• Transactions of the Korean Society of Automotive Engineers
• /
• v.6 no.4
• /
• pp.17-23
• /
• 1998

This paper presents the motion of dynamically loaded journal in the connecting rod bearing of reciprocation internal combustion engine. Journal motions in engine bearings have been composed of two components, which was rotational and translational motion. Early study of journal locus in engine bearing had been performed on each motion. This paper has been considered two motions simultaneously. Reynolds equation including the squeeze effect has been analyzed using the ADI method, and real engine bearing and crankshaft system has been considered to calculate the cyclic external force. The equations are performed by 4th order Runge-Kutta method. This paper gives various journal orbits in connecting rod bearing depending on cyclic external forces, rotation speeds, and bearing parameters.

• Physical Therapy Korea
• /
• v.17 no.1
• /
• pp.1-8
• /
• 2010

The purpose of this study was to compare EMG activity for pectoralis major muscle during shoulder movement with various abduction angle and rotation position in supine position. Fifteen healthy subjects were recruited for this study. All subjects performed shoulder horizontal adduction holding a 2 kg dumbbell in shoulder abduction $40^{\circ}C$, $70^{\circ}C$, $90^{\circ}C$, $130^{\circ}C$, $160^{\circ}C$ with shoulder neutral, internal rotation (IR), and external rotation (ER). Surface EMG activity was recorded from pectoralis major clavicle part and pectoralis major sternum part for 5 seconds and EMG activity was normalized to the value of maximal voluntary isometric contraction (%MVIC). Dependent variables were examined with 3 (Neutral, IR, ER) ${\times}$ 5 ($40^{\circ}C$, $70^{\circ}C$, $90^{\circ}C$, $130^{\circ}C$, $160^{\circ}C$) analysis of variance with repeated measures. The EMG activity of pectoralis major muscle was significantly different between shoulder abduction angles and between shoulder rotation positions (p<.05). The highest value of EMG activity of pectoralis major clavicle part among shoulder abduction angles was in $70^{\circ}C$ and, $90^{\circ}C$ in that order. The highest value of EMG activity of pectoralis major sternum part among shoulder abduction angles was in $130^{\circ}C$ and, $90^{\circ}C$ in that order. According to the rotation degree, shoulder ER showed the highest value and IR showed the lowest value in both muscle parts. These results suggest that shoulder abduction $70^{\circ}C$, $90^{\circ}C$, $130^{\circ}C$ will be effective during manual muscle testing (MMT) and strengthening exercise for pectoralis major muscle. It is also supposed that shoulder ER is the efficient posture for strengthening of pectoralis major muscle.

• Physical Therapy Rehabilitation Science
• /
• v.5 no.3
• /
• pp.132-137
• /
• 2016

Objective: Eversion of the foot is created with internal rotation of the shank, and inversion of the foot is created with external rotation of the shank. The purpose of the study was to investigate the effect of continuous changes in the angle of the subtalar joint on lower extremity alignments. Design: Cross-sectional study. Methods: Seventeen healthy young adult subjects recruited. The subjects were asked to stand up in a natural standing position on a footplate with eye open and equal weight on each foot for 10s in two different conditions: The right subtalar joint was everted continuously $0^{\circ}-20^{\circ}$ and in separate segments of $0^{\circ}$, $5^{\circ}$, $10^{\circ}$, $15^{\circ}$, $20^{\circ}$. The averages of three trials were used. The observation of the changes in the lower extremity was performed with the use of 3-dimensional motion analysis. For data analysis, the SPSS 18.0 software using paired t-test and repeated measures analysis of variance (ANOVA) was applied. Results: The angle was significantly increased at the horizontal rotation angle of the shank, thigh, and ankle without anterior rotation of the pelvis (p<0.05). The maximum horizontal rotation angle at the thigh on $20^{\circ}$ was $-4.52^{\circ}$ in static, and $-3.10^{\circ}$ in the dynamic conditions compared to $0^{\circ}$. Conclusions: Increased unilateral foot pronation, thigh, shank, ankle horizontal rotation variance was significantly effective. The observation of the changes in foot abduction with the use of a 3-dimensional motion analysis augmented in predicting the angle values of each segment of the lower extremity. In further studies, a comparison of the right and left subtalar joints need to be investigated.

• Korean Journal of Applied Biomechanics
• /
• v.26 no.4
• /
• pp.369-375
• /
• 2016

Objective: The purpose of this study was to investigate the possibility of injuries and the types of movement related to damage by body parts, and to prepare for prevention of injuries and development of a training program. Method: For this study, the experiment was conducted according to levels of 60 percentages (ST) and 85 percentages (MA) and 10 subjects from the Korean elite national weightlifting team were included. Furthermore, we analyzed joint moment and muscle activation pattern with three-dimensional video analysis. Ground reaction force and EMG analyses were performed to measure the factors related to injuries and motion. Results: Knee reinjuries such as anterior cruciate ligament damage caused by deterioration of the control ability for the forward movement function of the tibia based on the movement of the biceps femoris when the rectus femoris is activated with the powerful last-pull movement. In particular, athletes with previous or current injuries should perceive a careful contiguity of the ratio of the biceps femoris to the rectus femoris. This shows that athletes can exert five times greater force than the injury threshold in contrast to the inversion moment of the ankle, which is actively performed for a powerful last pull motion and is positively considered in terms of intentional motion. It is activated by excessive adduction and internal rotation moment to avoid excessive abduction and external rotation of the knee at lockout motion. It is an injury risk to muscles and ligaments, causing large adduction moment and internal rotation moment at the knee. Adduction moment in the elbow joint increased to higher than the injury threshold at ST (60% level) in the lockout phase. Hence, all athletes are indicated to be at a high risk of injury of the elbow adductor muscle. Lockout motion is similar to the "high five" posture, and repetitive training in this motion increases the likelihood of injuries because of occurrence of strong internal rotation and adduction of the shoulder. Training volume of lockout motion has to be considered when developing a training program. Conclusion: The important factors related to injury at snatch include B/R rate, muscles to activate the adduction moment and internal rotation moment at the elbow joint in the lockout phase, and muscles to activate the internal rotation moment at the shoulder joint in the lockout phase.

• Physical Therapy Korea
• /
• v.26 no.1
• /
• pp.67-74
• /
• 2019

Background: Uncontrolled lumbopelvic movement leads to asymmetric symptoms and causes pain in the lumbar and pelvic regions. So many patients have uncontrolled lumbopelvic movement. Passive support devices are used for unstable lumbopelvic patient. So, we need to understand that influence of passive support on lumbopelvic stability. It is important to examine that using the pelvic belt on abdominal muscle activity, pelvic rotation and pelvic tilt. Objects: This study observed abdominal muscle activity, pelvic rotation and tilt angles were compared during active straight leg raise (ASLR) with and without pelvic compression belt. Methods: Sixteen healthy women were participated in this study. ASRL with and without pelvic compression belt was performed for 5 sec, until their leg touched the target bar that was set 20 cm above the base. Surface electromyography was recorded from rectus abdominis (RA), internal oblique abdominis (IO), and external oblique abdominis (EO) bilaterally. And pelvic rotation and tilt angles were measured by motion capture system. Results: There were significantly less activities of left EO (p=.042), right EO (p=.031), left IO (p=.039), right IO (p=.019), left RA (p=.044), and right RA (p=.042) and a greater right pelvic rotation angle (p=.008) and anterior pelvic tilt angle (p<.001) during ASLR with pelvic compression belt. Conclusion: These results showed that abdominal activity was reduced while the right pelvic rotation angle and anterior pelvic tilt angle were increased during ASLR with a pelvic compression belt. In other words, although pelvic compression belt could support abdominal muscle activity, it would be difficult to control pelvic movement. So pelvic belt would not be useful for controlled ASLR.

• Physical Therapy Korea
• /
• v.23 no.2
• /
• pp.84-92
• /
• 2016

Background: Strengthening the supraspinatus is an important aspect of a rehabilitation program for subacromial impingement and tendinopathy. Many authors recommended empty-can (EC), full-can (FC), and prone full-can (PFC) exercises to strengthen the supraspinatus. However, no ultrasonography study has yet investigated supraspinatus muscle architecture (muscle thickness; MT, pennation angle; PA, fiber bundle length; FBL) in relation to supraspinatus strengthening exercises. Objects: The purpose of this study was to compare the architecture (MT, PA, and FBL) of the supraspinatus muscle during three different types of exercises (EC, FC, and PFC) using diagnostic ultrasound. Methods: Participants performed three different exercises: (A) EC; the arm was maintained at $60^{\circ}$ abduction with full internal rotation in the sitting position, (B) FC; the arm was maintained at $60^{\circ}$ abduction with full external rotation in the sitting position, and (C) PFC; the arm was maintained at $60^{\circ}$ abduction with full external rotation in the prone position. Ultrasonography was used to measure the MT, PA and FBL of the supraspinatus. One-way repeated analysis of variance with Bonferroni's post-hoc test was used to compare between the three exercises and the initial position of each exercise. Results: Compared with each initial position, the FC exercise showed the greatest mean difference in muscle architecture properties and the PFC exercise showed the least mean difference. Conclusion: The findings suggest that the FC exercise position may have an advantage in increasing the amount of contractile tissue or producing muscle power and the PFC exercise position may be useful in a rehabilitation program because it offers the advantage of maintaining the muscle architecture properties.

• Journal of the Korean Society of Physical Medicine
• /
• v.13 no.2
• /
• pp.11-19
• /
• 2018

PURPOSE: The aim of this study was to identify the effects of joint mobilization intervention combined with exercise on range of motion (ROM), pain intensity, and functional performance in adolescent baseball players with internal impingement syndrome of the shoulder. METHODS: The subjects were 30 adolescent baseball players diagnosed with internal impingement. Ten subjects were randomly assigned to each of 3 groups: Group 1 (exercise only), Group 2 (joint mobilization combined with exercise), and Group 3 (rest-only control group). Three weekly interventions were given for 4 weeks (the control group rested for 4 weeks). The main outcome measures were goniometer, visual analogue scale (VAS), and Korean Kerlan Jobe shoulder-elbow (K-KJOC) scores. The ROM (external and internal rotation), pain intensity (at the moment of throwing), and functional performance were compared among the groups. RESULTS: No significant difference was observed among the groups in the range of external rotation of the shoulder before and after the intervention, but the range of internal rotation was significantly increased in Group 2 compared to Groups 1 and 3. Pain intensity was significantly lower in Group 2 than in Group 1 and 3, and functional performance was significantly increased in Group 2 compared to Group 1 and 3. CONCLUSION: An intervention that combined joint mobilization with exercise was more effective than resting or exercise alone for rapid recovery from sports injury and improvement in athletic performance.

• The Journal of Korean Academy of Orthopedic Manual Physical Therapy
• /
• v.9 no.1
• /
• pp.39-52
• /
• 2003

The test for internal and external rotation of hip joint, was donet from September 2 to 9, 2002, with the participation of 50 male/female university students who are in a normal health condition. Results are : 1. When applying the external rotation of 45 degrees angle ; 1) In a sitting position, for male it results in an increase of 5 degrees on right and left sides each. 2) In a sitting position, for female there is no change on both right and left sides. 3) In a supine position, for both male and female it results in an increase of 5 to 10 degrees on right and left sides each. 4) In a prone position, for male it results in an increase of 5 degrees on the left side only. 5) In a prone position, for female it results in an increase of 5 to 10 degrees on right and left sides each. 2. When applying the internal rotation of 45 degrees angle ; 1) In a sitting position, for male it results in a decrease of 5 degrees on right and left sides each. 2) In a sitting position, for female there is no change on both right and left sides. 3) In a supine and prone position, there is no change for male. 4) In a supine position, for female it results in an increase of 5 to 10 degrees on right and left sides each. 5) In a prone position, for female it results in an increase of 5 degrees on right and left sides each.

• Korean Journal of Applied Biomechanics
• /
• v.18 no.3
• /
• pp.51-59
• /
• 2008

The objective of this study is to kinematically analyze forehand & backhand strokes of abscission handicap wheelchair table tennis athletes. The participant of this study were picked out of national athletes who have abscission handicap. Forehand stroke movement was expected to show a throw like motion. However, external rotation and internal rotation of the right arm created a backswing and an impact. Backhand stroke was expected to show a push like motion, and as expected, proximal part of the body didn't participate in the stroke motion, but the distal part, the right arm, rotated internally to backswing and external rotated to impact to form a push like motion. Forehand swing was expected to show throw like motion according to the Link Segmental System principle. However, abscission handicap athlete didn't show clear linking structure connecting proximal and distal parts. Successful strokes were dependant only on the angle of arm rotation.

• Korean Journal of Applied Biomechanics
• /
• v.31 no.3
• /
• pp.214-219
• /
• 2021

Objective: The aim of this study was to evaluate the differences in muscle activity of hamstring muscle depending on the position of the feet during Swiss ball hamstring curl exercise. Method: Total of 15 male participants with no history of hamstring muscle injuries and musculoskeletal disorders in the past 6 months were participated in this study (Age: 29.27 ± 4.96 yrs, Height: 173.47 ± 5.18 cm, Body mass: 75.47 ± 12.50 kg). The muscle activation of semitendinosus and biceps femoris with four different feet positions including neutral stance, internal rotation, external rotation, and wide stance were measured during a Swiss ball hamstring curl exercise. For the analysis, the Swiss ball exercise movement comprised of 3 events (90°→ 0°→ 90°) based on the knee angle and 2 phases relative to the mechanism of muscle contraction (eccentric/concentric contraction). To pursue the study goal, an one-way ANOVA with repeated measures was performed with statistical significance as α = 0.05. Results: There was no statistically significant feet position effect found during the Swiss ball hamstring curl with eccentric contraction phase (p>.05). It is, however, semitendinosus showed an enhanced muscle activation in concentric contraction phase, displaying the highest muscle activity in wide stance and the lowest in external rotation (p<.05). Conclusion: Our findings suggest that this exercise can be beneficial in selectively training the semitendinosus. In other words, Swiss ball hamstring curls performed in wide stance strengthens semitendinosus, which improves the stability of knee and are effective in preventing knee injuries and reinforces rehabilitation.