• Korean Journal of Applied Biomechanics
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• v.23 no.4
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• pp.335-345
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• 2013

The purpose of this study was to investigate the effects of foot type and ankle joint fatigue levels on the trajectories of center of pressure and center of mass during a single-leg stance. The study subjects included 24 healthy women (normal foot group, n=10; pronated foot group, n=14). Ankle joint muscle fatigue was induced by using an isokinetic dynamometer, where the fatigue levels were measured on plantar flexion and dorsiflexion at angular velocities of $30^{\circ}/s$ at 50% and 30% of the peak torque of ankle plantar flexion. Following assessments in the anteroposterior direction according to the level of fatigue, the pronated foot group showed decreased single-leg stance ability at 50% and 30% of the fatigue level. Moreover, the normal foot group showed better single-leg stance ability than the pronated foot group at 30% of the fatigue level. Following assessments in the mediolateral direction, we noted that the single-leg stance ability did not differ significantly according to the levels of fatigue or foot type. In conclusion, ankle plantar flexion at 50% and 30% of the peak torque reduced the ability of the pronated foot group to achieve a single leg stance in the anteroposterior direction. Moreover, the normal foot group showed better single-leg stance ability than the pronated foot group.

• The Journal of Korean Physical Therapy
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• v.35 no.2
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• pp.53-57
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• 2023

Purpose: The purpose of this study was to compare the changes in the muscle activation of the quadriceps muscle (rectus femoris, vastus lateralis, vastus medialis) during the stand-to-sit (StandTS) movement according to the plantar flexion angle of the ankle joint. Methods: A total of 22 healthy young females participated in this study. During the StandTS under the three conditions (plantarflexion angle 0°, 20°, and 45° of the ankle), electromyography (EMG) data (% maximum voluntary iso¬metric contraction) of the rectus femoris, vastus lateralis, and vastus medialis were recorded using a wireless surface EMG system. Results: There was a significant difference in the muscle activation of rectus femoris, vastus lateralis, and vastus medialis according to the plantar flexion angle (0°, 20°, and 45°) of the ankle. The muscle activation of the quadriceps was the highest at a 45° angle of plantarflexion and the lowest at 0°. One-way repeated ANOVA was used to analyze the muscle activation data of the lower extremity muscles according to the angle of the ankle joint. Conclusion: Based on the results of our study, it was confirmed that the muscle activity of the quadriceps can be increased even in the StandTS movement, which involves the eccentric contraction of the quadriceps muscle. This suggests that maintaining a plantar flexion posture for a long time, say by wearing high-heeled shoes, can quickly cause muscle fatigue in the lower-limb muscles, which can cause a decrease in balance ability leading to falls.

• Journal of Fashion Business
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• v.26 no.4
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• pp.112-122
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• 2022

The purpose of this study is to investigate the effect of using socks combined with EMS on ankle pain reduction and ankle function improvement in home training participants. In this study, the conductive fabric was combined using socks that can properly compress the ankle. First, VAS was measured during EMS training after fatigue was induced and compared with fatigue during rest. It was confirmed that the level of VAS after EMS training was lower than after rest and fatigue. It was also confirmed that EMS training, which combines EMS with socks, was effective in reducing pain. The experimental action is a measurement action of WBLT and lying posture, and the situation before and after EMS training was compared by performing 30 minutes on the treadmill to cause delayed muscle pain during exercise. As a result of this study, it was found that pain reduction and ROM function were improved when electrical stimulation was performed using EMS socks. It was also confirmed that the application of electrical stimulation to EMS socks effected on ankle fatigue and function improvement. From the study results, it is expected that wearing socks equipped with EMS significantly reduces ankle injuries and improves functional recovery for home training participants.

• Korean Journal of Applied Biomechanics
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• v.25 no.3
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• pp.311-322
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• 2015

Objective : The purpose of this study was to investigate the effects of landing height and knee joint muscle fatigue on the movement of the lower extremity during cutting after landing. Method : Subjects included 29 adults (age: $20.83{\pm}1.56years$, height: $172.42{\pm}9.51cm$, weight: $65.07{\pm}10.18kg$). The subjects were asked to stand on their dominant lower limb on jump stands that were 30 and 40 cm in height and jump from each stand to land with the dominant lower limb on a force plate making a side step cutting move at a $45^{\circ}$ angle with the non-dominant lower limb. The fatigue level at 30% of the knee extension peak torque using an isokinetic dynamometer. Results : The results showed that the difference of landing height increased maximum range of motion and angular velocity of hip, knee, and ankle joints in the sagittal plane, and in the angular velocity of motion of the hip joint in the sagittal plane. The maximum range of motion of the knee joint in the sagittal plane and the frontal plane decreased on landing from both heights after the fatigue exercise. The angular velocity of the hip joint in the sagittal plane, and the maximum range of motion of the hip joint in the transverse plane decreased for both landing heights after the fatigue exercise. The angular velocity of the hip joint in the frontal plane decreased for the 30 cm landing height after the fatigue exercise. On the other hand, the angular velocity and maximum range of motion of the ankle joint in the sagittal plane for both landing heights, and the angular velocity and maximum range of motion of the ankle joint in the frontal plane increased on landing from the 40 cm height after the fatigue exercise. Conclusion : Different landing heights of 30 and 40 cm and 30% fatigue of peak torque of knee extensor found a forefoot and stiff landing strategy, when cutting after landing. These results might be due to decline in the shock absorption capability of the knee joint and the movement capability related to cutting while increasing the contribution of the ankle joint, which may cause increased ankle joint injuries.

• Journal of the Korean Society of Physical Medicine
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• v.18 no.2
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• pp.83-92
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• 2023

PURPOSE: This study examined the effect of using a smartphone according to the direction of wearing a bag on muscle characteristics and balance ability in adults in their 20s with chronic ankle instability. METHODS: Twelve people with chronic ankle instability were examined for three weeks. The types of carrying a bag were classified into three conditions: to the right, to the left, and on both sides. The muscle characteristics and balance ability were measured and analyzed. The one-way ANOVA was used to obtain a difference between conditions. RESULTS: A significant difference in the muscle tone of medial gastrocnemius was observed between the dominant group and the non-dominant group. The muscle tone and stiffness of the peroneus longus decreased significantly after walking with a smartphone and carrying a bag. The maximum slope of the forward and reverse directions increased and decreased significantly, respectively, after walking with a smartphone and carrying a bag on both sides. CONCLUSION: In this study, muscle fatigue causes a decrease in muscle tone and stiffness with chronic ankle instability when carrying a heavy back while walking, and there were asymmetric changes in the balance ability. Therefore, adults with chronic ankle instability should carefully avoid carrying a heavy bag for extended times, irrespective of the style or type of the bag.

• Korean Journal of Applied Biomechanics
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• v.24 no.1
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• pp.59-66
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• 2014

The purpose of this study was to investigate the effects of knee joint muscle fatigue and overweight on shock absorption during single-leg landing of adult women. Written informed consent forms, which were approved by the human subject research and review committee at Dong-A University, were provided to all subjects. The subjects who participated in this study were divided into 2 groups: a normal weight group and an overweight group, consisting of 15 young women each. Both the normal weight group and the overweight group showed that use soft landing and ankle dominant strategy. The peak vertical ground reaction force, the knee joint absorption power, and eccentric work done, as the increase of knee joint muscle fatigue level, showed a decrease. And the hip joint absorption power and eccentric work done, as the increase of weight, was less than the overweight group showed the normal weight group. In conclusion, the accumulation of the knee joint muscle fatigue and the increase of body weight may lead to an increased risk of injury during landing.

• The Journal of Korean Physical Therapy
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• v.21 no.4
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• pp.57-63
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• 2009

Purpose: To better understand falls in elderly women, we measured differences in muscle activities of 4 lower extremity muscles (tibialis anterior, soleus, rectus femoris, biceps femoris) based on angle plantar-flexion in elderly women. Methods: Subjects were 15 healthy elderly women. No subjects had musculoskeletal or nervous disorders. EMGs were used to check muscle activity of lower extremity muscles. For statistic analysis, data were expressed as a percentage of maximal voluntary isometric contraction (%MVIC). We measured %MVIC for 5 sec under 4 conditions and did not use data for the first and last second. Muscle activities of the muscles of the lower extremities were measured based on the degree of plantar-flexion of the ankle joint. The 4 conditions corresponded to different degrees of: 0, 10, 20 and 30 degrees. This was done using a 50 cm board for measuring the degrees. Results: The tibialis anterior, soleus, and bicpes femoris showed increasing muscle activity associated with increasing degree of plantar-flexion of the ankle joint. All muscles showed a significant increase in muscle activities in association with increasing degrees. Rectus femoris showed a significant increase in muscle activity for 0 degrees and for the other degrees, but there were no further changes when plantar flexion of the ankle joint was over 10 degrees. Conclusion: Activities of the muscles of the lower extremities except rectus femoris were higher with increasing degree of plantar flexion. High muscle activity may result in muscle fatigue. Thus, increasing degree of plantar flexion may be risk factors of falls in elderly women.

• Journal of the Korean Society of Safety
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• v.10 no.4
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• pp.103-108
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• 1995

This study was performed to investigate a relationship between a biomechanical analysis of compressive force at L5/S1 and electromyographic analysis of erector spinae muscle during lifting task. In the experiment, isometric contractions at 25, 50, 75, 100%MVC for short duration and sustained isometric contractions at 50%MVC were performed. For muscle recruitment patten and compressive force analysis, rectified EMG amplitudes analysis and computerized biomechanical analysis were used. To achieve data, angles of neck, shoulder, elbow, wrist, hip, knee, ankle and length of body segments were measured. Results shows that trends of initial EMG rectified amplitude were similar to those of biomechanical calculation value and for sustained isometric contraction at 50%MVC EMG rectified amplitude of erector spinae muscle after 40seconds was increased up to level of 75%MVC. Based on the results of this study, biomechanical analysis should be supplemented considering muscle fatigue, and it is also suggested that work-rest cycle critera and the evaluation of back-pain injuries should include muscle fatigue.

• Korean Journal of Applied Biomechanics
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• v.26 no.4
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• pp.413-420
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• 2016

Objective: The purpose of this study was to analyze and compare different kinds of outdoor walking shoes in terms of muscle fatigue and ground reaction force on walking, and to provide foundational data for developing and choosing outdoor walking shoes that fit the users. Method: The study subjects were 30 healthy men. The experiment was conducted by using outdoor walking shoes with different inner and outer harnesses of the midsole, and shapes of the outsole. For data collection, electromyography was used to measure the muscle fatigue of the anterior tibial muscle and gastrocnemii, which contribute to the dorsiflexion and plantarflexion of the ankle joint, and the biceps muscle of the thigh and lateral great muscles, which contribute to the flexion and extension of the knee joint. A GRF measurement device was used to measure the X, Y, and Z axes. Results: In the type A outdoor walking shoes, regarding the hardness of the midsole, the inner part was soft, while the outer part was hard. The vertical ground reaction force was the lowest, which means least impact while walking and light load to the knees and ankles. The type C outdoor walking shoes were intended to provide a good feel in wearing the shoes. The tibialis anterior, biceps femoris, and gastrocnemii indicate low fatigue, which means that during a long-distance walk, it will minimize the fatigue in the muscles of the lower limbs. Conclusion: To sum up the study results, the different types of outdoor walking shoes indicate their unique characteristics in the biomechanical comparison and analysis. However, the difference was not statistically significant. Thus, a systematic and constant follow-up research should be conducted to cope with expanding market for outdoor walking shoes. Lastly, this study is expected to present foundational data and directions for developing outdoor walking shoes.

• 대한근관절건강학회:학술대회논문집
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• 2001.04a
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• pp.179-190
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• 2001

The purpose of this study was to explore the effects of GEAP on pain, joint function, activities of daily living(ADL) and fatigue in chronic arthritis patients. The GEAP was held twice a week for 6 weeks for chronic arthritis patients at one university hospital in Seoul, Korea. Thirty four subjects completed the program, who were recruited at four times from September, 1999 to September, 2000. The effect of GEAP were evaluated as follows: Pain severity and number of painful joints ADL, fatigue were measured before and after the GEAP. In order to examine the joint flexibility and strengthening, the followings were measured: the extent of the upward arm reach in both sides(flexibility of shoulder), the ability to touch fingertips of the both hands in back pat and rub(flexibility of arm), the degree of range of motion (ROM) of both ankles in their dorsiflexion(flexibility of ankle) and plantarflexion with standing with toe(strengthening of ankle), and the degree of knee extension, and the grip strength. Paired t-test and Wilcoxon signed rank test were used for data analysis and the significance of the differences in the variables was examined to compare the data obtained before and after the GEAP. After the GEAP, followings were found: 1. Pain severity and number of painful joints was significantly decreased. 2. The flexibility of both shoulders and arms, knee, both ankle were significantly improved. 3. The strengthening of both arms was significantly improved, but the strengthening of ankle was not changed. 4. ADL was significantly increased. 5. Fatigue was significantly decreased. In conclusion, GEAP used in this study was clearly proved to be an effective exercise program to reduce pain and fatigue, to enhance joint function and ADL in people with chronic arthritis. It is suggested that the GEAP should be recommended as one of the useful and appropriate nursing interventions for chronic arthritis patients.