Lumbar curvature in standing and sitting in two types of chairs: relationship of hamstring and hip flexor muscle length

A purpose of this study was to determine the difference in the lumbar curves of subjects while they stood compared with while they sat in two chairs with different seat angles--the Balans Multi-Chair (BMC) and a standard conventional chair (SCC). An additional purpose was to determine the relationship between lumbar curvature and 1) anthropometric factors and hamstring and hip flexor muscle length during standing and during sitting in the two chairs and 2) amount of time spent sitting. Sixty-one men between 20 and 30 years of age served as subjects. Lumbar curve measurements were taken with a flexible ruler with the subjects first standing and then sitting in the two chairs. Hamstring and hip flexor muscle lengths were indicated by range-of-motion measurements taken with a gravity goniometer. Age, number of hours spent sitting per day, upper body length, and right leg length also were recorded. Subjects had significantly more lumbar extension when they sat in the BMC than when they sat in the SCC. Hip flexor length was the only factor that appeared to relate significantly to the difference between the standing lumbar curve and the lumbar curves in the BMC and the SCC.     

Comparison of lumbar curves when sitting on the Westnofa Balans Multi-Chair, sitting on a conventional chair, and standing

The purpose of this study was to determine whether the Balans Multi-Chair (BMC) approximates the amount of standing lumbar curve better than a standard conventional chair (SCC) in seated subjects writing at a desk. The length of the curve from L1 to S2 was measured with a flexible ruler in 44 healthy subjects who were standing and sitting on both an SCC and a BMC. A one-way analysis of variance for repeated measures and the Student-Newman-Keuls test were used to examine the differences in the curves created in the three positions. The frequency of subjects sitting in lumbar flexion was compared using a chi-square test with those not in flexion. Lumbar curves measured in the three positions were significantly different (p less than .01). The BMC approximated the standing lumbar curve in seated subjects writing at a desk to a greater degree than the SCC. In addition, the BMC produced lumbar flexion less frequently (chi 2 = 4.33, p less than .05) than did the SCC. These data suggest that the BMC may be an appropriate adjunct in client care when minimal lumbar flexion or lumbar extension is indicated.     

Technique to measure lumbar curvature in the ergonomic evaluation of chairs: description and validation

Objective. To describe and validate a system to record the lumbar curvature, specially designed for the ergonomic evaluation of chairs.

Design. The technique consists of a flexible goniometer and requires a model of lumbar flexion (relationship between length and angle).

Background. Most of the techniques do not allow using the backrest of the chair or do not record continuously.

Methods. Precision, repeatability and reproducibility of the measurements have been analysed, as well as the lumbar flexion model.

Results. A suitable lumbar model of flexion and the repeatability and reproducibility errors obtained are presented.

Conclusions. The linear model is a good one to represent the flexion of the lumbar spine. The measurements are reproducible and the errors are similar or lower than with conventional inclinometers.Relevance

The device may help to investigate the relationship between lumbar pain and curvature, and to evaluate the lumbar curvature in sedentary work.     

Static trunk posture in sitting and standing during pregnancy and early postpartum

OBJECTIVE: To investigate the postural alignment of the upper body in the sagittal plane during sitting and standing postures as pregnancy progressed and then in the postpartum period. DESIGN: Longitudinal, repeated-measures design. SETTING: Biomechanics laboratory in an Australian university. PARTICIPANTS: A volunteer convenience sample of 9 primiparous and multiparous women and 12 nulliparous women serving as a control group. INTERVENTIONS: Not applicable. MAIN OUTCOME MEASURES: Subjects were filmed while sitting and during quiet standing at intervals throughout pregnancy and at 8 weeks postpartum. A repeated-measures analysis of variance was used to assess systematic changes in the alignment of the pelvic, thoracic, and head segments, and the thoracolumbar and cervicothoracic spines. Student t tests were used to compare the postpartum and nulliparous control groups. RESULTS: There was no significant effect of pregnancy on the upper-body posture, although there was a tendency in some subjects for a flatter thoracolumbar spinal curve in sitting as pregnancy progressed. Postpartum during standing, the pelvic segment had a reduced sagittal plane anterior orientation, and the thoracolumbar spine was less extended, indicating a flatter spinal curve compared with the control group. CONCLUSIONS: There was no significant effect of pregnancy on upper-body posture during sitting and standing, although individuals varied in their postural response. A flatter spinal curve was found during standing postpartum.     

Comparison of the kinetic characteristics of standing and sitting Tai Chi forms

Purpose. To compare the kinetic characteristics of Tai Chi forms performed in standing and seated positions.

Methods. An experienced Tai Chi master was invited to perform the Tai Chi Qi Qong 18-form while standing and seated. Two force platforms were used to track the centre of pressure (COP) during the Tai Chi movements. Centre of mass (COM) displacement was measured using a video motion analysis system.

Results. In standing, the maximum COP displacements in the anteroposterior and mediolateral directions ranged from 2.6% to 9.5%, and 0.3% to 29.6% of the subject's height, respectively. The maximum COP displacements in sitting were smaller, with mean displacements of 0.7% and 0.1% of height in the anteroposterior and ML directions, respectively. The subject's COM moved in the vertical direction in slow, coordinated and smooth patterns.

Conclusions. The kinetic data on each of the 18 Tai Chi forms studied can guide the choice of suitable Tai Chi forms for balance training. Sitting Tai Chi is recommended for rehabilitating the balance of frail older adults who have difficulty standing. Because of the minimal demands of sitting Tai Chi for balance control, progressing to practice in standing as quickly as possible is recommended.     

Oblique abdominal muscle activity in standing and in sitting on hard and soft seats

The activity of the oblique abdominal muscles was investigated with the trunk in unconstrained, symmetrical and static postures. Electromyographic recordings in six healthy subjects revealed that in all subjects the activity of both the internal and the external obliques is significantly higher in unconstrained standing than in supine posture. Activity of the internal oblique was higher than that of the external oblique abdominal. The sacrospinal, gluteus maximus and biceps femoris muscles showed practically no activity in unconstrained erect posture. During unconstrained sitting both oblique abdominals are active. In most subjects the activity of the oblique abdominals was significantly smaller when sitting on a soft car seat than when sitting on an office chair with a hard seat. The possibility is discussed that contraction of the oblique abdominals in unconstrained standing and sitting may help in stabilizing the basis of the spine and particularly the sacroiliac joints. During standing and sitting the oblique abdominal muscles apparently have a significant role in sustaining gravity loads. RELEVANCE: Back pain and pelvic pain are often experienced in prolonged standing and sitting postures. In these postures the oblique abdominals are shown to be active. The present study gains clinical significance by the studies showing relatively small oblique abdominal muscle strength in patients with low back pain. A soft seat may be helpful in treatment and prevention, because it substitutes oblique abdominal muscle activity.     

Comparison of electromyographic activity in the lumbar paraspinal muscles of subjects with and without chronic low back pain

My purpose, in this study, was to test the reflex-spasm model of chronic pain by comparing the levels of muscle activity in the lumbar paraspinal muscles of subjects with and without chronic low back pain (CLBP). Each group, the CLBP group and the nonpain (NP) group, comprised 11 subjects who were matched by age and sex. I used surface electrodes to record integrated electromyographic (IEMG) activity from each side of the low back. All subjects performed three experimental tasks and a reference (normalizing) task. The three experimental tasks were quiet sitting, standing, and sitting during a repetitive unilateral upper extremity task (active sitting). The CLBP and NP groups showed no significant difference for any of the three experimental tasks. For both groups, the active sitting IEMG levels were significantly higher than the quiet sitting and standing IEMG levels. The quiet sitting and standing IEMG levels were not significantly different from each other. The findings of similar levels of IEMG activity in both the CLBP and NP groups while they performed these tasks suggested that the reflex-spasm cycle was not present and, therefore, was not a cause of pain in the subjects with CLBP.     

Validation of smoothness evaluation during standing and sitting motions using an accelerometer

[Purpose] To quantitatively evaluate smoothness during standing and sitting motion analysis using an accelerometer and to clarify the relationship between indices. [Participants and Methods] Seventeen healthy males participated in this study. We attached a 9-axis motion sensor to the spinous process of the third lumbar spine and measured the acceleration of standing and sitting motions under normal and unstable conditions. We estimated and compared the root mean square and entropy in the lateral, vertical, longitudinal, and triaxial composite directions. [Results] On comparing both conditions, the unstable condition indices were significantly high, except for the lateral direction of entropy. The root mean square was significantly negatively correlated with entropy under normal conditions. [Conclusion] The study results suggested that the acceleration index quantitatively evaluates motion smoothness. Since each index had different characteristics, the motion-specific index was observed to be significant.Key words: Accelerometer, Standing and sitting motions, Smoothness     

Spinal shrinkage during work in a sitting posture compared to work in a standing posture

Objective. The objective was to measure the possible differences in shrinkage of the thoracolumbar spine in subjects working in a sitting and a standing posture for 6.5 h at work, in a realistic work environment. The isolated shrinkage of the thoracic and the lumbar spine was also examined.

Study design. This study presents a new protocol to measure shrinkage of the thoracic and lumbar spine separately.

Background. Controversies still exist with regard to the load on the spine in a sitting compared to a standing position. Some report that shrinkage is greatest in the sitting position while others report the reverse. However, nothing is known about the height reduction of the thoracic and the lumbar spine during loading for 6.5 h in a real work environment. Therefore, the behaviour of the thoracic and the lumbar spine under practical condition has to be investigated.

Method. A stadiometer with a measurement error of 0.51 mm was used to measure changes in spinal height during work. To exclude first-time behaviour of the spine, a pre-test lasting 50 min was undertaken. The mean of the last three measurements was used as the reference height. During work, height measurements of the spine were performed every 20 min. To separate the behaviour of the thoracic and the lumbar spine, two benchmarks were placed at the vertebrae prominens and at the thoracic-lumbar junction. Shrinkage of the spine was investigated within three different cohorts: (I) work in a sitting posture for 6.5 h; (II) relaxed sitting for 2 h vs work for 2 h in a sitting position and (III) work in a standing position for 6.5 h.

Results. Relaxed sitting leads to a gain in stature compared to work in a sitting position for 2 h. The major gain in stature occurred in the lumbar spine. Comparison of cohort (III) working in a standing position with cohort (I) working in a sitting position shows that the shrinkage of the spine is greatest when work is performed in a standing posture. The major differences were found in the shrinkage of the lumbar spine e.g. shrinkage of the lumbar spine in the standing cohort (III) was 4.16 mm compared to 1.73 mm in the sitting cohort (I).

Conclusions. There is a gain in stature during relaxed sitting compared to work in a sitting posture. The load on the spine is greatest when work in a standing position is performed. The greater shrinkage of the lumbar spine during work in a standing position compared to a sitting posture is probably due to: (i) differences in lumbar lordosis and (ii) the effect of bending and torsion while handling the work materials.     

金属植入物作用下腰椎后路3种融合方式的比较

背景:融合是腰椎减压椎弓根螺钉置入内固定后稳定运动节段的重要方式,经典的融合方式包括后外侧融合、后方椎间融合、后外侧融合并后方椎间融合。很多研究报道过几种融合方式的优势、技术要求、临床疗效和融合后并发症,但结论各异,很难明确最佳融合方式。目的:比较后外侧融合、后方椎间融合、后外侧融合并后方椎间融合的疗效差异,以期寻求最佳融合方式。方法:选择167例因退变性腰椎疾病行1个或2个节段融合,随访时间最短为3年的患者,分为3组,后外侧融合组62例,后方椎间融合组57组,后外侧融合+后方椎间融合组48例。通过目测类比评分、ODQ问卷和Kirkaldy-Willis量表评价患者的腰痛、下肢疼痛和功能状况,并进行影像学评价,包括椎间盘高度、腰前凸、病变节段间角度、融合情况及融合后并发症。结果与结论:最后1次随访结果表明,后外侧融合组患者中50例(80.7%)疗效优良,后方椎间融合组患者中50例(87.8%)疗效优良,后外侧融合+后方椎间融合组41例(85.5%)疗效优良,3组差异无显著性意义(P=0.704)。3种融合方式都明显改善了椎间盘高度(P<0.05),其中后外侧融合组椎间盘高度丢失最多,腰前凸和节段间角度明显增大,3种融合方式的节段间角度变化差异有显著性意义(P<0.05)。最后1次随访时,3种融合方式的不融合率差异无显著性意义(P>0.05)。治疗后并发症包括3例深部感染,4例暂时神经麻痹,1例永久神经麻痹,6例取骨处疼痛。提示3组融合方式在临床疗效和融合率方面无明显差异,后方椎间融合比后外侧融合能更好维持矢状面平衡。单纯后方椎间融合在缩短手术时间、减少失血量及避免取骨处疼痛方面有明显优势。     

金属植入物作用下腰椎后路3种融合方式的比较

背景：融合是腰椎减压椎弓根螺钉置入内固定后稳定运动节段的重要方式,经典的融合方式包括后外侧融合、后方椎间融合、后外侧融合并后方椎间融合。很多研究报道过几种融合方式的优势、技术要求、临床疗效和融合后并发症,但结论各异,很难明确最佳融合方式。目的：比较后外侧融合、后方椎间融合、后外侧融合并后方椎间融合的疗效差异,以期寻求最佳融合方式。方法：选择167例因退变性腰椎疾病行1个或2个节段融合,随访时间最短为3年的患者,分为3组,后外侧融合组62例,后方椎间融合组57组,后外侧融合＋后方椎间融合组48例。通过目测类比评分、ODQ问卷和Kirkaldy-Willis量表评价患者的腰痛、下肢疼痛和功能状况,并进行影像学评价,包括椎间盘高度、腰前凸、病变节段间角度、融合情况及融合后并发症。结果与结论：最后1次随访结果表明,后外侧融合组患者中50例（80.7%）疗效优良,后方椎间融合组患者中50例（87.8%）疗效优良,后外侧融合＋后方椎间融合组41例（85.5%）疗效优良,3组差异无显著性意义（P=0.704）。3种融合方式都明显改善了椎间盘高度（P〈0.05）,其中后外侧融合组椎间盘高度丢失最多,腰前凸和节段间角度明显增大,3种融合方式的节段间角度变化差异有显著性意义（P〈0.05）。最后1次随访时,3种融合方式的不融合率差异无显著性意义（P〉0.05）。治疗后并发症包括3例深部感染,4例暂时神经麻痹,1例永久神经麻痹,6例取骨处疼痛。提示3组融合方式在临床疗效和融合率方面无明显差异,后方椎间融合比后外侧融合能更好维持矢状面平衡。单纯后方椎间融合在缩短手术时间、减少失血量及避免取骨处疼痛方面有明显优势。     

Biomechanical model predicting electromyographic activity in three shoulder muscles from 3D kinematics and external forces during cleaning work

BACKGROUND: The shoulder region is a common site of work-related musculoskeletal disorders. Biomechanical models may reveal the relative importance of force, joint-moments, and angular velocity for predicting muscle activity, thereby contributing to identify risk factors. OBJECTIVE: The aim of the present study was to predict muscle activity patterns from joint kinetics during cleaning work and to identify the most important variables requesting muscle activity.Design. A comparative study of six cleaners performing five different floor cleaning tasks (combinations of tool and working method) in a laboratory setting. METHODS: Net forces and moments at the glenohumeral joint were estimated using a video-based 3D link segment model together with 3D force-transducers at each hand, separately. Angular velocities of the upper arm were calculated, and electromyographic activity was recorded bilaterally from the muscles trapezius, deltoideus, and infraspinatus. RESULTS: The biomechanical model revealed abduction moment in the glenohumeral joint to be the most important factor for development of muscle activity in m. deltoideus and m. infraspinatus, while for m. trapezius vertical force was most important. CONCLUSION: Muscle specific determinants for shoulder muscle activity could be identified from glenohumeral joint kinetics. RELEVANCE: This study documents that mechanical work requirements in terms of joint forces, moments of force and angular velocities can predict major fractions of muscle activity patterns in the upper extremities. The biomechanical model used for this prediction revealed different factors of importance for individual muscles. This knowledge is fundamental for work place interventions aiming at minimizing overloading of specific muscles to prevent or rehabilitate muscle disorders.     

Practice-related changes in lumbar loading during rapid voluntary pulls made while standing

Objective. To determine if five days of practice on a novel dynamic, multi-joint pulling task resulted in lower magnitudes of lumbar loading or a more consistent relationship between pulling force and lumbar loading.

Design. A repeated measures design compared how practice influenced the magnitude of lumbar torque and the correlations between lumbar torque and pulling force.

Background. Previous studies suggest that practice can decrease the magnitude of lumbar loading on simple manual material handling tasks, but it is unknown whether practice reduces lumbar loading for more complex tasks. Neither is it known whether the consistency of lumbar loading increases with practice.

Methods. Ten healthy adults practiced impulse-like horizontal pulls to targets equaling 20%, 40% and 80% of their estimated maximal dynamic pulling force over 5 days. Movements were unrestrained, other than keeping the feet flat on the ground. We used a four-segment, sagittal plane inverse dynamics model to compute lumbar, hip, knee, and ankle torques on days 1 and 5 from ground reaction forces and moments, pulling forces, and kinematics.

Results. An analysis of variance showed significant practice-related changes in lumbar torque at the time of peak pulling force (lumbar torque_peakPF). The lumbar torque_peakPF decreased for the 20% pulls, did not change for the 40% pulls, and increased for the 80% pulls. Two subjects showed a significant decrease in lumbar torque_peakPF for all three force levels. Coefficients of determination between pulling force and lumbar torque (r²_PF,LT: a measure of the consistency of the relationship between these two variables) were significantly higher on day 5 than day 1.

Conclusions. Practice on a novel pulling task changed the magnitude of lumbar torques and increased their correlation with pulling force, suggesting that subjects learned strategies that improve motor control of lumbar torques.Relevance

The study showed that the magnitude and consistency of lumbar loading changed spontaneously as subjects practiced a novel multijoint pulling task. Such changes may decrease the risk of low-back injury.     

Perceived body discomfort and trunk muscle activity in three prolonged sitting postures

[Purpose] This study aimed to investigate the perceived discomfort and trunk muscle activity in three different 1-hour sitting postures. [Subjects] A repeated-measures design study was conducted on 10 healthy subjects. [Methods] Each subject sat for an hour in three sitting postures (i.e., upright, slumped, and forward leaning sitting postures). Subjects rated perceived body discomfort using Borg’s CR-10 scale at the beginning and after 1 hour sitting. The electromyographic activity of the trunk muscle activity was recorded during the 1-hour period of sitting. [Results] The forward leaning sitting posture led to higher Borg scores in the low back than those in the upright (p = 0.002) and slumped sitting postures (p < 0.001). The forward leaning posture was significantly associated with increased iliocostalis lumborum pars thoracis (ICL) and superficial lumbar multifidus (MF) muscle activity compared with the upright and slumped sitting postures. The upright sitting posture was significantly associated with increased internal oblique (IO)/transversus abdominis (TrA) and ICL muscle activity compared with the slumped sitting posture. [Conclusion] The sitting posture with the highest low back discomfort after prolonged sitting was the forward leaning posture. Sitting in an upright posture is recommended because it increases IO/TrA muscle activation and induces only relatively moderate ICL and MF muscle activation.Key words: Pain, Sitting posture, Electromyography     

Acute effect of core stability and sensory-motor exercises on postural control during sitting and standing positions in young adults

SummaryCore stability exercises and exercises that stimulate sensory-motor information are recommended for the prevention of injuries and the maintenance and rehabilitation of deficits related to postural control (PC). However, the comparison of results between core stability and sensory-motor exercises in the literature is limited to sitting and standing positions.ObjectiveTo determine the acute effect of core stability and sensory-motor exercises on PC during sitting and standing in young adults.MethodsA total of 39 participants, with a mean age of 23 years, were randomly divided into three groups (1) Core stability exercises; (2) Sensory-motor exercises; (3) Control. Each group performed a sequence of five specific exercises of core stability and sensory-motor exercises (except controls). PC was evaluated before and after exercise in the seated and the one-legged stance conditions using a force platform.ResultsNo significant difference was found for any variables of postural oscillation (P > 0.05) among the three groups studied. The magnitude of the effect of interventions in general was a small to moderate effect (d = 0.02/-0.48).ConclusionThe findings show that acute intervention with core stability and sensory-motor exercises did not produce any significant effects (reduction of postural oscillation) on PC during sitting and standing positions in young adults.     

Changes in blood pressure in the sitting and standing positions in hypertensive patients

Ersoy S, Pinar R, Ersoy IH. International Journal of Nursing Practice 2011; 17 : 105–109 Changes in blood pressure in the sitting and standing positions in hypertensive patients Most guidelines for management of hypertension do not give special preference to a specific position of patient during blood pressure (BP) measurement, suggesting that BP readings taken with patients sitting, supine and standing are equivalent. The objective of this study was to examine whether there was any difference between BP readings with hypertensive participants comfortably sitting on chair and those with participants standing with the arm supported horizontally at the right atrial level. BP was measured twice each for 168 hypertensive patients (medicated and unmedicated) at sitting, standing and sitting positions, respectively, with a mercury‐filled column sphygmomanometer. We found significantly lower in systolic and diastolic BP readings in standing position than in sitting position. The present study indicates that the BP readings are related to the posture; thus, BP measured in different positions cannot automatically be regarded as equivalent.     

Kinematics and muscle activity of the head,lumbar and knee joints during 180° turning and sitting down task in older adults

Background

The “180° turning and sitting down task” is a very conscious movement that requires focusing on turning at the exact moment, and very few studies address on this topic in older adults. The purpose of the study was to compare kinematics and electromyography of the head, lumbar and knee joints during 180°turning in older and young adults.

Methods

Twenty older adults and 20 younger adults were assessed. A 16-channel telemetry electromyography system with electrogoniometers and an inclinometer were used to record the head, lumbar and knee joint kinematic and electromyography data during the 180° turning. This movement had been further divided into 4 phases (braking, mid-stance, swing, and terminal loading) for analysis.

Findings

There were significant differences in the joint displacement and muscular activity among the different phases. Comparison between groups showed that the older adults group had less lateral lumbar flexion, less knee flexion and lower velocity of the head and knee flexion compared to young adults during turning. The electromyography data of the left biceps femoris, left gastrocnemius and left erector spinae muscles in the older adults group showed significantly higher levels than in the young adults.

Interpretation

Older adults need to adjust velocities of moving joints and increase the extensor synergy muscles of the back and the stance leg to provide posture stability. Kinematics and neuromuscular modulations of the head, lumbar and knee are required according to the various phases of the turn movements and change with aging.