• Journal of Mechanical Science and Technology
• /
• 제17권6호
• /
• pp.825-835
• /
• 2003

Previous studies have demonstrated the importance of joint angle errors mainly due to skin artifact and measurement errors during gait analysis. Joint angle errors lead to unreliable kinematics and kinetic analyses in the investigation of human motion. The purpose of this paper is to present the Joint Averaging Coordinate System (JACS) method for human gait analysis. The JACS method is based on the concept of statistical data reduction of anatomically referenced marker data. Since markers are not attached to rigid bodies, different marker combinations lead to slightly different predictions of joint angles. These different combinations can be averaged in order to provide a "best" estimate of joint angle. Results of a gait analysis are presented using clinically meaningful terminology to provide better communication with clinical personal. In order to verify the developed JACS method, a simple three-dimensional knee joint contact model was developed, employing an absolute coordinate system without using any kinematics constraint in which thigh and shank segments can be derived independently. In the experimental data recovery, the separation and penetration distance of the knee joint is supposed to be zero during one gait cycle if there are no errors in the experimental data. Using the JACS method, the separation and penetration error was reduced compared to well-developed existing methods such as ACRS and Spoor & Veldpaus method. The separation and penetration distance ranged up to 15 mm and 12 mm using the Spoor & Veldpaus and ACRS method, respectively, compared to 9 mm using JACS method. Statistical methods like the JACS can be applied in conjunction with existing techniques that reduce systematic errors in marker location, leading to an improved assessment of human gait.

• 한국운동역학회지
• /
• 제22권3호
• /
• pp.357-363
• /
• 2012

The purpose of this study was to investigate the effects of different saddle heights on lower-limb joint angle and muscle activity. Six elite cyclists(age: $32.2{\pm}5.2years$, height: $171.0{\pm}3.5cm$, weight: $79.7{\pm}5.6kg$, cycle career: $13{\pm}6.2years$) participated in three min. submaximal(90 rpm) pedaling tests with the same load and cadence based on saddle heights where subject's saddle height was determined by his knee flexion angle when the pedal crank was at the 6 o'clock position. Joint angles(hip, knee, ankle joints) and the activity of lower limb muscles(biceps femoris(BF), vastus lateralis(VL), tibialis anterior(TA) and gastrocnemius medial(GM)) were compared by measuring 3D motion and electromyography(EMG) data. Results showed that there were significant differences in minimum hip & knee joint angle and range of motion of hip and knee joint between saddle heights. Onset timing and integrated EMG of only BF among 4 muscles were significantly different between saddle heights. Especially there was a negative relationship between minimum hip joint angle and onset timing of BF in most subject, which means that onset timing of BF became fast as the degree of bending of the hip joint became larger by saddle height. Optimal pedaling will be possible through increased amount of muscle activation due to the appropriate burst onset timing by proper pedaling posture with adjusted saddle height.

• 국제물리치료학회지
• /
• 제4권2호
• /
• pp.595-599
• /
• 2013

The purpose of this study is to identify the bridge exercise posture for the efficient exercise by comparing the muscle activity of the lower limbs according to the changes in muscle length because of knee angle in bridge exercise. The subjects of this study were 9 randomly selected males in their 20s living in D city from those who satisfied inclusion criteria. The measured muscles were Vastus medialis oblique, Vastus lateralis, Semitendinosus, Biceps femoris, Gluteus maximus, Gluteus medius, Tensor faciae latae, and Adductor longus. Data were analyzed through paired comparison test. In the result, ST, BF, and TFL muscle activities were high when knee joint flexion angle was $90^{\circ}$ Although in most cases higher muscle activity was shown at $90^{\circ}$ than $60^{\circ}$ there was no statistical significance. Interestingly, it was lower at $90^{\circ}$ than $60^{\circ}$ in VL. In ST, BF, and TFL, it was significantly higher at $90^{\circ}$ than $60^{\circ}$ (p<.05). Conclusively, knee angles in bridge exercise may affect the muscle activity, and in particular when the activity of two joint muscles such as semimenbranosus muscle, biceps femoris muscle, and tensor fasciae latae muscle increase as the angle gets higher. Therefore, it is considered that this study will provide helpful tips to develop muscular strength enforcement program for the patients with damages in the lower limbs through bridge exercise in clinical situations.

• 한국운동역학회지
• /
• 제24권3호
• /
• pp.239-248
• /
• 2014

The purpose of this study was to quantify kinematic and kinetic characteristics of Yin-yang Bo gait according to their motor expertise, one of the Seokmun Ilwol martial art gait patterns. Yin-yang Bo gait pattern shows initial forefoot contact instead of heel contact, and increased time of stance phase time, internal-external rotation of ankle-knee-hip joints and pelvic. It aims to produce and store the more energy through continuous homeostasis of center of gravity (COG) and performance of stretch-shortening cycle. Some of these characteristics also were similar to the gait modification strategies for reducing knee adduction moment such as toe-out progression, medial thrust, internal rotation of hip joint. To identify the characteristics, four factors of expert Yin-yang Bo gait performance group were compared to that of none expert group; 1) angles of COG displacement and rotation 2) distal joint pre-rotation in internal-external rotation of ankle-knee-hip joints and pelvic, 3) invariability pelvic potential and pelvic segment total energy 4) knee abduction moment. Six healthy(three male) subjects participated in the experiment to perform Yin-yang gait pattern. Three-dimensional and force plate data were collected. Kinematic and kinetic data were compared between two groups using t-tests. Results showed that 1) the peak point of COG internal rotation angle was reduced in expert group, 2) kneeexternal and hip joint -internal and pelvic rotation angle peak frames were more near points in expert group.

• 대한물리의학회지
• /
• 제15권1호
• /
• pp.43-54
• /
• 2020

PURPOSE: This study examined the effects of mild-intensity exercise (MIE) and high-intensity interval exercise (HIIE) on the recovery of the motor function over time in sciatic nerve crush injury rats. METHODS: The MIE group ran on a treadmill at a speed of 8.3 m/min to perform low-intensity training with maximum oxygen uptakes ranging from 40 to 50%. The HIIE group ran on the treadmill at a speed of 25 m/min to perform high-intensity training with a maximum oxygen uptake of 80%. The interval training was performed based on a 1:1 work-to-rest ratio. The effects of each form of exercise on the rats' walking abilities following their recovery from the peripheral nerve injuries were evaluated based on the results of behavior tests performed at one and 14 days. RESULTS: According to the test results, the MIE group showed significant improvements in the rats' ankle angle in the initial stance phase, and in the ankle and knee angles in the toe-off phase (p<.05). The HIIE group exhibited significant improvements in the ankle and knee angles in the initial stance phase, SFI(p<.05). CONCLUSION: The state of such patients can be improved by applying the results of this study in that MIE and HIIE on a treadmill can contribute to the recovery of the peripheral nerve and motor skill. In particular, MIE is used as a walking functional training in the toe-off stance phase, while HIIE is suitable in the initial stance stage.

• 한국안전학회지
• /
• 제23권1호
• /
• pp.35-45
• /
• 2008

This study was performed to compare the kinematics among three different safety shoes(type 1: ergonomically designed and high quality shoes, 2: curved and cushioned safety shoes, and 3: regular safety shoes) and to find the effect of insole during walking. Ten healthy subjects were recruited for this study. The range of motion of knee and ankle joint, angle of rear foot and angle of heel contact were measured using a three dimensional motion analysis system. In the second peak, the angle of heel contact showed statistically significant difference between safety shoes and insole, however, there was no statistical significance among three different safety shoes. The angle of ankle increased significantly at initial contact, first peak, the second peak and the toe off phase compared with type 1 and 2 safety shoes, and the angle of ankle showed statistically significant difference between with and without applying the insole. During the first peak, the second peak and the toe off phase, the angle of knee was statistical significance between safety shoes and insole. In heel contact, the angles of Achilles' tendon showed statistically significant difference between safety shoes and insole. The rear foot angles showed statistically significant difference between safety shoes and insole during heel contact and early heel contact. These results suggest that the type 1 safety shoes were superior to others in the statistics, and applying insole could be a possible method to prevent fatigue of lower extremity and musculoskeletal disorders. Further studies are needed to find the effect of ergonomically designed safety shoes and insole on practical value in prevention of musculoskeletal disorder, fatigue and satisfaction of workers.

• 한국운동역학회지
• /
• 제21권5호
• /
• pp.511-520
• /
• 2011

The purpose of this study was to provide scientific information to track and field coaches and athletes through the analyses of the biomechanics characteristics of the top 4 sprinters in the men's 100 m final in the IAAF World Championships Daegu 2011. Twelve video cameras (Sony, Japan) were used to capture the mid portion of the race (40 m - 70 m) with a sampling frequency of 60Hz. Biomechanical variables including the right ankle, knee and hip angles, the trunk angle, and the velocity of center of mass (COM) in the running direction, were calculated with the Kwon 3D program (Visol, Korea). Correlation coefficients between the COM velocity and each variables were calculated using Matlab 2008a (MathWorks, USA) at an alpha level of 0.05. The findings indicated that Yohan Blake (JAM) showed greater range of motion at the ankle and hip. Walter Dix(USA) showed greater knee and trunk movement, and Kim Collins (SKN) showed more dorsi-flexed and extended trunk angles during the race. Finally, Christophe Lemaitre (FRA) showed more plantar-flexed ankle with a less trunk motion, throughout the analyzed race.

• Physical Therapy Rehabilitation Science
• /
• 제6권1호
• /
• pp.7-13
• /
• 2017

Objective: The aim of this study was to investigate the inter-rater and intra-rater reliability of rehabilitative ultrasound imaging (RUSI) for measurement of muscle thickness with changes in angles of the gluteus maximus (GM) at rest and during contraction. Design: Cross-sectional study. Methods: Twenty-two healthy men volunteered for this study. GM muscle images were obtained in the resting position and during prone hip extension with knee flexion at hip abduction angles of $0^{\circ}$ and $30^{\circ}$, respectively. Two examiners randomly measured the thickness of the GM twice in three different positions. The first position was a comfortable prone position. The second position was prone hip extension with knee flexion (PHEKF) to $90^{\circ}$. The third position was achieved by hanging a 1-kg weight on the ankle of the lifted leg during PHEKF with the angle of the lifted leg the same as the second position. Intra-class correlation coefficients (ICCs), standard error measurements, and minimal detectable changes were used to estimate reliability. Results: The intra-rater reliability ICCs (95% confidence interval) of the GM were >0.870, indicating good reliability. Inter-rater reliability ICCs ranged from 0.668 to 0.913. The reliability of measurements of muscle thickness at each position was similar to the reliability of the angle change. Differences in muscle thickness and ratios for each position with $0^{\circ}$ and $30^{\circ}$ of hip abduction were not statistically significant. Conclusions: In the present study, the intra-rater reliability of muscle thickness measurements of the GM was good, and the inter-rater reliability was moderate to good. Reliable RUSI measurements of wide and large muscles, such as the GM muscle at rest and during contraction, are feasible. Further investigation is required to establish the reproducibility of the protocols presented in this study.

• 한국운동역학회지
• /
• 제20권4호
• /
• pp.437-445
• /
• 2010

This study was aimed at comparing selected joint angles at the golf address stance by categorizing three different body types. 43 elite male golfers were selected and 9 of them turned out to be the ectoderm while 24 of them to be the mesoderm. The remaining 10 subjects were the endoderm. The measurement was carried out at the address stance with the number 7 iron and the driver. The result showed that the angle of trunk flexion did not different among body types. The trunk tilting angle became more inclined to the right side, which confirmed the guidelines from most of golf lesson books, for bigger people since they tended to put more weight on the right foot. The angle of both knees showed similar but the right knee was bent more than the left knee. The target direction and body alignment faced more to the left side than the target spot because of the influence of open stance and natural aiming position. It seems that pelvis and knees turned a little bit more to the right side than the target direction in order to maintain the parallel. Overall, significant differences among body types were found at the trunk tilting angle and pelvis-target alignment and golf address configuration can be differentiate by these factors.

• 한국운동역학회지
• /
• 제26권4호
• /
• pp.361-367
• /
• 2016

Objective: The aim of this study was to compare three-dimensional kinematic changes of the lower extremity between the two different braking distances during snowplow in alpine skiing. Method: Six alpine ski instructors (age: $25.3{\pm}1.5yr$, height: $169.3{\pm}2.9cm$, weight: $66.2{\pm}5.9kg$, career: $4.2{\pm}2.9yr$) participated in this study. Each skier was asked to perform snowplow on the two different braking distances (2 and 4 m). Results: Snowplow and edging angles (p = .006 and p = .005), ankle adduction and inversion (p = .033 and p = .002), knee extension (p = .003), and hip abduction and internal rotation (p = .043 and p = .006) were significantly greater in the 2 m than in the 4 m braking distance. Conclusion: Based on our results, we suggest that skiers should make greater snowplow and edging angles on the shorter braking distance. In this situation, ankle joint adduction/inversion angle and hip joint internal-rotation make greater snowplow angle, and hip joint abduction make greater edging angle. In addition, greater knee joint extension angle may lead to more posteriorly positioned center of mass.