• Korean Journal of Applied Biomechanics
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• v.27 no.3
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• pp.197-203
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• 2017

Objective: The purpose of this study was to determine how exercise intensity affects muscle activity and kinematic variables during squat. Method: Fifteen trainers with >5 years of experience were recruited. For the electromyography (EMG) measurements, four surface electrodes were attached to both sides of the lower extremity to monitor the rectus femoris (RF) and biceps femoris. Three digital camcorders were used to obtain three-dimensional kinematics of the body. Each subject performed a squat in different conditions (40% one-repetition maximum [40%1RM], 60%1RM, and 80%1RM). For each trial being analyzed, three critical instants and two phases were identified from the video recording. For each dependent variable, one-way analysis of variance with repeated measures was used to determine whether there were significant differences among the three different conditions (p<.05). When a significant difference was found, post hoc analyses were performed using the contrast procedure. Results: The results showed that the average integrated EMG values of the RF were significantly greater in 80%1RM than in 40%1RM during the extension phase. The temporal parameter was significantly longer in 80%1RM than in 40%1RM and 60%1RM during the extension phase. The joint angle of the knee was significantly greater in 80%1RM than in 40%1RM at flexion. The range of motion of the knee was significantly less in 80%1RM than in 40%1RM and 60%1RM during the flexion phase and the extension phase. The angular velocity was significantly less in 80%1RM than in 40%1RM and 60%1RM during the extension phase. Conclusion: Generally, the increase of muscle strength decreases the pace of motion based on the relation between the strength and speed of muscle. In this study, we also found that the increase of exercise intensity may contribute to the increase of the muscle activity of the RF and the running time in the extension phase during squat motion. We observed that increased exercise intensity may hinder the regulation of the range of motion and joint angle. It is suitable to perform consistent movements while controlling the proper range of motion to maximize the benefit of resistance training.

• Journal of the Korea Computer Graphics Society
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• v.24 no.3
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• pp.49-59
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• 2018

Simulator sickness is one of the important side effect of virtual reality. Simulator sickness is influenced by various factors, and field of view (FOV) is one of them. The FOV is a viewing angle limited by the screen, and when the FOV is reduced, the simulator sickness is reduced, and the presence is lowered. Previous study developed a Dynamic FOV Restrictor (Center-fixed FOV Restrictor) to reduce simulator sickness while maintaining presence. It is a method that limits the FOV dynamically by reflecting the speed and angular velocity of the avatar. We also developed Eye-tracking Based Dynamic FOV Restrictor (Eye-tracking FOV Restrictor) by adding head rotations and eye movements. This study attempts to compare the simulator sickness and the presence of the No FOV Restrictor condition, the Center-fixed FOV Restrictor condition, and the Eye-tracking FOV Restrictor condition. The results showed that the simulator sickness of the Center-fixed FOV Restrictor condition is significantly lower than other two conditions. The results also showed that there were no significant differences in presence in three conditions. The interpretations and limitations of this study are discussed in this paper.

• The Journal of Korean Physical Therapy
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• v.10 no.1
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• pp.81-98
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• 1998

Isokinetic evaluation of trunk flexors and trunk extensors was performed at $60^{\circ}/sec\;and\;120^{\circ}/sec$ of angular velocity by using cybex 6000TEF Unit on 31 healthy male white workers and 15 post-operative HILD patients with no significant difference in mean age and mean body weight between two groups, and compared each other. The purpose of this study is to obtain the isokinetic normative strength values and endurance latins for Dunk extensors and trunk flexors, and is to provide a guideline for rehabilitation program of post-operative HILD patients. The collected data were analyzed by ANOVA, Duncan's Nyktuoke Range Test, and Pearson correlation coefficiency in PC-SAS program, The results obtained were as follow ; 1. Post-operative subjects has lower isokinetic values than normal subjects in peak torque, peak torque $\%$ by body weight, total work, total work $\%$ by body weight, average power, average power $\%$ by body weight, TAAE of trunk flexors and trunk extensors, and there are significant differences with statistic value in trunk extensors at $60^{\circ}/sec$ and in trunk flexors and trunk extensors at $120^{\circ}/sec$ between two groups(p<0.05). 2. Pest-ooperative subjects has lower values for angle of peak torque than normal subjects in trunk extensors, and there are significant differences with statistic value at $60^{\circ}/sec$ and $120^{\circ}/sec$ between two groups. 3. Post-operative subjects has higher values for endurance ratios than normal subjects in trunk extensors and flexors, but there are no significant differences with statistic value between two groups. 4. Post-operative subjects has higher values than normal subjects in peak torque ratios, total work ratios, average power ratios of trunk flexors to trunk extensors, and there are significant differences with statistic value between two groups(p<0.01). 5. There is significant positive-correlation with statistic valve between peak torque and height and body weight in normal subjects(p<0.05), but Thjere is significant negative-correlation between peak torque of trunk extensor at $120^{\circ}/sec$ and age (p<0.05). 6. There is significant positive-correlation with statistic value between peak torque of trunk flexors and body weight in post-operative subjects (p<0.05), but There is significant negative-correlation between peak torque of trunk extensor add age (p<0.05). In conclusion, post-operative subjects have greater weakness in trunk musculature than normal subjects, especially there is more significant weakness in trunk extensors than in trunk flexors

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.25 no.2
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• pp.70-74
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• 1989

This paper, described on the maneuverabilities of M.S. Cheju 402, the stern trawler (159 G.T.), training ship of Cheju National University which carried out the turning circle tests at helm angle 35$^{\circ}$ and 10$^{\circ}$, 20$^{\circ}$, 30$^{\circ}$Ztests of her. The results obtained were as follows; 1. The advances of the starboard and port turning circles were 79.1m, about 2.6 times of the length of the ship, and 81.4m, about 2.7 times of it, respectively. 2. The rates of speed reduction were about 0.49 together, and mean values of turning angular velocity of her at helm angle 35$^{\circ}$ into the starboard and port sides were 4.3$^{\circ}$/sec and 4$^{\circ}$/sec during the turning movement. 3. Overshoot angles of starboard side werelarger than those of port side at all Z tests, and mean values of them of the starboard and port sides at 10$^{\circ}$, 20$^{\circ}$, 30$^{\circ}$Z tests were 110.5$^{\circ}$ 20.5$^{\circ}$, 28.5$^{\circ}$ respectively. 4. The maneuvering indices K and T of experimental ship at 10$^{\circ}$, 20$^{\circ}$, 30$^{\circ}$, Z tests were 0.755 and 3.468, 0.566, and 1.621, and 0.481 and 1.547 respectively. Consequently, the experimental ship showed that her turning ability was more in effective as the helm angle was becomed larger and her obeying ability was more effective as it was becomed larger.

• Journal of Korean Foot and Ankle Society
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• v.19 no.4
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• pp.142-150
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• 2015

Purpose: Restoration of ankle stability through the strengthening exercise of peroneus muscles is considered an important factor for achievement of successful outcomes, in the rehabilitation program following ankle ligament injuries. However, there were few definitive data on normal muscle strength, including eversion power by peroneus muscles. This study was conducted to evaluate the muscle strength of ankle joint measured using an isokinetic dynamometer in normal Koreans. Materials and Methods: Sixty adults (120 ankles) were recruited and divided into three groups (20 in their twenties, 20 in thirties, and 20 in forties). Each group consisted of 10 males and 10 females. The selection criteria were no history of ankle injury and no evidence of instability. The peak torque, total work, and deficit ratio were measured using the Biodex$^{TM}$ (Biodex Medical Systems). Differences in muscle strength by age, gender and dominant versus non-dominant side were analyzed. Results: The peak torque of dorsiflexion was average 31.5 Nm at $30^{\circ}/s$ of angular velocity and 18.8 Nm at $90^{\circ}/s$; average 69.3 Nm ($30^{\circ}/s$) and 42.4 Nm ($90^{\circ}/s$) on plantarflexion; average 19.6 Nm ($30^{\circ}/s$) and 10.8 Nm ($90^{\circ}/s$) on inversion; average 12.9 Nm ($30^{\circ}/s$) and 8.0 Nm ($90^{\circ}/s$) on eversion. The deficit ratio of strength in women was average 61.1% of men on dorsiflexion; average 66.2% on plantarflexion; average 48.5% on inversion; average 55.4% on eversion. The deficit ratio in non-dominant foot was average 88.6% of dominant foot on dorsiflexion; average 90.1% on plantarflexion; average 85.1% on inversion; average 85.6% on eversion. Conclusion: The muscle strength of the ankle joint showed a tendency to weaken with age. There were significant differences in muscle strength by gender and dominancy. Further studies for comparison of patients with ankle instability, a comparison between before and after surgery for instability, the correlation between clinical outcomes and the recovery in muscle strength will be needed.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.53 no.2
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• pp.177-186
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• 2017

This study is intended to provide navigator with specific information necessary to assist in the avoidance of collision and in operation of ships to evaluate the maneuverability of research vessel Jera. Authors carried out full-scale sea trials for turning test, zig-zag test, and spiral test at actual sea-going condition, which were performed on starboard and port sides with 10-20 rudder angle at service speed of 10 knots. The turning circle was much different at both of the turning of port and starboard which was longer at the starboard than at the port. In the zig-zag test results, the port and starboard was $10^{\circ}$ the first and second overshoot angles were $6.0^{\circ}$, $5.8^{\circ}$ and $6.3^{\circ}$, $7.1^{\circ}$ respectively and the first overshoot angles were $16.4^{\circ}$, $17.6^{\circ}$ when using $20^{\circ}$. Her maneuverability index T and N can be easily determined by using an analogue computer with the data obtained from the zig-zag tests where K is a constant representing the turning ability and T is a constant representing her quick response. In the zig-zag tests under $10^{\circ}$ or $20^{\circ}$ at rudder angle, the value K is 0.149. 0.123 sec- and T is 11.853 and 6.193 sec and angular velocity is $0.937^{\circ}/sec$ and $1.636^{\circ}/sec$. In the spiral test, the loop width was unstable at $+0.51^{\circ}$ and $-1.19^{\circ}$ around the midship of rudder, but the tangent line at $0^{\circ}$ was close to vertical. From the sea trial results, we found that she did comply with the present criterion in the standards of maneuverability of IMO.

• Journal of Institute of Control, Robotics and Systems
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• v.7 no.9
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• pp.723-732
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• 2001

In this paper, the neurofuzzy controller of optically guided AGV is proposed to improve the path-tracking performance A differential steered AGV has front-side and rear-side optical sensors, which can identify the guiding path. Due to the discontinuity of measured data in optical sensors, optically guided AGVs break away easily from the guiding path and path-tracking performance is being degraded. Whenever the On/Off signals in the optical sensors are generated discontinuously, the motion errors can be measured and updated. After sensing, the variation of motion errors can be estimated continuously by the dead reckoning method according to left/right wheel angular velocity. We define the estimated contour error as the sum of the measured contour in the sensing error and the estimated variation of contour error after sensing. The neurofuzzy system consists of incorporating fuzzy controller and neural network. The center and width of fuzzy membership functions are adaptively adjusted by back-propagation learning to minimize th estimated contour error. The proposed control system can be compared with the traditional fuzzy control and decision system in their network structure and learning ability. The proposed control strategy is experience through simulated model to check the performance.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.10 no.12
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• pp.3902-3909
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• 2009

The purpose of this study was to investigate the spontaneous therapy, TENS(transcutaneous electrical nerve stimulation) and ice therapy after induction of DOMS(delayed onset muscle soreness) through application of eccentrically exercise in ralation to biceps brachii muscle of opposite-dominance. And to explain this, we analyzed VAS(visual analogue scales), peak torque, RMS(roots mean square) when exercising elbow joint. The subjects were 30 adults without any physical defect. Subjects were divided into three groups that spontaneous therapy, TENS therapy and ice therapy after DOMS induction, choosen movement could get the maximal peak torque in angular velocity of $60^{\circ}$/sec, and mearsured peak torque, RMS and VAS. 1. The VAS was significantly decreased after 3 days application of TENS than other groups(p<.05). 2. The peak torque was significantly increased after 3 days application of TENS than other groups(p<.05). 3. The RMS was significantly increased after 3 days application of TENS than other groups(p<.05). This study showed that TENS therapy application were effective treatment strategy on DOMS than spontaneous therapy and ice therapy. Therefore, it could be considered as a treatment method in the patients with DOMS.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.21 no.2
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• pp.167-174
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• 2020

The purpose of this study was to investigate the kinematic comparison between successful and failed trials of Lopez vault techniques in male gymnastics. The subject, an Olympic gold medalist, was YHS (age: 27 years, height: 1.6 m, and mass: 53 kg) and fourteen high speed motion capturing cameras were used for data collection. The 26 reflective sensors were attached on major anatomical positions and 15 segment-body model was used to calculate the kinematic variables. According to results, the contact duration of the spring-board for successful trial(ST) was longer and that of failed trial(FT) and the range of motion of knee joint for ST was greater than that of FT. The movement times during pre-flight between ST and FT were same, but the movement time of horse contact period for ST was shorter than that of FT. The ST showed a longer movement time during post-flight and the longer horizontal distance than those of FT. Conclusively, YHS needs to approach the horse with a higher position of the body and higher incidence angle, as well as make faster twist angular velocity in an attempt to achieve ST.

• Korean Journal of Applied Biomechanics
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• v.14 no.2
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• pp.69-83
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• 2004

The purpose of this study is searching for technical merits and demerits of each weight lifting player through qualitative motion analysis system. Moreover, It is also analysis the repeating the establishment of exercise purpose and studying for the effect of the field adaptation. The subject of this study was five male weight lifting players who have been engaged in Korean Delegation Team. The institution of exercise target was made through two times qualitative analysis and the result of studying for the effect of the field adaptation was produced before offering feedback. Moreover, two time analysis added after offering feedback. All analysis was based on 2-D visual analysis. The results of this study are as follows: 1. Maximal barbell moving speed in starting phase was decreased after offering feedback. This result implies advancement of technical skills after offering feedback. 2. From starting posture to 앉아받기, forward and backward moving distance of hip joint was decreased after offering feedback in all subjects. This result represents advancement of technical skills after offering feedback. 3. In terms of pull phase, forward and backward moving distance of hip and shoulder joint was decreased after offering feedback in all subjects. This result represents advancement of technical skills after offering feedback. 4. In terms of pull phase, the difference of horizontal value of coordinates was decreased after offering feedback in all subjects. This result represents advancement of technical skills after offering feedback. 5. In terms of pull phase, the motion range of hip joint was decreased after offering feedback in three of five subjects and this represents advancement of technical skills after offering feedback. However, the rest of them were not variable or narrow decreasing. This result represents that feedback system could not brought tremendous effects. 6. From apex point of barbell to 앉아받기, the difference of barbell height was decreased after offering feedback in three of five subjects and this represents advancement of technical skills after offering feedback. However, the rest of them weren't variable or narrow increasing. This result represents that feedback system could not brought tremendous effects. 7. In terms of last-pull phase, the angular velocity of knee joint was increased after offering feedback in four of five subjects and this represents advancement of technical skills after offering feedback. However, the rest of them, only one subject, decreased. This result represents that feedback system could not brought tremendous effects. 8. In terms of last-pull, the conversional tendency of maximal extension to flextion came out all but simultaneously without offering feedback in four of five subjects. This is well-performed technique. Only one subject, however, could not use power effectively because the fact that his maximal extension came out in serial, from ankle to knee and waist means dispersion of power. In addition to, after offering feedback, only one subject made increasing the maximal extension of knee in last-pull and this result represents advancement of skills after offering feedback. However, the rest of them could not make meaningful development after offering feedback. 9. It might be assumed that searching for technical merits and demerits of each weight lifting player through qualitative motion analysis system could improve player's skill.