• Transactions of the Korean Society of Mechanical Engineers B
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• v.36 no.8
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• pp.797-802
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• 2012

In this study, the potential performance enhancement in a dual heat pump system through series operation was investigated by a comparison between the performance for parallel and series operation for a heating supply temperature of $60^{\circ}C$. To compare the performance of each configuration fairly, the heat transfer surface area of the heat exchangers was fixed. The inlet temperatures and the flow rates of the heat source and the load were also fixed. In addition, the heat transfer and pressure drop characteristics of the working fluids were considered to achieve a more realistic comparison. The results show that the heating coefficient of performance (COP) of the series configuration is approximately 5% higher than that of the parallel configuration under the simulation conditions considered in the present study.

• Korean Journal of Applied Biomechanics
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• v.34 no.2
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• pp.93-103
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• 2024

Objective: The purpose of this study was to investigate whether dancers with chronic ankle instability (CAI) exhibit different characteristics in dynamic postural control ability and ankle joint laxity compared to dancers without CAI and non-dancers with CAI. Method: Twelve dancers with CAI, 14 dancers without CAI, and 12 non-dancers with CAI participated in the study. Dynamic balance was evaluated using the Star Excursion Balance Test (SEBT) and the single-leg hop balance. The laxity of the ankle joint was evaluated through the anterior drawer test and the talar tilt test. SEBT measured maximum reach distances in anterior, posteromedial, and posterolateral directions. Single-leg hop assessed center of pressure (COP) and time-to-boundary (TTB) outcomes. One-way ANOVA and Chi-square tests were performed to compare the outcome variables among the three groups. Results: Dancers with CAI demonstrated greater reach distance in the posterolateral direction compared to non-dancers with CAI during SEBT (p=.014). Secondly, dancers without CAI showed greater reach distance in the posterolateral (p<.001) and posteromedial (p=.001) directions during SEBT compared to non-dancers with CAI. Additionally, dancers without CAI exhibited better postural control with higher TTB AP mean of minima (p=.003) and TTB AP standard deviation of minima (p=.012) during single-leg hop compared to nondancers with CAI. Thirdly, dancers with CAI showed a lower positive rate during the anterior drawer test compared to non-dancers with CAI (p=.019). Conclusion: Dancers with CAI demonstrated better ankle function and reduced mechanical instability compared to non-dancers with CAI. Therefore, to elucidate the underlying mechanisms of lateral ankle sprain and CAI development exacerbation in dancers, additional factors that can affect ankle sprain, such as visual dependence during postural control and evaluation in dance movements, should be explored.

• Korean Journal of Applied Biomechanics
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• v.17 no.3
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• pp.147-154
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• 2007

This study's purpose is to investigate the effects on leg muscle activity caused by perturbation, using a trapdoor system during the support phase of gait for healthy adults (n = 6, height $177.5{\pm}5.5cm$, weight $81.0{\pm}9.5kg$, age $30.0{\pm}3.3yrs$). The trapdoor had the functional ability of causing inversion or eversion. The release time for the trapdoor was specified for two times, 0.3 and 0.5 seconds after heel contact. While altering these variables, EMG was recorded for the leg muscles (rectus femoris, biceps femoris, vastus lateralis, tibialis anterior, gastrocnemius, soleus). The following conclusions were derived. The steptime was longer for the 0.5s eversion than 0.3s inversion condition. So in order to regain stability after the perturbation the unsupporting leg reached forward rapidly. This quick reflex can be observed through the center of pressure (COP) and its rapid change in direction. The gastrocnemius was activated throughout the total experiment. There was a low amount of activity recorded in the rectus femoris, vastus lateralis and tibialis anterior except for the condition of inversion 0.3s. For most of the conditions, the highest average EMG peak values were recorded during the condition of inversion 0.3s. The iEMG patterns were similar for the conditions of inversion 0.3s and eversion 0.3s. To cope with the rapid change in these conditions, the biceps femoris was activated. During the experiment except for the condition of normal gait, the activity of the soleus and gastrocnemius was relatively high. Therefore, to prevent injury from perturbation of the lower leg strengthening of the soleus and gastrocnemius is required. Likewise to prevent injury to the thigh strengthening for the biceps femoris.

• Korean Journal of Applied Biomechanics
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• v.34 no.1
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• pp.34-44
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• 2024

Objective: This study aimed to investigate how the movements occurring during the follow-through phase after releasing an arrow among elite compound archers, are associated with the arrow impact points on the target. Method: Nine elite archers performed consecutive compound archery shooting under conditions identical to actual competitions using their own bows and equipment. Motion capture system and force platform were utilized to record the changes in joint positions and center of pressure, respectively. Principal component analysis was employed to identify the patterns in which multidimensional joint positions and COP changes were organized with horizontal and vertical coordinates of arrow impact points. Subsequently, correlation analysis quantified the relationship between individual variables and the coordinates of arrow impacts on the target. Results: We found a common organizational pattern in which the two axes of the impact point coordinates were grouped into the first two principal components. The movements of the upper and lower limbs following release exhibited opposite patterns in the anterior-posterior axis, with significant correlations observed between the arrow impact points of the horizontal axis and the left shoulder, right elbow, left hip, and both knees. Additionally, the lateral movements induced by the reaction force upon arrow release showed significant associations with the vertical coordinates of the impact points. Particularly, the correlations between the movements of the left shoulder and elbow, as well as the bilateral hip and right knee, were consistently observed among all participants. Conclusion: These findings implied that the post-release movements could significantly influence the trajectory and impact points of the arrows in compound archery. We suggest that a consistent and controlled movement during the follow-through phase may be more beneficial for optimizing shooting accuracy and precision rather than minimizing movements.

• Journal of Korean Academy of Medicine & Therapy Science
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• v.10 no.2
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• pp.31-37
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• 2018

Objective: The purpose of this study was to evaluate the effects of closed chain lower limb exercise with abdominal breathing exercise on stroke patients and their effects on trunk control ability and balance. Method: The subjects were 40 stroke patients, 19 patients in the experimental group and 18 patients in the control group. The period was 5 weeks, 5 times a week, 30 minutes per session. The experimental group was subjected to a closed chain lower limb exercise with abdominal breathing exercise and the control group was subjected to a closed chain lower limb exercise. The posture assessment scale for stroke(PASS), trunk impairment scale(TIS) were used for trunk adjustment ability, and the balance ability was measured as center of pressure(COP) and limit of stability(LOS). Results: Results of this study showed that the PASS and TIS test significantly increased the experimental group compared to the control group. As a result of comparing the changes of pre and post intervention intervals between the two groups, the TIS test was significantly lower in the experimental group than in the control group, but the LOS test was not significantly increased in the experimental group. Conclusion: Closed chain lower limb exercise with abdominal breathing exercise showed a significant improvement in the trunk control and balance ability of the stroke patients compared to the closed chain lower limb exercise without the abdominal breathing exercise.

• Journal of the Korean Society of Physical Medicine
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• v.17 no.1
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• pp.21-30
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• 2022

PURPOSE: This study examined the effects of treadmill training with taping on the affected ankle joint on the gait and balancing ability in patients with sub-acute stroke. METHODS: Nineteen patients with sub-acute hemiplegic stroke in a rehabilitation hospital were assigned randomly to either the experimental group (n = 10), who received treadmill training with taping on the affected ankle joint or the control group (n = 9), who received general treadmill training. All participants performed 60 min of comprehensive rehabilitation therapy (five sessions per week for four weeks). Each group received treadmill training with or without taping on the affected ankle joint for 20 min (three sessions per week for four weeks). The gait and balancing ability were measured before and after the four-week training. RESULTS: Post-training scores of 10-meter walk test (10 MWT), timed up and go (TUG) test, and center of pressure (COP) path length and velocity for the experimental group increased significantly compared to that pre-training (p < .05). The experimental group showed a larger decrease in the 10 MWT and TUG test than the control group (-3.5 s vs. -1.01 s, p < .05; -4.9 s vs. -1.7 s, p < .05; respectively) CONCLUSION: Treadmill training with taping on the affected ankle joint might improve the gait and balancing ability of stroke patients and is considered a more effective method for improving gait and balancing ability than the method of general treadmill training.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.35 no.11
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• pp.1185-1190
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• 2011

The lower limb somatosensory deficit observed among peripheral neuropathy patients is partially related to the decline in their balance ability. In general, balance ability has been examined by measuring the postural response (i.e., action). However, body motion is induced by integrated multisensory cues (i.e., motion perception). In this study, we hypothesized that the reduced lower limb somatosensation might also lower motion perception. We induced lower limb sensory deficits through ischemia and then measured the cutaneous sensory sensitivity and directional motion perception. The sensory deficit was successfully induced, and it also lowered the motion perception. However, the center of pressure (COP) variation did not significantly change under the sensory deficit. This result implies that measuring motion perception could enable the detection of precursors of sensory deficits.

• Journal of the Korea Convergence Society
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• v.9 no.10
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• pp.109-120
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• 2018

The purpose of this study was to investigate the effects of functional electrical stimulation (FES) with mirror therapy on balance and gait ability in chronic stroke patients. Thirty-five subjects who met the inclusion criteria were randomly allocated into three groups: the functional electrical stimulation with mirror therapy group(FMT group, n=11), mirror therapy group(MT group, n=12), and control group (n=12). The exercises were conducted for 30 min per day, five, per week for four weeks. Balance and gait ability were examined at baseline and after 4 weeks of intervention. After training, the FMT group showed significant improvement in berg balance scale (BBS), center of pressure (COP) length, affected step length (ASL), Cadence and average gait speed (AGS) compared MT group and control group(p<0.05). This findings show that FES and MT convergence can be an effective intervention for stroke patients balance and gait ability. Continued development of convergence interventions for stroke patients with balance and gait ability in practice, are suggested.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.13 no.7
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• pp.3074-3084
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• 2012

The purpose of this study lies in examining how sling lumbar stabilization exercise affects static standing balance of adolescent idiopathic scoliosis patients. The subjects were forty patients who were diagnosed with idiopathic scoliosis. They were randomly assigned either to a experimental group (n=20) that received sling lmubar stabilization exercise program or to a control group (n=20) that received only education. Data were obtained for each patient from total sway path and sway velocity in standing on both feet with eyes closed and standing on both feet with eyes open were measured, using balance performance monitor. All variables were measured at pre- and post-exercise. There were significantly differences between the both groups for all variables at post-exercise (p<.05). The experimental group showed a significantly decreases in all variables at pre- and post-exercise (p<.05). But the control group showed a no significantly differences. These results revealed that sling lumbar stabilization exercise improved static standing balance, by reducing COP(center of pressure) sway path and sway velocity of idiopathic scoliosis patients, and it is expected that sling lumbar stabilization exercise will be used as balance enhancement exercise intervention for the treatment of adolescent idiopathic scoliosis patients.

• Korean Journal of Applied Biomechanics
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• v.26 no.4
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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.