Influences of posterior-located center of gravity on lumbar extension strength, balance, and lumbar lordosis in chronic low back pain

BACKGROUND DATA: In patients with chronic low back pain, the center of gravity (COG) is abnormally located posterior to the center in most cases. OBJECTIVE: The purpose of this study was to examine the effects of posterior-located COG on the functions (lumbar extension strength, and static and dynamic balance) and structure (lumbar lordosis angle and lumbosacral angle) of the lumbar spine. MATERIAL AND METHODS: In this study, the COG of chronic low back pain patients who complained of only low back pain were examined using dynamic body balance equipment. A total of 164 subjects participated in the study (74 males and 90 females), and they were divided into two groups of 82 patients each. One group (n = 82) consisted of patients whose COG was located at the center (C-COG); the other group (n = 82) consisted of patients whose COG was located posterior to the center (P-COG). The following measures assessed the lumber functions and structures of the two groups: lumbar extension strength, moving speed of static and dynamic COGs, movement distance of the static and dynamic COGs, lumbar lordosis angle, and lumbosacral angle. The measured values were analyzed using independent t-tests. RESULTS: The group of patients with P-COG showed more decreases in lumbar extension strength, lumbar lordosis angle, and lumbosacral angle compared to the group of patients with C-COG. Also this group showed increases in moving speed and movement distance of the static COG. However, there were no differences in moving speed and movement distance of the dynamic COG between the two groups. CONCLUSIONS: These findings suggest that chronic LBP patients with P-COG have some disadvantages to establish lumbar extension strength and static and dynamic balance, which require specific efforts to maintain a neutral position and to control posture.