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To determine the effect of very high stimulation frequency (150 and 200 Hz) with wide pulse duration versus 50 Hz with wide pulse duration on stimulated force and fatigue of quadriceps femoris in healthy participants.
Thirty-four healthy participants underwent fatigue test using three stimulation frequency conditions (50, 150, and 200 Hz) with pulse duration of 0.9 ms. Normalized force values at the end of each fatigue protocol and curve fitting patterns were compared among stimulated frequencies.
Very high stimulation frequency (150 and 200 Hz) conditions showed a trend of having more decline in normalized stimulated force during fatigue test compared to a low stimulation frequency at 50 Hz. However, the difference was not statistically significant. Responder group showed the same slope of a linear fitting pattern, implying the same pattern of muscle fatigue among three stimulation frequency conditions (−3.32 in 50 Hz, −2.88 in 150 Hz, and −3.14 in 200 Hz, respectively).
There were high inter-subject variations in the response to different frequency stimulation conditions. However, very high stimulation frequency generated the same fatigue pattern as the low stimulation frequency in the responder group. Further research is needed to explore the mechanism involved.
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To investigate the effect of gastrocnemius muscle fatigue on postural control ability in elderly people.
Twenty-four healthy elderly people participated in this study. The postural control ability of single leg standing was evaluated with Health Improvement & Management System (HIMS) posturography before and after fatiguing exercises. After evaluating initial postural control ability, the maximal voluntary contraction (MVC) of ankle plantarflexion was assessed using a surface electromyogram from the medial belly of the gastrocnemius muscle. After a 5-minute resting period, subjects began submaximal isometric ankle plantarflexion (40% MVC) until 40% of MVC was dropped below 95% for 5 seconds, or subject couldn't continue working out due to muscle fatigue. And postural control ability was assessed after fatiguing exercise. The mean deviation of center of pressure (COP), length of COP movement, occupied area of COP were measured, and analyzed by paired t-test.
Mediolateral deviation, length of COP movement, and area of COP occupied were increased after fatiguing exercise of the gastrocnemius muscle. Anteroposterior deviation and length of COP movement were also increased, but had low statistical significance.
These findings suggest that the gastrocnemius muscle fatigue affects mediolateral stability and accuracy during single leg standing in elderly people. Therefore muscle endurance training is necessary to prevent falls in elderly people.
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To investigate associations between angiotensin-converting enzyme (ACE) polymorphisms and muscle fatigability in 65-year-old Koreans.
The study participants were 49 Koreans aged 65 years. ACE insertion/deletion (I/D) polymorphisms were determined by polymerase chain reaction and serum ACE activity, by spectrophotometry. Body mass index (BMI), body fat mass (BFM), and lean body mass (LBM) were determined. To evaluate muscle fatigability, dynamic Electromyography was used to measure maximum voluntary isometric contractions (MVICs) of ankle plantar flexor muscles. Patients were seated with their hips flexed at 90°, knees fully extended, and ankles at 0°. Continuous submaximal VICs (40% MVIC) were then performed, and contraction duration and EMG frequency changes during the initial 2 min were measured. A self-reported physical activity questionnaire was used to evaluate effects of ACE activity levels on muscle fatigability.
Among the 49 volunteers, 15 showed II genotype; 22, ID genotype; and 12, DD genotype. Serum ACE activity levels were significantly higher in DD genotype subjects than in II genotype subjects (p<0.05). Furthermore, the duration of submaximal isometric contractions was longer in II and ID genotype subjects than in DD genotype subjects (p<0.05). Dynamic EMG showed significantly lower mean frequency changes in II genotype subjects than in DD genotype subjects (p<0.05). However, LBM, BFM, and BMI were independent of ACE genotypes.
ACE II genotype subjects showed significantly higher resistant to muscle fatigue than that by DD genotype subjects. However, body composition and BMI showed no correlations with ACE I/D polymorphisms.
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Objective: This study was performed to evaluate the prevalence of new neuromuscular symptoms and disabilities and the psychological characteristics-depressioin, anxiety, type A behavior, loneliness, and also to determine any relationships between physical and neuropsychological characteristics in a group of post-polio syndrome (PPS).
Method: By 70 answered questionnaire, the polio survivors were grouped into PPS and Non- PPS. This questionnaire consisted of questions about acute polio problems; new health problems, fatigue severity scale, visual analog scale, weakness scale, Frenchay activity index, ambulation disability index; socio-economic problems; neuro-psychological inventories, Beck depression index, Spielberger state-trait anxiety inventory, revised UCLA loneliness scale, type A personality score.
Results: The median time from polio to the onset of new health problems was 27.6 years. Fatigue, muscle and/or joint pain, weakness in previously affected and unaffected muscles were most common newly appearing problems. The symptoms of PPS was consistent with the distribution of the anterior horn cell; spinal cord, brain stem, cerebral hemisphere, Reticular Activating System (RAS). Neuro-psychological evaluations revealed that fatigue scale was correlated with depression, type A personality.
Conclusion: In PPS group, pain, weakness, fatigue, autonomous symptoms, decreased concentration were more serious than in Non-PPS group. The fatigue in PPS group was correlated with type A personality, depression, sleep disturbance and concentration problem.
Objective: To determine whether muscle fatigue affects knee joint proprioception.
Method: Thirty healthy subjects (18 male and 12 female) with an average age of 22.1 years were selected for this study. Angular errors were measured to test propriocetive function in the knee joint. In a sitting position, the subject's dominant leg was passively positioned to the 45o knee flexion stimulus point for 2∼4 second, while the subject concentrated on this position, the leg was passively returned to the 90o flexion position, afterward the subject was asked to duplicate the stimulus point actively. The difference, in degrees between the stimulus point and the reproduced point is an angular error. All subjects were blindfolded and underwent proprioception measurement before and after the muscle fatigue. Isokinetic exercises performed at 180 degree/sec on the Cybex Orthotron II(Cybex, a division of Lumex, Inc. USA) were used to induce the muscle fatigue. All subjects performed an isokinetic exercise with their dominant leg. Exercise was continued until 50% of the initial peak torque was reached. When the subjects were fatigued to less than 50% of the initial peak torque, the isokinetic exercises were discontinued. Then we immediately retested the proprioception using the same method.
Results: The mean and standard deviation of the angular error increased from 2.79⁑1.17o to 6.40⁑3.42o after muscle fatigue.
Conclusion: The proprioception significantly decreased after the muscle fatigue(p＜0.001). This result suggests that the muscle fatigue must be considered when an injured professional athlete a patient with fatigable disease is set in a rehabilitation program. Further studies are required to determine the physiological mechanisms of the role of muscle fatigue for the decreasing proprioception.
The purpose of this study was to determine the effects of high heeled shoes on plantar pressure and muscle fatigue. The subjects were 36 women who were divided into three groups, i.e., high heel, middle heel and low heel. The mean height of each heel was over 7 cm, 5 cm and below 2 cm respectively. The plantar pressure was measured by F scan system.
The fatigue of subjects was evaluated with endurance time and voluntary maximal contraction that was measured by Cybex 6000 system and the degrees of foot pain and fatigue by visual analogue scale.
With high heeled shoes, the plantar pressure was shifted from hindfoot to forefoot, and from the lateral part to the medial part in forefoot. With all shoes, the plantar pressure was generally increased in the forefoot after 8 hours. Especially the pressure of medial and middle parts of forefoot was significantly increased on high heeled shoes. Voluntary maximal contraction and endurance time was significantly decreased in subjects with high heeled shoes for 8 hours. The degrees forefooot pain and fatigue by visual analogue scale were very significantly increased in subjects with high heeled shoes. With low heeled shoes, the fatigue was the least degree and the middle heeled shoes are recommendable for cosmetic needs and lesser fatigue and pain.
In conclusion, when women were in high heeled shoes for a long time, the pressure of forefoot and foot pain and fatigue were increased. Therefore, these effects of high heeled shoes on the plantar pressure and fatigue should be considered in women with high heeled shoes.
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