• Korean Journal of Applied Biomechanics
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• v.16 no.3
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• pp.137-148
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• 2006

The purpose of this study was to compare muscle activity in the lower extremity during walking wearing jogging and roller shoes. Twelve male middle school students (age: 15.0 yrs, height 173.7 cm, weight 587.7 N) who have no known musculoskeletal disorders were recruited as the subjects. Seven pairs of surface electrodes (QEMG8, Laxtha Korea, gain = 1,000, input impedance >$1012{\Omega}$, CMMR >100 dB) were attached to the right-hand side of the body to monitor the rectus femoris (RF), vastus medialis (VM), vastus lateralis (VL), biceps femoris (BF), tibialis anterior (TA), and medial (GM) and lateral gastrocnemius (GL) while subjects walked wearing roller and jogging shoes in random order at a speed of 1.1 m/s. An event sync unit with a bright LED light was used to synchronize the video and EMG recordings. EMG data were filtered using a 10 Hz to 350 Hz Butterworth band-passdigital filter and further normalized to the respective maximum voluntary isometric contraction EMG levels. For each trial being analyzed, five critical instants and four phases were identified from the recording. Averaged IEMG and peak IEMG were determined for each trial. For each dependent variable, paired t-test was performed to test if significant difference existed between shoe conditions (p<.05). The VM, TA, BF, and GM activities during the initial double limb stance and the initial single limb stance reduced significantly when going from jogging shoe to roller shoe condition. The decrease in EMG levels in those muscles indicated that the subjects locked the ankle and knee joints in an awkward fashion to compensate for the imbalance. Muscle activity in the GM for the roller shoe condition was significantly greater than the corresponding value for the jogging shoe condition during the terminal double limb stance and the terminal single limb stance. Because the subjects tried to keep their upper body weight in front of the hip to prevent falling backward, the GM activity for the roller shoe condition increased. It seems that there are differences in muscle activity between roller shoe and jogging shoe conditions. The differences in EMG pattern may be caused primarily by the altered position of ankle, knee, and center of mass throughout the walking cycle. Future studies should examine joint kinematics during walking with roller shoes.

• Korean Journal of Applied Biomechanics
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• v.16 no.1
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• pp.101-108
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• 2006

The purpose of this study was to compare GRF characteristics during walking wearing jogging and roller shoes. Twelve male middle school students (age: $15.0{\pm}0.0\;yrs$, height: $173.6{\pm}5.0\;cm$, weight: $587.6{\pm}89.3\;N$) who have no known musculoskeletal disorders were recruited as the subjects. Kinematic data from six S-VHS camcorders(Panasonic AG456, 60 fields/s) and GRF data from two force platform; (AMII OR6-5) were collected while subjects walked wearing roller and jogging shoes in random order at a speed of 1.1 m/s. An event sync unit with a bright LED light was used to synchronize the video and GRF recordings. GRF data were filtered using a 20 Hz low pass Butterworth. digital filter and further normalized to the subject's body weight. For each trial being analyzed, five critical instants and four phases were identified from the recording. Temporal parameters, GRFs, displacement of center of pressure (DCP), and loading and decay rates were determined for each trial. For each dependent variable, paired t-test was performed to test if significant difference existed between shoe conditions (p <.05). Vertical GRFs at heel contact increased and braking forces at the end of initial double limb stance reduced significantly when going from jogging shoe to roller shoe condition. Robbins and Waked (1997) reported that balance and vertical GRF are closely related It seems that the ankle and knee joints are locked in an awkward fashion at the heel contact to compensate for the imbalance. The DCP in the antero-posterior direction for the roller shoe condition was significantly less than the corresponding value for the jogging shoe condition. Because the subjects tried to keep their upper body weight in front of the hip to prevent falling backward, the DCP for the roller shoe condition was restricted The results indicate that walking with roller shoes had little effect on temporal parameters, and loading and decay rates. It seems that there are differences in GRF characteristics between roller shoe and jogging shoe conditions. The differences in GRF pattern may be caused primarily by the altered position of ankle, knee, and center of mass throughout the walking cycle. Future studies should examine muscle activation patterns and joint kinematics during walking with roller shoes.

• Korean Journal of Applied Biomechanics
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• v.29 no.3
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• pp.197-204
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• 2019

Objective: The purpose of this study was to identify the effect of high-heels (HH) modification on metatarsal stress in female workers. Method: Seven females who work in clothing stores ($heights=160.4{\pm}3.9cm$; $weights=47.4{\pm}4.1kg$; $age=31.3{\pm}11.1yrs$; $HH\;wear\;career=8{\pm}6.5yrs$) wore two types of HH (original and modified). The modified HH had been grooved with 1.5 cm radius and 0.2 cm depth around the first metatarsal area inside of the shoes using the modified shoe-last. Participants were asked to walk for 15 minutes on a treadmill and to stand for 10 minutes with original and modified HH, respectively. Kinetics data were collected by the F-scan in-shoe system. After each test, participants were asked to rate their perceived exertion using the Borg's 15-grade RPE scale and interviewed about their feeling of HH. Nonparametric Wilcoxon signed-rank test and effect size (Cohen's d) were used to determine the difference of the variables of interest between the original and modified HH. Results: In the present study, modified HH of the peak contact pressure of 1st metatarsal (PCP) left, PCP right, pressure time integral (PTI) left, peak pressure gradient (PPG) left during standing and PPG right during walking are greater than original HH. And even it didn't show statistically significant, the average in all pressure values of modified HH showed bigger than original HH. It surmised to be related to awkward with modified HH. Even though they said to feel the comfortable cause of big space inside of HH in the interview, they seemed to be not enough time to adapt with new HH. So their walking and standing postures were unstable. Conclusion: Modified the fore-medial part of HH can reduce the stress in the first metatarsal head and big toe area during standing and walking.

• Korean Journal of Applied Biomechanics
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• v.13 no.3
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• pp.355-366
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• 2003

본 연구의 목적은 뛰어 내리기 동작 시 신발과 뛰어 내리는 높이가 지면반력과 충격감소에 미치는 영향을 연구하였다. 10명의 건강한 피험자가 신발 또는 맨발로 네 가지 다른 높이에서 (30, 45, 60 &75 cm) 다섯 번의 뛰어 내리기를 시도하였다. 수직지면반력(VGRF), 영상분석, 경골과 앞이마의 가속도가 함께 측정되었다. 첫 번째 정점의 수직지면반력 (VGRF1)은 75cm의 높이에서 맨발보다는 신발을 신은 상황에서 더 큰 값을 보여 주었다. 두 번째 정점의 수직지면반력 (VGRF2)은 신발을 신은 것보다는 맨발의 조건에 더 큰 값을 보여 주었다. 앞 이마의 가속도 (AccHead)는 높이와 지면에 거의 변화를 보이지 않았다. 첫 번째 정점의 경골 가속도 (AccHead)는 높이와 지면에 거의 변화를 보이지 않았다. 첫 번째 정점의 경골 가속도 (AccTibia1)는 맨발의 조건보다 신발을 신은 조건에서 더 크게 나타났다. 반면에 두 번째 정점의 경골 가속도 (AccTibia2)는 특히 60 그리고 75cm조건에서 신발을 신었을 때 보다 맨발일 때 더 큰 값을 보여 주었다. 충격감소지수 (AtteIndex)는 모든 높이에서 맨발의 조건이 신발을 신은 조건 보다 통계적으로 유의하게 높게 나타났다. 결론적으로 뛰어 내리기 동작 시 신발이 지면반력을 최소화시키고 충격을 감소시키는데 부가적인 완충물로 제공되었음을 뒷받침 해준다.

• Korean Journal of Applied Biomechanics
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• v.12 no.2
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• pp.361-380
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• 2002

The purposes of this study were to a analysis of friction relation between tennis outsole and tennis playing surfaces. Tennis footwear is an important component of tennis game equipment. It can support or damage players performance and comfort. Most importantly athletic shoes protect the foot preventing abrasions and injuries. Footwear stability in court sports like tennis is incredibly important since it is estimated that as many as 45% of all lower extremity injuries occur in the foot and ankle. The friction force is the force exerted by a surface as an object moves across it or makes an effort to move across it. The friction force opposes the motion of the object. Friction results when two surfaces are pressed together closely, causing attractive intermolecular forces between the molecules of the two different surfaces. The outsole provides traction and reduces wear on the midsole. Today's outsoles address sport specific movements (running versus pivoting) and playing surface types. Different areas of the outsole are designed for the distinct frictional needs of specific movements. Traction created by the friction between the outsole and the surface allows the shoe to grip the surface. As surfaces, conditions and player motion change, traction may need to vary. An athletic shoe needs to grip well when running but not when pivoting. Laboratory tests have demonstrated force reductions compared to impact on concrete. There is a correlation between pain, injury and surface hardness. These are a variety of traction patterns on the soles of athletic shoes. Traction like any other shoe characteristic must be commensurate and balanced with the sport. The equal and opposite force does not necessarily travel back up your leg. The surface itself absorbs a portion of the force converting it to other forms of energy. Subsequently, tennis court surfaces are rated not only for pace but also for the percentage of force reduction.

• Korean Journal of Applied Biomechanics
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• v.12 no.1
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• pp.89-114
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• 2002

The purpose of this study was to analyze impact absorption function of midsole in cushioned marathon shoes. The foot is made up of a complex interaction of bones, ligaments, and muscles. These structures help the foot alternate between being a mobile, flexible adaptor and a stable rigid lever. The foot is broken down into two functional parts, the forefoot and the rearfoot. Cushioned marathon shoes for high arches have generous cushioning for efficient and high-mileage runners. Cushioned marathon shoes are made for feet that have high arches or no excessive motion and don't roll inward or roll outward. This condition is known as underpronation. Especially, Cushioned marathon shoes are designed to reduce shock and generally have the softest (or most cushioned) midsoles and the least medial support. They are usually built on a semicurved or curved last to encourage foot motion, which is helpful for underpronators (who have rigid, immobile feet). Cushioning marathon shoes recommended for the high-arched runner, whose foot may roll outward (supinate) rather than the natural slight inward roll, or whose feet may be relatively rigid. Cushioning shoes emphasize flexibility and usually are built on a curved or semicurved last to encourage a normal motion of the foot. Cushioning shoes usually offer no medial (inner foot) support. Cushioned marathon shoes have the single-density midsole, which is stable and relatively firm for a cushioned shoe, stays the same. But the forefoot is more rounded, and the rearfoot now includes a new and supportive rearfoot cradle. A foam midsole, perhaps with layers of different densities, to provide cushioning and shock absorption. EVA (ethylene vinyl acetate) and PU (polyurethane), the materials from which these foams usually are made. EVA is slightly softer than PU. EVA and PU may be layered together in a shoe, or a shoe may have more than one density of EVA.

• Korean Journal of Applied Biomechanics
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• v.22 no.1
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• pp.105-111
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• 2012

The purpose of this study was to investigate the effect that difference in forefoot of shoe flexibility during the quick lunge from a jump smashing on the lower limbs and the plantar pressure distribution. For this 10 elite badminton players with over 10 years experience and right handed participated. Two kinds of badminton shoes were selected and tested mechanical testing for the forefoot flexibility. Motion analysis, ground reaction forces and plantar pressure distribution were recorded. It was required to conduct lunge movement after jumping smashing as possible as high. Photo sensor was located in 3 meter away from standing position and its height was 40 cm. Subjects were conducted to return original position after touching the sensor as under clear movement as possible as fast. Forefoot stiffness had an effect on shoe peak bending degree and peak bending angular velocity in propulsion phase. Forefoot flexibility had an effect on ankle plantar flexion and knee flexion moment. It appears that joint power on lower limb and peak plantar pressure were not influenced by the flexibility of shoes.

• Korean Journal of Applied Biomechanics
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• v.16 no.1
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• pp.19-30
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• 2006

The purpose of this study was to examine the effect of foot orthotics on the overall comfort and muscle activity during running. The subjects were 10 members from the joggers' club which consisted of 2 women and 8 men. These individuals ran on the treadmill by 4.0m/s speed with and without the custom foot orthotics. The data concerning the overall comfort was collected by a questionairre that examined the overall comfort, heel cushioning, forefoot cushioning, medio-lateral control, arch height, heel cup fit, shoe heel width, forefoot width, and shoe length The MegaWin ver. 2.1(Mega Electronics lid, Ma. Finland) was used to gain electromyography signals of the muscle activity; Tibialis anterior, medial gastronemius, lateral gastronemius, vastus lateralis, vastus medialis, biceps femoris, and rectus femoris were measured. The results of the study were as follows. 1. During running the overall comfort was higher for the foot arthotic condition than the nonorthotic condition. Among the inquiries the overall comfort showed the biggest difference comparing the two conditions. and the shoe heel width showed the highest score for contort. 2 The muscle activity of the biceps femoris, and vastus lateralis in the stance period decreased. due to the foot orthotics. The muscle activity of the vastus medialis in the swing period also decreased and the muscle activity tibialis anterior in the stance and swing stance decreased as well During running, orthotics showed positive result in foot comfort. The foot comfort related to decreased stress, muscle activity, and foot arch strain. Overall comfort and the adequate decrease of muscle activity were associated with injury prevention and the best method to prevent injury semms to be the maintenance of foot comfort.

• Korean Journal of Applied Biomechanics
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• v.27 no.3
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• pp.219-227
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• 2017

Objective: The aim of this study was to analyze the effects of bobsleigh shoes on the lower extremity range of motion and start speed lap time and to develop bobsleigh shoes suitable for winter environments and Korean players based on sports science and optimized biomechanical performance. Background: The bobsleigh shoes used in the start section of the sport are one of the most important equipment for improving athletes' performances. Despite the importance of the start section, there are no shoes that are specifically designed for Korean bobsleigh athletes. Thus, Korean athletes have to wear sprint spike shoes instead of bobsleigh shoes to practice the start. Method: The subjects included four bobsleigh athletes from the Gangwon Province Bobsleigh Skeleton Federation. The study selected the bobsleigh shoe type A (company A) and type B (company B). We analyzed the lower extremity range of motion and sprint time (start line to 10 m) using a Motion Analysis System (USA). Results: In the measurement of the time required for the bobsleigh start section (10 m), the type A shoes demonstrated the fastest section record by $2.765{\pm}0.086sec$ and yielded more efficient movements, hip and knee flexion, hip extension, ankle dorsiflexion, plantar flexion, and inversion than the type B shoes. Conclusion: Type A shoes can yield a better performance via effective lower extremity movements in the bobsleigh start section. Application: In the future, functional analysis should be conducted by comparing the upper material properties, comfort, and muscle fatigue of bobsleigh shoes based on the Type A shoes to develop such shoes suitable for Koreans.

• Korean Journal of Applied Biomechanics
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• v.19 no.2
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• pp.217-225
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• 2009

Recently, intensive research efforts are world-widely forced on the development of sport shoes improving both the injury protection and the playing performance by taking kinesiology and biomechanics into consideration. However, the success of this goal depends definitely on the reliable evaluation of the dynamic responses of sport shoes and human foot, particularly the landing impact characteristics. It is because the landing impact force is a main source of unexpected injuries and influences the playing performance in court sport activities. This paper addresses the application of finite element method to the evaluation of landing impact characteristics of barefoot and several representative court sport shoes in running. In order to accurately reflect the coupling effect between human foot and shoes accurately, we construct a fully coupled three-diemensional foot-shoe FEM model which does not rely on the independent experimental data any more. Through the numerical simulation, we assessed the reliability of the numerical FEM model by comparing with the experimental results and investigated the landing impact characteristics, such as GRF, MIF, acceleration and frequency responses, of representative court sport shoes.