BACKGROUND: Prolonged standing has been hypothesized as a vital contributor to discomfort and muscle fatigue in the workplace. The objective of this study was to develop a decision support system that could provide systematic analysis and solutions to minimize the discomfort and muscle fatigue associated with prolonged standing. METHODS: The integration of object-oriented programming and a Model Oriented Simultaneous Engineering System were used to design the architecture of the decision support system. RESULTS: Validation of the decision support system was carried out in two manufacturing companies. The validation process showed that the decision support system produced reliable results. CONCLUSION: The decision support system is a reliable advisory tool for providing analysis and solutions to problems related to the discomfort and muscle fatigue associated with prolonged standing. Further testing of the decision support system is suggested before it is used commercially.
Fatigue ; Human Engineering ; Muscle Fatigue

Muscle fatigue is a common complaint in clinical practice. In humans, muscle fatigue can be defined as exercise-induced decrease in the ability to produce force. Here, to provide a general understanding and describe potential therapies for muscle fatigue, we summarize studies on muscle fatigue, including topics such as the sequence of events observed during force production, in vivo fatigue-site evaluation techniques, diagnostic markers and non-specific but effective treatments.
Humans ; Muscle Fatigue*

At present, fatigue state monitoring of upper limb movement generally relies solely on surface electromyographic signal (sEMG) to identify and classify fatigue, resulting in unstable results and certain limitations. This paper introduces the sEMG signal recognition and motion capture technology into the fatigue state monitoring process and proposes a fatigue analysis method combining an improved EMG fatigue threshold algorithm and biomechanical analysis. In this study, the right upper limb load elbow flexion test was used to simultaneously collect the biceps brachii sEMG signal and upper limb motion capture data, and at the same time the Borg Fatigue Subjective and Self-awareness Scale were used to record the fatigue feelings of the subjects. Then, the fatigue analysis method combining the EMG fatigue threshold algorithm and the biomechanical analysis was combined with four single types: mean power frequency (MPF), spectral moments ratio (SMR), fuzzy approximate entropy (fApEn) and Lempel-Ziv complexity (LZC). The test results of the evaluation index fatigue evaluation method were compared. The test results show that the method in this paper has a recognition rate of 98.6% for the overall fatigue state and 97%, 100%, and 99% for the three states of ease, transition and fatigue, which are more advantageous than other methods. The research results of this paper prove that the method in this paper can effectively prevent secondary injury caused by overtraining during upper limb exercises, and is of great significance for fatigue monitoring.
Electromyography/methods* ; Fatigue ; Humans ; Muscle Fatigue ; Muscle, Skeletal ; Upper Extremity

BACKGROUND: Performing cognitive tasks and muscular fatigue have been shown to increase muscle activity of the lower extremity during quiet standing. A common intervention to reduce muscular fatigue is to provide a softer shoe-surface interface. However, little is known regarding how muscle activity is affected by softer shoe-surface interfaces during static standing. The purpose of this study was to assess lower extremity muscular activity during erect standing on three different standing surfaces, before and after an acute workload and during cognitive tasks. METHODS: Surface electromyography was collected on ankle dorsiflexors and plantarflexors, and knee flexors and extensors of fifteen male participants. Dependent electromyography variables of mean, peak, root mean square, and cocontraction index were calculated and analyzed with a 2 × 2 × 3 within-subject repeated measures analysis of variance. RESULTS: Pre-workload muscle activity did not differ between surfaces and cognitive task conditions. However, greater muscle activity during post-workload balance assessment was found, specifically during the cognitive task. Cognitive task errors did not differ between surface and workload. CONCLUSIONS: The cognitive task after workload increased lower extremity muscular activity compared to quite standing, irrespective of the surface condition, suggesting an increased demand was placed on the postural control system as the result of both fatigue and cognitive task.
Ankle ; Electromyography ; Fatigue ; Humans ; Knee ; Lower Extremity ; Male ; Muscle Fatigue

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.
Fatigue ; Female ; Foot ; Heel* ; Humans ; Muscle Fatigue* ; Shoes*

OBJECTIVE: 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. METHODS: 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. RESULTS: 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). CONCLUSION: 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.
Electric Stimulation ; Fatigue* ; Healthy Volunteers* ; Muscle Contraction ; Muscle Fatigue ; Quadriceps Muscle

OBJECTIVE: The purpose of this study is to determine the proper hand position during driving by measuring of the wheel rotation strength according to the wheel angle and hand position to the wheel. METHOD: BTE Work Simulator was used to measure the clockwise and counter clockwise static wheel rotation force of twenty healthy men in three different hand position (2~10 spot, 3~9 spot, and 4~8 spot) and two different wheel angle (45 degrees and 60 degrees), average and peak force were measured during maximal isometric contraction. RESULTS: The average and peak force was significantly different by the wheel angle, and hand position (p<0.01), but the direction of rotation didn't an effect on the rotation force. The hand position was the most significant factor, especially wheel rotation force at 2~10 spot hand position was significantly lower than that of 3~9 spot and 4~8 spot (p<0.05). The rotation force by the wheel angle was influenced by hand position, and lower in 60 degrees wheel angle in the 2~10 spot (p<0.05). CONCLUSION: The rotation force of wheel was influenced by the hand position. Therefore proper hand position is recommended during driving to reduce muscle fatigue.
Hand* ; Humans ; Isometric Contraction ; Male ; Muscle Fatigue

Injuries and pains of musculoskeletal joint in human body is common onset in industrialized world. However, muscle fatigue plays a very significant role in contributing causes of many pains associated with musculoskeletal joints. Based on this hypothesis, degree of muscle fatigue was investigated using electromyography measurement technique during isometric and concentric/eccentric muscle contractions. Different response of the muscle fatigue between two different muscle contractions (isometric and concentric/eccentric contractions) was examined by comparison of parameters which were median frequency, median power and RMS value. Healthy 16 young persons without previous musculoskeletal diesease history were tested with Noraxon Myosystem 2000 EMG measurement system. In this study, two different exercises were performed. First exercise was concentric/eccentric exercise. Second exercise was isometric muscle contraction. In the case of the isometric exercise, median frequency was decreased, but median power and RMS were increased. However, during the concentric/eccentric exercse, median frequency was increased, but median power and RMS were decreased. Both of those revealed that the pattern of the median frequency was W type, but median power and RMS were M type as time passed. In this study, the patterns of the muscle fatigue during concentric/eccentric exercise as well as isometric exercise were identified. It will be helpful to prevent musculoskeletal injury from over-working andexercising.
Electromyography* ; Exercise ; Human Body ; Humans ; Joints ; Muscle Contraction ; Muscle Fatigue*

In this study, a surface electromyography (sEMG) and blood oxygen signal real-time monitoring system is designed to explore the changes of physiological signals during muscle fatigue, so as to detect muscle fatigue. The analysis method of sEMG and the principle of blood oxygen detection are respectively introduced, and the system scheme is expounded. The hardware part of the system takes STM32 as the core. Conditioning module composition; blood oxygen signal acquisition is based on near infrared spectroscopy (NIRS), specifically including light source, light source driving, photoelectric conversion, signal conditioning and other modules. The system software part is based on the real-time uC/OS-III software system. The characteristic parameters of sEMG were extracted by isometric contraction local muscle fatigue experiment; the relative changes of oxyhemoglobin (HbO₂) and deoxyhemoglobin (Hb) were calculated in the forearm blocking experiment, thereby verifying that the system collects two signals effectiveness.
Muscle, Skeletal ; Oxygen ; Electromyography ; Muscle Fatigue/physiology* ; Computers

Based on the joint analysis of EMG spectrum and amplitude method (JASA), a study on muscle fatigue assessment of spinal surgical instruments based on surface EMG signals was carried out, and a comparative evaluation of the operating comfort before and after the optimization of spinal surgical instruments was completed. A total of 17 subjects were recruited to collect the surface EMG signals of their brachioradialis and biceps. Five surgical instruments before and after optimization were selected for data comparison, and the operating fatigue time proportion of each group of instruments under the same task was calculated based on the RMS and MF eigenvalues. The results showed that when completing the same operation task, the operation fatigue time of the surgical instruments before optimization was significantly higher than that after optimization (P<0.05); there was no significant difference in the fatigue status of brachioradialis and biceps when operating the same instrument (P>0.05). These results provide objective data and reference for the ergonomic design of surgical instruments and fatigue damage protection.
Humans ; Muscle Fatigue/physiology* ; Muscle, Skeletal ; Electromyography ; Ergonomics