Muscle activity patterns in different standing postures in people with recurrent lower back pain

Abstract

Background: Excessive lordosis or kyphosis of the spine is thought to be a cause of lower back pain (LBP), and reportedly creates irregularities in lumbar extensor activity (Shirado, 1995). The iliopsoas (ILIO) is thought to play a role in LBP in patients with recurrent LBP (RLBP) (Lee, 2013). Recent research has shown that activity of local muscles deep in the trunk is important in preventing LBP (Hodges, 2009), althoughmany details of this remain unclear. There have been no reports on differences in lumbar extensor activity related to different postures between people with and without RLBP. Purpose: To clarify differences in lumbar extensor activity between people with and without RLBP with respect to different standing postures, and to elucidate how the trunk and hip flexors used in lumbar extension are responsible for controlling lower back and spinal alignment. Methods: Subjects included 11 adults with RLBP (RLBP group), and nine healthy adults with no history of orthopedic diseases in the legs or trunk (pain-free group). We measured activity of the ILIO, multifidus (MF), iliocostalis lumborum (IL), and iliocostalis thoraces (IT) muscles using an MQ16 (Kissei Comtec). Each subject stood in a relaxed standing posture, a flat posture, a swayback posture, and a lordosis posture. Subjects maintained the postures for ten seconds with the help of pictures, verbal instructions, and manual guidance while we measuredmuscle activity. Additionally, we placedmarkers in eleven locations, including T1, T7, T12, L3, S2, ASIS, PSIS, the greater trochanter, and the knee joint lateral epicondyle. We took pictures of each posture with a digital camera, and defined each posture by calculating the alignment of the thoracic vertebra, the lumbar, and the pelvis based on the angle change at each. Differences in muscle activity between the two groups were assessed by an independent t-test using SPSS 12.0J. A P-value < 0.05 was considered significant. Results: In the standing posture, there were no significant differences in muscle activity between the two groups. In the flat posture, MF and IT muscle activity was greater in the RLBP group than in the pain-free group (P< 0.05). In the swaybackposture, ITmuscle activitywas greater in theRLBP group than in the pain-free group (P< 0.05). In the lordosis posture, MF muscle activity was greater in the RLBP group than in the pain-free group (P< 0.05). Conclusion(s): Muscle activity increased in global muscles and decreased in local muscles in people with RLBP. However, muscle activity in the upright and lordosis postures suggested that hyperkinesia in the MF, which is a local muscle, plays a role in lumbar lordosis. Furthermore, in the RLBP group, maintenance of vertical stability in the spine seems to be attained not only by the lumbar extensors, but also due to hyperkinesia in the IT,which plays a role in lumbar extension. Implications:This studywill lead to newdevelopments in physical therapy for people with RLBP by clarifying posture control patterns in these patients.