• 한국운동역학회지
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• 제24권2호
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• pp.139-149
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• 2014

The purpose of this study was to evaluate the effect of angle change of forefoot's adhesive outsole on the electromyographic activity (EMG) of the erector spinae and selected lower limbs muscle during downhill walking over $-20^{\circ}$ ramp. Thirteen male university students (age: $25.4{\pm}3.9$ yrs, height: $176.2{\pm}5.1$ cm, weight: $717.4{\pm}105.0$ N) who have no musculoskeletal disorder were recruited as the subjects. To assess the myoelectric activities of selected muscles, six of surface EMG electrodes with on-site pre-amplification circuitry were attached to erector spinae (ES), rectus femoris (RF), biceps femoris (BF), tibialis anterior (TA), lateral gastrocnemius (LG), and medial gastrocnemius (MG). To obtain maximum EMG levels of the selected muscles for normalization, five maximum effort isometric contraction were performed before the experimental trials. Each subject walked over $0^{\circ}$ and $20^{\circ}$ ramp with three different forefeet's EVA outsole (0, 10, $20^{\circ}$) in random order at a speed of $1.2{\pm}0.1$ m/s. For each trial being analyzed, five critical instants and four phases were identified from the recording. The results of this study showed that the average muscle activities of MG and LG decreased in $20^{\circ}$ shoes compared to $0^{\circ}$ and $10^{\circ}$ ones in the initial double limb stance (IDLS). In initial single limb stance (ISLS) phase, the average muscle activities of ES increased with the angle of forefoot's adhesive outsole, indicating that the increment of shoes' angle induce upper body to flex anteriorly in order to maintain balance of trunk. In terminal double limb stance (TDLS) phase, average muscle activities of TA significantly increased in $20^{\circ}$ outsole compared to $0^{\circ}$ and $10^{\circ}$ ones. There was no external forces acting on the right foot other than the gravity during terminal single limb stance (TSLS) phase, all muscles maintained moderate levels of activity.

• 한국운동역학회지
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• 제18권3호
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• pp.33-42
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• 2008

이 연구는 생횔체육 프로그램으로서의 태권에어로빅스 옆차기 동작의 운동학적 분석으로 대상자는 숙련자와 비숙련자 각 7명으로 하였다. 자료는 Qualisys사의 Proreflex MCU-240 카메라 7대를 샘플링 율(sampling rate), 100frames/sec로 촬영한 후 Qualisys System(SWEDEN)의 QTM(Motion Capture Software)으로 위치 좌표를 얻었으며 Visual3D를 사용하여 연구변인을 산출하였고, 두 집단간의 평균치 차이 검정은 SPSS 12.0K의 독립 t-test를 유의수준 p<.05로 실시하였다. 그 결과는 다음과 같다. 1. 구간별 소요시간은 전 구간에서 통계적으로 유의한 차이가 없었다. 2. 무릎 각도의 경우 제2 무릎최대굴곡순간(p=0.046, F=4.925)에서 통계적으로 유의한 차이가 있었다. 3. 무릎 각속도의 경우 제1 무릎최대굴곡순간(p=0.031, F=5.940)에서 통계적으로 유의한 차이가 있었다. 4. 힙의 굴곡/신전 각도는 제2 무릎최대굴곡순간(p=0.012, F=8.668)에서 통계적으로 유의한 차이가 있었다. 5. 힙의 외/내전 각속도는 무릎최소굴곡순간(p=0.019, F=7.324)에서 통계적으로 유의한 차이가 있었다. 6. 힙의 외/내측 회전각속도는 무릎최소굴곡순간(p=0.005, F=11.87)에서 통계적으로 유의한 차이가 있었다.

• 한국운동역학회지
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• 제18권3호
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• pp.61-69
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• 2008

본 연구는 평균대에서 필수요구조건(EGR)에 해당되는 동작인 옆공중돌기 동작의 성공과 실패를 운동역학적으로 비교 분석하였다. 연구대상은 국가대표 선수들로 하였으며, 연구의 목적은 기술의 실수 요인을 규명하여 지도자 및 선수들에게 과학적으로 유용한 정보를 제공하는데 있다. 성공시 옆공중돌기 동작의 신체중심은 평균대 중앙 중심으로 좌-우축으로 벗어나는 결과가 나타나고 동작의 특성상 회전하는 방향으로 신체중심이 이동한다는 것을 나타내고 있다. 도약구간인 event2와 3에서 성공시 상 하 변화가 크게 나타나 체공시간을 높이는 것으로 투사변인이 실패시 보다 높게 나타나는 결과를 뒷받침 해 주고 있다. 또한 공중 비약을 위해 다리를 차는 동작을 하는 오른쪽 고관절 각도와 속도, 각속도가 실패시 보다 성공시 동작에서 모두 크게 나타나 도약의 최적조건을 수행하고 있다. 어깨를 중심으로 상지분절의 속도와 견관절 각속도를 크게 함으로써 운동량을 증가시켰으며 그중 오른쪽 견관절 각속도가 크게 나타난 이유는 오른쪽 다리를 잡기 위한 결과이다. 옆 공중돌기 동작에서 실패시 보다 성공시 동작에서 x축을 중심으로 각운동량이 크게 나타나 공중 비행 동작은 x축을 중심으로 각운동량을 크게 하는 것이 중요한 요인으로 나타났으며 옆공중돌기 특성상 y축과 z축으로 각운동량도 적정한 비율로 동작이 이루어져야 성공적인 동작을 만들수 있다.

• 한국운동역학회지
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• 제17권3호
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• pp.31-39
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• 2007

The purpose of this study was to observe the kinematic pattern of elite women 100m hurdler race from start to finish and analyze how the change of horizontal velocity makes an influence on the athletes' performance. The analysis was based on the performance of Korean elite 100m hurdler A and international elite hurdlers B and C. Following results were drawn from the analyzation of elite 100m hurdlers' technical characteristics; During the race, hurdler A made more than 8 m/s of horizontal velocity at the 3rd, 4th, 6th, and the 7th hurdle. The horizontal velocity peaked at the 4th hurdle with 8.23 m/s. On the other hand, hurdler B and hurdler C maintained more than 8 m/s of horizontal velocity from the 2nd hurdle through the 10th hurdle. Hurdler B's fastest horizontal velocity was 8.67 m/s from the 6th to the 7th hurdle and hurdler C's fastest horizontal velocity was 8.85 m/s from the 5th to the 8th hurdle. From the start line to the 3rd hurdle, the times achieved by hurdlers A, B, and C were 4.90 sec, 4.65 sec, and 4.52 sec. In the middle of the race, which is from the 4th hurdle to the 7th hurdle, hurdlers A, B, and C ran in 9.10 sec, 8.60 sec, and 8.38 sec. And the latter part of the race to the 10th hurdle, the times hurdlers A, B, and C hit were 12.32 sec, 11.66 sec, and 11.32 sec. To the finish line, it took 1.15 sec for hurdler A, 1.1 sec for B, and 1.06 sec for C. Hence, to set the record of sub-13 sec, hurdler A should improve her acceleration from the start line to the 1st hurdle with the speed more than 5.4 m/s and should maintain more than 8 m/s of horizontal velocity from the 2nd hurdle through the 10th hurdle. In addition, hurdler A should improve her speed endurance to minimize the deceleration of horizontal velocity from the 4th hurdle to the final hurdle. If hurdler A could shorten 0.05 sec of time in each hurdle section, she would be able to set the record under 13 seconds.

• 한국운동역학회지
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• 제26권4호
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• pp.343-351
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• 2016

Objective: The purpose of this study was to help improve game performance and provide preliminary data to enhance the efficiency of the kick and stability of the support foot by comparing the kinematic characteristics of the repeated side kick (geodeupyeopchagi) in poomsaeKoryo between expert and non-expert groups. Method: The subjects were divided into 2 groups according to proficiency in Taekwondo, an expert group and a non-expert group (n = 7 in each group), to observe the repeated side-kick technique. Four video cameras were set at a speed of 60 frames/sec and exposure time of 1/500 sec to measure the kinematic factors of the 2 groups. The Kwon3D XPprogramas used to collect and analyze three-dimensional spatial coordinates. Ground reaction force data were obtained through a force plate with a 1.200-Hz frequency. An independent samplesttest was performed, and statistical significance was defined as .05. The SPSS 18.0 software was used to calculate the mean and standard deviation of the kinematic factors and to identify the difference between the experts and non-experts. Results: The angular displacement of the hip joint in both the expert and non-expert groups showed statistical significance on E1 and E4 of the left support foot and E5 of the right foot (p<.05). The angle displacement of the knee joint in both groups showed statistical significance on E4 of the left support foot, and E1 and E2 of the right foot (p<.05). The angular velocity of the lower leg in both groups showed no statistical significance on the left support foot but showed statistical significance on E2 and E6 of the right foot (p<.05). The angular velocity of the foot in both groups showed no statistical significance on the left support foot but showed statistical significance on E2 of the right foot (p<.05). The vertical ground reaction force in both groups showed statistical significance on E2 (p<.05). The center of pressure in all directions in both groups showed statistical significance (p<.5). Conclusion: While performing the repeated side kick (geodeupyeopchagi), the experts maintainedconsistency and stability of the angle of the support leg while the kick foot moved high and fast. On the other hand, the angle of the support foot of non-experts appeared inconsistent, and the kick foot was raised, relying on the support leg, resulting in unstable and inaccurate movement.

• 한국운동역학회지
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• 제26권4호
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• pp.397-405
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• 2016

Objective: Pilates is a low/mid-intensity exercise that can be easily performed by elderly individuals as it is an individual body-oriented exercise. It is also a cardio workout that can be performed anywhere to develop strength and flexibility. Therefore, we investigated the effects of 8 week Pilates program on the balancing ability of elderly individuals. Method: The research participants were selected from elderly residents in B city. Ten individuals voluntarily signed an agreement to undergo free measurements as well as to participate in the workout program. (Height: $157.1{\pm}11.9cm$, Weight: $61.7{\pm}8.0kg$). The Pilates exercise was performed 60 minutes a day, three times a week for a total of eight weeks. The measurement variables used to test balance were the vestibular test, 5 m habitual and maximum walk test and 3 m tandem walk test. A series of paired t-test were conducted using IBM SPSS Statistics 23.0 to analyze all the research data collected in order to determine the balance ability of the participants before and after the Pilates program. Additionally, the statistically significant level for all analysis was set to ${\alpha}=.05$. Results: In the vestibular test, some meaningful changes were observed in the length envelope area (ENV) while standing on one foot, but there were no significant differences in the ENV, rectangle(REC), root mean square, and total length. Results also revealed that statistically significant differences existed in the 5 m habitual and maximum walk test, as well as the 3 m tandem walk test. Conclusion: To summarize the findings, the 8 week Pilates program employed in this study significantly improved the dynamic balance of the elderly participants. Thus, elderly individuals that frequent perform Pilates are expected to enjoy positive benefits such as increased balance and fewer falling accidents.

• 한국운동역학회지
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• 제31권4호
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• pp.276-282
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• 2021

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.

• 한국운동역학회지
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• 제29권3호
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• pp.157-166
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• 2019

Objective: This study examined the effects of stimulating fingertip temperature on the patterns of force sharing and stability properties during multi-finger force production tasks. Method: 9 adult subjects (male: 3, female: 6, age: $26.11{\pm}4.01yrs$, height: $169.22{\pm}5.97cm$, weight: $61.44{\pm}11.27kg$) participated in this study. The experiment consisted of three blocks: 1) maximal voluntary contraction (MVC) task, 2) single-finger ramp task to quantify enslaving (i.e., unintended force production by non-task fingers), and 3) 12 trials of multi-finger steady-state force production task at 20% MVC. There were three temperature conditions including body-temperature (i.e., control condition), $40^{\circ}C$, and $43^{\circ}C$, and the stimulation was given to the index finger only for all experimental conditions. Results: There were no significant differences in the MVC forces, enslaving, and the accuracy of performance during the steady-state task between the conditions. However, the share of stimulated index finger force increased with the index fingertip temperature, while the share of middle finger force decreased. Also, the coefficient of variation of both index and middle finger forces over repetitive trials increased with the index fingertip temperature. Under the framework of the uncontrolled manifold (UCM) hypothesis used to quantify indices of multi-finger synergies (i.e., stability property) stabilizing total force during the steady-state task, the two variance components within the UCM analysis increased together with the fingertip temperature, while no changes in the synergy indices between the conditions. Conclusion: The current results showed that fingertip temperature stimulation only to index finger does not affect to muscle force production capability of multi-finger, independence of individual fingers, and force production accuracy by the involvement of all four fingers. The effect of fingertip temperature on the sharing pattern and force variation may be due to diffuse reflex effects of the induced afferent activity on alpha-motoneuronal pools. However, the unchanged stability properties may be the reflection of the active error compensation strategies by non-stimulated finger actions.

• 한국운동역학회지
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• 제31권1호
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• pp.72-78
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• 2021

Objective: The purpose of this study was to investigate relations and effectiveness about mountain climbling exercise with different level of support surfaces by analyzing heart rate and EMG data. A total of 10 male college students with no musculoskeltal disorder were recruited for this study. Method: The biomechanical analysis was performed using heart rate monitor (Polar V800, Polar Electro Oy, Finland), step-box, exercise mat, and EMG device (QEMG8, Laxtha Inc. Korea, sampling frequency = 1,024 Hz, gain = 1,000, input impedance > 1012 Ω, CMRR > 100 dB). In this research, step-box were used to create different surface levels on the upper body (flat surface, 10% of subject's height, 20% of subject's height, and 30% of subject's hight). Based on these different conditions, data was collected by performing mountain climbing exercise during 30 seconds. Subjects were given 5 minutes of break to prevent muscular fatigue after each exercise. For each dependent variable, a one-way analysis of variance with repeated measures was conducted to find significant differences and Bonferroni post-hoc test was performed. Results: The results of this study showed that exercise intensity was reduced statistically as increased surface level on the upper body. Muscle activity of the upper rectus abdominis and biceps femoris for 30% of surface level was significantly higher than the corresponding values for flat surface. However, the opposite was found in the rectus femoris. In general, muscle activity of the lower rectus abdominis, erector spinae, external oblique abdominis, and gluteus maximus increased when surface level increased, but the differences were not significant. Conclusion: As a result, the increase in surface level of the body would change muscle activity of the upper body, indicating that different surface level of the upper body may cause significant effect on particular muscles to be more active during mountain climbing exercise. Based on results of this study, it is suggested to set up an appropriate surface level to target particular muscle to expect an effective training. It is also important to set adequate surface levels to create an effective training condition for preventing exercise injuries.

• 한국운동역학회지
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• 제31권1호
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• pp.1-15
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• 2021

Objective: The aim of this study was to investigate 1) the difference in static lower extremity alignment (SLEA) according to a history of lateral ankle sprain (LAS), 2) to identify SLEA factors affecting LAS, and 3) to present the cut-off value and 4) the usefulness and limitations of the SLEA measurement. Method: This case-control study recruited 88 men (age: 27.78±4.69 yrs) and 39 women (age: 24.62±4.20 yrs) subjects with and without LAS. SLEA measurement protocol included Q angle, tibiofemoral angle, genu recurvatum, rear foot (RF) angle, tibal varum and torsion, navicular drop, ankle dorsiflexion range of motion (DF ROM). Independent t-test, logistic regression and receiver operating characteristic (ROC) curve were used for statistical analysis. Results: Men with a history of LAS had significantly smaller Q angles both in standing and in supine position, while women with a history of LAS had significantly greater DF ROM in non-weight bearing (NWB; p < 0.05). Logistic regression model suggests tibial varum (OR = 0.779, p = 0.021) and WB DF ROM (OR = 1.067, p = 0.045) were associated with LAS in men. In case of women, there were no significant SLEA factors for LAS, however, ROC curve analysis revealed standing RF angle (AUC = 0.647, p = 0.028) and NWB DF ROM (AUC = 0.648, p = 0.026) could be affecting factors for LAS. Conclusion: There are differences in SLEA according to the history of LAS, furthermore, the identified items were different by sex. In case of men, tibial varum and WB DF ROM affect LAS occurrence. Standing RF angle and NWB DF ROM of women could be a predictor for LAS. However, since the sensitivity and specificity in most of the SLEA measurements are low, kinematic in dynamic tasks should be considered together for a more accurate evaluation of LAS risk.