Young-Tae Lim

The Differences of the Normalized Jerk According to Shoes, Velocity and Slope During Walking

The purpose of this study was to evaluate normalized jerk according to shoes, slope, and velocity during walking. Eleven different test subjects used three different types of shoes (running shoes, mountain climbing boots, and elevated forefoot walking shoes) at various walking speeds(1.19, 1.25, 1.33, 1.56, 1.78, 1.9, 2, 2.11, 2.33m/sec) and gradients(0, 3, 6, 10 degrees) on a treadmill. Since there were concerns about using the elevated forefoot shoes on an incline, these shoes were not used on a gradient. Motion Analysis (Motion Analysis Corp. Santa Rosa, CA USA) was conducted with four Falcon high speed digital motion capture cameras. Utilizing the maximum smoothness theory, it was hypothesized that there would be differences in jerk according to shoe type, velocity, and slope. Furthermore, it was assumed that running shoes would have the lowest values for normalized jerk because subjects were most accustomed to wearing these shoes. The results demonstrated that elevated forefoot walking shoes had lowest value for normalized jerk at heel. In contrast, elevated forefoot walking shoes had greater normalized jerk at the center of mass at most walking speeds. For most gradients and walking speeds, hiking boots had smaller medio-lateral directional normalized jerk at ankle than running shoes. These results alluded to an inverse ratio for jerk at the heel and at the COM for all types of shoes. Furthermore, as velocity increased, medio-lateral jerk was reduced for all gradients in both hiking boots and running shoes. Due to the fragility of the ankle joint, elevated forefoot walking shoes could be recommended for walking on flat surfaces because they minimize instability at the heel. Although the elevated forefoot walking shoes have the highest levels of jerk at the COM, the structure of the pelvis and spine allows for greater compensatory movement than the ankle. This movement at the COM might even have a beneficial effect of activating the muscles in the back and abdomen more than other shoes. On inclines hiking boots would be recommended over running shoes because hiking boots demonstrated more medio-lateral stability on a gradient than running shoes. These results also demonstrate the usefulness of normalized jerk theory in analyzing the relationship between the body and shoes, walking velocity, and movement up a slope.

Analysis of golf putting for Elite & Novice golfers Using Jerk Cost Function

The purpose of this study was to identify critical parameters of a putting performance using jerk cost function. Jerk is the time rate of change of acceleration and it has been suggested that a skilled performance is characterized by decreased jerk magnitude. Four elite golfers() and 4 novice golfers participated in this study for the comparison. The 3D kinematic data were collected for each subject performing 5 trials of putts for each of these distances (random order): 1m, 3m, 5m The putting stroke was divided into 3 phases such as back swing. down swing and follow-through. In this study, it was assumed that there exist smoothness difference between elite and novice golfers during putting. The distance and jerk-cost function of Putting stroke for each phase were analyzed Results showed that there was a significant difference in jerk cost function at putter toe (at media-lateral direction) and at the center of mass between two groups by increasing putting distance. From these it could be concluded that jerk can be used as a kinematic parameter for distinguishing elite and novice golfers.

An Analysis of decision Factor on Drive Distance for University Golf Player`s Object Execution Using Late Hitting Method

The purpose of this research was to conduct an analysis on the factors that determine the distance at the time of target swing based on the use of late hitting of outstanding college golfers to verify the difference between late hitting and the distance that target increases in regular swing and the distance. Then, this research conducts an analysis on the correlation between club head velocity, ball velocity, launch angle, back spin, meet ratio and distance that become kinematics variables at the time of target swing. To attain the above mentioned purpose, 25 outstanding college players with average experience and handicap of 6 years and 5, respectively, were targeted Comparative analysis on two swing that target increase in regular and the distance was conducted by used driver. When it pertained to two types of swing. analysis system comprised of an analytical software called the Science Eye of the Bridgestone and peripheries was used to define the relationship between variables of club head velocity, ball velocity, launch angle, back spin, meet ratio that become kinematics variables. As for the method of processing data pertaining to the factors that determine the distance, differences of distance by the type of swing was verified by using independent T-test that leveraged SPSS 120 statistics program. Moreover, level of correlation between variables that contribute to the increase in distance through relation of correlation, and analysis of tendencies was conducted to analyze tendency of non-distance to increase in accordance to the increase of each variable. Key results produced through this experiment are as follows: 1. Artificial late hitting for increased non-distance that targets skilled players had effect on increased the distance(p

Development of Putting Grip Sensor System

As a preliminary study of finding the relationship between the force at the grip and the success rate during putting stroke, the putting grip sensor system using FSR sensors was developed. The system consisted of the hardware which had the sensor part with 8 sensors per putting glove and data acquisition part as well as the software which had the real-time monitoring program and the offline post-processing program. After experiments with elite-golfer using this system, it is possible to suggest the proper force ranges at the grip during putting stroke.

Electromyographical Analyses of Muscle Activities of Upper Trunk for Ssireum Dutguri Technique

The purposes of this study were to analyze the muscle activities and the characteristics of muscle recruiting patterns of upper trunk for Ssirum dutguri technique using three top-ranked elite Ssirum players. The EMG technique was used to record muscle activities of both right and left sides of latissimus dorsi, biceps brachii, and erector spinae. Six surface electrodes were placed on the surface of the selected muscles and one ground electrode was also attached on the back of neck(C7). One video camera was also used to record the Ssirum motion to define 4 events and 3 phases for further analysis. The raw EMG data were filtered with band pass filter (50-400 Hz) to remove artifacts and then low pass filtered (4 Hz) to find the linear envelope which resemble muscle tension curve. This filtered EMG data were normalized to MVIC for the purpose of comparion between the subjects. The results were indicated that each subject with different physical characteristics showed very different muscle activity patterns. Although Ssirum dutguri is considered as foot technique the player grasped opponent`s satba(belt) with both hands when they play. Because of this reason, activities of upper trunk muscles were relatively high. However, direct comparison between upper and lower body muscles was not possible due to the lack of the data in present study. Interestingly, all threes subjects showed that erector spinae muscle activity was comparatively higher than those of latissimus dorsi and biceps brachii. This implies to reinforce back muscle as a routine of training to improve performance or to prevent back injury.

The Study of Muscle Contraction Effect of Vibration Exercise Device Using Surface Electromyography

The purpose of this study was to investigate the effects of vibration exercise using surface electromyography. Seven male collegiate wrestlers were participated in this study. Each subject stood on the platform and the vibration was induced for 1min. WEMG8 EMG system was used to record muscle activity from Vastus lateralis, Biceps Femoris, Tibialis Anterior, and Gastrocnemius. The EMG data were sampled for 30 sec. during non-vibration and vibration half squat position, respectively. The raw data were band pass filtered to remove noise and full wave rectified Paired sample t-test were performed to see the differences of maximum and average EMG between non-vibration and vibration trials. The results indicated that vibration produced much more muscle contraction than that of non-vibration trial for all selected muscles even though the significant difference was found only from Biceps Femoris. This phenomenon was due to the individual differences so care must be taken to evaluate vibration intensity and position before personal training.

A Kinematics Analysis of Back Armstand 2 Somersault in Platform Dives a Case Study

A platform diving with categorizing 624C motion was video taped and 3D kinematic variables were analyzed. This motion is consist of 3 parts from the headstand position to the act of turning after take-off. The results indicated that it took a very short time from the moment of take-off to the act of 1/2 turning because the turning motion has already started from preparing motion even before the fingertips have parted from the ground. Also, there was barely any jumping height due to the use of upper limbs segment and there was little difference in the moving distance compared to the standing events judging from horizontal movement of 1.1m. The horizontal velocity of the center of human body was increased before take-off while the vertical velocity was decreased right after take-off and the velocity of lower limbs segment was faster than the upper limbs segment showing contrary results to the standing events. In the aspects of angular velocity, the upper limbs segment starts the turning motion when take-off by rapidly extending its angular velocity while lower limbs segment make large angular velocity even before take-off.

Effects of Obesity on Lumber Strength and Visual Analogue of Back Pain in Disc Surgical Operated Patients after Rehabilitation

The purpose of this study were to compare the differences of isometric lumber extension strength and subjective pain degrees between obesity patients group and normal body fat group in disc surgical operated patients. The research purposed to indicate how isometric lumbar extension exercise for 12 weeks affected to lumbar strength and visual analogue scale of patients suffered by chronic back pain. The subjects were 65 low back pain patients(male 30, female 35)who had disease on lumbar in W hospital. The lumbar extension strength was measured at seven degrees of angles, which were and before and after the exercise program. We got the results of subjective pain degree using the modified visual analogue scale(VAS) of Lawlis et al(1989) and measured the maximal isometric lumbar strength of all subjects using MedX lumbar extension machine. Results were as follows; After the exercise, the lumbar extension strength of normal body fat patients groups included males and female were greater than that of the obesity patients groups in all angles(p

The Frequency of Sport Injury for the Junior Elite Golf Players in Korea

The purpose of this study was to investigate the frequency of sports injury among Korean junior elite golf players. The survey was made through the questionnaire which consist of eight categories and 280 valid answers were used to perform frequency analysis. The results indicated that 197 out of 280 participants experienced golf injuries (30%: during a game, 70%: during a practice) and 70% of them also experienced injuries within a year. The frequency analysis for the site of injury has shown that back was the most vulnerable area for all players(33%), followed by the right wrist, left shoulder and elbow for male players. Among female players, left wrist was the second weak site of injury, followed by the right wrist, right thoracic spine, and left shoulder. A few of them also have shown abnormal symptoms of ruptured lumbar disk, scoliosis, and lordosis and these injuries might be caused by the lack of flexibility and the fatigue due to over-practice. High frequency of wrist injury also demonstrated that excessive chopping or punching shot and poor environmental course conditions may cause this injury to be common. Overall, lack of warm up time, lack of strength and flexibility, and excessive amount of practice were the major reasons of injury for the junior elite golfers in Korea. The study also proved that these young Korean golfers actually had more chances to be faced with the injury than average. Thus, it is necessary to develop systematic and scientific methods of training, and prevention, treatment of these injuries with medical professionals.