Introduction
Chronic low back pain (CLBP) is one of the most important medical conditions worldwide in terms of reducing quality of life, disability and increasing social and economic costs [1]. In general, CLBP has two non-specific and mechanical types. Non-specific CLBP (NSCLBP) includes 90-95% of low back pains and affects 20% of the world’s population [2, 3]. It is a complicated disease and its pathophysiology is unknown, occurring for three months or more [4]. There is strong evidence that CLBP is related to a complex interaction of cognitive [5], physical [6], psychological [7], neurophysiological [7], and lifestyle [8] factors. Although many of these factors are potentially modifiable, the CLBP rehabilitation protocols often, focus on physical interventions [9]. Physical interventions may not affect psychological factors [10]. Psychological factors not only change the activity of the cortex involved in pain processing, but also change the function of the brain areas related to attention, prediction and emotions [11].
Recently, neurofeedback training (NFBT) has attracted the attention of researchers because it provides reliable information about brain function during rest, sensory stimulation, and cognitive tasks. It is a safe, inexpensive, and noninvasive method, making it a valuable technique for clinical and research purposes [19, 20]. Despite the widespread use of neurofeedback to assess cortical changes in chronic musculoskeletal pain conditions, little is known about brain wave activity changes in CLBP patients. The results of a systematic review showed that the experience of pain is related to the activity of brain waves (EEG). In people with chronic pain such as CLBP, alpha waves decrease and beta and theta waves increase [21, 22]. Few studies have been conducted on the effect of interventions that change brain activity in people with chronic musculoskeletal pain. There are many questions in this field, the most common questions are related to the mechanism of the effectiveness of these interventions in reducing pain and how to design treatment protocols. This study aims to assess the effect of NFBT on psychological variables in women with NSCLBP.

Methods
This is a controlled clinical trial with a pre-test/post-test design. The study population includes women with NSCLBP referred to orthopedic or sports medicine clinics in Hamedan province, Iran. The G*Power software, version 3.1.9.2 was used to estimate the sample size. The software output for the sample size was 30. Considering a 10% sample dropout, it increased to 40. In this regard, 40 patients were purposefully selected and randomly divided into two groups of training and control (20 in each group). Inclusion criteria were: history of pain for more than 12 weeks, no history of spine surgery and hip joint replacement, and age 30-50 years. Exclusion criteria were: pain in other segments of the body, severe deformity of the lower and upper limbs, history of surgery, use of painkillers in the past 6 months, physical therapy in the past year, participation in sports activities, sciatica pain, spondylolysis, neuromuscular, neurological, or respiratory disorders, muscle spasm, and vertebral fracture.
The collected data were analyzed in SPSS software, version 26. At first, the Shapiro-Wilk test was used to ensure the normal distribution of the data. In addition, Levene’s test was used to check the homogeneity of variances. As a result, the analysis of covariance (ANCOVA) was used to compare the results between groups. The significance level was set at 0.05. The effect size of interventions was calculated using Cohen’s d (0.01 as small effect size, 0.06 as medium effect size and 0.14 large effect size).

Results
The demographic characteristics of the participants are summarized in Table 1.


The results of ANCOVA are presented in Table 2.


Covariance results showed that NFBT had a large significant effect on reducing pain (P=0.000, ƞ2=0.693), disability (P=0.005, ƞ2=0.253), and fear of movement (P=0.000, ƞ2=0.904) in women. In Table 3, descriptive statistics showed that the training group had a 40% reduction in pain, 31% in disability, and 32% in fear of movement.



Conclusion
The results of the present study showed a significant reduction in pain intensity, disability and fear of movement in women with NSCLBP after eight weeks of NFBT. It is recommended that rehabilitation specialists use NFBT along with physical exercises for better effectiveness in women with NSCLBP.

Ethical Considerations
Compliance with ethical guidelines
This study was approved by the Ethics Committee Of Hamadan University of Medical Sciences, Hamadan, Iran (Code: I R.BASU.REC.1401.026).

Funding
This research did not receive any grant from funding agencies in the public, commercial, or non-profit sectors.

Authors' contributions
Conceptualization, study design, data acquisition, data analysis, review and editing: Ali Yalfani; Data collection, statistics analysis and initial draft preparation: Azadeh Asgarpoor. 

Conflicts of interest
The authors declared no conflict of interest.


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