• Proceedings of the ESK Conference
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• 1997.04a
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• pp.90-94
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• 1997

Many workers like welders are working in squat sitting postures with te object on the ground for an entire work shift. It is suspected that such prolonged squat sitting without any supporting stool would gradually cause musculoskeletal injuries to workers. This study is to quantitatively evaluate the physical stress caused by the prolonged squat sitting and to recommend a safe work/rest schedule for the task with squat sitting posture based on the lab experiment. In this study, 8 healthy student subjects participated in the experiment. They maintained a squat sitting posture for 16 minutes with 4 different stool height conditions: no stool, 10cm hight, 15cm height, 20cm height. Every 2 minutes, the discomfort was subjectively assessed using the magnitude estimation method for the whole body, lower back, upper leg and lower leg. Based on discomfort rating, we found that 10cm height stool relieved the workload most. Discomfort rating results also indicated that 20cm height stool showed the heghest workload, and that there was no difference in workload between 15cm height and no stool. We recommend to provide the workers with 10cm height stool for prolonged squat sitting tasks.

• The Journal of Korean Physical Therapy
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• v.23 no.3
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• pp.43-47
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• 2011

Purpose: This study determined the best adjustable height supporter for stroke patients in wheelchairs for the maintenance of a symmetric sitting posture. Methods: Thirty-one stroke participants and 20 age-matched control participants were recruited. The enrolled participants were evaluated by the Force Sensitive Application (FSA) System that was used to assess weight shift and symmetry in wheelchair sitting and assess the symmetric index (SI) of subjects according to 1, 2 and 3 cm height supporters. Results: When a 1 cm height supporter was applied to the paretic side of stroke survivors, sitting postures of stroke patients were significantly more symmetrical (p<0.01). Cross tabulation between the SI of wheelchair sitting and that of the paretic side of stroke patients caused? by a 1 cm supporter showed that 21 SIs of 26 stroke patients were improved by a 1 cm supporter to the paretic side (k=0.26, p<0.01). Conclusion: The findings of the present study demonstrate that stroke patients can maintain a more symmetrical sitting posture (than is possible when simply sitting in a wheelchair seat) if a 1 cm supporter is applied to the paretic side of stroke patients.

• Physical Therapy Korea
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• v.8 no.2
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• pp.55-63
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• 2001

For spinal flexibility measurements to be meaningful to clinicians or researchers, they must have a normative information and an understanding of how different variables affect spinal range of motion (ROM). Normal spinal ROM measurements are influenced to differing degrees by many factors. These factors include age, gender, time of day, leisure activities, previous history of low back pain, warming up, and the techniques with which normative data are collected. The additional variables of standing height, ratio of standing height to sitting height, and obesity had not been previously studied extensively and were shown to have a significant effect on flexibility in the sagittal plane. These relationship cannot be explained easily. Thus, the purpose of this study was to determine the relationship between spinal flexibility and individual factors (weight, standing height, and ratio of standing height to sitting height) that influence it. Fifteen healthy subjects between the ages of 20 and 27 years were studied. Two physical therapists measured independently the spinal forward bending ROM in the sagittal plane by Remodified Schober test and Finger-to-floor test. In order to determine the statistical significance of the result the Pearson's correlation was applied at the .05 level of significance. The results of this study were as follows: 1) Significant relationship was not identified between spinal flexibility and weight. 2) Significant relationship was not identified between spinal flexibility and standing height. 3) Significant relationship was not identified between spinal flexibility and ratio of standing height to sitting height.

• Physical Therapy Korea
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• v.26 no.4
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• pp.1-9
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• 2019

Background: Cervical dysfunction is a common pathomechanical marker in individuals with forward head posture (FHP). To overcome the limitations of the isometric chin-tuck (ICT) exercise, dynamic neuromuscular stabilization (DNS), which emphasizes an entire spinal chain exercise, has recently shown promising clinical results. Objects: Purpose of this study was to compare the immediate effects between ICT and DNS techniques. Methods: 43 young subjects (mean age, $24.0{\pm}5.0$ years) were recruited. Group of subjects with FHP were measured under baseline, ICT, and DNS conditions. Outcome measures included sitting height, longus colli (LC) and sternocleidomastoid (SCM) muscle thickness and LC/SCM thickness ratio. One-way repeated measures ANOVA was used to compare the continuous dependent variables among FHP, ICT, and DNS conditions at p<.016. Results: Both ICT and DNS exercise conditions yielded significantly increased LC muscle thickness, LC/SCM thickness ratio and sitting height than did FHP condition (p<.0001, respectively). Sitting height was significantly greater in DNS exercise than in the ICT exercise (p<.0001). Conclusion: The present results demonstrated that sitting height was greater in the DNS exercise than in the ICT exercise, as well as both corrective postural training exercises were effective on LC/SCM muscle balance ratio when compared with the baseline FHP condition. Therefore, it is considered that DNS exercise can be the recommended exercise for people with FHP.

• Journal of the Ergonomics Society of Korea
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• v.30 no.5
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• pp.605-611
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• 2011

Objective: The aim of this study was to investigate the influence of seat heights for optimizing the ingress/egress performance in the elderly people. Background: Recently elderly users have been increasing in number and the ease of ingress/egress of the vehicle becomes an important issue. Method: Seven elderly subjects participated in this study(age: 71.7${\pm}$3.6yr, height: 167.7${\pm}$5.4cm, weight: 68.1${\pm}$11.5kg). Each subject performed the sitting and rising task from comfortable seated position on the chair under the following conditions: (1) with a lumbar support and (2) without a lumbar support. We measured EMG activities of seven muscles(tibialis anterior, soleus, gastrocnemius, vastus lateralis, rectus femoris, biceps femoris and erector supinae) and ranges of motion in lower limb during sitting and standing from three different heights (400mm, 500mm and 600mm from ground) of slide-up seat. Results: Muscle activities and angular movements of hip and knee joints during standing-up and sitting-down with a high seat height(600mm) were reduced mean 30.4% in extensor muscles, 57.11% in flexor muscle, 18.74% in erector muscle and 31.0% in joints compared with a low seat height(400mm). Conclusion: Muscle activities and joint movements in hip and knee were reduced when rising/sitting from a high seat height(600mm) compared with a low seat height(400mm). Application: This study can be used to design vehicle that are easy to get in and out of by older peoples with or without impairments.

• Proceedings of the ESK Conference
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• 1995.04a
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• pp.124-133
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• 1995

A field study was conducted to assess the preferred height and the range of discomfort recognition of school desks and chairs for students from elementary school to high school. For this study 43 male subjects and 44 female subjects in Taejon area were surveyed. The result shows that the preferred height of chairs is about 1.7cm higher than the popliteal sitting height, while the preferred height of desks shows no significant difference with the elbow sitting height which is known to be the ergonomically proper desk height. The threshold value between comfort and discomfort recognition of chair height is 1.88cm below the most prefeered height and 1.79cm about it. The threshold value between comfort and discomfort recognition of desk height is 1.76cm below the most prefeered height and 2.62cm about it.

• Journal of the Ergonomics Society of Korea
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• v.14 no.2
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• pp.41-50
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• 1995

A field study was conducted to assess the preferred height and the range of discomfort recognition of school desks and chairs for students from elementary school to high school. For this study 43 male subjects and 44 female subjects in Taejon metropolitan area were surveyed. The result showed that the preferred height of chairs were found to be about 1.7cm higher than the popliteal sitting height, while the preferred height of desks showed no significant difference with the elbow sitting height which is known to be the ergonomically proper desk height. The threshold value between comfort and discomfort recognition of chair heigth was 1.88cm below the most preferred height and 1.79cm above it. The threshold value between comfort and discomfort recognition of desk height was 1.76cm below the most preferred height and 2.62cm above it.

• Journal of the Ergonomics Society of Korea
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• v.6 no.2
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• pp.3-8
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• 1987

In order to secure reliable values of measurement of the data about children's longitudinal develop- ment and physique examination and their growth states for 6 years from first grade through sixth grade in elementary school was collected based on their school health records. A sample physique group and general physique group were investigated and compared classified into girls and boys. The results are as follows; (1) Whe the difference of physiques in the sample group and general group is compared, boys and girls show little difference in height but boys differ greatly in weight and sitting-height but girls do in weight, girth of chest and sitting-height between 8 and 11 years old. (2) In the verification of the two groups; the body height in 7 years old show a significant difference at the P<0.5 level and their weights do at 7.8 and 11 years old. Girls' sitting-height at 11 years old shows a significant difference at the P<0.5 level. In the light of the above results because possibility of instrumental error in measurement is high between the two groups and also in case of the comparison of past sample data, the physique examination used in every school seems to be in need of reconsideration to reduce errors in measurement.

• PNF and Movement
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• v.19 no.2
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• pp.279-285
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• 2021

Purpose: This study aimed to develop new digital navicular drop test (ND-NDT) equipment and to determine its validity and reliability. Methods: A total of 24 healthy male and female adults, who fully understood the purpose of the study and gave consent to participate in the study, were selected as participants. The NDT and ND-NDT were conducted in the dominant foot of the participants in a random order. For the NDT, the position of the navicular bone was marked with a pen first; then, the height of the navicular bone from the ground was measured in both sitting and standing positions. For the ND-NDT, after the sticker-type reflection markers were attached to the position of the navicular bone, the height of the navicular bone from the ground was measured in both sitting and standing positions. To assess the validity of the diagnostic tests, the same examiner measured the height of the medial longitudinal arch (MLA) three times in both the sitting and standing positions. To assess the inter-rater reliability of the ND-NDT, three examiners, in a random order, attached the sticker-type reflection markers to the position of the navicular bone and then measured the height of the MLA in both positions. Results: In the sitting position, the Pearson correlation coefficient (r) between the two diagnostic tests was very high (r = 0.97) and statistically significant. In the standing position, the Pearson correlation coefficient (r) between the two tests was 0.95, which was also statistically significant. The ICC_2,1 values in the sitting and standing positions were 0.93 and 0.95, respectively, indicating significantly high inter-rater reliability. Conclusion: The ND-NDT equipment showed very high diagnostic validity, as well as excellent inter-rater reliability, indicating the clinical usefulness of the equipment as a diagnostic system for confirming pes planus.

• Journal of the Korean Society of Physical Medicine
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• v.18 no.3
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• pp.113-119
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• 2023

PURPOSE: This study aimed to determine the effects of using a smartphone in the sitting position on the pelvic posture and the low back pressure pain threshold (PPT). METHODS: Thirty participants (15 women and 15 men) were recruited for this study. The participants were asked to sit in a normal sitting position without using a smartphone, followed by sitting while watching a video using a smartphone. The pelvic posture was measured using the back range of motion II (BROM II) device and a palpation meter. We measured PPT using the digital pressure algometer. RESULTS: Pelvic posterior tilting was significantly greater when sitting while using a smartphone relative to sitting without using a smartphone (p < .05). There was no significant difference in the height of the iliac crest when sitting while using a smartphone compared to sitting without using a smartphone (p > .05). The PPTs of L1, L3, and L5 were significantly lower when sitting while using a smartphone relative to sitting without using a smartphone (p < .05). CONCLUSION: Based on these results, it can be concluded that frequent smartphone use while sitting may potentially increase the risk of developing low back problems.