• Korean Journal of Applied Biomechanics
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• v.25 no.1
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• pp.85-94
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• 2015

Purpose : The purpose of this study was to investigate the influence on the ground reaction force parameters according to wearing positions of backpack for during stair ascending and descending. Methods : Participants selected as subject were consisted of young female(n=10) and performed stairs walks(ascending and descending) with 2 types of wearing position(front of trunk[FT], rear of trunk[RT]). Passive(Fz 1) and active(Fz 2) forces of the vertical GRF were determined from time function and frequency domain. Also shear forces(Fx, Fy 1, Fy 2), dynamic postural stability index(MLSI, APSI, VSI, DPSI), loading rate and center of pressure (${\Delta}COPx$, ${\Delta}COPy$, COP area) were calculated from time function and frequency domain. Results : Fx, Fy 1, Fy 2, and Fz 1 in GRF didn't show significant differences statistically according to the wearing positions of backpack(p>.05), but stair descending showed higher forces than that of stair ascending. Particularly, Fz 2 of stair ascending showed higher forces than that of stair descending(p<.001), RT types showed higher than that of FT types(p<.05). MLSI, APSI, VSI, and DPSI of stair descending showed the increased stability index than that of stair ascending(p<.05), MLSI of RT types showed the decreased stability index than that of FT types(p<.05). Loading rate didn't show significant differences statistically according to the wearing positions of backpack(p>.05), but stair descending showed higher loading rate than that of stair ascending(p<.001). Also, ${\Delta}COPx$ in stair descending showed the increased movement than that of stair ascending(p<.05). Conclusions : A backpack of 10 kg(10 kg(ratio of body weights $17.61{\pm}1.17%$) showed significantly change GRF parameters according to wearing positions during stair ascending and descending. If possible, we suggest that the dynamic stability, in case of stairs walking with a smaller weights can be further improved.

• Korean Journal of Applied Biomechanics
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• v.18 no.1
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• pp.169-178
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• 2008

The goals of this study were to provide data of 3 dimensional ground reaction force(GRF) parameters during stair ascent and descent on three different stair runs and to investigate variability and asymmetry index of them. 10 healthy adults participated in this study and performed 7 different types of gait with 10 trials each. After data analysis, following results were found. Firstly, stair run did not affect on the pattern of GRF parameters, coefficient of variation and asymmetry index. Secondly, a significant different GRF pattern was found between level walking and stair walking. Especially, ascending stair walking has only large Fz1 and small Fz3 while level walking and descending stair walking have a "M" shape connected by Fz1, Fz2 and Fz3. Thirdly, only vertical GRF parameters of stair walking revealed acceptable coefficient of variation and asymmetry index.

• Korean Journal of Applied Biomechanics
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• v.18 no.4
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• pp.161-169
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• 2008

The purpose of this study was to investigate kinetic variables of the lower extremity during walking on three different stair widths in healthy adults. Ten healthy college-aged adults($23.5{\pm}3.5$) recruited for this study. Each stairs with the same height and length(l8cm and 90cm) under the Korean Constructional Law but three different widths(26cm, 31cm and 36cm) were conducted for this study. One force plate(9286AA, Kistler Co.) was put on third stairs. One-way ANOVA was performed to find the stair width effects during stair walking and the following findings ware obtained. There was significantly decreased in ankle resultant joint moment at Pull-Up phase(p<.05) and, significantly increased in knee extension moment during mid-stance phase as stair width increase(p<.05), but there was no significance in ankle resultant joint moment was found at Forward Continuance Phase in Ascending Stair Walking and There was significantly increased in ankle resultant joint moment as stair width increase during mid-stance phase(p<.05) and no significance in knee and hip resultant moments among the stair width in descending stair walking.

• Korean Journal of Applied Biomechanics
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• v.25 no.3
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• pp.323-333
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• 2015

Objective : The purpose of this study was to investigate the changes of gait patterns and muscle activations with increased loads during stair walking. Also, it can be used as descriptive data about continuous stair walking in a real life setting. Method : Twelve sedentary young male adults(Age: $27.0{\pm}1.8yrs$, Weight: $65.8{\pm}9.9kg$) without any lower extremity injuries participated in this study. Participants performed stair walking up 7 floors and their ascending and descending motion on each floor was analyzed. A wireless electromyography(EMG) were attached on the Rectus Femoris(RF), Biceps Femoris(BF), Gastrocnemius(GN), Tibialis Anterior(TA) muscle to calculate integrated EMG(iEMG), median frequency(MDF) and co-contraction index(CI). Chest and left heel accelerometer signal were recorded by wireless accelerometer and those were used to calculate approximate entropy(ApEn) for analyzing gait pattern. All analyses were performed with SPSS 21.0 and for repeated measured ANOVA and Post-hoc was LSD. Results : During ascending stairs, there were a statistically significant difference in Walking time between 1-2nd and other floors(p=.000), GN iEMG between 2-3th and 6-7th(p=.043) floor, TA MDF between 1-2nd and 5-6th(p=.030), 6-7th(p=.015) floor and TA/GN CI between 2-3th and 6-7th(p=.038) floor and ApEn between 1-2nd and 6-7th(x: p=.003, y: p=.005, z: p=.006) floor. During descending stairs, there were a statistically significant difference in TA iEMG between the 6-5th and 3-2nd(p=.026) floor, and for the ApEn between the 1-2nd and 6-7th(x: p=.037, y: p=.000, z: p=.000) floor. Conclusion : Subjects showed more regular pattern and muscle activation response caused by regularity during ascending stairs. Regularity during the first part of stair-descending could be a sign of adaptation; however, complexity during the second part could be a strategy to decrease the impact.

• Korean Journal of Applied Biomechanics
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• v.25 no.3
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• pp.241-248
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• 2015

Objective : The purpose of this study was to investigate the theta on the components of ground reaction force according to the ground conditions during gait. Method : Six healthy women(mean age: 22 yrs, mean height: $166.14{\pm}2.51cm$, mean body weights: $56.61{\pm}4.58kg$) participated in this study. The medial-lateral GRF(Fx 1), anterior-posterior GRF(Fy 1, Fy 2), vertical GRF(Fz 1, Fz 2, Fz 3), and impact loading rate were determined from time function and frequency domain. Also, GRF theta were time function and forces. Results : Fx 1, Fy 1 and Fy 2 of stair descending showed significant statistically higher forces than that of level walking, and ascending. Fz 1 of stairs descending showed significant statistically higher forces than that of level walking and stairs ascending(theta $88.62^{\circ}$). Also, Fz 2 of level walking showed significant statistically higher forces than that of stairs ascending and descending(theta $65.78^{\circ}$). Fz 3 of stairs ascending showed significant statistically higher forces than that of level walking and stairs descending($65.26^{\circ}$). Impact loading rate of stairs descending showed significant statistically higher forces than that of level and ascending walking. The GRF showed similar correlation with GRF theta(r=.603) according to the ground conditions during gait. Conclusion : These results suggest that the GRF theta can be used in conjunction with a gait characteristics, prediction of loading rate and dynamic stability.

• Journal of rehabilitation welfare engineering & assistive technology
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• v.6 no.2
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• pp.15-22
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• 2012

The mechanical system of wearable walking assist robot needs to be optimized for adapting with human body structure and the planned control algorithm should have a secure procedure when a incongruity situation which can cause musculoskeletal injury occurs because a wearable robot is attached to a body. The understanding of walking or musculoskeletal motions characteristics must be preceeded and analyzed for developing novel wearable walking assist robot. In this study we tried to find out the capacities of powers and torques of joint actuators to design optimized performances of system and to obtain the analysis data to figure out the characteristics of joint movements during some types of walk. The major types of walk and motion are stair climbing and descending, sit-to-stand motion, and slope walking. In this study all these motions were analyzed experimentally except slope walking.

• Journal of the Institute of Electronics and Information Engineers
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• v.52 no.3
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• pp.181-189
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• 2015

Powered prosthesis is used to assist walking of people with an amputated lower limb and/or weak leg strength. The accurate gait phase classification is indispensable in smooth movement control of the powered prosthesis. In previous gait phase classification using physical sensors, there is limitation that powered prosthesis should be simulated as same as the speed of training process. Therefore, we propose EMG signal based gait phase recognition method to classify stairs ascending and stairs descending into four steps without using physical sensors, respectively. RMS, VAR, MAV, SSC, ZC, WAMP features are extracted from EMG signal data and LDA(Linear Discriminant Analysis) classifier is used. In the training process, the AHRS sensor produces various ranges of walking steps according to the change of knee angles. The experimental results show that the average accuracies of the proposed method are about 85.6% in stairs ascending and 69.5% in stairs descending whereas those of preliminary studies are about 58.5% in stairs ascending and 35.3% in stairs descending. In addition, we can analyze the average recognition ratio of each gait step with respect to the individual muscle.

• Journal of the Korean Society for Precision Engineering
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• v.23 no.4 s.181
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• pp.75-82
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• 2006

In this paper, we propose an optimal trajectory for biped robots to move up-and-down stairs using a genetic algorithm and a computed-torque control for biped robots to be dynamically stable. First, a Real-Coded Genetic Algorithm (RCGA) which of operators are composed of reproduction, crossover and mutation is used to minimize the total energy. Constraints are divided into equalities and inequalities: Equality constraints consist of a position condition at the start and end of a step period and repeatability conditions related to each joint angle and angular velocity. Inequality constraints include collision avoidance conditions of a swing leg at the face and edge of a stair, knee joint conditions with respect to the avoidance of the kinematic singularity, and the zero moment point condition with respect to the stability into the going direction. In order to approximate a gait, each joint angle trajectory is defined as a 4-th order polynomial of which coefficients are chromosomes. The effectiveness of the proposed optimal trajectory is shown in computer simulations with a 6-dof biped robot that consists of seven links in the sagittal plane. The trajectory is more efficient than that generated by the modified GCIPM. And various trajectories generated by the proposed GA method are analyzed in a viewpoint of the consumption energy: walking on even ground, ascending stairs, and descending stairs.

• Proceedings of the KOSOMBE Conference
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• v.1998 no.11
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• pp.84-85
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• 1998

This study was conducted to characterize the gait of a person climbing or descending the stairs. Using our motion analysis system (Vicon 370), gait patterns of ten healthy females (18.8 - 19.6 yrs. old) were measured 1) when a subject tip-toed the stairs, 2) when a subject climbs the stairs with the whole foot, and 3) when a subject went down the stair, respectively. The results of each cases were compared with the data for the level walking collected from 21 healthy females in the previous studies. The stairway gait data can be used as a useful reference in the design of artificial limbs for the lower-limb amputee.

• The Korean Journal of Emergency Medical Services
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• v.11 no.1
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• pp.11-25
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• 2007

Objective: The purpose of this study was to investigate the effects of combined exercise on the change of postural control, functional status in patients with osteoarthritis of the knee. Methods : The subjects were consisted of 24 women patients fifties and sixties with knee osteoarthritis. Each group had a exercise for 30 minutes per day and three times a week during 8 weeks period. Was used to measure muscular function(60, $180^{\circ}/sec$), postural control. functional capacity(15 M walking test, Rising form a chair test, stair climbing and descending test) and the functional state of a joint(WOMAC). Results: This study results in following 1. In case of muscular function have significantly increased in both groups. 2. There was no significant difference in the postural control of the bilateral between two groups. However, the postural control of a isokinetic exercise program group showed a significant difference in the bilateral side(overall, $M{\cdot}L$ stability index). Especially, the change of postural control in the isokinetic plus postural control exercise program group decreased more significantly in the bilateral(overall, $A{\cdot}P$ stability index). 3 It was significantly decreased in climbing and descending the stairs, and rising from the chair, although functional capacity decreased in lam walking in both groups. 4. The functional state of a joint(WOMAC) showed a significant decrease in both groups. Conclusion : In order to improve the functional status and postural control of patients with osteoarthritis of the knee, performing exercise programming of isokinetic plus balance will be more effective than the exercise program composed of only the isokinetic exercise program.