• Physical Therapy Korea
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• v.14 no.4
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• pp.66-74
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• 2007

The aim of the present study was to investigate age-related differences in stepping behavior in response to sensory perturbations of postural balance. The participants for this study were 2 healthy elderly adults (mean age=76.0) and 2 younger adults (mean age=25.5). Subjects were asked to step over a 10 cm high obstacle at self-paced speed with the right limb to land on the primary target (normal step length) that is 10 cm in diameter. However, if, during movement, the light was illuminated, then the subject had to step on the secondary target (long step length). It was planned that the onset of the light would be prior to peak Fx of swing limb, between swing peak Fx and swing toe-off, and after swing toe-off. In the younger adults these secondary visual cues were provided at mean times of 240 ms (standard deviation (SD)=11), 402 ms (SD=13), and 476 ms (SD=88) following the movement onset. Corresponding mean times for the healthy elderly were 150 ms (SD=67), 352 ms (SD=39), and 562 ms (SD=115). Results showed great changes in both group and visual cue condition in Fx ground reaction forces and temporal events following the swing toe-off. Swing limb acceleration force (Fx) and stance peak Fx1 was much greater in the young adults compared to the older adults. Both young and older adults increased stance peak Fx2 in the visual cue condition compared to normal stepping. There was no difference in stance peak Fx2 between the visual cue conditions in both groups. Similarly, the time to stance peak Fx2 was much longer for the visual cue condition than for the normal stepping. It was not different between the visual cue conditions in the young adults, but in the elderly mid and late cue was much greater than early cue. In addition, time to stance peak Fx2 and swing and stance time were much longer in the older adults compared to the young adults for the visual cue conditions. These results suggest that unlike young adults, elderly adults did not flexibly modify their responses to unexpected changes in step length while stepping over obstacles.

• The Journal of Korean Physical Therapy
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• v.23 no.3
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• pp.21-27
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• 2011

Purpose: The purpose of the present study was to examine, in stroke patients, differences between backward walking training applied on a treadmill and the same training applied on the ground. Methods: Twenty seven stroke patients were divided into a treadmill backward walking group of 14 patients and a ground backward walking group of 13 subjects. Each group performed their respective training method for 8 weeks (15 min per day, 4 days a week). Walking ability was measured using a 10 m MWS (Maximal Walking Speed) test and the GAITRite system to examine changes in walking. Cadence, stridelength, step time, step length and symmetry index of the less affected side were measured to examine changes in stance phase of the lower extremity of the more affected side. Results: 10 m MWS, cadence, stride length, step time and step length of the less affected side significantly increased and symmetry index significantly decreased after training in both groups. The treadmill backward walking group experienced a significantly greater increase in step time and step length and a significantly greater decrease in symmetry index than the ground backward walking group. Conclusion: The two walking training methods were effective for improving stability in stance phase of the lower extremity of the more affected side, but the treadmill method was more effective. The present study is meaningful in that it analyzed the effects of backward walking training methods on walking and the differences of the training methods to provide information necessary for effective treatment of stroke patients.

• Korean Journal of Applied Biomechanics
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• v.27 no.1
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• pp.75-81
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• 2017

Objective: The purpose of this study was to compare and analyze the kinematic variables and electromyography (EMG) findings that change with varying characteristics of crouch start and feedback provision, and to provide the fundamental data for record improvement in 400 mH. Method: Four short-distance runners participated in the experiment. The analyzed variables were elapsed time per interval, stride length, and muscle activities in three lower limb muscles. These variables were analyzed by using Kwon3d XP and Noraxon Myoresearch. The participants were subjected to three conditions, including two conditions that relate to the thrusting foot on the rear block and another condition pertinent to feedback provision. Results: In terms of a one-step interval, the elapsed time in condition A was longer than that in condition B, and the one after the feedback was the longest. The stride length of a one-step interval was the longest in condition A. The stride length of a two-step interval was the shortest in condition A. The muscle activity during a one-step interval showed differences in vastus medialis and medial gastrocnemius, with condition A being the highest. Conclusion: When the non-dominant left foot was located at the back, negative results were observed in terms of elapsed time and stride length. Moreover, an imbalance in muscle activity was observed between the left and right feet when the left foot was placed at the back. As a result, significant differences in elapsed time, stride length, and muscle activity were observed depending on the foot placed on the rear block. In conclusion, we identified the characteristics of crouch start in 400 mH, and a specialized program must be suggested.

• Physical Therapy Rehabilitation Science
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• v.3 no.1
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• pp.43-48
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• 2014

Objective: The purpose of this study was to examine the influences on gait features during mobile phone use while ramp walking. Design: Cross-sectional study. Methods: Thirty-three healthy adult subjects performed four walking conditions on an outside ramp with a 5 m length, 1.5 m width, and a $5^{\circ}$ angle. All participants were touch screen mobile phone users. Four walking conditions were used: 1) ramp ascent, 2) ramp descent, 3) texting during ramp ascent, and 4) texting during ramp descent. In conditions 3) and 4), subjects texted the words of "Aegukga"-the song of patriotism-while walking. Upon the signal of start, the subjects walked the ramp during texting. Gait parameters were measured at the length of 3 m excluding 1 m of the start and end of the total length. Each situation was repeated three times for each subject, and mean values were calculated. For gait examination, a gait analyzer was used (OptoGait). Results: Subjects ranged in age from 23 to 38 years (mean age, 27.73). Eighty-three percent of subjects in our study had experienced an accident during mobile phone use. Texting on a mobile phone while walking significantly decreased ramp gait, speed, cadence, stride length, step length, and single support (p<0.05) and significantly increased stride time, step time, gait cycle, and double support (p<0.05). There was a significant difference in cadence, step length, stride time, step time, and single support during ramp ascent and descent (p<0.05). Conclusions: Texting on a mobile phone while walking significantly decreased gait quality.

• Korean Journal of Applied Biomechanics
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• v.14 no.3
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• pp.149-163
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• 2004

This study analyzed kinematic variables about the cross step, the delivery and the release for women's javelin athletics recorded over 50m in the 2004 Busan International Athletics Competition. It was used the Kwon3D Motion Analysis Package Ver. 3.1 Program(Kwon, 2000) for analysing the kinematic variables about the distance, the velocity, and the angle, then we had the results as follows; 1 In the Cross step phase, the COG velocity was low because their step length was short. To keep the CM velocity from the approach to the last cross over step contact, the athletes have to keep the longer step length within about 130% of the athletics' height. 2. In the Delivery phase, the athletics' COG height was gradually lower, and the deceleration of the COG was going up. As the same in the cross step, Therefore the athletes have to increase the step length within about 100% of their height, in order to increasing the COG velocity. And it was shown they have to make small angle of the elbow as possible from the right foot contact to the left foot contact in order to being the big acceleration of the upperarm at the release phase. 3. In the release phase, it was shown to being low position of the release point as the COG was low and then the release velocity of the upperarm was low. Specially when the shoulder lean lateral angle is big at the release phase, it was shown they have a excessive release angle. And, when it was shown the high rotation angle of the shoulder, the shoulder was opened forward bigger than the trunk was opened forward. So the transmission of velocity from the proximal segments was a fast change.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2004.10a
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• pp.347-350
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• 2004

In this paper, the acceleration is studied for the rigid-plastic FEM of metal forming simulation. In the FEM, the direct iteration and Newton-Raphson iteration are applied to obtain the initial solution and accurate solution respectively. In general, the acceleration scheme for the direct iteration is not used. In this paper, an Aitken accelerator is applied to the direct iteration. In the modified Newton-Raphson iteration, the step length or the deceleration coefficient is used for the fast and robust convergence. The step length can be determined by using the accelerator. The numerical experiments have been performed for the comparisons. The faster convergence is obtained with the acceleration in the direct and Newton-Raphson iterations.

• Geomechanics and Engineering
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• v.5 no.6
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• pp.519-540
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• 2013

This paper presents an optimal design method for determining pile lengths of piled raft foundations. The foundation settlement is evaluated by taking into account the raft-pile-soil interaction. The analysis of settlement is simplified by using Steinbrenner's equation. Then the total pile length is minimized under the settlement constraint. An extended sequential linear programming technique combined with an adaptive step-length algorithm of pile lengths is used to solve the optimal design problem. The accuracy of the simplified settlement analysis method and the validity of the obtained optimal solution are investigated through the comparison with the actual measurement result in existing piled raft foundations.

• Journal of the Korean Society of Clothing and Textiles
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• v.22 no.1
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• pp.18-28
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• 1998

The objective of the study was to observe the difference of moving function of lower-limb in relation to the length 8t silouutte of tight skirt. Four types of tight skirts (2 lengths$\times$2 silhouettes) were made for the experiment. The surface E.M.S in four different locations of leg muscles (Rectos femoris, Semitendinosus, Tibalis anterior, Gastrocnemius) were recorded. The sensory test to decide how to be fatigued after longtime wearing of skirt were examined two times per a day. The fatigue sensory test was scored a Likert-type scale (1= no fatigue, 5=heavy fatigue). Data were analyzed by the repeated ANOVA ann Duncan's multiple range test with use of SAS Package. The main results of this study were as follows: 1. As a result of analysis of E.M.S., in case of walking on the floor there was significant difference in the moving function according to length of skirt and in case of stepping there was significant differnce in three ways (length silhouette, length, silhouette). 2. From the record of walking the step-length, stride-length, step-width were found affected by garments, but foot-angle was not affected. The moving function of slim type was lower than that of semi type and that of ankle-length skirt was lower than that of knee-length skirt. 3. The results of the sensory test agreed with that of E.M.G and Footprints.

• Korean Journal of Applied Biomechanics
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• v.26 no.2
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• pp.221-228
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• 2016

Objective: The purpose of this study was to investigate differences in gait parameters and symmetry between walking speed by using the Froude number and preferred walking speed. Method: Fifty adults (age: $21.0{\pm}1.7years$, body weight: $71.0{\pm}9.2kg$, height: $1.75{\pm}0.07m$, leg length: $0.89{\pm}0.05m$) participated in this study. Leg length-applied walking speed was calculated by using the Froude number, defined as Fr = ${\upsilon}^2$/gL, where v is the velocity, g is the gravitational acceleration, and L is the leg length. Video data were collected by using eight infrared cameras (Oqus 300, Qualysis, Sweden) and the Qualisys Track Manager software (Qualisys, Sweden), with a 200-Hz sampling frequency during two-speed walking (preferred walking speed [PS] and leg length-applied walking speed [LS]) on a treadmill (Instrumented Treadmill, Bertec, USA). The step length, stride length, support percentage, cadence, lower joint angle, range of motion (ROM), and symmetry index were then calculated by using the Matlab R2009a software. Results: Step and stride lengths were greater in LS than in PS (p < 0.05). The right single-support percentage was greater in LS than in PS (p < 0.05). The hip joint angle at heel contact and toe-off were greater in LS than in PS (p < 0.05). The hip and knee joint ROM were greater in LS than in PS (p < 0.05). Conclusion: Based on our findings, we suggest that increased walking speed had a significant effect on step length, stride length, support percentage, and lower joint ROM.

• Transactions of the Korean Society of Mechanical Engineers
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• v.19 no.9
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• pp.2328-2341
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• 1995

An experimental study on the flow over the axisymmetric backward-facing step was carried out. The purposes of the present study are to investigate the effect of the free stream turbulence intensity on the reattachment length and to understand the turbulence structure of the recirculating flows. Local mean and fluctuating velocity components were measured in the separated and reattaching axisymmetric turbulent boundary layer over the wall of convex cylinder placed in a water tunnel by using 2-color 4-beam fiber optics laser Doppler velocimetry. As the free stream turbulence intensity increased, the reattachment length became shorter due to the enhanced mixing in the separated shear layer. It was also observed that the reverse flow velocity and turbulent kinetic energy increase with increasing free stream turbulence intensity. Spectral data and flow visualization showed that low-frequency motions occur in the separated flow behind a backward-facing step. These motions have a significant effect on the time-averaged turbulence data.