• Journal of Korean Institute of Industrial Engineers
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• v.34 no.1
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• pp.90-97
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• 2008

Wedged insoles are frequently used to reduce the pains caused by the knee arthritis or the foot overuse syndrome. The present study analyzed the effect of wedged rear-foot insoles on the foot pressure in walking. Three medially wedged insoles with three angles (5, 8 and 15") and three laterally wedged insoles with the same angles were made, and a flat insole were prepared. Ten healthy males in twenties walked in a specified line with each insole. Center of pressure (COP), relative vertical force and maximum force on anatomical areas were analyzed from the measured foot pressure data. At heel contact, medially wedged insoles significantly increased the pressure of the medial foot side (COP moved medially by 2-5 mm and maximum pressure of 1st metatarsal head increased by 110-120% relative to the flat insole), In contrast, laterally wedged insoles significantly increased the lateral side pressure (COP moved laterally by 1-5 mm and the ratio of $2^{nd}$ metatarsal head pressure to $1^{st}$ metatarsal head increased by 0.5-2.0 relative to the flat insole). At toe off, both wedged insoles significantly increased the pressure of the medial foot side (COP moved medially by 0.5-10 mm and the ratio of $1^{st}$ metatarsal head pressure to $5^{th}$ metatarsal head increased by 2.0 relative to the flat insole). Especially, the laterally wedged insoles significantly increased the relative vertical force (6-12%) of the rear-foot more than the flat insole.

• The Journal of Korean Physical Therapy
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• v.23 no.2
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• pp.1-5
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• 2011

Purpose: This study examined the difference in the center of pressure (COP) displacement time in older adults according to the obstacle height during stance at each sub.phase when crossing obstacles. Methods: Fifteen older adults were enrolled in this study (${\geq}65$ years of age). The F-scan was used to measure the COP displacement time when crossing a 0, 10 and 40cm obstacle, and the stance phase was divided into 4 sub-phases according to the foot contact pattern. Results: During the stance phase, the COP displacement time increased with increasing obstacle height. During the mid-stance, terminal stance and pre-swing except for the loading response, there were significant differences in the COP displacement time according to the obstacle height. Conclusion: This study suggests that older adults show differences in the COP displacement time according to the stance sub-phase while crossing obstacles, and they use different mechanisms according the sub-phases to maintain balance during obstacle crossing.

• Journal of Navigation and Port Research
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• v.38 no.5
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• pp.485-491
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• 2014

In this paper, it is proposed that the effects of simulator sickness due to scene movement in ship handling simulator can be measured by using center of pressure (COP) and a simulator sickness questionnaire (SSQ). For experiments of simulator sickness, twelve participants are exposed to scenes movement from ship handling simulator according to three steps of sea states. During experiments, COPs for subjects are measured by force plate. After exposure to scenes movement, subjects describe their sickness symptoms by answering the SSQ. Throughput analysing the results of scene movement, SSQ, and COP, the relation between the simulator sickness and COP is investigated. It is suggested that formulations for SSQ score and COP with respect to sea state are obtained by the curve fitting technique, and the longitudinal COP can be used for measuring the simulator sickness.

• The Journal of Internal Korean Medicine
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• v.36 no.4
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• pp.478-485
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• 2015

Objectives: The purpose of this study was to analyze the change of area and average velocity of the center of pressure (COP) according to gait improvement in post-stroke hemiplegic patients.Methods: We measured the area and the average velocity of COP displacement of ten post-stroke hemiplegic patients while they stood quietly on a force plate at the time of dependent and independent gait . We also measured the area and the average velocity of COP displacement of normal persons to verify differences between them and post-stroke hemiplegic patients.Results: The area of COP displacement decreased significantly, and the average velocity of COP displacement tended to decrease, but not significantly. There were significant differences in the area and the average velocity of COP displacement between post-stroke hemiplegic patients and normal persons.Conclusions: The results of this study show that postural control ability improves as gait improves.

• Journal of the Korean Society of Physical Medicine
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• v.16 no.2
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• pp.1-8
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• 2021

PURPOSE: This study examined the effects of changes in the head direction (forward, upward 10° and downward 10°) on the quadriceps, center of pressure (COP), and foot pressure during squat exercises. The aim was to determine if the head direction could better activate the quadriceps muscle and provide a safer and stable squat posture during squat exercise. METHODS: Fifteen healthy college students were asked to stand on a Zebris, and three electrodes for sEMG were attached to their vastus medialis oblique (VMO), vastus lateralis (VL), and rectus femoris (RF) muscles. The participants then performed squatting exercises under three head directions (forward, upward 10°, and downward 10°). Surface electrodes were then used to record the EMG data during exercise. The Zebris FDM-SX was used to measure the foot pressure and COP of the participants. RESULTS: In squat exercise, the upward head direction group showed significantly higher VL activation than the downward head direction group (p < .05). The upward head direction group showed a significant backward change in the deviation of the COP than the downward and forward groups (p < .05). The upward head direction group showed a significant decrease in forefoot pressure than the downward and forward groups (p < .05) and an increase in the hindfoot pressure compared to the downward and forward groups (p < .05). CONCLUSION: The head direction upward in squat exercise has a positive effect on the quadriceps.

• The Journal of Korean Physical Therapy
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• v.22 no.1
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• pp.47-51
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• 2010

Purpose: The purpose of this study was to determine whether there are any differences, with and without a toe spreader (TS), in dynamic foot pressure distribution in children with spastic diplegic cerebral palsy. Methods: Dynamic foot pressure recording using the RSscan system were obtained during walking in 12 participants (male=7, female=5) with and without TS. Mean force was measured for four different plantar regions; great toe, forefoot, midfoot, hindfoot. Displacement of center of pressure (COP), velocity of COP displacement and stance time were also measured during gait. Results: TS walking exhibited statistically significant decrease of mean force under great toe and forefoot (p<0.05), compared with a barefoot walking. Also, TS walking exhibited statistically significant increase of antero-posterior displacement of COP (p>0.05). Conclusion: These findings indicate the potential clinical utility of toe spreader to correct dynamic foot pressure during stance phase in children with spastic diplegic cerebral palsy.

• PNF and Movement
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• v.19 no.3
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• pp.375-382
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• 2021

Purpose: The objectives of the present study were to investigate the disadvantages of tire pressure asymmetry of a wheelchair tire and recommend the criterion for appropriate tire pressure without generating negative changes in the musculoskeletal system in asymptomatic participants. Methods: Fourteen asymptomatic participants were asked to sit in pressure-controlled wheelchairs and perform desk work for 20 minutes in each tire condition. The asymmetry of the tire conditions was set as 0% difference, 25% difference, and 50% difference from the recommended pressure. The pelvic alignment and muscular recruitment represented as a flexion-relaxation ratio (FRR) were measured at pre-test, and after each condition of desk work. The displacement of the center of pressure (COP) was measured during the desk work. Results: The tire air pressure condition significantly affected the FRR and COP (P < 0.05). Both sides of the FRR values were significantly higher under the symmetrical tire conditions (0% difference) and pre-test, compared with the asymmetrical tire condition of 50% difference (P < 0.05). The mediolateral COP displacement of the asymmetrical tire conditions (25% and 50% difference) was significantly higher than that of the symmetrical tire conditions (0%) (P < 0.05). Conclusion: Asymmetrical tire conditions could cause changes in the muscle recruitment pattern of the erector spine and mediolateral COP displacement. Tire pressure asymmetry higher than 50% could be a risk factor for prevalence of back pain, so this level of asymmetry in tire pressures should be cautioned against for wheelchair users.

• Physical Therapy Korea
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• v.28 no.1
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• pp.77-83
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• 2021

Background: Although symmetry of spatio-temporal parameter and center of pressure (COP) shift during walking is associated with knee adduction moment, research on clinical association with knee osteoarthritis (OA)-related knee pain and functional scores is lacking. Objects: The aims were 1) to compare symmetry of gait parameters and COP-shift in patients with unilateral knee OA and pain and matched controls, and 2) to investigate the relationship between symmetry of gait parameters and COP-shift, and clinical measures. Methods: Female subjects (n = 16) had with unilateral radiological knee OA and pain. Healthy controls (n = 15) were age-matched to OA group. Symmetry of foot rotation, step length, stance and swing phase, lateral symmetry of COP and anterior/posterior symmetry of COP during walking was assessed. To assess the clinical variables, pain intensity, pain duration and function using Knee Osteoarthritis Outcome Survey (KOOS) subscales were collected. We compared symmetry between groups using Mann-Whitney U-test or independent t-test. Relationships between clinical measures and symmetry index measured using Spearman's correlation test. Statistical significance was set at α = 0.05. Results: Knee OA group showed significantly greater values of only lateral symmetry of COP (p < 0.01) than healthy group. Values of lateral symmetry of COP had moderate or strong correlation significantly with the intensity of knee pain, pain duration, and scores of all KOOS subscales (p < 0.01). Conclusion: Patients with unilateral knee OA and pain showed more asymmetry of lateral COP-shift during walking compared with matched healthy controls. In addition, larger asymmetry of lateral COP-shift has the moderate or strong association with worse of knee pain, worse in KOOS scores and longer duration of knee pain. Asymmetry of lateral COP-shift during walking may be one of the characteristics of unilateral knee OA as the compensatory strategy response to unilateral OA of the knee.

• Journal of the Korean Society of Physical Medicine
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• v.5 no.1
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• pp.15-24
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• 2010

Purpose : The purpose of this study was to investigate the effect of loading position on plantar center of pressure(COP) displacement when carrying a schoolbag during walking. Methods : Forty-four normal subjects were randomly assigned to five groups according to the method of carrying a schoolbag. The carrying a schoolbag methods were classified into five conditions: no bag (condition 1), a backpack (condition 2), a shoulder bag (condition 3), a cross bag (condition 4), a one-hand bag (condition 5). COP displacement such as anteroposterior distance and mediolateral distance of COP were measured with F-scan system. The repeated one-way analysis of variance (ANOVA) and independent t-test were used to confirm the statistical significance. Results : In the comparison of parameters of COP displacement between conditions, anteroposterior distance and mediolateral distance in the left foot and mediolateral distance in the right foot were not significantly different(p>.05), but anteroposterior diatance in the right foot was significantly different(p>.05). Between left and right foot, at condition 1 and 5 the mediolateral distance of COP was significantly different(p<.05) but anteroposterior distance at condition 1 and 5, anteroposterior distance and mediolateral distance of COP at condition 2, 3 and 4 were not significantly different(p>.05). Conclusion : These findings showed that the various loading position by five types of carrying a schoolbag didn't have influence significantly on COP displacement on during walking because of mechanism of postural adaption.

• Physical Therapy Korea
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• v.17 no.4
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• pp.1-7
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• 2010

The aim of this study was to investigate the effects of lumbar stabilization on both trunk and lower limb muscle activity and center of pressure (COP) in single leg standing. Surface electromyography (EMG) was used to collect muscle activity data, the mean velocity of COP was measured using a force plate, and a pressure biofeedback unit was used for lumbar stabilization training. The findings of this study are summarized as follows: 1) The EMG activity of the erector spinae decreased significantly and the activity of the rectus abdominis, internal oblique, external oblique, gluteus maximus, and gluteus medius increased significantly with lumbar stabilization single leg standing. 2) No differences in activity in the tibialis anterior, medial gastrocnemius, rectus femoris, and medial hamstrings were found with single leg standing. 3) The mean velocity of COP in the antero-posterior and medio-lateral directions in the lumbar stabilization single leg standing decreased significantly compared with the preferred single leg standing. The findings of this study therefore indicate that lumbar stabilization can facilitate the co-activation of deep stabilization and global muscles that improve postural control capability during single leg standing.