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

Adult ; Back ; physiology ; Electromyography ; Humans ; Lumbosacral Region ; physiology ; Male ; Muscle Fatigue ; Muscle, Skeletal ; physiology ; Posture ; physiology

There are actually no sufficient data for lifting technique assessment. A laboratory study was undertaken to determine the effect of 3 regular lifting techniques on erector muscle activation, cardiovascular strain and subjective response. Thirty student volunteers participated in the study, and were required to lift a weight with different techniques. Stoop-, squat-, semi-squat-lifting resulted in 3, 2 and 1 time of the highest percentage of the maximum voluntary electrical activation (MVE%) respectively. In the same order, the lowest median frequency (MF) existed 1, 1 and 2 times. Muscle fatigue was 4 times in squat, 36 in semi-squat and 43 in stoop lifting. Heart rate was the highest in squat and lowest in stoop respectively, with a middle level in semi-squat lifting. It may be recommended to adopt mainly the semi-squat technique for daily lifting works. For heavy lifting, it should use the squat technique. Stoop lifting may also be used alternatively but for light things.
Adult ; Biomechanical Phenomena ; physiology ; Female ; Humans ; Lifting ; Male ; Muscle Fatigue ; physiology ; Muscle, Skeletal ; physiology ; Young Adult

OBJECTIVETo analyze and evaluate the fatigue of shoulder skeletal muscle caused by different lifting loads with surface electromyography (sEMG).

METHODSAccording to the loading standard of1 Repetition Maximum (1RM), ten male volunteers performed 3 tasks of upper limb flexion, i.e. 10%, 50% and 90%-1RM. During action process, the signals of Upper Trapezius (UT), Lower Trapezius (LT), Serratus Anterior (SA) and Anterior Deltoid (AD) were recorded by sEMG. The Mean Amplitude (MA) served as an index to evaluate the changes in skeletal muscle fatigue.

RESULTSThe scores of Borg were 15.6, 15.9 and 15.2 for 3 loads of 10%-1RM, 50%-1RM and 90%-1RM, respectively (P > 0.05). The mean amplitudes (MAs) of Upper Trapezius, Lower Trapezius, Anterior Deltoid and Serratus Anterior in shoulders increased obviously. Under the load intensity of 10%-1RM, the MAs of Upper Trapezius and Anterior Deltoid increased significantly (P < 0.05), which were 0.898 and 0.736, respectively. After the exhaustion, the contribution of mean amplitude in shoulder muscle did not change significantly (P > 0.05).

CONCLUSIONThe low-load action for long time can induce easily the fatigue of upper trapezius and anterior deltoid.

Adult ; Electromyography ; Humans ; Lifting ; Male ; Muscle Fatigue ; physiology ; Muscle, Skeletal ; physiology ; Shoulder ; physiology ; Workload

Surface myoelectric signal analysis has proved effective for assessing the electrical manifestations of localized muscle fatigue. In the past, the analysis of muscle fatigue was restricted to isometric, constant force contractions due to the limitation of signal processing technique. The development and recent availability of spectral estimation techniques specifically designed for nonstationary signal analysis have made it possible to extend the employment of muscle fatigue assessment to dynamic contractions, thus opening new application fields such as ergonomics rehabilitation and sports medicine. This paper reviews the current study achievements of using surface myoelectric signals in muscle fatigue assessment, particularly in that during dynamic contractions. The conclusions provide theoretical bases for encouraging further studies on the mechanisms of muscle fatigue.
Electromyography ; methods ; Humans ; Muscle Fatigue ; physiology ; Muscle, Skeletal ; physiology ; Signal Processing, Computer-Assisted

OBJECTIVEUsing surface electromyography (SEMG) technique to evaluate repetitive lifting task-induced fatigue of back muscles.

METHODSThirteen volunteers lifted and lowered an 8 kg weight from floor to waist level for 100 times. Fatigue in the erector spinae muscles was quantified by comparing the frequency content of the EMG signal during static contractions performed before, and immediately after the 100 lifts.

RESULTSEMG average amplitude rose gradually during 100 lifts, the difference was significant at T10 right (P < 0.05) and L3 left (P < 0.01), the difference was not significant at T10 left and L3 right (P > 0.05). The median frequency intercept at T10 right, T10 left, L3 right, L3 left erector spinae muscles decreased by 2.0% (P > 0.05) 10.9% and 29.9% (P < 0.05), 27.9% (P < 0.01), respectively. The mean power frequency intercept decreased by 9% at L3 left erector spinae muscle (P < 0.05), the decrease was not statistically significant at other sites (P > 0.05).

CONCLUSIONRepetitive lifting may induce measurable fatigue in the erector spinae muscles. Erector spinae muscle at L3 is more easily fatigued than at T10. Using the median frequency intercept to assess muscle fatigue is more sensitive than using mean power frequency intercept.

Adult ; Back ; Electromyography ; Humans ; Lifting ; Male ; Muscle Fatigue ; physiology ; Muscle, Skeletal ; physiology

The mechanomyography (MMG) records and quantifies the low-frequency lateral oscillations of active muscle fibers. It can represent the mechanical characteristics of muscle activity. MMG has been used to evaluate muscle fatigue. Hilbert-Huang transform (HHT) is a time-frequency method with the feature of self-adaptation, and designed specifically for nonlinear and nonstationary signal analysis. In this study, MMG signal was recorded from biceps brachii during isometric fatigue contraction. HHT was used to calculate the difference between the maximum and minimum values of instantaneous frequency, named as the band ratio, to estimate muscle fatigue. The results showed that the band ratios were 0.431 +/- 0.607 and 0.286 +/- 0.218 after fatigue for the maximum voluntary contraction (MVC) of 50% and 70%, respectively. These indicated that the frequency declined after muscles fatigue.
Algorithms ; Electromyography ; methods ; Humans ; Muscle Fatigue ; physiology ; Muscle, Skeletal ; physiology ; Signal Processing, Computer-Assisted

AIMTo explore the factors affect the change of sEMG signal by investigating the relationship between power spectral changes of sEMG signal and H+ in muscle during the short period of recovery after muscular fatigue.

METHODSAfter a fatiguing constriction of the muscle, its pH value would not be featured any apparent changes in a short period of time. However, we were able to observe the movement rule of the sEMG power spectrum within 30 s of its reversion duration. Surface EMGs of biceps brachii muscle were recorded from 8 healthy human volunteers during tasks. Muscle fatigue induced by isometric loading that included 60% of maximal voluntary contraction. Restitution of sEMG by recording 2 s, 4 s, 6 s, 8 s, 10 s, 20 s and 30 s by the same load after the end of the fatigue experiments of 60% MVC.

RESULTSThere was a significant monotonous decline in MPF during isometric fatigue contraction of 60% MVC. MPF was restituted rapidly in the short recovery period after muscular fatigue. It was recovered 26.5% of its whole declining scope only 2 s by the end of muscle movement, and has been reached 87.7% of its total decreasing value till 30 s after the exercise.

CONCLUSIONOur results suggested that the accumulation of H+ in muscle was not the only factor that affected "spectrum shift" during muscle fatigue. The change of CNS drive strategy might be the important mechanisms that attributed to the change of SEMG signal during isometric contractions.

Adult ; Electromyography ; Exercise ; Humans ; Isometric Contraction ; physiology ; Male ; Muscle Fatigue ; physiology ; Muscle, Skeletal ; physiology ; Physical Endurance ; physiology ; Young Adult

OBJECTIVETo explore the response of electroencephalography (EEG) signal to biceps brachii fatiguing induced by sustained isometric (non-maximal) voluntary contraction (non-MVC) and to lay a foundation for effective and reliable fatigue evaluation system and for understanding fatigue mechanisms.

METHODSTen male undergraduates performed two different isometric fatiguing tasks with the elbow flexion muscles under a load of 5 and 10 kg respectively, and synchronously EEG signals were collected from scalp. Then amplitude, spectral and Lempel-Ziv complexity C(n) of EEG were calculated.

RESULTSThe average EEG(AEEG) increased while the average mean power frequency (MPF) and complexity of EEG decreased in muscle fatigue. Furthermore, this phenomenon was distributed evenly across the entire scalp, but load only influenced AEEG, MPF and C(n) at Fz.

CONCLUSIONAEEG of EEG increases generally while MPF and C(n) increase generally during local muscle fatigue. This pattern of EEG reflects the central mechanism of muscle fatigue. AEEG, MPF and C(n) at prefrontal area show load dependence.

Adult ; Electroencephalography ; Exercise ; physiology ; Humans ; Isometric Contraction ; physiology ; Male ; Muscle Fatigue ; physiology