• The Transactions of The Korean Institute of Electrical Engineers
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• v.56 no.5
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• pp.990-992
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• 2007

The purpose of this study is to develop a practical gait-event detection system which is necessary for the FES (functional electrical stimulation) control of locomotion in paralyzed patients. The system is comprised of a sensor board and an event recognition algorithm. We focused on the practicality improvement of the system through 1) using accelerometer to get the angle of shank and dispensing with the foot-switches having limitation in indoor or barefoot usage and 2) using a rule-base instead of threshold to determine the heel-off/heel-strike events corresponding the stimulation on/off timing. The sensor signals are transmitted through RF communication and gait-events was detected using the peaks in shank angle. The system could detect two critical gait-events in all five paralyzed patients. The standard deviation of the gait events time from the peaks were smaller when 1.5Hz cutoff frequency was used in the derivation of the shank angle from the acceleration signals.

• Journal of the Korean Society of Physical Medicine
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• v.10 no.3
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• pp.95-100
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• 2015

PURPOSE: The purpose of this study is to investigate the effects of the angles of the knee and heel-off on the muscle activity during a bridge exercise. METHODS: 15 healthy adult men and women with the balance ability and joint working range required for performing a bridge exercise participated in this study, in which $120^{\circ}$, $90^{\circ}$ and $60^{\circ}$ angles of the knee-flexion and heel-off were applied during the bridge exercise. RESULTS: Our data showed that there were significant differences in muscle activities of elector spinae and rectus abdominis when $120^{\circ}$ and $60^{\circ}$ angles of the knee were applied, of internal oblique when $120^{\circ}$ and $60^{\circ}$ were applied, and external oblique when $90^{\circ}$ and $60^{\circ}$ were applied. When heel-off was applied, there were significant differences in muscle activities of elector spinae and rectus abdominis when $120^{\circ}$ and $60^{\circ}$ were applied, of internal oblique when $120^{\circ}$ and $60^{\circ}$ were applied, and external oblique when $90^{\circ}$ and $60^{\circ}$ were applied. CONCLUSION: In this study on an application of heel-off to the bridge exercise, we showed that the effect of the angles of the knee on the muscle activities of elector spinae, rectus abdominis, internal oblique and external oblique were all similar to the regular bridge exercise, but overall muscle activities were increased with heel-off when compared with the regular bridge exercise.

• Korean Journal of Applied Biomechanics
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• v.15 no.3
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• pp.1-7
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• 2005

Excessive pronation and impact force during running are related to various running injuries. To prevent these injuries, three type of running shoes are used, such as cushioning, stability, and motion control. Although there were may studies about the effect of midsole hardness on impact force, no study to investigate biomechanical effect of motion control running shoes. The purpose of this study was to determine biomechanical difference between cushioning and motion control shoes during treadmill running. Specifically, plantar and rearfoot motion, impact force and loading rate, and insole pressure distribution were quantified and compared. Twenty male healthy runners experienced at treadmill running participated in this study. When they ran on treadmill at 3.83 m/s. Kinematic data were collected using a Motion Analysis eight video camera system at 240 Hz. Impact force and pressure distribution data under the heel of right foot were collected with a Pedar pressure insole system with 26 sensors at 360 Hz. Mean value of ten consecutive steps was calculated for kinematics and kinetics. A dependent paired t-test was used to compare the running shoes effect (p=0.05). For most kinematics, motion control running shoes reduced the range of rearfoot motion compared to cushioning shoes. Runners wearing motion control shoe showed less eversion angle during standing less inversion angle at heel strike, and slower eversion velocity. For kinetics, cushioning shoes has the effect to reduce impact on foot obviously. Runners wearing cushioning shoes showed less impact force and loading rate, and less peak insole pressure. For both shoes, there was greater load on the medial part of heel compared to lateral part. For pressure distribution, runners with cushioning shoes showed lower, especially on the medial heel.

• Korean Journal of Applied Biomechanics
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• v.19 no.2
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• pp.379-386
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• 2009

During running, the human body experiences repeated impact force between the foot and the ground. The impact force is highly associated with injury of the lower extremity, comfort and running performance. Therefore, shoemakers have developed shoes with various midsole properties to prevent the injury of lower extremity, improve the comfort and enhance the running performance. The purpose of this study is to investigate the influence of midsole hardness on vertical ground force and heel strike angle during men's and women's running. Five male and five female expert runners consented to participate in the study and ran at a constant speed with three different pairs of shoes with soft, medium and hard midsole respectively. In conclusion, regardless of gender, there was ill significant difference among three shoes in maximum vertical ground reaction force, impact force peak and stance time. However, the loading time decreased and the loading rate increased as the midsole became harder. Female subjects showed more sensitive reaction with respect to the midsole hardness, while male subjects showed subtle difference. The authors expect to apply this results for providing a guideline for utilizing proper midsole hardness of gender-specific shoe.

• Physical Therapy Rehabilitation Science
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• v.9 no.1
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• pp.10-17
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• 2020

Objective: Hallux valgus (HV) is a common musculoskeletal deformity that is accompanied with pain and continues to decrease one's quality of life and ability to perform daily life activities by affecting gait and static stability. Therefore, this study aimed to investigate the effect of the angle of HV (HVA) and to compare the one-legged stance and gait parameters in young adults with less HV and severe HV. Design: Cross-sectional study. Methods: Forty young adults were divided into two groups, where HVA ≥15° (n=20) was defined as HV, and HVA <15° (n=20) was defined as normal. For balance ability, the center of pressure (COP) path, velocity, length of axis of the COP path, deviation of the x-axis and y-axis, and percentage of foot pressure were measured, and gait, the foot rotation angle, step length, percentage of each phase of the gait cycle, time change from the heel to forefoot, and maximum pressure of the forefoot and midfoot were measured. Results: Significant differences were found in sway length and time change from heel to forefoot during walking between the normal and HV groups (p<0.05). Most parameters were not associated with the HVA, but parameters such as length of axis and time to change from heel to forefoot were significantly associated with the HVA (p<0.05). Conclusions: These results suggest that most one-legged stance and gait parameters were not significantly affected by the HVA in young adults; therefore, future studies are needed in order to address other dynamic parameters and other methods of gait analysis for detecting clinically meaningful conditions.

• Journal of the Korean Society of Marine Environment & Safety
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• v.27 no.3
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• pp.409-420
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• 2021

The decrease in under keel clearance (UKC) due to the increase of draft that occurs during advancing and turning of very large vessels of different types was analyzed based on computational fluid dynamics (CFD). The trim change in the Duisburg test case (DTC) container ship was much smaller than that of the KRISO very large crude oil carrier 2 (KVLCC2). The sinkage of both ships increased gradually as the water depth became shallower. The amount of sinkage change in DTC was greater than that in KVLCC2. The maximum heel angle was much larger for DTC than for KVLCC2. Both ships showed outward heel angles up to medium-deep water. However, when the water depth became shallow, an inward heel was generated by the shallow water effect. The inward heel increased rapidly in very shallow water. For DTC, the reduction ratio was very large at very shallow water. DTC appeared to be larger than KVLCC2 in terms of the decreased UKC because of shallow water in advancing and turning. In this study, a new result was derived showing that a ship turning in a steady state due to the influence of shallow water can incline inward, which is the turning direction.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• 2019.11a
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• pp.269-269
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• 2019

The ships are turning for the purpose of collision avoidence and change of course. It is possible that ships have capsizing accident when improper loading of cargo and excessive use rudder angle in turning. It is difficult for navigation officers to recognize the danger of heeling during a turn, because the dynamic state of the ship changes in real time. Thus, in this study, ship's heeling angle was predicted during turning using the maneuverability indices estimated from the ship's autopilot. The maneuverability indices estimated through the Kalman filter of Autopilot is real-time predictable. The turning radius was obtained from the estimated Index of turining ability and calculations of the heeling angle were possible in turning. It is intended to be used as a basic data on the prevention of danger heeling angle during turning.

• Journal of Navigation and Port Research
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• v.40 no.6
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• pp.353-360
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• 2016

The International Maritime Organization (IMO) has issued international standards for ship maneuverability and stability. These have been established to improve marine safety and influence the direction of research. The previous literature has been researched, but there are few studies on the relationship between ship maneuverability and stability. This study carried out a fundamental experiment to quantitatively evaluate that relationship. Radius of turn and maximum heel angle depending on changing were analyzed through a turning test using a free running model ship. The test results show the change tendency of decreasing turn radius and increasng maximum heel angle according to a GM decrease. A rough estimate equation is proposed to predict the change tendency on radius of turn and angle of maximum heel as GM decreases. Many ships can suddenly experience reduced GM due to unexpected reasons during sailing. The results in this study can be used as fundamental data to estimate a ship's tactical turn diameter and variable heel angle for steering as GM decreases.

• Korean Journal of Applied Biomechanics
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• v.12 no.1
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• pp.15-30
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• 2002

The purpose of this study was analyzed the effect of kinematical and kinetical factors of lower extremity of form change in the cause of growth an unborn child during in pregnancy. Three pregnant women were selected from pregnant 24 weeks as subjects. Each subjects were required to walk with usual walking speed. Cinematographic and GRF data were collected during walking, and the kinematical and kinetical variables were calculated using Kwon3d. Based on the results of the study, the following conclusions were drawn : 1. Step width and Step length The change of form during the period of pregnancy was not statistically found significant in the step width and the step length. 2. Angle of lower extremity 1) The change of form during the period of pregnancy was not statistically found significant in the hip angle at right heel contact, mid stance, but it was statistically found significant in the hip angle at toe off on p<.05. 2) The change of form during the period of pregnancy was not statistically found significant in the knee angle at right heel contact, mid stance, but it was statistically found significant in the knee angle at toe off on p<.05. 3) The change of form during the period of pregnancy was not statistically found significant in the ankle angle at right heel contact, mid stance, but it was statistically found significant in the ankle angle at toe off on p<.05. 3. Ground reaction force 1) The change of form during the period of pregnancy was statistically found significant in medial-lateral force(Fx) on p<.001. 2) The change of form during the period of pregnancy was not statistically found significant in post-anterior force(Fy). 3) The change of form during the period of pregnancy was statistically found significant in impulse force and minimum peak of vertical reaction force on p<.001, p<.01 but it was not statistically found significant in second maximum force.

• The Journal of Korean Physical Therapy
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• v.13 no.2
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• pp.467-475
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• 2001

The purpose of this study was to evaluate changes of static lumbar lordosis by different heel heights in normal adults and patients with herniation of nucleus pulposus(HNP). The lumbar lordosis was examined while standing on barefoot, on heel support with 4cm heel, and with 8cm heel in 10 normal adults and 10patients with HNP. Standing lumbar lateral view was performed by 20 minutes adaptation with corresponding shoe types. The angle of lumbar lordosis was taken with Wiltse and Winter's method(angles between upper margin of 1 st lumbar body and upper margin of 5th lumbar body). The results of this study were as follow: 1. Significant statistical decrease in lumbar lordosis was observed as heel heights were increased from barefoot to 8cm high heel in normal adults(p<0.05). 2. There were no significant differences in lumbar lordosis according to three different heel heights in patients with HNP(p>0.05). 3. In comparison of barefoot, There were statistically significant decrease in HNP patients compared with normal adults in terms of lumbar lordosis(p<0.05).