OBJECTIVE: To analyze the motion characteristics of lumbar facet joints and to observe the effect of weight-bearing on lumbar facet joints in the sitting position.
METHODS: Ten normal subjects (5 males and 5 females) were recruited and scanned by CT, and their lumbar 3D models were reconstructed by software. The images of flexion and extension of lumbar facet joints in the sitting position were collected without weight-bearing and weight-bearing 10 kg, and the 2D model was constructed by software. The 2D-3D model was matched to restore the flexion and extension motion changes of the subjects\' lumbar spine in the sitting position. Coordinates were established in the middle of the vertebral body and copied to the facet joints. Measure and record the lumbar facet joint movement distance through coordinate system. The relevant data of facet joints were collected.
RESULTS: In the L3/4 segment, after weight loading, the displacement of the left facet joint in the X axis became larger, while that in the Y axis and Z axis decreased. The displacement of the right facet joint in the X axis and Y axis increased, and the Z axis displacement decreased. The rotation angle of the bilateral facet joints also decreased. In the L4/5 segment, after loading, the displacements of the X, Y, and Z axis displacements of both sides increase, while the rotation angles of α and β increase, while the rotation angle of γ decreases. In the L5/S1 segment, the displacements of the X, Y, and Z axes on the left side decrease. The displacement of the X and Y axes on the right side decreases, while the displacement on the Z axis increases. The rotation angles of α and γ increase, and the rotation angle of the β axis decreases.
CONCLUSIONS: When sitting, the flexion and extension distance and rotational displacement of lumbar facet joints are not affected by weight-bearing. In addition, there is asymmetry in the movement of the left and right facet joints, and weight bearing has no effect on the asymmetry of the motion.

Objective: To examine the acute arterial stiffness changes after maintaining one bout of balance on Swiss ball using different postures in young and middle-aged adults, and to evaluate the cumulative exposure effects on arterial stiffness after multiple exercise bouts in middle-aged adults. Methods: Using crossover design, we first enrolled 22 young adults (24.0 ± 1.1 years) and randomized them to non-exercise control (CON), on-ball balance exercise trial lasting 1 × 5 min in kneeling posture (K1) and sitting posture (S1). In a following crossover experiment, 19 middle-aged adults (53.0 ± 4.7 years) were randomized to non-exercise control (CON), on-ball balance exercise trial lasting 1 × 5 min in kneeling posture (K1) and in sitting posture (S1), and on-ball balance exercise trial lasting 2 × 5 min in kneeling posture (K2) and in sitting posture (S2). Cardio-ankle vascular index (CAVI), an indicator of systemic arterial stiffness, was measured at baseline (BL), immediately after (0 min), and every 10 min after exercise. CAVI changes from BL in the same trial (⊿CAVI) were used for analysis. Results: In K1 trial, ⊿CAVI decreased significantly at 0 min (p < 0.05) in both young and middle-aged adults; however in S1 trial, ⊿CAVI at 0 min increased significantly in young adults (p < 0.05), with ⊿CAVI tending to increase in middle-aged adults. Bonferroni post-test revealed that at 0 min, ⊿CAVI of K1 in both young and middle-aged adults, and ⊿CAVI of S1 in young adults differed significantly from that of CON (p < 0.05). In middle-aged adults, ⊿CAVI decreased significantly at 10 min compared to BL in K2 trial (p < 0.05), and increased at 0 min compared to BL in S2 trial (p < 0.05); however, difference compared to CON was not significant. Conclusion: Single on-ball balance bout in kneeling posture improved arterial stiffness transiently in both young and middle-aged adults; however, sitting posture elicited opposite changes, and this happened only in young adults. Multiple balance bouts resulted in no significant change in arterial stiffness in middle-aged adults.

The concepts of \"optimal posture (OP)\" and \"harmful posture (HP)\" are commonly used, and specific spinal postures can contribute to back pain. However, quantitative descriptions of optimal and harmful standing (StP) and sitting (SP) postures are currently lacking, particularly for different body mass indices (BMIs). Therefore, this study aimed to identify and quantify the OPs and HPs of StP and SP at different BMIs and investigate the attitudes and beliefs of rehabilitation practitioners toward OPs and HPs. Overall, 552 rehabilitation practitioners were recruited to participate in a questionnaire survey to select the optimal position from seven sitting and five standing postures for each BMI healthy volunteer. The segmental relationships of each posture were qualified using the Vicon software. For normal BMI, the physiotherapists chose two SPs (48.19% and 49.64%) and one StP (80.42%) as the OP. One sitting SP (83.7%) and two standing StPs (43.48% and 48.19%) were selected as optimal for obese BMI. All the most commonly selected OPs had an upright lordotic posture, while the postures with slouched spinal curves or forward head postures were almost all selected as HP. Additionally, 96.74% of participants considered education about optimal SP and StP to be \"quite\" or \"very\" important. The OP of the StP and SP postures was mostly based on the vertical alignment of gravity lines and sagittal balance. For obese people, the rehabilitation practitioners\' observations may be erroneous, and further physical examination is necessary. Rehabilitation practitioners generally believe that postural education is essential in clinical practice.

To investigate the impact of lumbar fusion on spinopelvic sagittal alignment from standing to sitting position and the influencing factors of postoperative functional limitations due to lumbar stiffness.
A total of 107 patients who undertook posterior lumbar interbody fusion were included. Patients were divided into two groups: Group A (lumbosacral fusion; n = 43) and Group B (floating fusion; n = 64). Spinopelvic parameters in standing and sitting position including pelvic incidence (PI), pelvic tilt (PT), sacral slope (SS), lumbar lordosis (LL), fusion segment lordosis (FSL), upper residual lordosis (URL), lower residual lordosis (LRL), thoracic kyphosis (TK), thoracolumbar kyphosis (TLK), sagittal vertical axis (SVA) and T1 pelvic angle (TPA) were measured before and after lumbar fusion. The Lumbar Stiffness Disability Index (LSDI) was used to assess functional limitations due to lumbar stiffness.
Accompanied by increased postoperative LSDI, the values of changes from standing to sitting (∆) were reduced in some parameters compared with the preoperative values. ∆PT and ∆SS significantly decreased in both two groups. In Group A, ∆LL significantly decreased with increased ∆URL. In Group B, ∆LL, ∆URL and ∆LRL showed no significant difference before and after surgery. Multiple linear regression analysis showed that age and ∆PT independently influenced the postoperative LSDI in Group A.
After lumbar fusion, changes of lumbopelvic sagittal parameters from standing to sitting would be restricted. Adjacent segment lordosis could partially compensate for this restriction. For patients with lumbosacral fusion, postoperative functional limitations due to lumbar stiffness were related to age and the postoperative ∆PT from standing to sitting.

OBJECTIVE: Sitting is a common weight-bearing posture, like standing, but there still lacks enough understanding of sagittal alignment in sitting position for patients after lumbar fusion. This study aimed to investigate the accommodation of fixed spine from standing to sitting position and its influence on unfused segments.
METHODS: Sixty-two patients after lumbar fusion (test group) and 40 healthy volunteers (control group) were recruited in this research. All subjects underwent lateral radiographs of entire spine in the standing and sitting positions. The spinopelvic parameters including sagittal vertical axis (SVA), T1 pelvic angle (TPA), lumbar lordosis (LL), thoracic kyphosis (TK), and pelvic tilt (PT) were measured. The changes in parameters of patients between two positions were compared with control group, and patients were divided in different groups based on fusion level and their parameters were compared.
RESULTS: When changing from standing to sitting positions, a forward-moving SVA and TPA were observed in both patients and control groups, accompanied by the decrease in LL, TK and increase in PT, but the changes of patients were smaller in TPA, LL, and TK (6.5° ± 7.2° vs 9.7° ± 6.0°, 7.7° ± 8.3° vs 13.6° ± 8.5°, 2.2° ± 6.5° vs 5.4° ± 5.1°, respectively, p < 0.05). Increase of PT in the lumbosacral fixation group was lower than that in the control group (4.4° ± 9.1° vs 8.3° ± 7.1°, p < 0.05). Patients who had adjacent segments degeneration (ASD) showed more kyphosis in unfused lumbar segments than the other patients (16.4° ± 10.7° vs -1.0° ± 4.8°, p < 0.05) from standing to sitting.
CONCLUSIONS: The spine straightens in lumbar and thoracic curve, combined with forward-moving axis and pelvic retroversion when changing to the sitting position. However, these changes are relatively limited in patients after lumbar fusion, so the adjacent unfused lumbar segments compensate to stress during sitting and this may be related to ASD.

BACKGROUND: Recognizing the kinematic characteristics of lumbar facet joints is important for the prevention and treatment of lumbar degenerative diseases. Previous studies have been conducted in either the supine or standing position, and there are no measurements regarding the kinematic characteristics of the lumbar facet joints while sitting. The aim of this study was to measure and analyze lumbar facet joint motion characteristics while sitting.
METHODS: Ten subjects (5 males and 5 females) performed the movements of flexion-extension, left bending-right bending, and left rotation-right rotation in a sitting position. Dual Fluoroscopic Image System and computed tomography technique were used to measure the displacement and rotation angle of the lumbar facet joints of the subjects for analysis. The movement characteristics of L3-S1 were measured.
RESULTS: When the subjects were in sitting position, the lumbar vertebra mainly changed in Z-axis and α, β angle when they performed flexion-extension activities. The displacement of the left facet joint was 4.65 ± 1.99 mm at L3-4, 1.89 ± 2.99 mm at L4-5, and 0.80 ± 2.27 mm at L5-S1 in the Z-axis, and the displacement of the right facet joint was 3.20 ± 2.61 mm at L3-4, 1.71 ± 3.00 mm at L4-5, and 0.31 ± 1.69 mm at L5-S1 in the Z-axis. The rotation in the α angle was 6.00 ± 4.49° at L3-4, 3.51 ± 5.24° at L4-5, and 0.97 ± 4.13° at L5-S1, which was significant different. The rotation in the β angle was 2.30 ± 2.94°at L3-4, 0.16 ± 2.06° at L4-5, and 0.35 ± 1.74°at L5-S1, which was significant different. When the lumbar spine performed the activity of left bending-right bending, there were changes in rotation mainly in the Z-axis and β angle. The displacement of left facet joint in the Z-axis was 1.34 ± 2.84 mm at L3-4, 2.11 ± 0.88 mm at L4-5, and 0.72 ± 0.81 mm at L5-S1; the rotation in the β angle was 5.66 ± 2.70°at L3-4, 7.89 ± 2.59° at L4-5, and 1.28 ± 2.07° at L5-S1; when the lumbar spine performed the activity of left rotation-right rotation, there were changes in the β angle. The rotation of β angle was 4.09 ± 2.86° at L3-4, 2.14 ± 3.38° at L4-5, and 0.63 ± 1.85° at L5-S1.
CONCLUSIONS: The lumbar facet joint motion in sitting position is different in each mode of motion. The horizontal displacement and rotation are predominant during flexion and extension activities, while there are different rotation in bending and rotation. The study shows the coupled motion of the lumbar facet joints while sitting, providing a new perspective on the kinematics of the lumbar spine and the etiology of lumbar degenerative diseases.

The World Health Organization released new guidelines on physical activity and sedentary behaviour in November 2020. This commentary summarises these guidelines, including the new elements. An evaluation of the guidelines for each specific sub-population is provided. Finally, as the author group includes physical activity researchers from four continents, we provide recommendations on how to support the implementation of the new guidelines.

(1) Background: This study examined the psychometric properties of the Chinese version of the Last 7-Day Sedentary Behaviour Questionnaire (SIT-Q-7d-Chi) in Hong Kong older adults; (2) Methods: Study 1 assessed the questionnaire\'s test-retest reliability, and Study 2 examined its validity. Place the question addressed in a broad context and highlight the purpose of the study; (3) Results: In Study 1, 84 older adults (aged 60-90) completed the SIT-Q-7d-Chi twice over a 2-week interval, and in Study 2, 38 older adults (i) completed the SIT-Q-7d-Chi and the Sedentary Behaviour Questionnaire for Older Adults (SBQOA) and (ii) wore a waist-mounted accelerometer for 7 consecutive days. In Study 1, the SIT-Q-7d-Chi\'s test-retest reliability (ICC = 0.91-0.99) was satisfactory, and adequate internal consistency was found for most domains of the SIT-Q-7d-Chi (Cronbach\'s alpha value being 0.7 or above). Study 2\'s results showed that the SIT-Q-7d-Chi results were significantly correlated with the SBQOA results, but not with the accelerometer results; (4) Conclusions: This study revealed the prevalence of sedentary behavior among Hong Kong\'s senior citizens, which can be used as a reference to plan or evaluate a future sedentary behavior intervention for older persons, including identifying the content and intensity of activities.

UNASSIGNED: Orientation of the lumbar facet joints (FJs) in the transverse plane is associated with degenerative lumbar spine disease. However, there is a lack of measurements of the sagittal and coronal facet angles, and the effect of 3D facet angles on joint motion in the sitting position is unknown. The present study was to investigate the 3D orientation and in vivo motion characteristics of the FJ in the sitting position.
UNASSIGNED: Dual fluoroscopic imaging system and computed tomography (CT) were used to determine the 3D orientation and kinematic characteristics of FJs. L3-S1 segments were studied in 10 asymptomatic participants (5 male and 5 female, age: 25-35 years, body mass index: 22.4±1.8). Angles of the facet in the sagittal, coronal, and axial planes, and the range of motion of the FJs in seated flexion and extension movements were measured.
UNASSIGNED: The difference in sagittal facet angles between the 2 sides of the L3-S1 facet joints was not significant. The superior coronal facet angle on the left side of L5 was significantly smaller than that on the right side by 6.4° (P=0.01). The inferior transverse facet angle on the left side of L5 was greater than that on the right side by 7.1; the results were not statistically significantly different. In the sitting position, the range of motion of the left and right sides of L5-S1 differed significantly, with the right side being 5.5° (P=0.004) and 11.7° (P=0.026) greater than the left side in the sagittal and coronal planes, respectively. There was a correlation between mobility and the 3D orientation angle of the FJs in each segment.
UNASSIGNED: Quantification of the 3D orientation of the lumbar spine FJs provides new perspectives to study the kinematics of the lumbar spine and the etiology of lumbar degenerative diseases. In sitting flexion and extension movements, there is a significant difference in the left-right lateral mobility of the FJs of the L5-S1 segments. With the exception of the transverse facet angle of the lumbar spine FJs, the sagittal and coronal facet angles also have an effect on lumbar spine mobility.

Although sedentary behavior (characterized by prolonged sitting without otherwise being active in daily life) is widely regarded as a risk factor for peripheral artery disease (PAD), underlying biomechanical mechanisms remain insufficiently understood. In this study, geometrical models of ten external iliac arteries were reconstructed based on angiographic data acquired from five healthy young subjects resting in supine and sitting (mimicked by side lying with bent legs) positions, respectively, which were further combined with measured blood flow velocity waveforms in the common iliac arteries (with each body posture being maintained for 30 min) to build computational models for simulating intra-arterial hemodynamics. Morphological analyses showed that the external iliac arteries suffered from evident bending deformation upon the switch of body posture from supine to sitting. Measured blood flow velocity waveforms in the sitting position exhibited a marked decrease in mean flow velocity while increase in retrograde flow ratio compared with those in the supine position. Hemodynamic computations further revealed that sitting significantly altered blood flow patterns in the external iliac arteries, leading to a marked enlargement of atheroprone wall regions exposed to low and oscillatory wall shear stress (WSS), and enhanced multidirectional disturbance of WSS that may further impair endothelial function. In summary, our study demonstrates that prolonged sitting induces atheropromoting hemodynamic changes in the external iliac artery due to the combined effects of vascular bending deformation and changes in flow velocity waveform, which may provide important insights for understanding the involvement of biomechanical factors in sedentary behavior-related PAD.