Effects of Extension-Based Trunk Control Exercise on Trunk Muscle Function, Lumbar Lordosis Angle, and Oswestry Disability Index in Patients with Flat-Back Syndrome and Nonspecific Low Back Pain

This study aimed to examine the effects of an extension-based trunk control exercise on trunk muscle function, lumbar lordosis angle, and the Oswestry Disability Index (ODI) in patients with flat-back syndrome (FBS) diagnosed with nonspecific low back pain. Twenty-four patients with FBS (lumbar lordosis < 30°) were randomly assigned to an extension-based trunk control exercise group (EEG, n = 12) or a control group (CON, n = 12). The EEG performed 40-minute exercise sessions (5-min warm-up, 30-min main exercise, 5-min cool-down) three times per week for eight weeks. Muscle activity of the gluteus maximus (GM), biceps femoris (BF), and erector spinae (ES) was measured using surface electromyography (Delsys Trigno), and muscle tone was assessed with MyotonPRO. Trunk control ability was evaluated using five functional movement tests, and lumbar lordosis and ODI were assessed using lateral X-ray imaging and the Oswestry Disability Index, respectively. After the intervention, the EEG showed a significant increase in GM activity and tone ( p < .05) and a significant decrease in ES activity and tone ( p < .05). Trunk control ability significantly improved ( p < .05), and ODI scores significantly decreased compared with the CON ( p < .05). These findings suggest that extension-based trunk control exercise enhances gluteus maximus activation and tone, reduces erector spinae overactivity, improves trunk control ability, and decreases functional disability associated with low back pain in patients with flat-back syndrome.