Differences in regional and global lumbar angle during slumped sitting and upright sitting among global three subgroups.

OBJECTIVE: The purpose of this study was to investigate differences in regional lumbar lordosis (RLL) and global lumbar lordosis (GLL) angle during slumped sitting and upright sitting among three global subgroups. METHODS: A total of 48 young asymptomatic volunteers stood in a comfortable posture, sat upright, and sat in a slumped position for 5 seconds, with inertial measurement units attached to the T10, L3, and S2 vertebrae. According to standing measurement, the participants were categorized into flat-back (GLL < 20∘), normal lordosis (20∘⩽ GLL < 30∘), and hyper-lordosis (30∘⩽ GLL < 40∘) groups. RESULTS: Both the GLL and RLL in the flat-back group were reduced lumbar lordosis in the upright sitting posture and increased lumbar kyphosis in the slumped sitting postures compared to the other groups (p< 0.05), but the range of motion during the transition from upright sitting to slumped sitting was lower than that of the normal and hyper-lordosis groups (p< 0.05). GLL in standing was a moderate correlation with GLL and RLL during upright sitting (p< 0.05). However, there was a strong correlation between GLL and RLL kinematics during upright and slumped sitting (p< 0.05). CONCLUSIONS: Flat-back posture is a potential source of low back pain during both upright and slumped sitting compared to the normal and hyper-lordosis groups. Posture measurements in a standing and sitting position conducted to assess lordosis should consider the relationship between GLL and RLL.

Non-structural misalignments of body posture in the sagittal plane.

BACKGROUND: The physiological sagittal spinal curvature represents a typical feature of good body posture in the sagittal plane. The cervical and the lumbar spine are curved anteriorly (lordosis), while the thoracic segment is curved posteriorly (kyphosis). The pelvis is inclined anteriorly, and the lower limbs' joints remain in a neutral position. However, there are many deviations from the optimal body alignment.The aim of this paper is to present the most common types of non-structural misalignments of the body posture in the sagittal plane. MAIN BODY OF THE ABSTRACT: The most common types of non-structural misalignments of body posture in the sagittal plane are as follows: (1) lordotic, (2) kyphotic, (3) flat-back, and (4) sway-back postures. Each one may influence both the skeletal and the muscular system leading to the functional disturbance and an increased strain of the supporting structures. Usually, the disturbances localized within the muscles are analyzed in respect to their shortening or lengthening. However, according to suggestions presented in the literature, when the muscles responsible for maintaining good body posture (the so-called stabilizers) are not being stimulated to resist against gravity for an extended period of time, e.g., during prolonged sitting, their stabilizing function is disturbed by the hypoactivity reaction resulting in muscular weakness. The deficit of the locomotor system stability triggers a compensatory mechanism-the stabilizing function is overtaken by the so-called mobilizing muscles. However, as a side effect, such compensation leads to the increased activity of mobilizers (hyperactivity) and decreased flexibility, which may finally lead to the pathological chain of reaction within the musculoskeletal system. CONCLUSIONS: There exist four principal types of non-structural body posture misalignments in the sagittal plane: lordotic posture, kyphotic posture, flat-back posture, and sway-back posture. Each of them can disturb the physiological loading of the musculoskeletal system in a specific way, which may lead to a functional disorder.When planning postural corrective exercises, not only the analysis of muscles in respect to their shortening and lengthening but also their hypoactivity and hyperactivity should be considered.