• Physical Therapy Korea
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• v.16 no.2
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• pp.31-39
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• 2009

This study is performed to investigate the difference of the spinal stability system with and without low back pain. There were 9 participants with low back pain and 9 asymptomatic subjects to be recruited, they were measured thoracic and lumbar curvature, trunk muscle activation in upright sitting postures and slump sitting, back muscle endurance, and lumbar proprioception. Spinal curvature and surface electromyography of 4 trunk muscles were measured in an upright sitting postures and slump sitting in 18 subjects. The result of the study was that there were significant differences between the groups in spinal curvature (p<.05), significantly higher external oblique activity and less internal oblique in the low back pain group than the healthy subjects (p<.05), and significantly less proprioception in the low back pain group (p<.05). But there was not a significant difference between the trunk muscle endurance groups. According to the result, the low back pain group had greater thoracic extension and higher global muscle activity in the upright sitting posture and less proprioception. This study was useful to suggest postural training for normal muscle activation, selective muscle strengthening to prevent chronic deterioration, and helpful in making a treatment plan to indicate a synthetic care method that includes increasing proprioception.

• Journal of the Ergonomics Society of Korea
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• v.27 no.1
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• pp.53-60
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• 2008

The purpose of this study is to provide basic data, such as exerting muscle power of the lower-extremity, EMG test and pressure distribution for designing ergonomic workstation in sitting posture. The exerting muscle power of the lower-extremity was measured by PRIMUS in 4 postures of 90$^{\circ}$, 120$^{\circ}$, 150$^{\circ}$ and 180$^{\circ}$. And performed ANOVA test on Max. and Mean 100%MVC. In EMG test for surveying muscle mobiligation, 5 muscles(Rectus Femoris, Vastus Lateralis, Gastrocnemius, Soleus, Tibialis Anterior) were employed. Additional experiment in pressure distribution in sitting posture by Pliance(16$\time$16 poles), Max. pressure was measured and performed ANOVA test on the results. Concludingly, sitting posture with 120$^{\circ}$ lower-extremity is the best design criterion for ergonomic workstation in sitting posture.

• Journal of the Korean Society of Clothing and Textiles
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• v.17 no.3
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• pp.415-427
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• 1993

The purpose of this study was to evaluate the thermoregulatory responses to postures under different environmental conditions and to obtain the basal information for standard clothing weight, indoor climates, and working condition. Two adult female (22.5yrs, 46kg) were participated in this study. The experimental conditions were divided into three groups ; 1) comfort($27{\pm}1^{\circ}C$, $60{\pm}10%$), 2) hot($34{\pm}1^{\circ}C$, $60{\pm}10%$), and 3) cold($21{\pm}1^{\circ}C$, $50{\pm}10%$) condition. The postures performed were as follows; standing, sitting on the chair, sitting on the floor, and supine on the floor. At each condition, subjective sensations, 12 points skin temperature, rectal temperature, total and local sweat rate, pulse rates, blood pressure, skin blood flow rate were measured. The results were as follows : 1. Rectal temperature was high significant among groups in order of supine, sitting on the floor, sitting on the chair, standing posture(p<0.01). 2. Skin temperature was high in part of contact with the surface of the floor or wall and the effect of posture was greater in peripheral temperature than torso temperature. Sitting on the chair and sitting on the floor posture showed higher peripheral temperature than standing and supine posture. And peripheral temperature was lower in supine posture than any other postures. 3. Total and local sweat rate were decreased in order of standing, sitting on the chair, sitting on the floor, supine posture. 4. Pulse rate and disastolic blood pressure were higher in standing posture than supine posture, and there was significant difference between two postures(p<0.001). 5. Blood flow rate of thigh was high in sitting on the chair and sitting on the floor posture and low in standing posture. Blood flow rate of leg was low in standing posture significantly(p<0.01). 6. In comfort and hot condition, temperature sensation and comfort sensation were higher in standing posture and lower in supine posture than any other postures. In cold condition, temperature sensation was lower and comfort sensation was higher in standing and supine posture than any other postures. And supine posture was appeared positive in hot condition and negative in cold condition. From this study, we confirmed the effects of posture on human thermoregulatory responses. Results indicate that even under same conditions and clothing weight, the insulation of clothing will be different to postures.

• Journal of Biomedical Engineering Research
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• v.33 no.2
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• pp.98-103
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• 2012

The purpose of this study was to compare premotor time(PMT) and electro-mechanical delay(EMD) between sitting and standing posture. Twenty four healthy young subjects(12 women and 12 men) participated in this study. Subjects were instructed to perform maximal, voluntary, isometric contraction of ankle muscle(tibialis anterior and gastrocnemius muscles) in reaction to auditory stimulus. PMT and EMD, calculated from stimulus, EMG and torque profile were compared between sitting and standing postures. As statistical analysis, paired t-test was performed to assess difference between sitting and standing posture. In both tibialis anterior and gastrocnemius muscles, EMD was found to be significantly longer for standing than sitting. However, PMT in standing posture was longer than that in sitting posture only in gastrocnemius muscles. These result indicate that increased reaction time, particularly, increased EMD of ankle muscles in standing posture may be caused by co-contraction of ankle muscles for postural control in standing posture.

• Journal of the Ergonomics Society of Korea
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• v.33 no.2
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• pp.143-153
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• 2014

Objective: The aim of this study is to investigate the effects of trunk-forearm supported sitting on trunk flexion angle, trunk extensor fatigue and seat contact pressure. Background: The relationship between sitting posture and musculoskeletal disorders of the trunk extensor fatigue and seat contact pressure has been documented. The trunk-forearm support type ergonomic chair was devised from the fact that trunk-forearm support has been reported to reduce trunk extensor activity and discomfort. Method: Using three different sitting postures, upright ($P_1$), trunk-forearm supported ($P_2$) and normal sitting ($P_3$), six healthy subjects participated in the study. Motion capture system was used to collect head and trunk flexion angle, and surface electromyography (sEMG) was used to collect myoelectric signal of upper trapezius, lower trapezius, erector spinae, multifidus, and pressure mat system was used to measure seat contact pressure. Results: When trunk and forearm were supported by the ergonomic chair, higher head flexion angle showed upright > trunk-forearm supported > normal in order, and muscle fatigue showed less than upright and normal sitting. Mean seat contact pressure decreased 19% than upright sitting. But muscle fatigue was not affected by each condition. Conclusion: Trunk-forearm supported sitting of the ergonomic chair showed positive effect in respect of trunk and head flexion angle, trunk extensor fatigue, seat contact pressure. To acquire comprehensive understanding of the effectiveness of the ergonomic chair, further studies such as anatomical effects from measurement of external applied loading effect to the body from interface pressure analysis are required. Application: The results of the publishing trend analysis might help physiological effects of trunk-forearm support type chair.

• Physical Therapy Korea
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• v.25 no.1
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• pp.62-70
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• 2018

Background: Sitting posture influences movements of scapulothoracic and glenohumeral joints and changes the shoulder muscle activities. The development and maintenance of correct sitting posture is important for the fundamental treatment of shoulder pain during rehabilitation. Objects: The purpose of this study was to investigate the effects of the sitting postures and the shoulder movements on shoulder muscle activities for both male and female. Methods: Twenty-eight subjects without shoulder-related diseases participated in this experiment. The subjects had randomly adopted three different sitting postures (upright posture, preferred posture, maximum slouched posture) and shoulder flexion angles in scapular plane ($30^{\circ}$, $90^{\circ}$, $120^{\circ}$). Surface electrodes were collected from upper trapezius (UT), anterior deltoid (AD), and posterior deltoid (PD) and the active shoulder range of motion was measured in each sitting posture and shoulder flexion angle. Results: The active range of motions of the shoulder external rotation and the flexion in the scapular plane decreased from the upright posture to the maximum slouched posture (p<.05, mixed-effect linear regression with random intercept, Tukey post-hoc analysis). All muscles showed the highest EMG activities at $120^{\circ}$ shoulder flexion with the maximum slouched posture and did not show the gender differences. Conclusion: Increased shoulder muscle activities may become the potential risk factor for the shoulder impairment and pain if people continuously maintain the maximum slouched posture. Therefore, an upright position is necessary during shoulder exercises, as well as in activities of daily living, including motions involving lifting the arms.

• Physical Therapy Korea
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• v.10 no.1
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• pp.63-76
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• 2003

This research was performed to compare spinal segment motion angle between low back pain (LBP) group and painless group during trunk flexion-extension and to investigate the effect of transversus abdominis strengthening exercise on spinal segment motion angle in LBP group. Nine subjects with LBP and ten subjects without LBP participated. Transversus abdominis strengthening exercise was performed in LBP group for three weeks, and spinal segment motion angles were compared before and after the exercise performance. Spinal segment motion angles were measured both in sitting and standing position. Results were as followed: 1) Subjects' average age was 24.79 years, height was 167.84 cm, and weight was 59.95 kg. 2) Spinal segment motion angle of T10/l1 was significantly higher in LBP group compared with painless group (p<.05) in sitting position during trunk flexion-extension. 3) In sitting position, whereas entire lumbar segment motion angles were lower in LBP group compared with painless group (p<.05), angle of L4/5 was higher in LBP group compared with painless group (p<.05). 4) There was no significant difference in thoracic segment motion angle in standing position. 5) After three weeks of transversus abdominis strengthening exercise, thoracic segment motion angle increased both in sitting and standing position (p<.05). 6) In painless group, there was no significant difference in entire spinal segment motion angles in sitting and standing position (p>.05). When spinal segment motion angles were compared between sitting and standing position, there were slight differences. In sitting position, there was no difference in spinal segment motion angle between LBP group and painless group while hip joint motion angle and sacral inclination angle of LBP group was lower than those of painless group (p<.05). In standing position, lumbar segment motion angle was significantly lower in LBP group than that of painless group. Transversus abdominis strengthening exercise influenced thoracic segment motion angle more significantly than lumbar segment motion angle.

• Physical Therapy Korea
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• v.24 no.2
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• pp.66-75
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• 2017

Background: After a stroke, the control of the trunk muscle may be severely impaired. Due to the importance of trunk control in complex daily postures, the ability to adopt a correct sitting posture is considered a determinant of the recovery of independent function after a stroke. Objects: The purposes of this study were to compare differences in buttock pressure between the left and right sides of hemiplegic patients and differences in their pelvic tilting angles (sagittal and coronal planes) after sitting training with visual biofeedback (VBF) in real time. Methods: Twenty-two individuals with unilateral strokes (11 left-side and 11 right-side hemiplegic stroke patients) participated in this study. Buttock pressure was measured using a pressure mat, and pelvic angles were measured using a palpation meter. Results: The asymmetry of pressure between the right and left (first and third chamber) sides was significantly decreased after the VBF training. The measurements obtained using the palpation meter revealed a significant decrease in the pelvic angles pre- versus post-intervention. Conclusion: VBF training may be distribute a patient's buttock pressure equally while in a sitting posture and increase the length of time a stroke patient can maintain a symmetrical sitting posture. It can also improve pelvic control while sitting in a neutral position.

• Journal of the Ergonomics Society of Korea
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• v.33 no.1
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• pp.15-25
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• 2014

Objective: This study aims to analyze the factors that affect the ability to maintain dynamic sitting balance (DSB), biomechanical characteristics, and physical characteristics in spinal cord injuries (SCI) patients. Background: Virtual ski training systems, ski equipment, and training protocols for disabled skiers are being studied to spread awareness. However, few studies have been reported on the sitting balance ability associated with chair mono skiing. Method: A dynamic sitting balance border system was built to investigate the ability to maintain dynamic sitting balance in SCI patients. Trunk muscle activity was evaluated by electromyogram while conducting dynamic sitting balance tests. The trunk muscle strength was tested with a portable handheld dynamometer. Physical activity scores were measured with the physical activity recall assessment. Results: There were high levels of correlation between the ability to maintain DSB and trunk flexor strength, extensor strength, rotator strength, and physical activity score. However, height, weight, and injury level in SCI patients were not correlated with the ability to maintain DSB. Additionally, strong negative correlations were found between muscle activities of the external oblique and lumbar erector spinae muscles and the ability to perform the backward tilt test. Trunk extensor muscle activity during the ball lifting test was significantly higher than in other tests. Conclusion: The results indicate that improving trunk muscle strength and physical activity can increase the ability to maintain DSB. Application: The findings of a close relationship between trunk strength, physical activity, and the ability to maintain DSB need to be reflected in the chair mono ski training program.

• PNF and Movement
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• v.16 no.3
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• pp.405-414
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• 2018

Purpose: The purpose of this study was to examine test-retest reliability and criterion-related validity of a trunk stability robot when measuring the weight-bearing symmetry static sitting and standing in stroke patients. Methods: For 27 stroke patients, weight-bearing symmetry was assessed twice, 7 days apart. The intraclass correlation coefficient (ICC2,1) and minimal detectable change (MDC) were used to examine the level of agreement between test and retest. The criterion-related validity of weight -bearing symmetry was demonstrated by Spearman correlation of modified Barthel index (MBI), the sit to stand test (STS), the timed up & go Test (TUG), and the function in sitting test (FIST). Results: the test-retest agreements were excellent for the weight-bearing symmetry of static sitting (ICC2,1: 0.90) and standing (ICC2,1: 0.89). It all showed that the acceptable MDC for the weight-bearing symmetry of static sitting and standing was 0.11 and 0.16, respectively (highest possible score<20 %), indicating that the measures had a small and acceptable degree of measurement error. The weight-bearing symmetry of static sitting was significantly correlated with the TUG(r=-0.45) and FIST(r=0.46)(p<0.05); the weight-bearing symmetry of static standing was also significantly correlated with MBI (r=0.65), TUG (r=-0.67), FIST (r=0.61)(p<0.01), and STS (r=-0.47)(p<0.05). Conclusion: The weight-bearing symmetry of static sitting and standing assessed by the trunk stability robot showed highly sufficient test-retest agreement and mild-to-moderate validity. It could also be useful for clinicians and researchers to evaluate balance performance and monitor functional change in stroke patients.