• Korean Journal of Applied Biomechanics
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• v.29 no.3
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• pp.167-172
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• 2019

Objective: The aim of this study was to investigate the effect of midsole hardness of running shoe on muscle fatigue and impact force during distance running. Method: Ten healthy college recreational runners who were performing distance running at least three times a week participated in this experiment. They were asked to run for 15 minutes in the treadmill at 10 km/h with running shoes having three different types of midsole hardness (Soft, Medium, Hard). EMG signal and insole pressure were collected during the first and last one minute for each running trials. Data were analyzed using a one-way analysis of variance (ANOVA) with repeated measures. Results: Midsole hardness did not affect the consistency of stride length. For the median frequency of the EMG signal, only VL was affected by midsole hardness; that of medium was greater than other midsoles (p<.05). The loading rate of impact forces increased by midsole hardness (p<.01). Conclusion: Although soft midsole could attenuate impact forces at heel contact, it might have a negative effect on the fatigue of muscle which could decelerate the body after heel contact. Therefore, it is necessary to select the optimum hardness of midsole carefully for both reduction impact forces and muscle fatigue.

• Physical Therapy Rehabilitation Science
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• v.4 no.2
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• pp.115-120
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• 2015

Objective: To examine the effects of different shoe weights on lower leg muscle fatigue when walking by electromyographic (EMG) analysis due to the most effective weight for loading not being established. Design: Cross-sectional study. Methods: Thirty healthy university students (15 male, 15 female) were enrolled and randomly assigned into three conditions, which included wearing athletic shoes with an addition of 300 g, 500 g, and 1,000 g weights respectively. Prior to walking, all subjects were instructed to sit in a chair for 10 minutes. All subjects walked at a speed of 3.6 m/s on a treadmill for 20 minutes without rest. EMG measurements were taken using the median power frequency to assess for the effect of the different weight of shoes on muscle fatigue of the soleus, gastrocnemius, and tibialis anterior while walking on a treadmill in an upright posture. EMG measurements were taken during the first and last 30 seconds of walking. Results: In terms of muscle fatigue, for the soleus, the median power frequency was significantly lower with 1,000 g compared with 300 g and 500 g (p<0.05). For the tibialis anterior, the median power frequency was significantly lower with 1,000 g than 300 g and 500 g (p<0.05). For the gastrocnemius, the median power frequency was significantly lower with 1,000 g compared with 300 g (p<0.05). Conclusions: Increased shoe weight increases soleus, gastrocnemius, and tibialis anterior muscle fatigue during ambulation.

• Physical Therapy Korea
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• v.9 no.2
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• pp.115-131
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• 2002

Functional electrical stimulation (FES) training of the knee extensors is a useful way to rehabilitate the ability to stand and walk. However, training using FES has not been able to solve the problem of fatigue; clinical application of FES quickly produces muscle fatigue, due to the continuous activation of the muscles of the lower extremity. Therefore, reduction of muscle fatigue is an important factor in increasing the effectiveness of FES training in paraplegia. Intermittent high frequency alternating stimulation is a method that combines the advantages of high frequency (leading to strong muscle contractions) and alternating stimulation (reducing muscle fatigue), thereby continuously strengthening muscles. It is not known whether low frequency simultaneous stimulation results in stronger muscle contraction than high frequency alternating stimulation. This study compared the effectiveness of high frequency alternating stimulation with low frequency synchronized stimulation. Muscle power using FES on the quadriceps of 20 normal subjects were compared. Intermittent high frequency alternating stimulation did not produce more powerful muscle contraction than intermittent low frequency synchronized stimulation, because the muscle characteristics differed individually. Significant individual variation according to muscle characteristics was founded when applying FES. Accordingly, when physical therapists use FES to treat patients, they must be aware of individual variation in muscle characteristics.

• Journal of Biomedical Engineering Research
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• v.15 no.4
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• pp.429-438
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• 1994

An electrical stimulator was designed to induce locomotion for paraplegic patients caused by central nervous system injury. Optimal stimulus parameters, which can minimize muscle fatigue and can achieve effective muscle contraction were determined in slow and fast muscles in Sprague-Dawley rats. Stimulus patterns of our stimulator were designed to simulate eleclromyographic activity monitored during locomotion of normal subjects. Muscle types of the lower extremity were classified according to their mechanical property of contraction, which are slow muscle (msoleus m.) and fast muscle (medial gastrocnemius m., rectus femoris m., vastus lateralis m.). Optimal parameters of electrical stimulation for slow muscles were 20 Hz, 0.2 ms square pulse. For fast muscle, 40 Hz, 0.3 ms square pulse was optimal to produce repeated contraction. Higher'stimulus intensity was required when synergistic muscles were stimulated simultaneously than when they were stimulated individually. Electrical stimulation for each muscle was designed to generate bipedal locomotion, so that individual muscles alternate contraction and relaxation to simulate stance and swing phases. Portable electrical stimulator with 16 channels built in microprocessor was constructed and applied to paraplegic patients due to lumbar cord injury. The electrical slimulator restored partially gait function in paraplegic patients.

• Journal of Biomedical Engineering Research
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• v.10 no.2
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• pp.109-111
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• 1989

An electrical stimulator was designed to induce locomotion for paraplegic patients caused by central nervous system injury. Optimal stimulus parameters, which can minimize muscle fatigue and can achieve effective muscle contraction were determined in slow and fast muscles in Sprague-Dawley rats. Stimulus patterns of our stimulator were designed to simulate electromyographic activity monitored during locomotion of normal subjects. Muscle types of the lower extremity were classified according to their mechanical property of contraction, which are slow muscle (msoleus m.) and fast muscle (medial gastrocneminus m., rectus femoris m., vastus lateralis m.). Optimal parameters of electrical stimulation for slow muscles were 20 Hz, 0.2 ms square pulse. For fast muscle, 40 Hz, 0.3 ms square pulse was optimal to produce repeated contraction. Higher stimulus intensity was required when synergistic muscles were stimulated simultaneously than when they were stimulated individually. Electrical stimulation for each muscle was designed to generate bipedal locomotion, so that individual muscles alternate contraction and relaxation to simulate stance and swing phases. Portable electrical stimulator with 16 channels built in microprocessor was constructed and applied to paraplegic patients due to lumbar cord injury. The electrical stimulator restored partially gait function in paraplegic patients.

• 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.

• Physical Therapy Rehabilitation Science
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• v.5 no.1
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• pp.34-39
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• 2016

Objective: Hip abductors play a role in providing stability and movement to the lower limbs. The purpose of this study was to examine the effects of hip abductor fatigue on static balance and gait in the general population. Design: One group pre-test post-test design. Methods: Thirteen university students in their twenties volunteered for the study and had underwent a functional assessment. To induce fatigue, the subjects were instructed to raise their dominant lower extremity up against a load of 50% of 1 repetition maximum while producing hip abduction in a side-lying position. Subjects were instructed to maintain an abduction speed of 30 repetitions per minute to induce fatigue. Muscle fatigue was considered to be established when subjects were unable to perform hip abduction three consecutive times along with the metronome. A post-test of balance and gait was performed immediately in order to prevent fatigue recovery. The center of pressure (COP) distance area was measured using the Zebris FDM-S Multifunction Force measuring plate. Gait performance was analyzed using the GAITRite. Results: The COP distance was increased after fatigue was induced. There was a significant increase in the standard deviation of the medio-lateral and antero-posteror distance (p<0.05). Although there was no significant difference in gait parameters, there was a significant decrease in single support time after fatigue was induced (p<0.05). Conclusions: There was an increase in static balance instability and a significant decrease in single support time during gait due to hip abductor muscle fatigue.

• Physical Therapy Korea
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• v.15 no.1
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• pp.1-11
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• 2008

The purpose of this study was to assess the influence of two shoe size conditions on foot pressure, ground reaction force (GRF), and lower extremity muscle fatigue. Seven healthy men participated. They randomly performed walking and running in two different conditions: proper shoe size and 10 mm greater than proper shoe size. Peak foot pressure, and vertical, anterior and mediolateral force components were recorded with the Parotec system and Kisler force platform. To assess fatigue, the participants performed treadmill running for twenty-five minutes twice, each time wearing a different shoe size. Surface electromyography was used to confirm localized muscle fatigue using power spectral analysis of four muscles (tibialis anterior, gastrocnemius medialis, rectus femoris, and biceps femoris). The results were as follows: 1) In walking conditions, there was a significantly higher peak pressure in the 10 mm greater than proper shoe size insole sensor 1, 2, 14, and 18 (p<.05). 2) In running conditions, there was a significantly higher peak pressure in the 10 mm greater than proper shoe size insole sensor 5, 14, and 15 (p<.05). 3) In walking conditions, there was a significantly higher first maximal vertical GRF in the 10 mm greater than proper shoe size (p<.05). 4) In running conditions, no GRF components were significantly different between each shoe size condition (p>.05). 5) Muscle fatigue indexes of the tibialis anterior and rectus femoris were significantly increased in the 10 mm greater than proper shoe size condition. These results indicate that wearing shoes that are too large could further exacerbate the problems of increased foot pressure, vertical GRF, and muscle fatigue.

• Korean Journal of Occupational Health Nursing
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• v.8 no.2
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• pp.156-161
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• 1999

The EMG(Electromyography) analysis was used to identify the fact the degree of inclined step was selected as dependent variable and feet muscle fatigue was selected as a independent variable. In a final result from EMG test. the shift in median frequency (MF) with 20, 25, 30, 35 degree of inclined steps indicated that 30 degree step was identified as most effective for a decrease in feet muscle fatigue. In a department store, 80% of the workers are female standing sales workers. They work at standing on average 10 hours per day. They performed heavy duty jobs such as lifting, lowering. packing and carrying heavy materials. Furthermore, even though they have work shoes, they usually use various kind of high heels. Eventually, this situation develops low-back-pain (LBP) problems for female workers. In conclusion, it is recommended that a particular branch in a department store claimed this step can effectively to circulate blood and significantly decrease feet muscle fatigue in lower extremity.

• Physical Therapy Rehabilitation Science
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• v.13 no.1
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• pp.53-70
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• 2024

Background: The conventional deadlift is a popular exercise for enhancing trunk, core, and lower extremity strength. However, its use in sports medicine is constrained by concerns of lumbar injuries, despite evidence supporting its safety and rehabilitative benefits. To optimize muscle activation using resistive bands in variable resistance therapy, we explored their feasibility in the deadlift. Design: Comparative experimental design Methods: Surface electromyography recorded muscle activity in the trunk and lower extremities during lifting, with normalization to the isometric Floor Lift using Maximal Voluntary Contraction. Kinematics were measured using inclinometer sensors to track hip and trunk sagittal plane angles. To prevent fatigue, each subject only used one of the three pairs of bands employed in the study. Results: Our study involved 45 healthy subjects (mean age: 30.4 ± 6.3 years) with similar baseline characteristics, except for years of lifting and strength-to-years-of-lifting ratio. Various resistance band groups exhibited significantly higher muscle activity than conventional deadlifts during different phases. The minimal resistance band group had notably higher muscle activity in the trunk, core, and lower extremity muscles, particularly in the end phase. The moderate resistance band group showed increased muscle activity in the mid-and end-phases. The maximum resistance band group demonstrated greater muscle activity in specific muscles during the early phase and overall higher activity in all trunk and lower extremity muscles in the mid and end phases of the deadlift (p<0.05). Conclusion: Our findings provide valuable insights into muscle activation with various resistance bands during deadlift exercise in clinical and gym settings. There appears to be a dose-response relationship between increased resistance bandwidth, external load, myoelectric activation, and range.