participate in the study, being supervised by researchers.Questionnaire had socio-demographic information on gender and age, in addition to evaluating sleeprelated issues and musculoskeletal complaints..This questionnaire identifies the level of complaints for each body part (neck, shoulders, upper back, elbows, wrists/hands, low back, hip/thighs, knees and ankles/feet), and four questions were asked, for which answers could be "yes" (with pain) or "no" (no pain).Questions were: "Did you have problems such as pain, tingling/numbness on … in the last 12 months?";"Were you prevented from performing normal activities (for example: work, home activities, leisure) due to problems on … in the last 12 months?";Have you looked for some health professional (physician, physiotherapist) due to this condition on … in the last 12 months?";and "Have you had any problem on … in the last seven days?"This tool was validated for Brazil by Pinheiro, Troccoli & Carvalho 30 .Descriptive analyses (means, frequencies and standard deviation) were performed.Kruskal-Wallis test was used to compare continuous variables among groups; and Chi-square test was used to check associations among variables.Spearman correlation was used to correlate variables "number of painful body parts" and "PSQI score".For all analyses significance level was 5%.This study was approved by the Ethics Committee for Research with Human Beings, UDESC (n.666548 -2013).

RESULTS
Participated in the sample 276 female athletes and 176 male athletes, with mean age of 21.16 (5.83) years.A total of 622 questionnaires were distributed to athletes and response rate was 72.66% (452 returned).The prevalence of short duration of sleep (<8 hours) was 48.5%.In addition, 38% of the sample was considered as having poor sleep.Many athletes, 55.6% and 34%, respectively, have reported sleep problems due to night time awakenings and pain during sleep (Table 1).There has been association between number of night time awakenings and night time pain (p<0.001).Table 2 shows prevalence of musculoskeletal complaints according to body regions.With regard to pain, tingling/numbness in the last 12 months, there has been high prevalence on most investigated body parts, especially on knees (50.6%), shoulders (47.5%) a low back (45.7%).These parts, together with ankle/feet were those preventing the most athletes' daily life activities in the last 12 months.Lower limbs (knees and ankles/feet) were the parts leading more athletes to visit health professionals in the last year.Finally, knees and shoulders had highest acute effect of musculoskeletal complaints in the last 7 days.Considering that knee was the joint with the highest prevalence of complaints on most investigated situations (problems with pain, tingling/numbness in the last 12 months, visit to health professionals and musculoskeletal problems in the last 7 days), figure 1 illustrates differences between mean sleep duration and PSQI scores between athletes with and without complaints.Based on this figure it is possible to identify that athletes with knee pain in the last 7 days had shorter sleep duration (p=0.036) and poor sleep quality (p=0.001).* Nordic Questionnaire domains for body parts with musculoskeletal complaints. (1)"Have you had problems such as pain, tingling/numbness on ... in the last 12 months?" (2)Were you prevented from performing normal activities (for example, work, home activities, leisure) due to a problem on ... in the last 12 months?" (3)"Have you visited some health professional (physician, physiotherapist) due to this condition on ... in the last 12 months?" (4)"Have you had any problem on … in the last 7 days?"Source: Primary data (2014).Table 3 shows musculoskeletal complaints prevalence, according to groups with short sleep duration and with adequate duration and to good or poor sleep quality.These results indicate differences for most body parts considering sleep quality, that is, those athletes with poor sleep quality had more frequent musculoskeletal complaints.As example, it is possible to mention the higher number of significance for all Nordic questionnaire domains in our analysis for ankles/feet.With regard to sleep duration, there have been some differences indicating that athletes sleeping less than eight hours are more affected by musculoskeletal complaints.However, these differences were not so evident in all Nordic questionnaire domains, such as in comparing sleep quality and body parts.
In addition, as illustrated in figure 2, there has been positive correlation between the number of parts with pain and PSQI (r=0.216;p<0.001), that is, the more parts with musculoskeletal complaints, the higher PSQI score, indicating poorer sleep quality.As to sleep duration, this analysis has identified just one correlation trend (r=-0.090;p=0.061).

DISCUSSION
For high performance athletes, the act of transposing obstacles is a constant search for overcoming goals, to get to victory.In addition, it is necessary to face physical and psychological challenges, among them pain.So, living with pain or injury has to be somehow faced for their objective to be met 18,19 20 .In comparing both studies it is observed that the two most affected sites were knees and low back, only in a different order.In light of the above, it is noted a trend to force those muscles aiming at performance, both of dancers and athletes, being that both investigated populations were professionals representing the elite of their modalities.
Studies on sleep and pain in athletes are scarce.When observed in other populations, such as fibromyalgia patients, there is similarity of results indicating that better sleep quality is associated to less pain sensation, as reported by Marta et al. 33 ; Moldofsky 34 ; Tonial, Stechman Neto & Hummig 35 .
According to the prevalence of musculoskeletal complaints impairing the most the performance of daily life activities of athletes in the last 12 months, there are knees, shoulders, low back and ankles/feet.Most prevalent body parts which led athletes to look for some health professional in the last 12 months were knees (24.8%), followed by ankles/ feet (23.2%) and shoulders (18.1%).So, it is possible to observe from percentages that lower limbs have taken more athletes to some health professional, since for daily life activities lower limbs directly participate in motion and actions as well as in fast return to training.
In line with this information, Astur et al. 36  In healthy male volunteers, ghrelin, cortisol and human growth hormone plasma levels were measured during two experimental sessions of 24 hours each.In the first, individuals have slept for eight hours (between 11 p.m. and 7 a.m.); in the second they were maintained awaken during the night.During sleep, ghrelin levels have increased in the first part of the night and have decreased in the morning.This nocturnal increase was abolished during sleep deprivation and ghrelin levels have just slightly increased until early morning.Ghrelin secretion during the first hours of sleep was positively correlated to growth hormone concentration peak.So, the conclusion is that nocturnal increase of ghrelin levels is more likely to be induced by sleep than by circadian influences.Still, during the first hours of sleep, ghrelin may contribute for growth hormone secre-tion and for promotion of slow waves sleep (stages 3 and 4), which is an especially restorative sleep stage for cognitive and physiological functions.However, limitations of this study were the use of questionnaires to identify variables related to musculoskeletal complaints with regard to intensity; however, in large samples, this type of strategy allows for the development of athletes' baseline profile with regard to associated variables.

CONCLUSION
There has been high prevalence of poor sleep quality among elite athletes of Santa Catarina and almost half of them sleep less than eight hours.Important percentages of musculoskeletal complaints were also identified, especially on knees, shoulders, low back and ankles/feet.Poor sleep quality was associated to most joints, not being so evident for short sleep duration.Most athletes have reported awaking during the night, once or more than three times a week.And correlating musculoskeletal pain to PSQI this is even more evident, in the measurement of increased body parts affected in the athlete.Athletes with higher numbers of night time awakenings had more night time pain.
Each component has specific scores, being maximum score 21.Scores above five indicate poor sleep quality; • Perception of body pain during sleep by means of the question: "How often have you had sleep problems due to pain?".Possible answers: "a) never last month, b) once or twice a week, c) less than once a week, d) three or more times a week".For the analysis of this variable we have categorized in [a) and c)] = little or no pain during the month; and [b) and d)] = one to three pain episodes during the week during the month; • Night time awakenings: by means of the question: "How often have you had sleep problems because you have awaked in the middle of the night or at dawn?" Possible answers: "a) never last month, b) once or twice a week, c) less than once a week, d) three or more times a week".For the analysis of this variable we have categorized in [a) and c)] = little or no pain during the month; and [b) and d)] = one to three pain episodes during the week during the month; • Musculoskeletal complaints by means of the Nordic Musculoskeletal Questionnaire

Figure 1 .
Figure 1.Sleep duration and Pittsburgh Sleep Quality Index of groups with and without musculoskeletal knee complaints in the last seven days *The highest the PSQI score, the worst the sleep quality; PSQI = Pittsburgh Sleep Quality Index Source: Primary data (2014).

Figure 2 .
Figure 2. Correlations between the number of painful parts (musculoskeletal complaints) in the last seven days and Pittsburgh Sleep Quality Index scores (sleep quality).PSQI = Pittsburgh Sleep Quality Index.

Table 2 .
Prevalence of musculoskeletal complaints according to body regions

Table 1 .
Sample descriptive data

Table 3 .
Prevalence of musculoskeletal complaints according to body regions and sleep duration and quality of athletes * Significant result (Chi-square test for differences among proportions).Source: Primary data (2014).
32nfirming such results, the study ofFietze et al. 11has evaluated German professional ballet dancers and has found poor sleep quality indices in more than 50% of the sample.Brand et al.31have observed similar indices, being 5.15(1.14)forfemalesand5.41 (1.29) for males in PSQI scores for Swiss elite athletes from different modalities.The prevalence of poor sleep quality observed in athletes is in general high, such as in the sample of Samuels32, which was approximately 80% in Canadian athletes.So, it is suggested that education of sleep during training is necessary.
So, follow-up studies are needed to establish cause and effect relationships between awakenings and pain.In principle, it is possible to question by considering a two-way path, because injuries may lead to night time awakenings and nights with poor sleep quality may increase the risk for injuries.According to PSQI results in athletes of Santa Catarina, mean was 5.09 (2.47) and prevalence of poor sleep quality was 38%.
20 the study by Pereira et al.37with professional musicians, most affected joints in the last seven days were neck (54.5%), shoulders (50.0%) and upper back.It is possible to note that musculoskeletal complaints frequency is directly related to positions needed to perform different motor skills and that preventive measures should be planned according to detailed movement analysis.In the athletes of our sample, poor sleep quality was significantly associated in the last 12 months to problems of pain/ tingling/numbness in all investigated body parts, except for shoulders.Pereira et al.38, using a different tool to analyze "pain and physical complaints", have also found positive correlation between this variable and sleep quality.Similarly, Dore & Guerra20have observed positive correlations between quality of sleep and low back and neck pain.