STRENGTH TRAINING IN PATIENTS WITH FIBROMYALGIA: A FEASIBILITY STUDY

Introduction: Fibromyalgia syndrome (FM) is characterized by the presence of diffuse pain lasting for more than three months and is often associated with sleep disorders. Studies have investigated the effect of strength training (ST) on pain and sleep quality in FM patients, but there continue to be diverse perspectives on the effects of this intervention in this population. Objective: The aim of the study was to examine the effects of strength training (ST) on pain and sleep quality in FM patients. Methods: Forty-eight women with FM participated in the study between August and October, 2012. Six (55±6.5 years) performed ST, conducted at Santa Catarina State University, and eight (47±9 years) comprised the control group. The Socio-Demographic and Clinical Questionnaire, the visual analog scale (VAS) for pain, and the Pittsburgh Sleep Quality Index were used. Data were collected before the first session and after the eight-week intervention and were analyzed using descriptive statistics and inferential tests. Results: The eight- week ST intervention decreased pain (p< 0.05) and significantly diminished the daytime sleep dysfunctions (p< 0.05), demonstrating that the proposed program contributes to improving patient quality of life. Conclusion: ST is a feasible treatment for patients with fibromyalgia. Level of evidence II; Therapeutic study.


INTRODUCTION
Fibromyalgia syndrome (FM) is characterized by the presence of diffuse pain lasting for more than three months, the presence of multiples specific points (tender points), located in the muscle and joints and painful on palpation, and its basic clinical diagnosis. 1 The pain reported by patients is defined generally as bilateral; above and below the waist and spinal region. 2 This syndrome is often associated with sleep disorders, which has relation with other symptoms such as fatigue, depression and anxiety. 3,4 FM patients usually complain of having short sleep periods at night, feeling tired when waking, and having insomnia. 5 Non-restorative sleep occurs in between 76% to 90% of cases.
Sleep disorders can play a significant role not only in the etiology of chronic pain, but also in perpetuating the symptoms. According Piedra et al., 6 the relationship of sleep disorders and pain is most common that the relationship pain and sleep disorders. To Olsen et al., 7 the causal relationship between sleep and pain remains uncertain; however, it is widely accepted as bidirectional. 8 Andrade et al. 9 (2018) found that pain symptoms were associated with all PSQI domains, including the total score.
Physical exercises can help in the treatment of chronic pain, prevention of some the sleep-wake cycle disorders by decreasing the sleep fragmentation, increased slow wave sleep time, and decreased latency to sleep onset. 3, 10 Driver and Taylor 11 emphasize that physical exercise has an important role to play as a treatment for sleep disorders. According to Lira et al., 12 a moderate exercise program induces the recovery of troubled sleep, and this improvement is partly due to aerobic capacity and metabolic improvement.
Studies investigated the effect of strength training (ST) on pain and quality of FM patients' sleep, [13][14][15][16][17] but there continue to be diverse perspectives on the effects of this intervention in this population. However, recently Andrade, Vilarino and Bevilacqua 18 concluded that ST is safe and effective in treating people with FM and that a significant decrease in sleep disturbances occurs after 8 wks of intervention. Moreover, Andrade, Scieczkowska and Vilarino 19 found that after 4 weeks of ST, patients with FM showed significant reduction in pain.
The study of ST in people with FM in Brazil is a recent topic; it is considered as an innovative area, causing insecurity among professionals who assist these patients. Taking this into consideration, the study objective was to verify the feasibility of a ST program for patients with FM and analyze the effects of eight weeks of ST exercises on pain and sleep quality in patients with FM.

METHODS
This feasibility study was an experimental controlled study, with a pre-and post-treatment design. The study was conducted within the ethical standards of the Declaration of Helsinki and according to Resolution 196/96 of the Ministry of Health. This study was approved by the Ethics Committee on Research Involving Human Subjects in writing form (No. 103/2010).

Participants
All patients participated in the extension program, "Psychology of sport and exercise applied to health", which is linked to the Psychology of Sport and Exercise Laboratory (LAPE) of the Health Sciences Centre and Sports (CEFID), Santa Catarina State University (UDESC). The criteria for inclusion in the study were have had a medical diagnosis by medical specialists in rheumatology, orthopedics or general practitioners, age over 18 years, and participated in 50% of the training sessions. At the end of the screening of participants' process, 34 patients were excluded due to not having attended the initial interview or the initial evaluation, had practice the exercise in other local areas, and declined to participate (personal problems and time limitations). At the end of the draw, there were eight patients in the Strength Training Group (STG) and six in the Control Group (CG). (Figure 1)

Procedures
The questionnaires were administered once per month by the study researchers, and always on different days of the training sessions. All patients in the study were informed about all study procedures and signed the Consent Form in this research.
The patients performed only the exercises applied in the study, not getting additional treatment. The ST sessions comprised 10 min of warm-up, with specific exercises for the muscles being worked during the session, 40 min of ST and 10 min of final stretches.
The ST comprised 24 treatment sessions, three times per week, and an individualized load was set for each participant in a subjective way in which the participant arrived at the 12th repetition of each exercise series at its maximum limit. There were three sets of 12 repetitions and the interval between each series was one min. During the session, the main part involved exercises relating to the major muscle groups, such as chest, latissimus dorsi, biceps, triceps, quadriceps, hamstrings, shoulders, and calves. The following exercises were performed: knee extension, knee flexion, bench press, fly, adductors, low rowing, high pulley, triceps in the pulley, lateral raise, arm curl, standing calf raise, and abdominal crunch.
The control group did not perform any type of exercise. The inclusion criterion for the study was involvement in 50% of the 24 sessions of training and having no impeditive diseases.

Instruments
The following instruments were used: (a) to assess pain intensity, the FIQ was used; (b) The polysomnography is considered the gold standard for the evaluation of sleep. But, owing to its high cost and low availability, the Pittsburgh Sleep Quality Index is often used as an effective alternative that provides quantitative and qualitative information on sleep quality. 20 The Pittsburgh Sleep Quality Index (PSQI) 21 was used.
The Fibromyalgia Impact Questionnaire (FIQ) is an instrument used to measure the impact of FM on patient health status and quality of life and was developed by Burckhardt et al. 22 This instrument is divided into 10 items, totaling 19 questions, with scores of 0 to 10; the higher the score, the greater the impact of FM on Quality of life. The items assessed functional ability: sense of well-being, absence from work, ability to work, pain, fatigue, morning tiredness, and stiffness; and psychological aspects: anxiety and depression during the prior week.
The PSQI is a self-reported instrument developed by Buysse et al., 21 which evaluates the quality of sleep in the prior month. The PSQI provides information about sleep duration, quality, and sleep latency. Our study used a short version of the PSQI that was adapted and validated for Brazil, already used in another study.10 This version evaluates the quality of sleep in the prior 7 days; it consists of 9 questions that evaluate the quality, latency, duration, and efficiency of sleep. The PSQI score ranges from 0 to 21; the higher the score, the worse the quality of sleep. A score >5 indicates difficulty in at least 2 domains.

Data analysis
The data were analyzed using descriptive statistics (mean, frequency, and standard deviation) and inferential tests. The Shapiro-Wilk test was performed to verify the normality of the data. To verify the differences in the average of the dependent variables (pre-and post-test), the Wilcoxon test for nonparametric data and the Student's t test for paired parametric data were used. The comparison between the SG and the CG in relation to pain and sleep quality was assessed using the Mann-Whitney U test for nonparametric data and the t test for independent parametric data. The significance level used in this study was p < 0.05.

RESULTS
The socio-demographic and clinical profile results are described in Table 1.
Patients of the SG and CG showed no significant differences before the first training session (pretest). This is a positive fact because it indicates that the groups included in the experiment started with similar characteristics in terms of the variables investigated, favoring the comparison between the groups after eight weeks of ST.
There were no significant differences in the pain intensity and sleep quality of the two groups after eight weeks of ST (post-test). However, the following relevant results were observed: reduction in most of the indices of sleep quality, of total sleep, and of the use of sleep medications, representing up to 50% improvement in comparison with the pretest scores. Moreover, we found a high reduction in the p-values when comparing the pretest pain score and those on most indices of sleep quality to those of the post test.
( Table 2) presents the results of the effects of ST on sleep quality after eight weeks. There were decreases in pain (p<0.05) and daytime sleep disorders (p<0.05) for the SG. The questions relating to daytime dysfunction are as follows: (a) 'During the last week, how often have you had trouble staying awake while driving the car, having meals, or taking part in social activities?' and (b) 'During the last week, how problematic was it to maintain enthusiasm in completing tasks?' In the CG, there were no significant changes.
When we compare the pain intensity of the SG patients before and after eight weeks of ST, we observed that there was a significant reduction in the media after the training period (p<0.05). Although we did not find significant differences in total sleep after eight weeks of treatment, we observed that this variable presented a behavior similar  to that of pain, in which the mean of the CG participants increased and that of the SG participants decreased considerably, as shown in (Figure 2) (mean and standard error). (Figure 3) represents the delta total sleep and pain intensity variation in the pretest and post-test assessments in both groups. It is evident that the mean in the SG reduced by about 3.0 points and that in the CG increased by approximately 0.5 points, indicating that ST for eight weeks reduced the intensity of pain in FM patients. In relation to total sleep, CG patients increased by one point and that in the SG patients decreased by an average of two points after eight weeks of training.

DISCUSSION
In the present study, patients with FM showed significant improvements regarding a reduction in pain intensity after eight weeks of ST. Comparing to the literature, Valkeinen et al. 14 investigated the effects of ST in 13 elderly women with FM, which was held twice weekly for 21 weeks; there was also a decrease in the number of tender points (pain points), but not in pain intensity. Bircan et al. 15 conducted a study in which 13 women with FM performed ST three times per week for eight weeks and a pain reduction was found in these patients. Concerning the ST program for patients with FM, it has been proved that this program is feasible and tolerable, with no adverse effects.
Using other types of exercise, Bressan et al. 23 investigated 15 patients with FM. Eight performed muscle stretching and seven patients underwent treadmill walking for eight weeks. Both groups had a weekly exercise session and there was no decrease in pain intensity after the eight weeks. Bircan et al. 15 results are similar to those in this study, which used the same duration and number of sessions per week of the study. The three weekly sessions may have explained the pain reduction. In the study by Valkeinen et al., 14 which involved two weekly sessions, and the study of Bressan et al., 23 which involved only one session per week. This demonstrates that a low number of weekly training sessions may have had a weak effect on pain improvement.
In our study, there were significant improvements for daytime dysfunction in sleep quality after eight weeks of ST. In Bircan et al. 14 study, which used an 8-week strenght training program three times per week, they also found significant improvements in sleep quality; however, this differed from the present study, which featured the same number of sessions, in that there was only an improvement shown in daytime sleep disorders. In two studies that used ST, there were no improvements in sleep quality. Häkkinen et al. 13 followed a 21-week training period, performed twice per week, and no statistically significant improvements in sleep quality were found. Valkeinen et al. 14 conducted a study with 37 women (13 in the FM treatment group, 13 in the CG with FM, and 11 in the healthy CG) who underwent 21 weeks of ST, and there was no significant improvement in sleep quality.
Other forms of exercise can be more efficient in improving sleep quality in patients with FM than ST is. In a study performed with nine women with FM who underwent 32 sessions of joint walking and yoga practice, an improvement in overall sleep quality was found, which was different from the present study in which there was only an improvement in daytime dysfunction. 24 This may be due to the greater number of sessions held in the walking and yoga study. 24 Steffens et al. 25 reported in their study, which involved a 16-week walking program, that if the exercises are held regularly, they can improve sleep quality in patients with FM. Richards et al., 26 whose study involved an aerobic exercise program, found benefits for FM patients in relation to sleep. In a study by Pasqua et al. 27 involving eight sessions walking program and sleep in patients with FM, there was an improvement in subjective sleep quality and reduction in this disorder. It can be seen that even with only eight sessions, an improvement in the quality and reduction of subjective sleep disturbances is possible; this is different from the current study in that these improvements do not occur when there is a greater number of sessions (24 sessions).
Sañudo et al. 28 used an exercise program consisting of warm-up activities for 10 min, aerobic exercise (10-15 min), ST (15-20 min), and flexibility exercises (10 min) over two sessions per week. Patients alternated between six months of training and six months with no exercise over a 30-month period. Significant improvements were observed in the impact of FM on the participants' quality of life.
A tendency for aerobic exercises to provide a greater effect on sleep quality in patients with FM compared to ST exercises can be seen in the literature. This should be investigated in future studies.