## 2 Materials and Methods
### Assessments  
Baseline evaluation included demographic data, such as age, anthropometric characteristics, gender and living place. In addition, the presence of other symptoms, comorbidities and pain medication were noted.  
* The primary outcome measures  
The primary outcome was pain, assessed by a Visual Analog Scale (VAS), and disability, evaluated by the Oswestry Disability Index (ODI).  
The visual analogue scale (VAS) was used to determine the severity of pain [25]. The pain intensity ranged from 0 to 10, where 0 = no pain, 1-3 = mild pain; 4-7 = moderate pain; 8-9 = severe pain and 10 = the worst possible pain.  
The Oswestry Disability Index (ODI) was used to assess the functional status and indicate the limitation in everyday life activities. The ODI is a questionnaire comprised of 10 items (scores 0-5) [26]. The higher scores indicate a more severe disability (bedridden).  
* The secondary outcome measures  
The secondary outcomes included the spinal mobility, hip flexion mobility, the flexion and extension muscle strength of the trunk, and the life quality.  
The mobility was assessed using the finger-to-floor distance (FTF), trunk right lateral flexion (TRLF), trunk left lateral flexion (TLLF) and hip flexion (HF) testing [27].  
To assess the muscle strength, we used the manual muscle technique for: muscle strength trunk forward flexion (MSTFF), muscle strength trunk extension (MSTE), muscle strength trunk right lateral flexion (MSTRLF) and muscle strength trunk left lateral flexion (MSTLLF) [28]. The manual testing of muscle strength uses a scale from 0 to 5, as follows: 0 = no visible contraction; 1 = visible contraction without movement of the limb; 2 = enough strength to produce motion, but not against gravity; 3 = sufficient strength to produce motion against gravity, but does not support additional resistance; 4 = enough strength to produce motion against gravity and additional resistance; 5 = normal muscle strength. For testing the muscle strength 4-5 involved in the flexion of trunk, the position of the patient was supine and the physiotherapist placed a counter resistance with the palm on the patient's chest. For evaluation of muscle strength 3, the patient remained supine and the physiotherapist did not apply resistance to the flexion movement. The patient performed the flexion and the physiotherapist examined the patient only visually. For testing muscle strength 4-5 involved in the extension of trunk, the position of the patient was ventral decubitus and the physiotherapist placed a counter resistance, with the palm between the shoulder blades. For evaluation of muscle strength 3, the patient remained in ventral decubitus and the physiotherapist did not apply resistance to the extension movement. The patient performed the movement and the physiotherapist examined the patient only visually. For testing the muscle strength trunk lateral flexion, the position of the patient was lateral decubitus, on the side opposite to the tested one.  
The health-related quality of life (HRQL) was evaluated using the Nottingham Health Profile (NHP) questionnaire. The NHP is a patient-reported questionnaire, composed of 38 items divided into six subareas (energy level, pain, emotional reaction, sleep, social isolation, and physical abilities) [29]. NHP scores are calculated by averaging domain scores. The items are scored from 0 to 100, where higher scores indicate a worse quality of life.