• Journal of Korean Institute of Industrial Engineers
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• v.35 no.1
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• pp.1-14
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• 2009

The efficiency of transportation requests fulfillment can be increased through extending the problem of vehicle routing and scheduling by the possibility of subcontracting a part of the requests to external carriers. This problem extension transforms the usual vehicle routing and scheduling problems to the more general integrated operational transportation problems. In this contribution, we analyze the motivation, the chances, the realization, and the challenges of the integrated operational planning and report on experiments for extending the plain Vehicle Routing Problem to a corresponding problem combining vehicle routing and request forwarding by means of different sub-contraction types. The extended problem is formalized as a mixed integer linear programming model and solved by a commercial mathematical programming solver. The computational results show tremendous costs savings even for small problem instances by allowing subcontracting. Additionally, the performed experiments for the operational transportation planning are used for an analysis of the decision on the optimal fleet size for own vehicles and regularly hired vehicles.

• Journal of the Ergonomics Society of Korea
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• v.25 no.2
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• pp.147-154
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• 2006

This study was conducted to evaluate the effect intentional contraction of abdominal muscles during lifting above shoulder on the muscles activities of the lower trunk and on the degree of lumbar extension. Fifteen healthy adult males were selected as test subjects. A 5kg weight was raised to the shoulder level, 20cm, and 40cm above the shoulder level. EMG activities of all muscles except the rectus abdominis were significantly greater when subjects were asked to contract their abdominal muscles intentionally during lifting(p<0.05). Degree of lumbar extension also significantly decreased with intentional abdominal contraction during the lifting. Also, degree of lumbar extension significantly increased with increase in lifting height(p<0.05). The results of this study show that intentional contraction of abdominal muscles during lifting above shoulder increases the EMG activities of external abdominis oblique, internal abdominis oblique, and erector spinae.

• Archives of Orthopedic and Sports Physical Therapy
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• v.14 no.2
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• pp.55-64
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• 2018

Purpose : The purpose of this study was to investigate the effect of the sprinter and skater combined patterns on muscle contraction onset time and muscle activation of body stabilizing muscles. Method : Our study included young and healthy men in their 20s. The participants used the sprinter and skater combined patterns of the proprioceptive neuromuscular facilitation (PNF) methods to measure muscle activation and muscle contraction onset time of the trunk muscles. To measure muscle contraction onset time and muscle activation, electrodes were attached to the rectus abdominis (RA), external oblique (EO), internal oblique (IO), and erector spinalis (ES) regions. Significant differences were identified using a paired t-test and a one-way analysis of variance (ANOVA) analysis. Result : In the sprinter combined pattern, the muscle with the fastest onset time of contraction was the RES, and that with the slowest was the RRA (p<.001). In the skater combined pattern, the muscle with the fastest onset time of contraction was the LES, and that with the slowest was the LRA (p<.001). In the sprinter combined pattern, the REO and LIO presented medium muscle contraction onset times (p<.001). In the skater combined pattern, the LEO and RIO presented medium muscle contraction onset times (p<.001). Conclusions: Based on these results, these patterns could be used as exercise methods for the elderly with delayed proactive response speeds of the body stabilization methods due to imbalances in body stabilizing muscles or limbs movement.

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

• Speech Sciences
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• v.1
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• pp.261-274
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• 1997

In spite of the presumed importance of the strap muscles on laryngeal valving and speech production, there is little research concerning the physiological role and the functional differences among the strap muscles. Generally, the strap muscles have been shown to cause a decrease in the fundamental frequency(Fo) of phonation during contraction. In this study, an in vivo canine laryngeal model was used to show the effects of strap muscles on the laryngeal function by measuring the Fo, subglottal pressure, vocal intensity, vocal fold length, cricothyroid distance, and vertical laryngeal movement. Results demonstrated that the contraction of sternohyoid and sternothyroid muscles corresponded to a rise in subglottal pressure, shortened cricothyroid distance, lengthened vocal fold, and raised Fo and vocal intensity. The thyrohyoid muscle corresponded to lowered subglottal pressure, widened cricothyroid distance, shortened vocal fold, and lowered Fo and vocal intensity. It was postulated that the mechanism of altering Fa and other variables after stimulation of the strap muscles is due to the effects of laryngotracheal pulling, upward or downward, and laryngotracheal forward bending, by the external forces during strap muscle contraction.

• Physical Therapy Korea
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• v.9 no.3
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• pp.23-37
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• 2002

This study examined the muscle recruitment order during extension of the hip joint in normal subjects, and evaluated whether the external support obtained from wearing a lumbosacral corset had an effect on muscle recruitment leading to increased lumbar stability. The subjects were 40 normal adults (32 male, 8 female) with no history of low back pain and no pathological findings in the nervous or musculoskeletal systems. All subjects extended their hip joints under 3 positions (prone, sidelying, standing). During extension, the onsets of contraction of the rectus abdominis, gluteus maximus, and semitendinosus muscles were measured. Electromyographic activity was measured using a surface electrode, and the muscle contraction onset time was designated as the point exceeding a threshold of 25 ms, using a mean plus twice of the standard deviation. To compare the average order of muscle contraction onset time, a Freedman two-way analysis of variance by ranks was used. The relative difference between muscle contraction onset time wearing and not wearing a lumbosacral corset was measured using a paired t-test. A difference in the average muscle contraction onset order for the rectus abdominis, gluteus maximus, and semitendinosus muscles was observed (p<.05) among three positions. However, wearing a lumbosacral corset did not. change the contraction order. In addition, wearing a lumbosacral corset produced a significant difference (p<.05) in the relative onset time between the rectus abdominis and gluteus maximus in the standing position, but no difference was observed for the other muscles or positions. In the future, patients suffering from low back pain should be compared with normal subjects to determine the effectiveness of a lumbosacral corset in changing muscle recruitment order.

• PNF and Movement
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• v.17 no.2
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• pp.293-302
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• 2019

Purpose: The purpose of this study was to investigate the effects of plank exercises involving the contraction of the adductor muscle of the hip joint on core muscle thickness and to propose an effective plank exercise method. Methods: A total of 30 healthy young adults (17 males, 13 females) voluntarily participated in the study. The subjects were randomized to the prone plank exercise with hip adductor contraction (n=10), the prone plank exercise (n=10), and the supine plank exercise (n=10) groups. Muscle thickness measurements were taken prior to starting the exercise program and after completing the program at the end of a 4-week period. The muscle thickness of the rectus abdominis (RA), multifidus (MF), external oblique (EO), internal oblique (IO), and transverse abdominis (TrA) muscles were measured using ultrasonography. Each group performed the stipulated plank exercise five times a week as follows: 5 sets of 20 seconds during the first week, 5 sets of 30 seconds in the second week, 5 sets of 40 seconds in the third week, and 5 sets of 40 seconds in the last week. Results: The three different types of plank exercises all showed significantly increased thickness of the RA, MF, EO, IO, and TrA (P<0.05). Furthermore, changes in the thickness of both the MF and TrA were statistically more significant in the groups that did the prone plank exercise with the hip adductor contraction and the supine plank exercise than in the prone plank exercise group (P<0.05). Conclusion: The study results suggest that the prone plank exercise with hip adductor contraction is a more effective method for overall activation of the RA, MF, EO, IO, and TrA than the prone plank exercise and the supine plank exercise.

• The Korean Journal of Physiology
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• v.18 no.2
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• pp.139-150
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• 1984

Vanadate is a potent inhibitor of Na-K-ATPase. Ouabain, the another specific inhibitor of Na-K-ATPase, induces the contraction in cardiac muscle and smooth muscle. But, some investigators observed the discrepancies between vanadate and ouabain-induced contraction in cardiac muscle. The difference of vanadate and ouabain-induced contraction was investigated in the cat ileal smooth muscle. The following results were obtained. 1) Ouabain-induced contraction was biphasic, but vanadate-induced contraction had one peak. 2) Atropine inhibited ouabain·induced contraction, but did not inhibit vanadate-induced contraction. 3) Changes in external $Ca^{++}$concentration or $Ca^{++}$ antagonists had a greater influence on the contraction induced hy vanadate than by ouabain. 4) Removal of $Na^+$ from incubation medium and high $K^+$ abolished ouabain-induced contraction, but had no effect on vanadate-induced contraction. 5) Vanadate-induced contraction was potentiated in the presence of ouabain. 6) After 3 hrs incubation with vanadate, there was no change in intracellular $Na^+$ concentrations in contrast with ouabain. These results suggest that vanadate contracts ileal smooth muscle through the mechanism different from ouabain, and this is independent of the inhibition of Na-K-ATPase activity.

• Physical Therapy Korea
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• v.25 no.4
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• pp.46-52
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• 2018

Background: The hamstring muscles in the lower extremity are highly important for knee joint stability and can be classified into medial and lateral hamstrings according to the anatomical position, which have some different functions. To measure the strength of the individual hamstring muscles, manual muscle testing is clinically performed by dividing rotation postures into internal and external postures. However, this has no sufficient scientific background. Objects: This study aimed to test the difference that the tibial rotation would cause in the muscle activity of the medial and lateral hamstrings. Methods: The muscle activities of the biceps femoris, semitendinosus, and semimembranosus were measured in a total of three different postures (neutral position and internal and external rotations) with 3 replications. During the maximal isometric contraction, resistance was constantly provided by the string attached to the strap, not by manual resistance of the examiner. Before and after electromyography measurements, the participants underwent hamstring flexibility measurement using the active knee extension test in the supine position on the treatment table. Results: The semitendinosus had a 12.56% reduction in muscle activity in external rotation as compared with that in neutral position. The biceps femoris and semimembranosus showed reduced muscle activities in both external and internal rotations as compared with those in neutral position. Only the women showed significant decreases in the comparison between pre and post-active knee extension. Conclusion: Only the semitendinosus muscle was consistent with the anatomical speculation. However, the reduction in the muscle activity of the semitendinosus as compared with that in neutral position was only 12.56%, the clinical value of which may be difficult to justify.

• PNF and Movement
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• v.18 no.2
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• pp.255-263
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• 2020

Purpose: The purpose of this study was to investigate the effect of proprioceptive neuromuscular facilitation (PNF) lower extremity pattern on the dominant leg on muscle activity of the lower extremity supported by the ground. Methods: The subjects were 20 healthy males living in Busan. All subjects performed four direction PNF lower extremity patterns, and data were collected by surface electromyography from the gluteus medius (GM), tensor fascia latae (TFL), vastus medialis oblique (VMO), vastus lateralis oblique (VLO), and semitendinosus (STD) muscles of the opposite lower extremity during PNF lower extremity pattern. The PNF lower extremity pattern applied to the dominant leg was (1) flexion/adduction/external rotation with knee flexion; (2) extension/abduction/internal rotation with knee extension; (3) flexion/abduction/internal rotation with knee flexion; and (4) extension/adduction/external rotation with knee extension pattern, repeated 3 times per pattern and using the average value of the collected results. Collected muscle activity values were analyzed by one-way ANOVA, and post-hoc Tukey testing was performed to check between-group differences. The statistical significance level was set at α = 0.05. Results: GM and TFL flexion/abduction/internal rotation pattern with knee flexion was significantly higher than other patterns. VMO and VLO extension/adduction/external rotation pattern with knee extension was significantly higher than other patterns. STD flexion/adduction/external rotation pattern with knee flexion was significantly higher than other patterns. Conclusion: The study confirms differences in lower extremity muscle activity for the PNF lower extremity pattern, indicating that selective muscle contraction induction is possible using a pattern appropriate to the purpose of treatment.