Cross-legged Sitting Research Articles

Impact of slouching on heart rate variability and cardiovascular health among medical students

Background: Medical students frequently adopt poor postures such as slouching potentially impacting health. Heart rate variability (HRV) serves as an indicator of autonomic nervous system function, correlated with cardiovascular health. Aims and Objectives: The objective of the study was to compare HRV parameters among medical students in three postures: Sitting erect, easy pose (cross-legged), and slouching (stooping head and shoulders). Materials and Methods: A comparative cross-sectional study enrolled 26 male medical students. Participants were instructed to maintain each posture for 5 min while HRV was recorded using a Polar V800. Time domain and frequency domain parameters among different postures were analyzed using Friedman’s test and post hoc tests for pairwise comparisons. P<0.05 was considered significant. Data were expressed as median interquartile range. Results: Significant differences were observed in HRV parameters between postures. The easy pose demonstrated a significantly higher median value of root mean square of differences of successive RR intervals (48.28 ms vs. 35.35 ms) and pNN50% (24.40% vs. 13.62%) compared to slouching. Frequency domain analysis revealed a significantly higher median value of high-frequency (HF) power in easy pose (626.56 ms² vs. 378.15 ms²) and HF normalized unit (33.78 vs. 22.55) compared to slouching. A lower low frequency (LF)/HF ratio and (1.96 vs. 3.43) lower LF normalized unit (66.18 vs. 77.30) was also seen in easy pose. Although statistically not significant, the parasympathetic indicators of HRV were higher in erect sitting compared to slouching posture. Conclusion: Among medical students, adopting the easy pose (cross-legged sitting) appeared to enhance HRV and thus increase parasympathetic activity, whereas adopting slouching postures decreased it.

“Pure Fat Flap”—Perforator-based Adiposal Layer Only Flap for Lateral Ankle Reconstruction

AbstractLateral ankle soft tissue defects pose challenges, especially in cases due to chronic pressure from cross-legged sitting, which usually present with a large dead space, small skin opening that often accompanies an open joint. Traditional reconstruction methods using fasciocutaneous flaps may result in donor site morbidity such as delayed wound healing or nerve injury. In this article, we present a case of diabetes-related lateral ankle defect successfully treated using adiposal layer only flap, also known as pure fat flap. The anatomy and the surgical technique of adiposal layer only flap were reviewed. These flaps preserve the subdermal plexus and deep fascia while obliterating dead space and providing a gliding surface for proper ankle movement. A perforator-based adiposal layer only flap was elevated from the peroneal artery and used to cover the defect. Flap perfusion was confirmed using indocyanine green video angiography and color duplex ultrasound. Patient had a successful recovery with minimal donor site morbidity. The technique expands the reconstructive microsurgeon's options for complex ankle coverage, ensuring optimal wound healing and functional outcomes.

Comparison of neuraxial acoustic target window of the spine among rider sitting, cross leg, hamstring stretch, and classical sitting position: An observational study.

To compare ultra-sonographic dimensions of acoustic target window of the spine in the participants at four different sitting positions namely cross leg sitting (CLP), hamstring stretch (HSP), classical sitting (CSP) and riders sitting position (RSP). The primary objective of this study was to measure the neuraxial acoustic target window (defined as interlaminar distance between L3-L4 lamina). The secondary objective was to compare ultra-sonographic measurements of the depth of ligamentum flavum from the skin, and to compare the diameter of intrathecal space and comfort score in the four different sitting positions. This study is a prospective observational study. Eighty participants were included and positioned in four different sitting positions to perform an ultra-sonographic scan and measure various parameters of the acoustic neuraxial window. The interlaminar distance, the distance of skin from the ligamentum flavum, and the diameter of the spinal canal or intrathecal space was measured in the L3-L4 intervertebral space in different positions. The mean value of interlaminar distance among four sitting positions was ranging from 1.40 cm to 1.44 cm (P value 0.725.) The distance of ligamentum flavum from skin and diameter of intrathecal space was also comparable in all the groups. The comfort score in CSP was significantly better when compared to other groups with a median score of 4 (P value < 0.001). There is no statistically significant difference in interlaminar distance in various sitting positions. All four positions are equally effective and can be used as an alternative to spinal/epidural intervention, but the CSP came out to be the most comfortable and more emphasis should be given to the comfort as it increases the chance of success rate of the procedure.

Left common peroneal nerve palsy caused by cross-legged sitting during epidural labor analgesia: a case report

BackgroundNerve injury in epidural labor analgesia can occur with various potential causes. We report a rare case of left common peroneal nerve palsy after delivery caused by a prolonged period of sitting cross-legged during epidural labor.Case reportEpidural labor analgesia in a 28-year-old primipara started at 39 weeks of gestation. She sat cross-legged to prompt delivery for approximately 4 h with a break of a few minutes every hour. She had numbness in her left lower limb and difficulty in dorsiflexion of the ankle joint that did not improve until 3 h after delivery. We made a diagnosis of left common peroneal nerve palsy. Most of the symptoms had improved at 2 months postpartum.ConclusionEpidural labor analgesia prevented recognition of prolonged peroneal head compression caused by sitting cross-legged. When this position is used to facilitate delivery, it should be released frequently owing to the possibility of a neurologic deficit.

Improvement of rotational arc during deep flexion range of a novel designed polyethylene insert for posterior-stabilised total knee arthroplasty

BackgroundOne of the remaining issues in total knee arthroplasty (TKA) is achieving sufficient rotational arc during deep flexion range of the knee for specific postures such as the ‘seiza’ or cross-legged sitting. This study aimed to evaluate whether there was a change in the actual in vivo rotational arc during deep flexion range before and after a design change of polyethylene (PE) inserts. MethodsIn 50 posterior-stabilised TKA cases, knee kinematics, including rotational movement, were measured intraoperatively using an image-free navigation system to compare a newly designed PE insert with reduced the posterior lip with a conventional PE insert. Femoral–tibial rotational angles at 30°, 45°, 60°, 90°, 120°, and 130° knee flexion were evaluated. Varus/valgus instability, knee range of motion, and femoral rollback were also measured. Obtained parameters were compared between new and conventional PE inserts. The independent factors associated with rotational arc during deep flexion range (120° and 130° knee flexion) were analysed using multivariate analysis. ResultsThe newly designed PE insert demonstrated a significant increase in the rotational arc at 120° (22.9 ± 8.7° vs. 30.1 ± 11.9°, P < 0.001) and 130° (24.3 ± 9.5° vs. 32.5 ± 12.4°, P < 0.001) knee flexion compared with that with the conventionally designed posterior-stabilised insert. Multivariate analysis demonstrated that using the newly designed PE insert was an independent predictor of improved rotational arc during deep flexion range: regression coefficient was 11.2 (95% confidence interval 7.1–15.3, P < 0.001). ConclusionThe design change, which reduced the posterior lip of the PE insert, contributed to improved rotational arc in 120° and 130° deep flexion ranges.

Post radiofrequency ablation management of complications of osteoid osteoma with Ayurveda

Osteoid osteoma is a benign bone tumour that usually develops in the long bones of the body such as femur &amp; tibia. It causes continuous, deep and severe pain at night, Swelling, joint stiffness. Modalities of management in modern medicine are limited and many patients suffer from post RFA complication like pain, general debility, gait disorder etc. Hence, there is a need of more efficient methods to treat this. Our present study comprises of one such way of dealing post radiofrequency management of Osteoid Osteoma through Ayurveda. A single case study of 18 year old male patient, diagnosed with Osteoid Osteoma of right hip joint who underwent RFA for same but did not get relief. Patient came to us with the complaint of severe pain in right hip joint with muscle lag associated with difficulty in doing daily activities such as walking, cross leg sitting, squatting &amp; Gait disorder from last two years.

Double-Row Root Repair with Bridging Centralization Using Double Nonsliding Anchors for Medial Meniscus Posterior Root Tear

Medial meniscal posterior root tears disrupt the “hoop” function of the meniscus and may lead to knee osteoarthritis. Although root repair could be a key to osteoarthritis prevention, this surgery does not necessarily guarantee an optimal result even when combined with meniscal centralization and high tibial osteotomy. To address this issue, we made five modifications to the original combined approach, namely two anchors to fix the root, instead of one; bridging centralization instead of single centralization; release of the meniscotibial capsule vs no release; release of valgus stress before knot tying vs no release; and prohibiting postoperative cross-legged sitting and sitting on heels. The advantages of this approach over the original approach are numerous and comprise ease of performing concurrent open wedge high tibial osteotomy, shorter fixation distance, better anatomical reattachment of the meniscal root, increased bone-meniscus contact and contact pressure, and larger contact area between the capsule and tibial rim. The disadvantages of the approach are that knot-tying is cumbersome, pie-crusting of the medial collateral ligament is necessary in patients not undergoing open wedge high tibial osteotomy, and tears >3 mm from the attachment are a contraindication. We describe the steps in this modified approach in detail.

The Biomechanical Effects of Cross-Legged Sitting on the Lower Limbs and the Implications in Rehabilitation

Background: While cross-legged-sitting (CLS) posture is widely practised in some communities, its biomechanical effect on the lower limbs is not clear. This study aimed to investigate whether CLS would affect biomechanical parameters in lower limbs during gait. Methods: Thirty healthy volunteers participated in this study and performed CLS on ground for 20 min. Their modes of gait were compared before and after CLS regarding to temporospatial parameters and the kinetic and kinematic parameters in the lower limb joints. Results: CLS significantly increased walking cadence and speed. In kinematics, the ranges of motion for almost all lower limb joints were increased after CLS except the knee in sagittal plane. In kinetics, the medial and lateral forces increased significantly after CLS in the lower limb joints, e.g., the hip posterior force was increased more than 14% on both sides. Furthermore, all hip, knee, and ankle powers were increased significantly after CLS. Conclusion: CLS has a positive impact on the biomechanical parameters of almost all lower limb joints except the knee flexion/extension angle and internal/external joint moments. Therefore, CLS can be used in the daily routine and in any rehabilitation programme to improve the biomechanical parameters of the lower extremities.

Bicruciate-retaining total knee arthroplasty procedure reduced tensile force in the middle and posterior components of lateral collateral ligament during deep knee flexion activities with no effect on tensile force of the medial collateral ligament.

To analyse the effects of bicruciate-retaining total knee arthroplasty (BCR-TKA) on the tensile force of the collateral ligaments during two deep knee flexion activities, cross-leg sitting and squatting. Thirteen patients (15 knees) treated using bicruciate-retaining total knee arthroplasty (BCR-TKA) for knee joint osteoarthritis were analysed. Knee joint kinematics during cross-leg sitting (open-chain flexion) and squatting (closed-chain flexion) were evaluated through fluoroscopy. The tensile force was calculated in vivo based on the change in the distance between the femoral and tibial attachment areas for the anterior, middle, and posterior components of the superficial (sMCL) and deep (dMCL) medial collateral ligament and the lateral collateral ligament (LCL). Differences in the calculated tensile forces of the collateral ligaments were evaluated using repeated measures of analysis of variance, with post hoc pairwise comparison (Bonferroni test). Statistical significance was set at P ≤ 0.05. The correction of the coronal alignment was related to the surgical technique, not to the implant design. No significant change in the tensile force in all three components of the sMCL from pre- to post-TKA (n.s.) was observed. For dMCL, a pre- to post-TKA change in the tensile force was observed only for the anterior dMCL component (p = 0.03). No change was observed in the tensile force of the anterior LCL with increasing flexion, with no difference in pre- to post-TKA and between activities (n.s.). In contrast, tensile force in the middle LCL slightly decreased with increasing flexion during squatting, pre- and post-TKA. After surgery, lower forces were generated at 40° of flexion (p = 0.04). Tensile force in the posterior LCL was higher in extension than flexion, which remained high in the extension post-TKA. However, after surgery, lower tensile forces were generated at 10° (p = 0.04) and 40° (p = 0.04) of flexion. The in vivo change in tensile forces of the collateral ligaments of the knee before and after BCR-TKA can inform the development of appropriate ligament balancing strategies to facilitate recovery of deep knee flexion activities after TKA, as well as for continued improvement of BCR-TKA designs. III.

Alteration of quadriceps muscle activity during functional step tasks after extended sitting session

BackgroundProlonged sitting with high knee flexion is a common activity that may affect patellofemoral joint compression and quadriceps length. Exploring the quadriceps activation after sitting may help to explain the mechanism underlying muscle changes and the resulting patellofemoral pain. ObjectivesTo examine changes in quadriceps activity after prolonged sitting in cross-legged sitting, side-sitting, and sitting on a chair. DesignLaboratory observational study. MethodThirty healthy women participated and were randomly allocated to three groups of different sitting positions (n = 10/group). Electromyography (EMG) of the vastus medialis (VM), rectus femoris (RF), and vastus lateralis (VL) was performed before and after 15 min after sitting. EMG was conducted during step-up and step-down tests and was reported as %MVIC. The results were analysed using Wilcoxon signed-rank test and Kruskal-Wallis ANOVA. ResultsVM activity and EMG activity during the step-down test after sitting increased significantly in the cross-legged group (p = 0.01). Sitting postures significantly influenced (p = 0.02) muscle activity changes in the VL and VM during the step-up test. Pairwise comparisons revealed significant differences between the cross-legged sitting and sitting on a chair groups. ConclusionsProlonged cross-legged sitting and side-sitting caused changes in VM and VL activity during step tasks in healthy young women. After cross-legged sitting, the VM exhibited a significantly higher activity in descending control, and changes in VM and VL activity increased significantly during the step-up task. Increased VM and VL activation possibly controls the patellofemoral joint. Therefore, they may fatigue more easily when many step tasks or squatting exercises are performed.

Cross-legged sitting posture effect on lumbar proprioception in young adults: a cross-sectional study

BackgroundThe cross-legged sitting posture (CLS) is assumed by young adults’ results in a bent and unbalanced posture. The study purpose was to assess the effect of sitting in a cross-legged position (knee on knee) on lumbar proprioception. Thirty-six participants of both genders aged from 18 to 25 were selected and divided equally into group A who adapt to a cross-legged sitting posture and group B who adapt to erect sitting (not prefer cross-legged sitting). The Biodex System 3 pro isokinetic dynamometer was utilized to assess the lumbar proprioception by testing the lumbar region repositioning accuracy.ResultsThe lumbar repositioning error of group A increased statistically significantly as compared to group B (p < 0.05).ConclusionsCross-legged sitting posture negatively affects lumbar proprioception compared with participants who adapt to erect sitting, and this effect should be considered in the avoidance of sitting in a cross-legged position and in prevention and intervention programs of lumbar proprioception impairment.

Social Norms Matter: University Students’ Misbehaviors in the Metro Carriage

Metro travelers’ travel experience is highly influenced by fellow passengers’ misbehaviors such as eating or littering in the carriage and sound blaster, which are common in the metro carriage. Although operators have implemented various regulations to reduce misbehavior, little theoretical research has investigated such behavior motivators to provide targeted guidelines for specific passenger segments. To this end, this study explores how demographic and perceived social norms of university students affect their misbehaviors, i.e., eating in the carriage, public display of affection, sound blaster, cross-legged sitting, leaning against the pole, and littering, in the metro carriage of Shanghai, China. With the structural equation model, it is revealed that both injunctive and descriptive norms impose significant impacts on passengers’ inappropriate behaviors, with the effect of the former generally to a greater degree. Gender heterogeneity in passenger misbehavior is also observed, where males significantly perform better in eating in the carriage and cross-legged sitting. These findings may decode the underlying motivation of passenger misbehaviors and provide guidelines for effective intervention with targeted policy design and implementation.

Three-dimensional motion analysis of ten common Asian sitting positions in daily living and factors affect range of hip motions

BackgroundSitting involves many activities of daily life and requires most motion in the hip joint. Asians have more hip flexion and external rotation motions than Westerners owing to cultural and lifestyle differences. Being aware of the normal range of hip motion is essential in clinical practice. Limited research has focused on the hip motions of common sitting positions. The objective was to determine the hip motions of 10 common sitting positions, and to determine whether gender or being overweight affects the range of hip motions.MethodsAn experimental cross-sectional study was conducted to determine hip motions by using a standard, three-dimensional, motion-analysis system. Healthy subjects performed 10 sitting positions during 3 trials. All hip-kinematic data were measured on the dominant leg of each participant, except for the right- and left-monk positions (both hips were analyzed). Density plots were constructed and statistical analyses were performed to detect the differences between groups (male and female; non-overweight and overweight).ResultsThe 48 participants comprised 24 males and 24 females. Most were right-leg dominant (45 participants, 93.8%). Of the 22 participants in the overweight group (body mass index ≥23 kg/m2), 18 (75%) were male. Squatting showed the highest flexion angle (99.7°, 47.3°–122°). Cross-legged sitting had the highest abduction angle (28.9°, 9.9°–45.7°) and the largest external rotation angle (62°, 37.6°–81.7°). In the female group, there were trends toward a greater flexion angle (4 out of 10 sitting positions) and a smaller abduction angle (6 out of 9 positions), with P values < 0.05. As to body weight, the overweight participants had a smaller flexion angle but a greater abduction angle, with 5 out of 9 positions having a P value < 0.05. Kinematic data of the transverse plane revealed that the heterogeneity of the rotational angles depended on the sitting position.ConclusionsThis study provided the functional hip motions of common Asian sitting positions. The kinematic data can be utilized in clinical practice as reference values to determine safe positions. Gender and being overweight affected the hip angles in the sagittal and frontal planes.Trial registrationNumber TCTR20181021004, retrospectively registered at the Thai Clinical Trials Registry (http//:www.clinicaltrials.in.th).

Assessment of Functional End Ranges of Lower Limb Joints in Positions Commonly Used for ADLs in India

Background: In many countries of Asian continent, floor sitting is preferred instead of chair supported sitting. Indian population differs noticeably in its cultural practice and daily tasks which involves squatting and cross-legged sitting on the ground.&#x0D; Aim: The purpose of the study was to assess the functional end-ranges of the hip, knee and ankle joints in healthy Indian subjects in positions commonly used for ADLs in India which includes squatting and cross-legged sitting.&#x0D; Methods: 66 healthy subjects were recruited from rural and urban populations with age range 30-50 years. Joint ROM of the lower extremities was measured using Universal Goniometer. All the subjects were asked to acquire squat and cross legged positions which were graded.&#x0D; Results: Our results finding showed that the subjects in cross leg sitting grade 2 (independent CLS) had hip flexion ranges ≥1150, hip abduction ≥ 410, hip external rotation ≥ 420, ankle plantar flexion ≥ 460, p&lt;0.005. For squatting, grade 2 (independent squat) had hip flexion ranges ≥ 1130,p&gt;0.005, Knee flexion ≥1200, p&gt;0.005 and ankle dorsiflexion ≥150, p&lt;0.005.&#x0D; Conclusion: From the results, it is suggested that squatting and cross-leg sitting multiple times a day can prevent the early closer of end ranges of the lower limbs.

In vivo kinematics and cruciate ligament forces in bicruciate-retaining total knee arthroplasty

We analyzed the effects of bicruciate-retaining total knee arthroplasty (BCR-TKA) on knee kinematics and cruciate ligament forces. Patients (N = 15) with osteoarthritis (OA) and an intact anterior cruciate ligament (ACL) underwent magnetic resonance imaging and single-plane fluoroscopy to measure tibiofemoral kinematics during two deep knee bend activities before and after BCR-TKA: (1) weight-bearing squat; (2) non-weight-bearing cross-legged sitting. Forces in ligament bundles were calculated using VivoSim. The dynamic range of varus-valgus angulation decreased from 3.9 ± 4.4° preoperatively to 2.2 ± 2.7° postoperatively. Preoperatively, the medial femoral condyle translated anteriorly from 10° to 50° of flexion, and posteriorly beyond 50° of flexion. Postoperatively, the medial and lateral femoral condyles translated posteriorly throughout flexion in a medial pivot pattern. ACL forces were high in extension and decreased with flexion pre- and postoperatively. PCL forces increased with flexion preoperatively and did not change significantly postoperatively. Preoperatively, ACL forces correlated with anteroposterior translation of the femoral condyles. Postoperatively, PCL forces correlated with anteroposterior translation of the lateral femoral condyle. BCR-TKA altered knee kinematics during high flexion activity which correlated significantly with changes in cruciate ligament forces.

Characteristic kinematics of floor-sitting activities after posterior-stabilized total knee arthroplasty determined using model-based shape-matching techniques

BackgroundDetailed kinematics of floor-sitting activities after total knee arthroplasty (TKA) have not been well explored. Knee kinematics of cross-legged sitting, seiza-sitting, and side-sitting after TKA were examined to clarify the differences in tibiofemoral kinematics of each activity. MethodsSubjects were 40 knees in 20 osteoarthritic patients who underwent bilateral TKA with a high-flexion fixed-bearing posterior-stabilized prosthesis. Dynamic radiographs of floor-sitting activities were taken, and the knee kinematics were compared among the three activities. The patients were also divided into two groups (possible/easy group and impossible/no-try group) for each activity, and group comparisons were conducted. ResultsThe maximum implant flexion angle was significantly greater in seiza-sitting. In valgus/varus rotation, seiza-sitting demonstrated neutral rotation, while cross-legged sitting showed varus of about 10°, and side-sitting exhibited valgus. In tibial internal/external rotation, seiza-sitting demonstrated a constant rotational angle, while cross-legged sitting showed tibial internal rotation with flexion, and side-sitting exhibited tibial external rotation with flexion. The kinematic pathway during deep flexion illustrated the medial pivot pattern in cross-legged sitting, a small amount of bicondylar rollback in seiza-sitting, and the weak lateral pivot pattern in side-sitting. A greater flexion angle was the important factor for the performance of each floor-sitting activity followed by varus laxity at 10° knee flexion. ConclusionsThis study successfully revealed characteristic kinematic patterns of TKA knees in three floor-sitting activities. Obtaining a greater knee flexion with adequate lateral laxity is the key to enhancing postoperative floor-sitting activities.

The association between femoroacetabular impingement and sitting positions: A three-dimensional simulation study

To investigate the relationship between femoroacetabular impingement (FAI) and different sitting positions. We retrospectively reviewed 24 patients with FAI. Femoral and pelvic parameters were measured, and 3D simulation software was used to create and analyze a 3D model of the hip. The data were divided into impingement and non-impingement groups according to whether impingement occurred in the normal or cross-legged sitting positions. The parameters were compared between these groups, and the effect of each parameter on impingement volume was estimated. Femoral anteversion and the difference in sacral slope (SS) between standing and sitting positions (ΔSS) were significantly lower in the impingement group than in the non-impingement group (both p<0.05). Alpha angle, sacral slope in the sitting position (sitting-SS), and femoral flexion angle (FFA) were significantly higher in the impingement group than in the non-impingement group (p<0.05, p<0.01, and p<0.05, respectively). Femoral neck shaft angle (FNSA) correlated with impingement volume in the normal sitting position (r=0.602 p<0.01). FNSA, SS, and FFA correlated with the impingement volume in the cross-legged sitting position (r=0.409, p<0.05; r=-0.438, p<0.05; r=0.420, p<0.05, respectively).Our simulation study demonstrated that, during normal and cross-legged sitting positions, FAI patients with increased sitting-SS, alpha angle, and FFA as well as decreased ΔSS and femoral anteversion were more likely to have impingement. These findings suggest that FAI patients with increased alpha angle and sitting-SS as well as decreased ΔSS and femoral anteversion should avoid excessive femoral flexion during sitting and cross-legged sitting positions.

Study and evaluation of acetabular anteversion angle in South Indian population for total hip arthroplasty

Aim: To determine the average acetabular antiversion angle in south Indian population, for ideal acetabular cup position in Total Hip Arthroplasty. Background: Abnormal acetabular anteversion of the hip, has been from many years the etiogenesis of early hip wear and tear leading to osteoarthritis [1]. In this era the demand for total hip replacements has increased worldwide and in India as well. The acetabular anteversion angle plays a very important role in terms of longevity of the implant and cup positioning. Since studies on acetabular anteversion are very few compared to western and Asian studies hence, the purpose of this study is to find out the acetabular anteversion angle for south Indian population. Materials and Methods: A retrospective study of 250 CT scans of hips where collected from 2017 to 2020 and the mean acetabular anteversion angle was measured which was compared with Asian and western population. Results: The average acetabular anteversion angle is 20.9±3.19 there was no statically significant difference between male and female population, as with the side, left and right side (p=0.02). There was a significant 2 to 3 degree increase in acetabular antiversion compared to US, European and Asian studies. Conclusion: The average acetabular anteversion angle 20.9 ±3.19 was significantly higher when compared to the western population due to the habitual cross legged sitting and squatting since childhood, hence this should be taken into consideration when designing and positioning acetabular cups during total hip arthroplasty.

The Effects of Cross-Legged Sitting on the Trunk and Pelvic Angles and Gluteal Pressure in People with and without Low Back Pain.

The purpose of this study was to investigate the effects of cross-legged sitting on the trunk flexion angle, pelvic obliquity, and gluteal pressure of subjects with and without low back pain (LBP). The study subjects were 30 LBP patients and 30 healthy individuals. They were instructed to sit on a chair, the height of which was adjustable, so that their knee and hip joints were bent at 90°. All subjects were asked to perform two sitting postures: erect sitting and cross-legged sitting. Trunk flexion angle and pelvic obliquity were measured using a three-dimensional motion-capture system, and gluteal pressure was measured using a force plate. Compared to erect sitting, cross-legged sitting showed a significantly lower trunk flexion angle and greater pelvic obliquity in both groups. Compared to healthy subjects, the patients with LBP had lower trunk flexion angles and greater gluteal pressure asymmetry during cross-legged sitting. The pelvic obliquity was greater in the cross-legged sitting posture than in the erect sitting posture, but there was no difference between the groups. We found that the trunk became more slouched in the cross-legged sitting posture than in the erect sitting posture, and this tendency was more pronounced in patients with LBP.

CLASSIFICATION OF SPINAL POSTURES DURING CROSS-LEGGED SITTING ON THE FLOOR

One of the most frequent sitting styles of Asians in everyday life is a cross-legged sitting. The cross-legged sitting results in higher compression load in spine than sitting on a chair, so a proper sitting posture is more needed. The purpose of this study was to classify the spinal posture during cross-legged sitting from the seat pressure pattern for future usage in the posture monitoring system. Twenty young men participated in this study. The seat pressure was measured for three spinal postures of flat, slump, and lordosis when subjects were instructed to pose a certain posture while seated on the floor with legs crossed. The contact area was divided into feet and buttocks by using a filter with a pressure threshold ([Formula: see text]). A decision tree was developed for the classification of three postures, with a decision variable of feet to buttocks pressure ratio. The three spinal postures were classified by comparison of feet-buttocks ratio ([Formula: see text] and thresholds ([Formula: see text], [Formula: see text]): a slump posture with a greater [Formula: see text] than [Formula: see text], a lordosis posture with a smaller [Formula: see text] than [Formula: see text]. Each threshold was calculated by adding or subtracting a certain percentage ([Formula: see text]) to or from the [Formula: see text] of flat posture and the classification accuracy was investigated with a range of thresholds. The accuracy of classification achieved 99.38% for certain ranges of thresholds. The developed algorithm showed the best performance when [Formula: see text] and [Formula: see text] were in the range of 2.85–5.67% and 1.58–2.20%, respectively. The feet-buttocks pressure ratio showed significant correlation with lumbar angle ([Formula: see text], [Formula: see text]). Anterior and posterior tilts of upper body in the slump and lordosis postures would result in more pressure concentration in the feet and buttocks, respectively, which was incorporated in the classification algorithm of this study. The result of this study could be extended to the real-time or offline monitoring of the sitting posture.