• Journal of Biomedical Engineering Research
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• v.31 no.3
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• pp.217-226
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• 2010

The lower limb orthosis with a pneumatic rubber actuator, which is intended for the assistance and the enhancement of muscular activities of lower limbs was developed in this study. Compared to other knee extension assistive devices being developed by other researchers, our device is designed especially for the elderly people and intended only for slight assistance so that the subjects can keep their muscular strength. For the effectiveness of system, muscular activities of major muscles in lower limbs during sit-to-stand (STS) and squat motion were measured and analyzed. Subjects were performed the STS and squat motion with and without lower limb orthosis. We made comparison muscular activities between with and without lower limb orthosis. Lower limb orthosis was controlled using muscular stiffness force feedback that is controlled by muscular activities of the measured muscle from force sensor. For analysis of muscular activities, electromyography of the subjects was measured during STS and squat motion, and these were measured using MP 150(BIOPAC Systems, Inc.). Muscles of interest were rectus femoris(RF), vastus lateralis(VL), vastus medialis(VM) and vastus intermedius(VI) muscles in lower limbs of the right side. A biodex dynamometer was used to measure the maximal concentric isokinetic strength of the knee extensors of wearing and not wearing orthosis on right side. The test were performed using the concentric isokinetic mode of test with the velocity set at 60°/s for muscles around the knee joints. The experimental result showed that muscular activities in lower limbs wearing orthosis using muscular stiffness force of a vastus medialis muscle was reduced and knee extension torque of an knee joint wearing lower limb orthosis was increased. With this, we confirmed the effectiveness of the developed lower limb orthosis.

• Physical Therapy Korea
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• v.15 no.2
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• pp.54-63
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• 2008

The purpose of this study was to examine the effect of the hip internal rotation on knee extensor and hip abductor electromyographic (EMG) activity during stair up and stair down mobility. Eighteen healthy subjects were recruited. All subjects performed stair up and down movements on a step of 30cm height while maintaining the hip in neutral (condition 1) and hip in internal rotation (condition 2). Surface EMG activity was recorded from five muscles (gluteus maximus, vastus lateralis (VL), vastus medialis oblique (VMO), posterior gluteus medius (Gmed), and tensor fascia latae (TFU)) and hip internal rotation angle was measured using a three dimensional motion analysis system The time period for stair up and down was normalized using the MatLab 6.5 program, and EMG activity was normalized to the value of maximal voluntary isometric contraction (%MVIC). The EMG activities according to the hip rotation (neutral or internal rotation) during the entire time period of stair up and down in each phase were compared using a paired t-test. During the entire period of stair up, the EMG activities of VL and TFL in condition 2 were significantly greater than in condition 1 (p<.05). During the entire period of stair down, the EMG activities of VL and TFL in condition 2 were significantly greater than in condition 1 (p<.05). However, the EMG activities of the other muscles were not significantly different between the conditions (p>.05). These results suggest that the stair up and down maintaining hip internal rotation was could be a contributing factor on patellar lateral tracking.

• The Journal of Korean Academy of Orthopedic Manual Physical Therapy
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• v.18 no.2
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• pp.41-47
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• 2012

Background: This study was designed to investigate the correlation between electromyography (EMG) activities in the vastus medialis oblique (VMO) vs vastus lateralis (VL) activity ratio and the valgus collapse knee position while stepping down. Methods: Twenty healthy women volunteered to participate in this study. We measured the frontal-plane projections of the knee valgus angle, knee valgus distance, and hip adduction angle by using a digital camcorder. After 3 repetitions of the step down (dominant side) exercise, the findings of the static and dynamic phases were analyzed. EMG activities data of the VMO:VL activity ratio were recorded during the step down exercise and were normalized to the maximal voluntary isometric contraction (MVIC) of the quadriceps. A paired t-test was used to compare the findings of the static and dynamic phases. We analyzed the Spearman's rank order correlation coefficient between the and VMO:VL ratio. Results: Hip adduction angle, knee valgus angle, VMO activity, VL activity, VMO:VL activity ratio were statistically higher in the dynamic phase than in the static phase (p<.05). Frontal-plane projections of knee valgus angle were significantly correlated with hip adduction angle (r=.459, p<.05) and knee valgus distance (r=.505, p<.05). However, the EMG activity ratio of the VMO and the VL did not show a significant change during step down exercise with respect to hip adduction angle (p=.875), knee valgus angle (p=.618), and knee valgus distance (p=.701). Conclusion: The results from this study indicate that frontal-plane projections of knee valgus angle were associated with hip adduction angle and knee valgus distance. On the basis of these results, the knee valgus distance may be used to determine the valgus collapse knee position while stepping down.

• Journal of the Korea Convergence Society
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• v.7 no.2
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• pp.43-52
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• 2016

The purpose of this study was to suggest the effective squat exercise position to strengthening vastus medialis oblique, and vastus lateralis in quadriceps. Subjects were twenty patients with patellofemoral pain syndrome (PFPS) volunteered to participate in this study. All subjects were applied to static squat convergence exercise with knee flexed $45^{\circ}$, $60^{\circ}$, and $90^{\circ}$ for 30 seconds total 5 times. Measurement variables were maximal voluntary isometric contraction (MVIC) of the quadriceps, Q angle and length of thigh. Those were measured before and after the squat exercise on knee joint angle, change rate of which were used for statistical analysis. As a result, squat exercise with knee flexed $90^{\circ}$ increase significantly among knee joint angle in the MVIC change rates of quadriceps (p<.05), however the rates of Q-angle and length change of thigh showed no significant difference. Therefore, this findings suggest that squat exercise with knee flexed $90^{\circ}$ strengthen quadriceps effectively in patients with PFPS.

• Journal of Digital Convergence
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• v.17 no.12
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• pp.319-327
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• 2019

The muscle activity and balance ability of the acute stroke patient has been checked by the functional electrical stimulation using biofeedback fusion postural control training in this study. Functional electrical stimulation using biofeedback fusion postural control training have been implemented on 15 trainees and general biofeedback fusion postural control training have been implemented on another 15 trainees for 30 minutes at 5 times per week during 8 weeks, and vastus lateralis, vastus medialis, rectus femoris and biceps femoris have been measured using the biceps femoris to evaluate the muscle activity of the lower extremity. The moving surface area, whole path length and limited of stability have been measured using biorecue to measure the balance ability. There was statistically meaningful difference on the vastus lateralis, vastus medialis, rectus femoris and biceps femoris in the muscle activity of the lower extremity and there was statistically meaningful difference on surface area, whole path length and limited of stability in the balancing ability. Based on above, it is realized that the functional electrical stimulation using biofeedback fusion postural control training is more effective than the general biofeedback fusion postural control training on the improvement of the muscle activity of the lower extremity and the balance ability.

• Korean Journal of Applied Biomechanics
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• v.25 no.2
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• pp.141-147
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• 2015

Objective : This study aimed to understand how increased heart rates at the time of drop landing during a step test would affect biomechanical variables of the lower extremity limbs. Background : Ballet performers do more than 200 landings in a daily training. This training raises the heart rate and the fatigability of the lower extremity limbs. Ballet performance high heart rate can trigger lower extremity limb injury. Method : We instructed eight female ballet dancers with no instability in their ankle joints(mean ${\pm}$ SD: age, $20.7{\pm}0.7yr$; body mass index, $19.5{\pm}1.2kg/m^2$, career duration, $8.7{\pm}2.0yr$) to perform the drop landing under the following conditions: rest, 60% heart rate reserve (HRR) and 80% HRR. Results : First, the study confirmed that the increased heart rates of the female ballet dancers did not affect the working ranges of the knee joints during drop landing but only increased angular speeds, which was considered a negative shock-absorption strategy. Second, 80% HRR, which was increased through the step tests, led to severe fatigue among the female ballet dancers, which made them unable to perform a lower extremity limb-neutral position. Hence, their drop landing was unstable, with increased introversion and extroversion moments. Third, we observed that the increasing 80% HRR failed to help the dancers effectively control ground reaction forces but improved the muscular activities of the rectus femoris and vastus medialis oblique muscles. Fourth, the increasing heart rates were positively related to the muscular activities of the vastus medialis oblique and rectus femoris muscles, and the extroversion and introversion moments. Conclusion/Application : Our results prove that increased HRR during a step test negatively affects the biomechanical variables of the lower extremity limbs at the time of drop landing.

• Journal of the Korean Society of Physical Medicine
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• v.8 no.4
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• pp.647-653
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• 2013

PURPOSE: The purpose of this study was to compare the lower extremities muscle activation between squatting exercise with gym ball and wall for improving muscle strengthening in lower extremities. METHODS: Participants were 21 university students (males 10, females 11) who didn't have any problem with orthopedic surgery. Participants performed squatting exercise with gym ball and wall. Squatting exercise with gym ball were performed using by gym ball behind back, and the gym ball were fixed in back and wall. We asked participants to push back the gym ball slightly to prevent fall of ball. Wall squatting exercise, we ask participants to contact their back in wall slightly in order to prevent trunk flexion during performed squatting exercise. Each squatting exercise had performed until knee joint were flexed at 60 degree, and maintained five seconds. We collected data from E.M.G of Biceps femoris, Gastrocnemius, Vastus medialis and lateralis, Tibialis anterior of lower extremity in isometric phase of knee joint angle 60 degree of each squatting exercise. We analysed data using by ANOVA and independent t-test of SPSS PC ver.20.0 in order to compare the muscle activation between squatting exercise with gym ball and wall. RESULT: All of lower extremities muscle activation showed more higher value in squatting exercise with gym ball than squatting exercise with wall, especially there was significantly difference of muscle activation in vastus medialis, tibialis anterior between squatting exercise with gymball and with wall. CONCLUSION: On comprehensively considering the results of the present study, we suggested that squatting exercise with gym ball was more effective method improving lower extremity muscle strengthening.

• Journal of the Korean Society of Physical Medicine
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• v.7 no.2
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• pp.173-182
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• 2012

Purpose : This study was investigated the effect of lower extremity muscle activity during open kinetic chain exercise (OKC) and closed kinetic exercise (CKC) in normal young adults. Methods : The participants were consisted of forty-one. All subjects were randomly assigned to two groups of open kinetic chain exercise group (n=21) and closed kinetic chain exercise group(n=20). It was perform 3 sets, 3 times per week for 6 weeks both open kinetic chain exercise group and closed kinetic chain exercise group. Subjects were assessed for each subject took pre-test, post-test in 2 weeks, post-test in 4 weeks, post-test in 6 weeks measurement the surface EMG data for vastus medialis and lateralis, lateral and medial hamstring, lateral and medial gastrocnemius, tibialis anterior. Results : The vastus medialis and lateralis muscle activity was significantly increased within the intervention period both group(p<.05). The lateral and medial part of hamstring muscle activity was significantly increased with in the intervention period(p<.05). The tibialis anterior muscle activity of open kinetic chain exercise group and closed kinetic chain exercise group was significantly increased in the intervention period(p<.05). The lateral and medial part of gastrocnemius muscle activity of open kinetic chain exercise group and closed kinetic chain exercise group was significantly increased with in the intervention period(p<.05). Conclusion : It was found that both open kinetic chain exercise and closed kinetic chain exercise was significantly increased muscle activity. Further studies are needed to analyzed long term effects and subjects resulting from these changed. these exercises can be selectively adapted not only as treatment exercise for patients but also as preventive exercise for normal person to improve balancing ability by conducting proper amount of exercise for each individual's condition and stage.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.13 no.1
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• pp.227-235
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• 2012

The purpose of this study was to analysis the effect of form of outsole on lower leg Electromyography (EMG) during gait. The subject were 11 women(mean age $47.33{\pm}4.4$ years, height $158.00{\pm}3.3$cm, weight $59.50{\pm}6.1$, body mass index $23.80{\pm}1.8kg/m^2$), who had no serious foot musculoskeletal disease within3years prior to study. The vastus medialis, gastrocnemius, semitendinosus, tibialis anterior were compared during gait with 2 types of shoe(complex function double rocker sole, negative-heel rocker sole) by using pair t-test(p<.05). The vastus medialis, gastrocnemius, semitendinosus were not found to be significantly different among the 2 types of shoe but tibialis anterior were found(p<.05). The complex function double rocker sole shoe caused a significant change in energy expenditure compared to the negative-heel rocker sole shoe.

• Journal of the Ergonomics Society of Korea
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• v.25 no.4
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• pp.93-101
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• 2006

This study examined whether there is a transfer effect to other joint angles and the angular specificity of muscle fatigue after 6 weeks of isometric training of the vastus medialis. Twenty subjects were randomly assigned to 30° and 90° knee flexion groups and were trained at 80% maximal voluntary isometric contraction(MVIC) three times a week for 6 weeks. The pre-and post-training values of the 80% holding time(endurance time) of MVIC, the Fatigue Index(FI), and the MVIC at 30°, 60°, and 90° were compared. After isometric training for 6 weeks, in the 30° knee flexion group, FI decreased significantly(p<0.05) only at 30°, which was the training angle; there was no change at other angles. By contrast, in the 90° knee flexion group, FI decreased significantly(p<0.05) at both the trained angle and at the other angles, indicating a transfer effect of training. MVIC did not increase significantly(p<0.05) at any trained angle in either the 30° or 90° knee flexion groups after 6 weeks of isometric training, neither did the 80% holding time of MVIC differ significantly compared with pre-training in either group. These findings suggest that training at 90° of knee flexion is more effective than training at 30° of knee flexion for obtaining a training transfer effect on muscle fatigue in the vastus medialis.