Earticle

Background Various therapeutic methods have been suggested to increase the flexibility of shortened muscles in patients with knee pain. However, no previous study has directly compared the hip joint range of motion (ROM) and muscle stiffness as a mechanical property following the active stretching (AS) and instrument-assisted soft tissue mobilization (IASTM) for shortened tensor fascia lata (TFL). Purpose To compare the effects of AS and IASTM on hip joint ROM and TFL stiffness in subjects with shortened TFL. Study design Two groups pre- and post-test design Methods Twenty healthy male subjects with shortened TFL were selected. The subjects were randomized between the AS group (n=10) and the IASTM group (n=10). A smartphone was used to measure the hip joint adduction ROM and Myoton was used to measure the TFL stiffness. Paired t-test was performed to analyze the within-group variation before and after the intervention, and an independent t-test was used to compare the between-group variation. Results In the within-group comparison, both the AS and IASTM groups showed a significant increase in the hip joint adduction ROM after the intervention, whereas neither group showed a significant difference in the TFL stiffness after the intervention. In the between-group comparison, a greater increase in the hip joint adduction ROM was observed for the AS group compared to the IASTM group. Conclusions This study found that the hip adduction ROM of the subjects with TFL shortness increased immediately in both AS group and IASTM group, although the TFL stiffness was not decreased. And the greater increase of the hip adduction ROM was revealed in AS group than IASTM group.

본 연구의 목적은 달리기 시 발목의 관절 강성과 충격력 및 부하율 간의 상관관계를 알아보고, 반복적인 부하로 인해 발생하는 하지 근 골격계의 상해의 원인을 파악하기 위한 기초자료를 제공하는데 있다. 연구 대상자는 6개월간 근 골격계 손상을 입지 않은 성인 남성 16명으로 선정하였다. 모든 대상자는 8 km/h, 12 km/h, 16 km/h의 속도에서 달리기 동작을 30초간 수행하였고, 이 중 10 스텝을 분석에 활용하였다. 이때, 8대의 적외선 카메라(Oqus 300+, Qualisys, Sweden; 100 Hz)와 2개의 지면반력기(instrumented dual belt treadmills, Bertec, USA; 1000 Hz)가 내장된 트레드 밀을 통하여 원자료를 취득하였다. 달리기 시 발목의 관절 강성이 충격력과 부하율의 상관관계를 알아보기 위하여, 발목의 관절 강성, 최대 수직 충격력, 수직 부하율을 계산하였다. 본 연구 결과, 8 km/h와 16 km/h의 속도에서만 발목의 관절 강성은 최대 수직 충격력과 정적인 상관관계를 나타냈다(r = .527, p < .05; r = .490, p < .05). 이는 달리기 시 속도의 증가에 따른 발목관절 강성의 증가가 연부조직의 상해를 방지하기 위한 보상작용으로써 작용하지만, 최대 수직 충격력을 증가시켜 골격계의 상해 발생률을 증가 시킬 수 있는 요인으로써 작용할 수 있다는 것을 나타낸다. 또한, 달리기 시 특정 속도에서 발목의 관절 강성과 최대 수직 충격력의 상관관계가 나타나, 관절 강성이 특정 속도 혹은 난이도에서 최대 수직 충격력에 대하여 더 큰 영향을 줄 수 있음을 암시하였다. 따라서 달리기 시 속도별 생체역학적 기전을 적절히 활용하며 주행하는 것은 과사용 손상으로 인한 상해를 예방 할 수 있는 하나의 전략으로써 제안될 수 있다.

The purpose of this study is to determine the correlation between ankle joint stiffness and impact force and loading rate during running and to investigate the mechanisms of the injuries caused by repetitive load. Sixteen healthy adults were participated in this study. They were asked to run with 8 km/h, 12 km/h and 16 km/h for 30 seconds and among the trials, 10 steps were selected to analyze. All trials were recorded with eight infrared cameras (Oqus 300+, Qualisys, Sweden; 100 Hz) and two instrumented dual belt treadmills (Bertec, USA; 1000 Hz). Ankle joint stiffness, impact force (Fz) and loading rate (Gz) were calculated. In result, ankle joint stiffness was significantly related to impact force at 8 km/h and 16 km/h(r = .527, p < .05; r = .490, p < .05). It means that fast running speed increases ankle joint stiffness which is the compensation for injury prevention of soft-tissue but, increased joint stiffness could cause the injuries of skeletal system. Also, the correlation showed at the specific speed of running. It may indicate that the specific speed of running can effect the impact force even more. Therefore, the controlling of running mechanism for each running speed could be one of the strategy to prevent running injury which can be caused by repetitive load.

Purpose: The purpose of this study was to examine the effects of aquatic exercise on joint angle, pain, stiffness and physical fitness in elderly women with osteoarthritis. Methods: Elderly women with osteoarthritis were offered aquatic exercise between October 2014 and December 2014. In experimental groups, patients were included in pre-determined exercise programs 3 times per week for 12 weeks. Eighteen participants were in the experimental group and 18 participants were in the control group. Joint angle and the Korean Western Ontario and McMaster Universities’ Osteoarthritis Index (pain, stiffness, physical function) were measured pre and post aquatic exercise. The study variables were analyzed using x2 test, Fisher’s exact test, Wilcoxon signed rank test, and Wilcoxon rank sum test with the SPSS statistical package. Results: The experimental groups showed statistically significant decreases in left and right joint angle. However there were no differences in pain, stiffness and physical function. Conclusion: After aquatic exercise program, there was no improvement in subjective symptoms for pain however, the objective index of joint angle index showed improvements which supported the positive effects.

In this paper, the 5 joint toggle link of a injection molding machine is analyzed. Considering toggle link kinematics and frictions at the pin joints, clamping forces for each cross head position are calculated. The maximum clamping force and the install position of a tail-stock are determined by the stiffness of links, plates and tie-bar. The kinematic results of a finite element analysis considering friction and stiffness are compared with measured results.

운동학 학술지, 2010, 12(4): -94. 달리기 시 하지관절의 에너지 반환 방법(Joint Power Method)을 이용한 마라톤화 Sole의 Optimal Bending Stiffness산출 [서론] 본 연구의 목적은 마라톤화 바닥의 Bending Stiffness도 증가되고 후족제어나 충격력 흡수가 잘 되는 최상의 조합(stiffness)을 규명하며, 종래의 연구방법과 Joint Power Method의 적정 신발바닥의 강도를 결정하기 위한 연구방법을 상호 비교하는데 있다. [방법] 본 연구에 동원된 피험자는 최근 1년 이내에 하지에 부상경험이 없는 남자 대학생 13명이었다. 본 연구에 사용된 마라톤화는 Bending Stiffness가 0.05 N.m/deg∼0.4 N.m/deg이며, 중저의 경도가 Shore A 40, Shore A 50, Shore A 60, Shore A 70의 4종류이었다. 달리기 시 하지동작을 3차원 영상분석법과 지면반력 측정을 통하여 분석하였다. [결과] 마라톤화의 경도가 증가함에 따라 구간별 걸린 시간도 감소하는 것으로 나타났고 충격흡수변인과 후족제어변인을 분석한 결과 마라톤화 중저의 경도는 50도가 적합한 것으로 나타났다. 하지관절의 에너지와 파워는 굴곡강도가 클수록 통계적인 차이는 없지만 증가하였으며 원위관절로 갈수록 증가하는 것으로 나타났다. [결론] 기존의 신발평가방법과 에너지 반환법을 비교했을 때 평가방법 성격의 차이에 의하여 적정굴곡강도를 선정하는데 차이를 보였다. 에너지 반환법을 이용한 마라톤화 바닥의 적정굴곡강도는 경도가 클수록 증가하는 경향을 보였지만 통계적인 차이를 나타내지 않아 현재의 연구결과로서 현장에 적용하기 어렵다고 사료된다.

KINESIOLOGY, 2010, 12(4): 81-94. The Study of Optimal Bending Stiffness of Marathon Shoe Sole by using Energy Return(Joint Power Method) in Lower Extremity Joint. [INTRODUCTION] The purposes of this study were to determine optimal bending stiffness of a marathon shoe which increased bending stiffness, rearfoot control and impact force absorption of marathon shoe sole, and to compare usual methodology with energy return method(joint power method) for determining optimal midsole hardness. [METHOD] The subjects employed for this study were 13 college students who did not have lower extremity injuries for the last one year and whose running pattern was rearfoot striker of normal foot. The shoes used in this study had 4 different midsole hardness of shoe A 40, shore A 50, Shore A 60, Shore A 70 and bending stiffness was 0.05 N.m/deg - 0.4 N.m/deg. The lower leg motion during at the speed of 4m/sec were measured using a force platform and motion analysis system. [RESULT] The findings of the study were as follows : 1. It was appeared that total contact time of each phase was decreased as the increment of marathon shoe midsole hardness. 2. Maximal impact force and maximal impact force loading rate increased except shore A 40 as the midsole hardness increased. It was shown that Shore A 40 and Shore A 70 were not fitted for a marathon shoe. 3. Initial achilles tendon angle of each midsole hardness was shown similar results, and a maximal achilles tendon angle and a angular displacement of achilles tendon angle was the largest at shore A 40 and the smallest at shore A 50. 4. Initial rearfoot angle was the smallest at shore A 60 and the largest at shore A 70. A minimum rearfoot angle and the displacement of rearfoot angle was the largest at shore A 50 and the smallest at shore A 60. 5. Maximal power in 1st contact contact phase was not shown any particular tendency, but in 2nd contact phase maximal power was increased as midsole hardness was increased and distal joint. 6. The energy in 1st phase was produced at hip joint and absorbed at knee joint and ankle joint, in 2nd contact phase the energy was largest at knee joint and increased as midsole hardness was increased. [CONCLUSION] The study confirmed the previous findings that the midsole hardness of marathon shoe did influence on impact force absorption, rearfoot stability and joint energy. The optimal midsole hardness of marathon shoe was most fitted at shore A 50 and the next shore A 60 by usual shoe methodology study. It was proved that shore A 40 and shore A 70 were not fitted for marathon shoe sole. Also it was appeared that shore A 50 was the most fitted for marathon shoe sole by new attempted joint power method results that the joint energy was largely generated as midsole hardness was most flexible or hard. However, the study suggests that the similar studies like energy return were performed verified optimal bending stiffness because these conclusions were based only on tendencies of current results.

This paper presents the mechanical joints normal contact stiffness model based on fractal geometry and contact mechanics theory. The joint normal dimensionless contact load and dimensionless contact stiffness relationship are analyzed in different fractal dimensions and materials. The result shows that relationship between joint normal contact load and contact stiffness plastic is the strongly nonlinear. At last, normal contact stiffness are compared and analyzed with the experimental values, as well as JZZ model used the present model. The comparison result indicates that the present model is consistent with experiment result.

[PURPOSE] The purpose of this study was to determine the optimal bending stiffness of volleyball shoe soles by using energy return method as a new shoe evaluation method. [METHODS] Nine healthy male college students were recruited for this study, who had previously attended a volleyball class. The running motion at the speed of 4.0±0.4m/sec and the volleyball jumping motion were measured and analyzed by using 3D motion analysis system and a force platform. [RESULTS] The maximal flexion power at each joint was increased as the mid-sole hardness decreased. The maximal extension power was increased as the mid-sole hardness increased. The energy absorption of each joint was increased as the mid-sole hardness was decreased. The energy production was increased as the mid-sole hardness increased. [CONCLUSIONS] Our study suggests that the energy return method may be a reliable biomechanical assessment technique to determine the optimal bending stiffness of volleyball shoes. Future studies with various shoes are warranted for determining the optimal bending stiffness.

Joint stiffness can affect the vibration characteristics of car body structures. Therefore, it should be included in vehicle system model. In this paper, a numerical approximation of joint stiffness is presented considering joint flexibility of thin walled beam-jointed structures. Using the proposed method, it is possible to optimize joint structures considering the change of section shapes in vehicle structures. The numerical approximation of joint stiffness is derived using the response surface method in terms of beam section properties. The study shows that joint stiffnesses can be effectively determined in designing vehicle structures.

In this paper, we focus on a configuration control method of a redundant manipulator. The configuration of a redundant manipulator has been determined by geometry constraints and additional conditions, such as obstacle avoidance and dexterity optimization. This paper also utilizes optimization, and the additional condition (or performance index) to be optimized is stiffness of the end-effector and joints' torque. Stiffness and torque may be a natural attribute to be controlled during working and those vary as manipulator configuration does. So the optimal configuration from the viewpoint of stiffness and joint torque is studied. If the servo control mechanism of the joints Is assumed to be a...

Idle shake vibration characteristics of a vehicle are mainly influenced not only by the stiffnesses of the beam type structures such as pillars and rockers, but also by the stiffnesses of the joint structures, at which several beam structures are jointed together. In the early design stage of the car body structure a simple FE model has been used, in which joints are modeled as linear springs to represent the stiffnesses of the joint structures. In this paper a new modeling technique for the joint structure is presented using an equivalent beam, instead of using a spring. The modeling technique proposed is utilized to design optimal joint structures that meet the required vibration performance of the total vehicle structure.

Vehicle body frame stiffness affects the dynamic and static characteristics. Vehicle frame structural performance is greatly affected by crossmember and joint design. While the structural characteristics of these joints vary widely, there is no known tool currently in use that quickly predicts joint stiffness early in design cycle. This paper presents the joint design factors affecting on low frequency vibration. The joint factors are joint panel thickness, section property, flange width and weld point space. To study the effect on vehicle low frequency vibration, case studies for these factors are performed. And Sensitivity analysis for section property is performed. The result can present design guide for high-stiffness vehicle.

Recently, several studies have been conducted to lower the cost of transport of human by adding external joint stiffness elements. However, it has not been clearly elucidated whether adaptation time is required for human subjects to adapt to the added external joint stiffness. In this study, carbon plates in the form of shoe midsoles were added to the metatarsophalangeal joint, and the lower limb joint torque and mechanical energy consumption were compared before and after a total of 5 sessions (2.5 weeks) of running. A total of 11 young healthy participants exhibited higher elastic energy storage in carbon plates in the fifth session compared to the first session, and lower power in the ankle joint. This suggests that a single training session may be insufficient to validate the efficiency effect of added joint stiffness, and the human body seems to increase the elastic energy stored in the assistive joint stiffness and its reutilization.

Objective: To investigate effects of Fibular Repositioning Taping (FRT) on lower extremity joint stiffness and angle during drop-landing. Method: Twenty-eight participants (14 healthy, 14 with chronic ankle instability [CAI]) performed drop-landings from a 60 cm box; three were performed prior to tape application and three were performed post-FRT. Three-dimensional kinematic and kinetic data were collected using an infrared optical camera system (Vicon Motion Systems Ltd. Oxford, UK) and force-plate (AMTI, Watertown, MA). Joint stiffness and sagittal angle of the ankle, knee, and hip were analyzed. Results: The hip [Healthy: p<.05; M ± SD: 29.43 ± 11.27 (pre), 33.04 ± 12.03 (post); CAI: p<.05; M ± SD: 31.45 ± 9.70 (pre), 32.29 ± 9.85 (post)] and knee [Healthy: p<.05; M ± SD: 53.44 ± 8.09 (pre), 55.13 ± 8.36 (post); CAI: p<.05; M ± SD: 53.12 ± 8.35 (pre), 55.55 ± 9.81 (post)] joints demonstrated significant increases in sagittal angle after FRT. A significant decrease in joint angle was found at the ankle [Healthy: p<.05; M ± SD: 56.10 ± 3.71 (pre), 54.09 ± 4.31 (post); CAI: p<.05; M ± SD: 52.80 ± 6.04 (pre), 49.86 ± 10.08 (post)]. A significant decrease in hip [Healthy: p<.05; M ± SD: 1549.16 ± 517.53 (pre), 1272.48 ± 646.73 (post); CAI: p<.05; M ± SD: 1300.42 ± 595.55 (pre), 1158.27 ± 550.58 (post)] and knee [Healthy: p<.05; M ± SD: 270.12 ± 54.07 (pre), 239.13 ± 64.70 (post); CAI: p<.05; M ± SD: 241.58 ± 93.48 (pre), 214.63 ± 101.00 (post)] joint stiffness was found post-FRT application, while no difference was found at the ankle [Healthy: p>.05; M ± SD: 57.29 ± 17.04 (pre), 59.37 ± 18.30 (post); CAI: p>.05; M ± SD: 69.15 ± 17.63 (pre), 77.24 ± 35.05 (post)]. Conclusion FRT application decreased joint angle at the ankle without altering ankle joint stiffness. In contrast, decreased joint stiffness and increased joint angle was found at the hip and knee following FRT. Thus, participants utilize an altered shock absorption mechanism during drop-landings following FRT. When compared to previous research, the joint kinematics and stiffness of the lower extremity appear to be different following FRT versus traditional ankle taping.

Following the earthquake that shook the city of Gyeongju, Korea, in 2016, it became apparent that research on the safety of cultural heritages against the seismic hazards is necessary in Korea. Predictions of how historically significant stone pagodas would behave the earthquakes anticipated in near future, which are the subject of this study, is also required. In this study, the dynamic characteristics of 15 cultural heritage designated stone pagodas of Korea were investigated, including natural frequency and damping ratio, and the stiffness of the stone material and its contact area were determined using eigenvalue analysis by assuming the stone pagodas to be multi-degree-of-freedom structures. The results of this study enable the structural modeling of stone pagodas using a finite element analysis program and the method is expected to be useful in assessing the structural safety of stone pagodas against vertical loads as well as lateral forces, including earthquakes. Also, by identifying the dynamic characteristics of the structures, the results of this study can be utilized as a nondestructive testing method to determine the rigidity of cultural heritage structures and to identify inherent problems. The natural frequencies of the Korean stone pagodas were measured to be within 3.5~8.3Hz, excluding cases with distinct natural frequency results, and it was determined that the natural frequencies of the stone pagodas are influenced by various parameters including the height and joint stiffness of the structures.

쉴드 TBM 터널의 라이닝은 세그먼트로 구성되므로, 각각의 세그먼트가 서로 연결되면서 세그먼트 이음부를 발생시킨다. 세그먼트 이음부는 쉴드 TBM 설계에 있어 강성계수로 적용되어지는데, 세그먼트 이음부 강성계수는 그 결정 방법에 따라 결과 값이 현저한 차이를 보인다. 따라서 서로 다른 강성계수를 설계에 적용하였을 경우 그 결과가 어떻게 다른지에 대한 검토가 필요하다. 본 연구에서는 세그먼트 이음부 강성계수를 이론식을 통해 결정한 후 일정한 범위를 선정하였다. 그 범위 내에서 강성계수를 변화해가며 터널 단면 수치해석을 실시하여 세그먼트 라이닝 부재력을 도출하였고, 이에 강도설계법을 적용하여 세그먼트 라이닝 안정성 검토를 실시하였다. 그 결과 세그먼트 이음부 강성계수는 세그먼트 라이닝 설계에 큰 영향을 미치지 않는 것으로 나타났다.

The lining of shield TBM tunnel is composed of segments, therefore segment joints are induced by connecting each segment. Segment joint is considered as joint stiffness in the design of TBM tunnel. Depending on the choice among the different stiffness equations, the joint stiffness values determined can be varied largely. Therefore, the influence of joint stiffness value on the design of segment lining should be verified. In this study, the joint stiffness values were determined firstly by using various equations and total change boundary was justified. Within the change boundary determined, the member forces were calculated by changing the joint stiffness through the numerical analysis and consequently the stability of segment lining was investigated by applying nominal strength. The results showed that the segment joint stiffness did not affect the design of segment lining largely.

Although concrete pavements were successfully widespread throughout the nation due to the desirable surface characteristics, durability, and economy, it still causes several transverse cracking and joint failure problems in some areas. In this paper, the major emphasis was given to provide a rational analytical approach on joint failure mechanisms, considering several sets of joint stiffnesses on different subgrade moduli. Besides , load transfer mechanisms on concrete pavement joints were highlighted with finite element method and computer modeling.