**2. Materials and Methods**

This prospective observational study was approved by the Institutional Review Board of the author's hospital and registered with the WHO International Clinical Trials Registry Platform (KCT0006046). This manuscript adheres to the applicable STROBE guidelines. After obtaining written informed consent, a total of 72 consecutive patients who visited our pain clinic in a tertiary care hospital due to LSS were enrolled in the study. Inclusion criteria were as follows: (1) age >40 years; (2) clinical LSS symptoms (radiculopathy +/− low back pain) more than 3 months; (3) symptom intensity with numeric rating scale (NRS; 0–10) of 4 or more; (4) radiologic confirmation of LSS through magnetic resonance imaging (MRI). Patients with a literacy problem or language difficulties; a history of psychotic disorder or drug abuse; chronic opioid usage over 3 months; a concomitantly complicated spinal disease, including epidural lipomatosis; ligament ossification or diffuse idiopathic skeletal hyperostosis; a definite indication for prompt surgery, such as cauda equina syndrome; a history of previous spinal surgery; orthopedic metal implants in any body region; and cardiac pacemaker or implantable cardioverter-defibrillator (ICD) were excluded from the study.

#### *2.1. Evaluation of Functional Disability in ADL and Group Allocation*

The functional disability in ADL was evaluated using a validated Korean version of the Oswestry Disability Index (ODI) [16]. All participants were asked to complete the self-reported ODI questionnaire in their first visit to our department. ODI is a widely used, self-reported questionnaire for assessing a patient's functional disability in ADL in patients with lumbar spinal pain. ODI consists of 10 items that are disease-associated health status measurements of how pain affects functional disability in ADL in patients with lumbar spinal pain. Each item is rated on a 6-point scale that ranges from 0 to 5, and the global score is added and multiplied by 2. Therefore, the global score ranges from 0 to 100. The higher the global score, the greater the functional disability in ADL. We divided participants into two groups, the mild to moderate disability group (ODI ≤ 40) and the severe disability group (ODI > 40), as previous studies suggested [17].

#### *2.2. Body Composition Analysis Using Bioelectrical Impedance Analysis (BIA)*

All participants underwent body composition measurement using a body composition analyzer (Inbody S10®, Biospace, Seoul, Republic of Korea), according to the manufacturer's guidelines, at their first visits to our department. Inbody S10® provides various information for body composition through BIA methods. Patients were asked to take a rest in the supine position on a nonconductive table for at least 10 min before measurements. The skin surface where the electrode would be placed was cleansed with an alcohol swab before application, in keeping with standard practice. Then, the surface electrodes were attached to both fingers (thumb and middle finger) and ankles, according to the manufacturer's instructions. Body composition parameters, such as body fat mass (kg), percent body fat (%), skeletal muscle mass (kg) and skeletal muscle index (kg/m2), were recorded.
