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

Objective To measure the prevalence of mental health symptoms and identify the associated factors among college students at the beginning of coronavirus disease 2019(COVID-19)outbreak in China. Methods We carried out a multi-center cross-sectional study via snowball sampling and convenience sampling of the college students in different areas of China.The rates of self-reported depression,anxiety,and stress and post-traumatic stress disorder(PTSD)were assessed via the 21-item Depression-Anxiety-Stress Scale(DASS-21)and the 6-item Impact of Event Scale-Revised(IES-6),respectively.Covariates included sociodemographic characteristics,health-related data,and information of the social environment.Data pertaining to mental health service seeking were also collected.Multivariate Logistic regression analyses were performed to identify the risk factors. Results A total of 3641 valid questionnaires were collected from college students.At the beginning of the COVID-19 outbreak,535(14.69%)students had negative emotions,among which 402(11.04%),381(10.49%),and 171(4.90%)students had the symptoms of depression,anxiety,and stress,respectively.Meanwhile,1245(34.19%)college students had PTSD.Among the risk factors identified,male gender was associated with a lower likelihood of reporting depression symptoms(AOR=0.755,P=0.037],and medical students were at higher risk of depression and stress symptoms than liberal arts students(AOR=1.497,P=0.003;AOR=1.494,P=0.045).Family support was associated with lower risks of negative emotions and PTSD in college students(AOR=0.918,P<0.001;AOR=0.913,P<0.001;AOR=0.899,P<0.001;AOR=0.971,P=0.021). Conclusions College students were more sensitive to public health emergencies,and the incidence of negative emotions and PTSD was significantly higher than that before the outbreak of COVID-19.More attention should be paid to female college students who were more likely to develop negative emotions.We should strengthen positive and proper propaganda via mass media and help college students understand the situation and impact of COVID-19.Furthermore,we should enhance family support for college students.The government and relevant agencies need to provide appropriate mental health services to the students under similar circumstances to avoid the deterioration of their mental well-being.
COVID-19/epidemiology* ; Cross-Sectional Studies ; Female ; Health Status ; Humans ; Male ; Students/psychology* ; Universities