• Korean Journal of Applied Biomechanics
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• v.21 no.2
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• pp.173-179
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• 2011

This study aims to analyse difference in biomechanical factors between dominant legs and recessive ones according to muscular imbalance during drop landing targeting talented children in sports. The subjects of the study were ten primary students who are attending to Sports Program for Talented Children organized by C university (age: $12.28{\pm}0.70$ year, height: $1.52{\pm}0.11$ m, and weight: $45.2{\pm}4.9$ kg). Strength legs were classified into dominant side and strengthless legs were classified into non-dominant legs. For three-dimensional analyses of the data collected, 6 video cameras(MotionMaster200, Visol, Korea) were used. To analyse ground reaction force, two force platforms(AMTI ORG-6, MA) were used and to analyse electromyograghy a 8-channeled wireless Noraxon Myoresearch made in USA was used at 1000 Hz for sampling. As a result, it was discovered that the dominants legs controlled knee bending motions more stably than strengthless legs as the maximum vertical ground reaction force was significantly high in dominant legs(p<.05), and joint moment of knee joints of the dominant legs was high(p<.05). Therefore, this study suggested that injury prevention program focusing on muscular balance as well as the existing sports programs for talented children should be developed based on results of the study and it is expected that the results will be useful for improvement of sports programs for talented children.

• Korean Journal of Applied Biomechanics
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• v.29 no.4
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• pp.255-261
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• 2019

Objective: The purpose of this study was to investigate differences of shock attenuation strategies between double-leg and single-leg landing on sagittal plane using statistical parametric mapping. Method: Nine healthy female professional soccer players (age: 24.0±2.5 yrs, height: 164.9±3.3 cm, weight: 55.7±6.6 kg, career: 11.2±1.4 yrs) were participated in this study. The subjects performed 10 times of double-leg and single-leg landing from the box of 30 cm height onto force plates respectively. The ground reaction force, angle, moment, angular velocity, and power of the ankle, knee, and hip joint on sagittal plane was calculated from initial contact to maximum knee flexion during landing phase. Statistical parametric mapping was used to compare the biomechanical variables of double-leg and single-leg landing of the dominant leg throughout the landing phase. Each mean difference of variables was analyzed using a paired t-test and alpha level was set to 0.05. Results: For the biomechanical variables, significantly increased vertical ground reaction force, plantarflexion moment of the ankle joint, negative ankle joint power and extension moment of the hip joint were found in single-leg landing compared to double-leg landing (p<.05). In addition, the flexion angle and angular velocity of the knee and hip joint in double-leg landing were observed significantly greater than single-leg landing, respectively (p<.05). Conclusion: These findings suggested that negative joint power and plantarflexion moment of the ankle joint can contribute to shock absorption during single-leg landing and may be the factors for preventing the musculoskeletal injuries of the lower extremity by an external force.

• Korean Journal of Applied Biomechanics
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• v.28 no.1
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• pp.1-8
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• 2018

Objective: The purpose of this study is to investigate the differences in biomechanical variables of golf driving motion according to gender. Method: A total of 21 healthy golfers (11 men and 10 women) who have more than 5 years of professional experience and have been registered in the Korea Golf Association was recruited. A 250-Hz 8-camera motion capture system (MX-T20, Vicon, LA, USA) was used to capture the motion trajectories of a total of 42 reflective markers attached to the golfer's body and club. Moreover, two 1,000-Hz AMTI force plates (AMTI OR6-7-400, AMTI, MA, USA) were used to measure the ground reaction force. The mean and standard deviation for each parameter were then calculated for both groups of 21 subjects. SPSS Windows version 23.0 was used for statistical analysis. The independent t-test was used to determine the differences between groups. An alpha level of .05 was utilized in all tests. Results: There were differences in joint angles according to gender during golf driver swing. Men showed a statistically significantly higher peak joint angle and maximum range of angle in sagittal and frontal axis of the pelvis, hip, and knee. Moreover, women's swing of the pelvis and hips was found to have a pattern using the peak joint angle and range of angle in the vertical axis of the pelvis and hip. There were the differences in peak joint moment according to gender during golf driver swing. Men used higher joint moment in the downswing phase than women in the extensor, abductor, and external rotator muscles of the right hip; flexor and adductor muscles of left hip joint; and flexor and extensor muscles of the right knee. Conclusion: This result reveals that male golfers conducted driver swing using stronger force of the lower body and ground reaction force based on strength of hip and thigh than female golfers.

• Korean Journal of Applied Biomechanics
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• v.24 no.4
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• pp.349-357
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• 2014

The purpose of this study was to examine the differences in the performance of dancing motions depending on the level of skill by investigating pulmonary functions, ground reaction force, and jerk cost. The subjects of this study were 12 professional dancers (career: 16 yrs) and 12 amateur dancers (career: 9 yrs) who had similar physical conditions. We selected four motion phases which included the diagonal line motion, the deep flexion motion, the breath motion, and the turn motion with one leg after a small step walking motion, with Goodguri Jangdan. In the experiment, 6 infrared cameras were installed in order to analyze the value of the jerk costs and the force plate form. Finally, we measured the pulmonary functions of the subjects. For data analysis, independent t-tests according to each event, were carried out in the data processing. According to the results of FVC % Predicted, the professional dancers showed greater lung capacities than the amateur dancers, indicating that the level of dancing skill influences lung capacity. Based on the result of the balance test, the professional dancers used more vertical power than did the amateur dancers when performing maximal flexion motion. The professional dancers used a propulsive force of pushing their body forward by keeping the center of body higher while the amateur dancers used a braking power by keeping their bodies backward. When performing medial-lateral movements, the amateur dancers were less stable than the professional dancers. There were no differences in values of jerk costs between the amateur dancers and the professional dancers.

• Korean Journal of Applied Biomechanics
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• v.28 no.2
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• pp.135-141
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• 2018

Objective: The purpose of this study was to investigate the effect of functional ankle instability (FAI) and surgical treatment (ST) on postural stability and leg stiffness during vertical-drop landing. Method: A total of 21 men participated in this study (normal [NOR]: 7, FAI: 7, ST: 7). We estimated dimensionless leg stiffness as the ratio of the peak vertical ground reaction force and the change in stance-phase leg length. Leg length was calculated as the distance from the center of the pelvis to the center of pressure under the foot. Furthermore, the analyzed variables included the loading rate and the dynamic postural stability index (DPSI; medial-lateral [ML], anterior-posterior [AP], and vertical [V]) in the initial contact phase. Results: The dimensionless leg stiffness in the FAI group was higher than that of the NOR group and the ST group (p = .018). This result may be due to a smaller change in stance-phase leg length (p = .001). DPSI (ML, AP, and V) and loading rate did not show differences according to the types of ankle instability during drop landing (p > .05). Conclusion: This study suggested that the dimensionless leg stiffness was within the normal range in the ST group, whereas it was increased by the stiffness of the legs rather than the peak vertical force during vertical-drop landing in the FAI group. Identifying these potential differences may enable clinicians to assess ankle instability and design rehabilitation protocols specific for the impairment.

• Korean Journal of Applied Biomechanics
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• v.26 no.3
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• pp.249-255
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• 2016

Objective: This purpose of this study was to analyze the relationship between dimensionless leg stiffness and kinetic variables during gait performance, and its modulation with body weight. Method: The study sample consisted of 10 young women divided into 2 groups (Control, n=5 and Obese, n=5). Four camcorders (HDR-HC7/HDV 1080i, Sony Corp, Japan) and one force plate (AMTI., USA) were used to analyze the vertical ground reaction force (GRF) variables, center of pressure (COP), low limb joint angle, position of pelvis center and leg lengths during the stance phase of the gait cycle. Results: Our results revealed that the center of mass (COM) displacement velocity along the y-axis was significantly higher in the obese group than that in control subjects. Displacement in the position of the center of the pelvis center (Z-axis) was also significantly higher in the obese group than that in control subjects. In addition, the peak vertical force (PVF) and dimensionless leg stiffness were also significantly higher in the obese group. However, when normalized to the body weight, the PVF did not show a significant between-group difference. When normalized to the leg length, the PVF and stiffness were both lower in the obese group than in control subjects. Conclusion: In the context of performance, we concluded that increased dimensionless leg stiffness during the gait cycle is associated with increased velocity of COM, PVF, and the change in leg lengths (%).

• Korean Journal of Applied Biomechanics
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• v.15 no.2
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• pp.167-183
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• 2005

The purpose of this study was to analyze the kinetical variables of the lower extremity joints when performing uchimata(inner thigh reaping throw) by uke(receiver)'s two posture(shizenhon tai), jigohon tai), by voluntary resistance level(VRL) in judo. The subjects, who were for 3 male Korean national representative judokas(elite group : EG) and 3 male representative judokas of Korean University(non-elite group: NEG), and were filmed 4 DV video cameras(60fields/sec.), that posture of uke were shizenhon-tai (straight natural posture), jigohon-tai(straight defensive posture), VRL of uke was 0%. The selected trials were subject to 3-dimensional film motion analysis and ground reaction force(MRF) analysis. The kinetical variable of this study were temporal, postures( ankle and knee angle of attacking leg), that were computed through video film analysis, MRF at events were obtained from the ground-reaction force analysis by AMTI force plate system. When performing uchi-mata according to each posture and by VRL, from the data analysis and discussion, the conclusions were as follows : 1) Temporal variables : total time-required(TR) when performing uchi-mata was shown EG 0.13sec the shorter than NEG(o.77sec.) in shizenhon-tai. and EG 0.17sec the shorter than NEG(o.76sec.) in jigonhon-tai. Also, all of two groups' jigohon-tai(0.68sec.) were faster than shizenhon-tai(0.71 sec.). 2) The posture variables : The angle of ankle in attacking when performing were plantar flexion in EG, and dorsi flexion in NEG by shizenhon-tai and jigohon-tai posture. The angle of knee in attacking when performing were extension in EG and NEG, but range of extension in EG were larger than in NEG. 3) MRF : Vertical MRF when performing uchi-mata was shown the strongest in the 2nd stage of kake phase(2.23BW) by EG in both posture, and it was same value by NEG(2.23BW), but shizenhon-tai (2.28BW), jigohon-tai(1.64BW), respectively.

• Physical Therapy Korea
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• v.23 no.3
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• pp.40-47
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• 2016

Background: Assessments of Sit-to-Stand (STS) and gait functions are essential procedures in evaluating level of independence for the patients after stroke. In a previous study, we developed the software to analyze center of pressure (COP) in standing position on Wii Balance Board (WBB). Objects: This purpose of this study is to measure test-retest reliability of ground reaction forces, COP and time using WBB on STS and gait in healthy adults. Methods: Fifteen healthy participants performed three trials of STS and gait on WBB. The time (s), vertical peak (%) and COP path-length (cm) were measured on both tasks. Additionally, counter (%), different peak (%), symmetry ratio, COP x-range and COP y-range were analyzed on STS, 1st peak (%), 2nd peak (%) of weight were analyzed on gait. Intra-class correlation coefficient (ICC), standard error measurement (SEM) and smallest real difference (SRD) were analyzed for test-retest reliability. Results: ICC of all variables except COP path-length appeared to .676~.946 on STS, and to .723~.901 on gait. SEM and SRD of all variables excepting COP path-length appeared .227~8.886, .033~24.575 on STS. SEM and SRD excepting COP path-length appeared about .019~3.933, .054~11.879 on gait. Conclusion: WBB is not only cheaper than force plate, but also easier to use clinically. WBB is considered as an adequate equipment for measuring changes of weight bearing during balance, STS and gait test which are normally used for functional assessment in patients with neurological problems and elderly. The further study is needed concurrent validity on neurological patients, elderly patients using force plate and WBB.

• Korean Journal of Applied Biomechanics
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• v.24 no.4
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• pp.385-390
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• 2014

The purpose of this study was to investigate the effects of landing tasks on the anterior cruciate ligament (ACL) injury risk factors in female basketball players. Fifteen female basketball players performed a drop landing and a drop landing with a vertical jump on the 40 cm height box. Three-dimensional motion analysis system and ground reaction force system was used for calculate the ACL injury risk factors. Paired samples t-test with Bonfferoni correction were performed. The drop landing with a vertical jump had the higher knee flexion angle, peak knee varus moment, trunk flexion angle than a drop landing. However, the drop landing had the higher trunk rotation angle than a drop landing with a vertical jump. These results indicate that seemingly minor variations between drop landing and drop landing with a vertical jump may influence the ACL injury risk factors. Caution should be used when comparing studies using different landing tasks.

• International Journal of Internet, Broadcasting and Communication
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• v.13 no.1
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• pp.47-53
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• 2021

Gait kinematics and kinetics have a similar tendency between men and women, yet it remains unclear how walking while carrying a load affects the gait mechanism. Twenty adults walked with preferred velocity on level ground of 20 m relative to change of a load carriage (no load, 15%, 30% of the body weights) aimed to observe gait mechanism. We measured gait posture using the three-dimensional image analysis and ground reaction force system during stance phase on left foot. In main effect of gender difference, men showed increased displacement of center of gravity (COG) compared to women, and it showed more extended joint angle of hip and knee in sagittal plane. In main effect of a load difference, knee joint showed more flexed postuel relative to increase of load carriage. In main effect of load difference on the kinetic variables, medial-lateral force, anterior-posterior force (1st breaking, 2nd propulsive), vertical force, center of pressure (COP) area, leg stiffness, and whole body stiffness showed more increased values relative to increase of load carriage. Also, men showed more increased COP area compared to women. Interaction showed in the 1st anterior-posterior force, and as a result of one-way variance analysis, it was found that a load main effect had a greater influence on the increase in the magnitude of the braking force than the gender. The data in this study explains that women require little kinematic alteration compared to men, while men in more stiff posture accommodate an added load compared to women during gait. Additionally, it suggests that dynamic stability is maintained by adopting different gait strategies relative to gender and load difference.