Survey on the occupational musculoskeletal disorder and its risk factors among male steelworkers / 中华预防医学杂志

<p><b>OBJECTIVE</b>To study the prevalence of occupational musculoskeletal disorders (OMSD) of male steelworkers and explore its occupational and individual risk factors.</p><p><b>METHODS</b>1620 male workers from a steel mill were selected as subjects through random cluster sampling in 2010. A revised Nordic Musculoskeletal disorder standard questionnaire and a questionnaire from National Institute for Occupational and Health of the Netherlands were used to ask and record the OMSD and its risk factors. The questionnaires were filled in by the workers. Annual prevalence of OMSD in different parts of the body were counted according to different age, working years and educational level, logistic regression was used to analyze its influence factors.</p><p><b>RESULTS</b>OMSD in these workers primarily located in waist, neck and shoulders, annual prevalence were 51.0% (825), 48.5% (785) and 37.7% (610) respectively. Annual prevalence of other body parts were 28.0% (454) for back, 23.6% (383) for knee, 21.0% (341) for wrist, 17.9% (290) for ankle/foot, 14.1% (229) for elbow and 12.7% (205) for coxa. The annual prevalence of OMSD for each part tended to increase with age, mainly in waist and neck. Of the different age groups ≤ 24, 25 - 29, 30 - 34, 35 - 39, 40 - 44, 45 - 49, ≥ 50, the annual prevalence in waist was 26.4% (43/163), 37.8% (71/188), 52.8% (162/307), 55.6% (160/288), 53.8% (99/184), 55.9% (80/143), 61.6% (204/331) respectively (χ(2) = 72.5, P < 0.05); correspondingly, the annual prevalence in neck was 22.7% (37/163), 40.4% (76/188), 50.2% (154/307), 48.6% (140/288), 56.0% (103/184), 53.1% (76/143), 57.7% (191/331) respectively (χ(2) = 65.3, P < 0.05). The annual prevalence of OMSD increased with the working years. Of the different working years groups ≤ 4, 5 - 9, 10 - 14, 15 - 19, 20 - 24, 25 - 29, ≥ 30, the annual prevalence in waist was 30.2% (85/281), 46.2% (66/143), 56.4% (162/287), 56.8% (137/241), 50.6% (78/154), 59.2% (90/152), 60.7% (173/285) respectively (χ(2) = 71.3, P < 0.05);correspondingly, the annual prevalence in neck was 28.8% (81/281), 49.0% (70/143), 52.6% (151/287), 50.2% (121/241), 51.9% (80/154), 53.9% (82/152), 59.3% (169/285) respectively (χ(2) = 61.5, P < 0.05). The annual prevalence of OMSD decreased with education level. Of the different groups of education level (junior high school level and below, senior high school level, university level or above), the OMSD prevalence in waist was 61.5% (176/286), 61.9% (359/692), 44.2% (272/615) respectively (χ(2) = 26.0, P < 0.05);correspondingly, the annual prevalence in neck was 56.3% (161/286), 50.0% (346/692), 42.3% (260/615)respectively (χ(2) = 21.2, P < 0.05). Univariate logistic regression showed that the work load factors such as the working years ≥ 30 (OR = 3.562, 95%CI: 2.514 - 5.046), maintain substantial stoop for a long time (OR = 2.003, 95%CI: 1.612 - 2.488), often stooping with vast scale (OR = 1.897, 95%CI: 1.557 - 2.312), and torso repeating same action many times per minute (OR = 1.870, 95%CI: 1.529 - 2.288) could increase the annual prevalence of OMSD in waist most likely (P < 0.05). The working years ≥ 30 (OR = 3.597, 95%CI: 2.535 - 5.105), neck leaning forward (OR = 2.455, 95%CI: 2.010-2.99), neck leaning back (OR = 1.999, 95%CI: 1.569 - 2.546), and neck rotation (OR = 2.381, 95%CI: 1.907 - 2.972) were main risk factors causing OMSD in neck (P < 0.05).</p><p><b>CONCLUSION</b>The most serious musculoskeletal disorders of male steelworkers were waist and neck pain. Personal factors such as age, working years, work load factors such as harmful working postures, manual heavy lifting, and labour organizational factors such as work overtime were the main risk factors of musculoskeletal disorders to the male steelworkers.</p>

Co-occurrence of musculoskeletal disorders and influence factors among Chinese auto workers / 中华劳动卫生职业病杂志

<p><b>OBJECTIVE</b>To analyze the prevalence and risk factors of multiple musculoskeletal disorders (MSDs) in auto workers and the associations between MSDs at different sites.</p><p><b>METHODS</b>A cross-sectional survey was conducted in 3998 workers, who were selected from a Chinese auto corporation by cluster random sampling, using the revised Nordic MSDs standard questionnaire; 3800 completed questionnaires were returned. Multinomial logistic regression analysis was performed to assess the risk factors for multiple MSDs. The logbinomial model was used to calculate the prevalence ratios (PRs) of MSDs at different sites and evaluate the associations between MSDs at different sites.</p><p><b>RESULTS</b>Of the 3800 subjects, 2452 (64.5%) had MSDs at two or more sites, and 469 (12.3%) had MSDs at one site. The PRs varied from 1.5 to 6.7, with significant differences among different sites (P < 0.01). Relatively close associations were found between the MSDs at neck and shoulders, back and shoulders/waist, elbows and wrists/hands, waist and neck, wrists/hands and waist, hip and waist, knees and waist, and ankles/feet and elbows. The multinomial logistic regression analysis indicated that the highest risk factor for MSDs was poor posture, including often working in an uncomfortable posture, neck bending forward, and neck twisting (ORs = 3.39, 1.93, and 1.38), followed by labor organization, in which break between tasks could decrease the risk of MSDs at three or more sites to 31%, staff shortage, which could increase the risk of MSDs by 75%, and pushing and pulling heavy objects (> 20 kg) (OR = 1.76).</p><p><b>CONCLUSION</b>Most auto workers with MSDs have multiple sites affected, and there are high associations between the MSDs at different sites. The major risk factors for multiple MSDs in auto workers include poor posture, labor organization, and heavy physical labor.</p>

Comparative experiment on nanoparticle-induced toxicity in human vascular endothelial cells / 中华劳动卫生职业病杂志

<p><b>OBJECTIVE</b>To compare the toxic effects of three different particles on vascular endothelial cells, and to investigate the influences of particle composition and sizes on the cardiovascular toxic effects.</p><p><b>METHODS</b>Nano-SiO2 particles, nano-TiO2 particles, and standard quartz particles were selected as the test substances, and the nano-TiO2 particles and standard quartz particles were used as composition controls and size controls, respectively. The human umbilical vein endothelial cells were exposed to different doses (5.0, 10.0, 20.0, 40.0 µg/ml) of the three particles as well as particle-free DMEM medium (0 µg/ml dust) for 24 h. Then, the culture supernatants were collected, and the activities of lactic dehydrogenase (LDH) and total superoxide dismutase (SOD) as well as the releases of NO, tumor necrosis factor-α (TNF-α), and interleukin-6 (IL-6) were measured.</p><p><b>RESULTS</b>Compared with those of 0 µg/ml dose group, the LDH activities of all nano-SiO2 groups, 10.0, 20.0, and 40.0 µg/ml nano-TiO2 groups, and 10.0, 20.0, and 40.0 µg/ml standard quartz groups were significantly increased (P < 0.01); the SOD activities of 5.0, 10.0, and 20.0 µg/ml nano-SiO2 groups, 40.0 µg/ml nano-TiO2 group, and 20.0 and 40.0 µg/ml standard quartz groups were significantly increased (P < 0.05), but that of the 40.0 µg/ml nano-SiO2 group was significantly decreased (P < 0.01); the TNF-α releases of 10.0, 20.0, and 40.0 µg/ml nano-SiO2 groups, all nano-TiO2 groups, and 40.0 µg/ml standard quartz group were significantly increased (P < 0.01); the IL-6 releases of 10.0, 20.0, and 40.0 µg/ml nano-SiO2 groups, 20.0 and 40.0 µg/ml nano-TiO2 groups, and 40 µg/ml standard quartz group were significantly increased (P < 0.01). When the dust doses were 5.0, 10.0, 20.0, and 40.0 µg/ml, the LDH activities of nano-SiO2 groups were significantly higher than those of standard quartz groups (P < 0.05); when the dust doses were 10.0, 20.0, and 40.0 µg/ml, the LDH activities of nano-TiO2 groups were significantly lower than those of standard quartz groups (P < 0.05). When the dust doses were 5.0, 10.0, 20.0, and 40.0 µg/ml, the SOD activities of nano-SiO2 groups were significantly higher than those of standard quartz groups (P < 0.01); when the dust dose was 20 µg/ml, the SOD activity of nano-TiO2 group was significantly higher than that of standard quartz group (P < 0.01). When the dust doses were 5.0, 10.0, 20.0, and 40.0 µg/ml, the TNF-α releases of nano-SiO2 groups were significantly higher than those of standard quartz groups (P < 0.01); when the dust doses were 5.0 and 10.0 µg/ml, the TNF-α releases of nano-TiO2 groups were significantly higher than those of standard quartz groups (P < 0.01). When the dust doses were 5.0, 10.0, 20.0, and 40.0 µg/ml, the IL-6 releases of nano-SiO2 groups were significantly higher than those of standard quartz groups (P < 0.05); when the dust doses were 20 and 40 µg/ml, the IL-6 releases of nano-TiO2 groups were significantly higher than those of standard quartz groups (P < 0.05).</p><p><b>CONCLUSION</b>All the three particles are able to exert certain toxic effects on vascular endothelial cells. Nano-SiO2 particles have the most toxic effects, and nano-TiO2 particles and standard quartz particles show uncertain effects. The toxicity of particles is linked to their composition and sizes.</p>

Risk factors analysis of low back pain among workers in a foundry factory of the automobile company / 中华劳动卫生职业病杂志

<p><b>OBJECTIVE</b>To study the main risk factors of low back pain of workers ina foundry factory of the automobile company using cross sectional epidemiological investigation, and to provide scientific base for preventing the disorder.</p><p><b>METHODS</b>The low back pain and work loads of 1340 workers in a foundry factory of the automobile company were investigated using questionnaire, and logistic regression analysis was used to analyze the risk factors.</p><p><b>RESULTS</b>The one-year morbidity of low back pain in workers was 58.9% the morbidities of low back pain in workers engaged in foundry, transportation and modeling were 64.6%, 64.6% and 62.5%, respectively. The lifting with squat postures, bending trunk heavily, bending trunk with twisting and moving the heavy objects were found to be the most dominant risk factors for low-back pain, the OR values were 2.085, 1.961, 1.967 and 1.956, respectively. The distributions of risk factors were different among the different jobs. The logistic regression analysis showed that moving the heavy objects, lifting with squat postures, bending trunk heavily, bending trunk with twisting existed simultaneously, also the work years and gender were the risk factors.</p><p><b>CONCLUSION</b>The manual moving heavy objects, awkward working posture or both were the most important risk factors for low-back pain. The intervene ergonomic study should be performed in future to reduce the morbidity of low-back pain.</p>

A field assessment on the risk factors of musculoskeletal disorders / 中华劳动卫生职业病杂志

<p><b>OBJECTIVE</b>To investigate the usability of quick exposure check (Quick Exposure Check, QEC) for the field assessment of occupational musculoskeletal disorder risk factors.</p><p><b>METHOD</b>In the shipyard and automobile manufacturing plants, QEC was used to observe the operations among workers with different jobs and to assess the work loads of workers. On the basis of results, the reliability of QEC was evaluated, and the correlation between QEC scores and morbidities of musculoskeletal disorders in workers was analyzed.</p><p><b>RESULTS</b>The inter-observer reliability (ICC) was in the range from 0.737 to 1.000, and intra-observer reliability (Spearman coefficient) was from 0.605 to 1.000. The order of exposure levels to risk factors of workers engaged in different jobs (QEC scores) in the shipyard factory was plumbers > assemblers > welders; The order of exposure levels to risk factors of workers engaged in different jobs (QEC scores) in the automobile factory was welders > punching workers > machinists > casters > assemblers. In different body parts, the exposure level at back and neck parts was the highest and the exposure level at the shoulder and wrist parts was the second. The regression analysis between QEC scores of body parts and the morbidities of musculoskeletal disorders showed that there was a good correlation between exposure levels and morbidities, the coefficients (r(2)) at the shoulder, wrist, and back (static work) were 0.670, 0.740 and 0.958, respectively (P < 0.05).</p><p><b>CONCLUSION</b>The QEC method is suitable and reliable as demonstrated by the field assessment on the exposure to risk factors in shipyard and automobile workers, and its results is correlated closely to the disease prevalence.</p>

Experimental simulated study on the break for manual lifting task by surface electromyography and electrocardiogram / 中华劳动卫生职业病杂志

<p><b>OBJECTIVE</b>To investigate the recovery duration of manual lifting tasks.</p><p><b>METHODS</b>30 college student volunteers with gender equally distributed were involved in the simulated stoop-, squart- and semi squart-lifting tasks in the laboratory. Signals of electromyography (EMG) at the back muscles (left and right thorax m. erector spinae, LT(10) and RT(10); left and right lumbar m. erector spinae, LL(3) and RL(3)) and electrocardiography (ECG) were recorded during the rest intervals. The percentage of maximum voluntary electrical activation (MVE%), EMG median frequency (MF), and heart rate (HR) were analyzed to predict the recovery time required.</p><p><b>RESULTS</b>During the break, MVE% at 4 back muscles of all the male subjects were recovered to resting level within 5 minutes and 91.8% were within 2 minutes. Except for RL(3) after squat- and stoop-lifting task, the MVE% of female subjects went back to resting level within 3 minutes and 67.8% were within 2 minutes. The MF of male subjects were recovered in 10 minutes and 74.9% within 2 minutes, with the exception of RL(3) after stoop- and squat-lifting tasks. All the female MF were recovered in 8 minutes and 83.4% were within 2 minutes. However, during the last 20 minute break after the lifting tasks, the MVE% and MF of all male and female subjects were recovered, while HR came back to resting level within 14 and 5 minutes, respectively.</p><p><b>CONCLUSIONS</b>For the three manual lifting tasks with 25% MVC workload lasting for 4.5 min, a break of 15 minutes is sufficient for most erectors spinae to recover from local muscle load. However, in terms of the HR, a break of 15 minutes is enough for the recovery of systematic load.</p>

Survey on prevalence of occupational musculoskeletal disorders among workers in a shipyard / 中华劳动卫生职业病杂志

<p><b>OBJECTIVE</b>To study the prevalence of occupational musculoskeletal disorders (OMSDs) in a shipyard and explore the relationship between type of work, age, length of service and OMSDs by cross sectional epidemiological survey.</p><p><b>METHODS</b>1570 workers from a shipyard were selected as survey objects, and a revised Northern Europe Standardized Questionnaire was used to investigate OMSDs. 253 technicians and clerks in the shipyard were selected as controls.</p><p><b>RESULTS</b>OMSDs in these workers primarily located in waist, neck and shoulder, prevalence were 58.0%, 54.6% and 44.3% respectively; There were significant differences among workers of different types of work (P < 0.05) in prevalence and the cumulative parts number of OMSDs. The control group in this study also showed a higher prevalence of neck, shoulder and waist OMSDs. Female workers had higher prevalence of OMSDs in neck and shoulder compared with male workers (P < 0.05). As well there was significant correlation between age and OMSDs prevalence except the wrist and ankle disorders (P < 0.05), OMSDs prevalence increased with years. In addition, there was correlation between length of service and OMSDs prevalence, the group of ≤ 5 years had the lowest prevalence and the prevalence of low-back, neck and shoulder increased with service years.</p><p><b>CONCLUSION</b>The OMSDs in workers engaged in shipyard are serious, the length of service, age, gender and type of work seem to be the risk factors, and it seems reasonable that the ergonomics intervention in the above aspects should be necessary for the prevention of OMSDs.</p>

Laboratory study of surface electromyography and electrocardiogram in assessing dynamic workload / 中华劳动卫生职业病杂志

<p><b>OBJECTIVE</b>To investigate the use of surface electromyography (sEMG) and electrocardiogram (ECG) in evaluation of dynamic workload.</p><p><b>METHODS</b>Through controlling the speed and gradient, 8 subjects ran on the treadmill power machine to simulate the dynamic work. The sEMG signal of anterior tibial muscle (AT) and gastrocnemius muscle (GC) of right lower limb and ECG signal were recorded. The root mean square value (RMS), median frequency (MF), mean power frequency (MPF), heart rate (HR), standard deviation of all normal to normal intervals (SDNN) and Borg scores were analyzed.</p><p><b>RESULTS</b>In the five sports, with the speed increasing, all the values of RMS increased in the AT and GC (P < 0.01). With the gradient increasing, the values of RMS increased in the GC (P < 0.01) while the values of RMS of AT had a trend of decrease (P > 0.05). In all five sports, both the values of MF and MPF in AT and GC were lowest in B sports. Compared to A sport, most of the values of MF and MPF increased in C, D, E sports (P < 0.01), with a highest value in the D sport. Compared with A sport, the HR of B, C, D, E sports significantly increased (P < 0.01), and the highest heart rate was found in B sport, however, the values of SDNN significantly decreased. With the increased speed and gradient, the scores of Borg scale significantly increased.</p><p><b>CONCLUSION</b>In the evaluation of dynamic workload, RMS and HR appear to be good indexes. However, in terms of stress reaction to dynamic workload, MF and MPF are more sensitive.</p>

Effect of Hg2+ on voltage-dependent calcium channels and intracellular free calcium in trigeminal ganglion neurons of rats / 中华劳动卫生职业病杂志

<p><b>OBJECTIVE</b>To investigate the effects of Hg2+ on voltage-dependent calcium channels and intracellular free calcium in trigeminal ganglion neurons of rats and explore the toxicity mechanism of Hg2+ on these neurons.</p><p><b>METHODS</b>Whole cell patch-clamp technique was used to determine ICa of voltage-dependent calcium channels in trigeminal ganglion neurons of rats. Intracellular free calcium was measured to explore [Ca2+]i dynamic changes from a single cell level by laser scanning confocal microscopy and fluorescence probe techniques.</p><p><b>RESULTS</b>0.01, 0.10, 1.00 and 10.00 micromol/L Hg2+ could reduce voltage-dependent calcium channel currents ICa by (1.80+/-0.32)%, (23.04+/-9.46)%, (58.20+/-7.90)% and (82.00+/-5.77)% in trigeminal ganglion neurons. The inhibiting effects reached their maximum in 5 minutes and could not be reversed significantly during wash with Hg2+-free solution. Also, 0.01, 0.10 and 1.00 micromol/L Hg2+ increased intracellular free calcium concentrations by (2.50+/-0.83)%, (82.81+/-35.36)% and (222.70+/-62.48)% in trigeminal ganglion neurons. Pre-administrated trigeminal ganglion neurons with nifedipine for 10 minutes could decrease the effects and delay the effecting time.</p><p><b>CONCLUSION</b>The inhibition of Hg2+ on the voltage-dependent calcium channel currents ICa depends on voltage-dependent calcium channels. And the increase of intracellular free calcium concentration in trigeminal ganglion neurons induced by Hg2+ is related to the release of intracellular stored calcium. However, the relationship between them needs further investigation.</p>

Characteristics of surface electromyography and work load of the forearm extensors in repetitive wrist extending / 中华劳动卫生职业病杂志

<p><b>OBJECTIVE</b>To evaluate the influence of the frequency, the weight and the motion angle on the stress and the fatigue of the forearm extensors in repetitive wrist extending at low force loading level with surface electromyography (SEMG).</p><p><b>METHODS</b>Sixteen male college student volunteers were recruited for the experiment. Eight tasks of wrist extending were performed for 20 minutes respectively in given weight (1.96, 4.90 N), frequency (8.0, 33.3 moves/minute) and motion angle (45 degrees, 90 degrees). The static wrist extending at the level of 20% maximum voluntary contraction (MVC) were performed before and after each task for 2 up to 3 seconds, and the SEMG signals of extensor carpi ulnaris muscle (ECU) and extensor digitorum (ED) were recorded and analyzed.</p><p><b>RESULTS</b>The weight loading level was approximately equal to 1.40% or 3.50% of the MVC force. The mean power frequency (MPF) and the median frequency (MF) were decreased with the increase of 3 kinds of loading levels. The decrease of MPF of the muscle ED was significant (P < 0.05 or P < 0.01). The MF was decreased with the increase of angle and weight loading levels (P < 0.05 or P < 0.01). The root mean square (RMS) value of SEMG could be divided into 3 or 4 groups with significant difference. All three kinds of loads had positive correlation with amplitude of SEMG according to the stepwise regression analysis.</p><p><b>CONCLUSION</b>The fatigue level of ED is the highest. The primary load factor for the forearm extensors is the frequency followed by the weight and the angle. MF, MPF and RMS can be used as sensitive indexes for evaluating the stress and the fatigue of the forearm extensors during repetitive performance at lower force loading level.</p>

Mental workload for mental arithmetic on visual display terminal / 中华劳动卫生职业病杂志

<p><b>OBJECTIVE</b>To investigate the possibility of subjective rate, primary task evaluation and psychophysiology evaluation as methods for mental workload assessment of mental arithmetic on visual display terminal (VDT).</p><p><b>METHODS</b>The indexes including Cooper-Harper scale score, correct rate, speed in answering questions, heart rate variability, pupil size and blink rate were recorded during the performance of three different difficult tasks.</p><p><b>RESULTS</b>With the variable number of formula increasing, the Cooper-Harper scale score increased, the right rate decreased, the speed decreased, pupil size increased, and blink rate significantly decreased. In comparison with rest, the value of TP, VLF, LF, LFnorm, LF/HF decreased remarkably in the mental arithmetic task, the value of HFnorm, HF/TP, rMSSD increased. However, the difference was not significant among three groups.</p><p><b>CONCLUSION</b>With the variable number of formula increasing, the participant's mental workload increases. Every method of mental workload evaluation can assess the mental workload information for three tasks at various different levels in a way. Multi-indexes may be appropriate for mental load assessment.</p>

Application of heart rate variability in evaluation of mental workload / 中华劳动卫生职业病杂志

<p><b>OBJECTIVE</b>To investigate if heart rate variability (HRV) can be used to evaluate mental workload.</p><p><b>METHODS</b>Forty-six volunteers were selected to simulate mental work by inputting the random number through keyboards. ECG was recorded by Holter 8800 during the performance and transferred into digital signal. Total power (TP), low frequency (LF), high frequency (HF) were analysed by Holter software.</p><p><b>RESULTS</b>Along with time, the inputting speed increased but accuracy decreased, and was positively correlated with TP, LF (r = 0.851 and 0.827 respectively, P < 0.05), showing a distinct dose-effect relationship. HRV values at rest were higher than during mental work [TP: (2 745.4 +/- 1 301.6) vs (686.2 +/- 420.7) ms(2)/Hz; HF: (670.6 +/- 393.8) vs (202.6 +/- 171.7) ms(2)/Hz; LF: (870.5 +/- 553.7) vs (206.0 +/- 187.9) ms(2)/Hz] indicating that they were decreased remarkably as the mental work started. Then, they were gradually increased with the workload (intensity and time) increased, but still at lower level.</p><p><b>CONCLUSION</b>HRV may be used as a parameter to evaluate mental workload but the change pattern of HRV needs to study further.</p>

Expression of Smads in lung tissue of quartz-induced pulmonary fibrosis in mice / 中华劳动卫生职业病杂志

<p><b>OBJECTIVE</b>To observe Smads protein expression in lung tissue of quartz exposed mice and to explore its association with pulmonary fibrosis in silicosis.</p><p><b>METHODS</b>The experimental mice were divided into control and quartz groups. 0.2 g/kg weight of quartz was injected intratracheally in quartz group. Samples were collected at the 1st, 3rd, 5th, 7th, 14th and 28th day after injection. Immunohistochemical methods with quantitative image analysis were used to assay the protein expression of transforming growth factor beta(1) (TGF-beta(1)), Smad 2/3, Smad 4, and Smad 7 protein levels. Protein expression level is presented by positive unit (PU).</p><p><b>RESULTS</b>Smad 2/3 protein expression increased from day 3, reaching its peak level in day 14 [(42.2 +/- 2.4) PU], and decreased gradually. The elevation of Smad 4 protein level began from day 5, and the highest degree came into day 14 [(40.0 +/- 1.8) PU], decreased thereafter. The expression of Smad 7 presented a decreasing tendency at the beginning and reaching the lowest level in day 14 [(33.5 +/- 3.3) PU]. It seemed to elevate in day 28, but was still lower than the controls. There were positive correlation between Smad 2/3, Smad 4 and TGF-beta(1) (r = 0.91, r = 0.71, respectively, P < 0.05) and also between Smad 2/3 and hydroxyproline contents of lung tissue (r = 0.85, P < 0.05) except Smad 7.</p><p><b>CONCLUSION</b>Smad protein may have certain association with pulmonary fibrosis in silicosis.</p>

Analysis of surface electromyography on repetitive lifting task-induced fatigue of back muscles / 中华劳动卫生职业病杂志

<p><b>OBJECTIVE</b>Using surface electromyography (SEMG) technique to evaluate repetitive lifting task-induced fatigue of back muscles.</p><p><b>METHODS</b>Thirteen 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.</p><p><b>RESULTS</b>EMG 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).</p><p><b>CONCLUSION</b>Repetitive 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.</p>

Estimation of intramuscular load of the upper limb in static postures and repetitive work by surface electromyography / 中华劳动卫生职业病杂志

<p><b>OBJECTIVE</b>To evaluate the intramuscular loads of the upper limb during static postures and repetitive work by surface electromyography.</p><p><b>METHODS</b>Twenty-six male college student volunteers were recruited for the experiment. The surface electromyography (SEMG) singal were recorded from the brachioradialis, biceps brachii, deltoid and trapezius of right arm during static postures including forward elevating, abducting, extending and a repetitive performance at different height of the bench, and root mean square (RMS) values were educed from the singal.</p><p><b>RESULTS</b>The SEMG amplitudes from forward elevating and abducting were in direct proportion to the angle of the elevating and abducting (r > 0.9, P < 0.01). The maximal voluntary electrical activation (MVE) of the deltoid were 6.4%, 10.1%, 12.6%, 16.2% and 20.8% while the arm elevated forward at an angle of 0 degrees , 45 degrees , 90 degrees , 135 degrees and 180 degrees respectively. The repetitive work showed that the height of the bench and the duration had more effects on deltoid and trapezius than the other muscles. The MVE% of the deltoid were 13.0%, 14.4% and 15.6% while the bench was 74, 79 and 84 cm in height respectively (P < 0.01).</p><p><b>CONCLUSION</b>SEMG which is suitable for determining and reflecting the muscle strain during static postures and repetitive work may be a reasonable indicator for the assessment of manual workload and the ergonomic design.</p>

Immunohistochemical method for the detecting expression of transforming growth factor-beta1 in lung tissues of silica-treated mice / 中华劳动卫生职业病杂志

<p><b>OBJECTIVE</b>To investigate the protein expression of transforming growth factor-beta(1) (TGF-beta(1)) in lung tissues of silica-treated mice.</p><p><b>METHODS</b>The experimental mice were divided into control and silica groups. 0.2 g/kg body weight of silica was injected intratracheally in mice of silica group. Samples of lung tissue were collected 1, 3, 5, 7, 14 and 28 d after injection. The immunohistochemical method was used to analyze the protein expression of TGF-beta(1).</p><p><b>RESULTS</b>In control mice, the expression of TGF-beta(1) in lung tissue was slightly positive while it was markedly increased in silica-treated mice. The expression was significantly elevated from the 7th day to 14th day. The expression in alveolar macrophages reached the peak on the 5th day [(93.4% +/- 2.8%) vs (42.2% +/- 12.0%), P < 0.01].</p><p><b>CONCLUSION</b>TGF-beta(1) may play an important role in early development of silicosis.</p>

RT-PCR method for detecting the expression of transforming growth factor-beta1 gene in lung tissues of silica-treated mice / 中华劳动卫生职业病杂志

<p><b>OBJECTIVE</b>To investigate the gene expression of transforming growth factor-beta(1) (TGF-beta(1)) in lung tissues of silica-treated mice.</p><p><b>METHODS</b>The experimental mice were divided into control and silica group. 0.2 g/kg body weight of silica was injected intratracheally in silica group. Samples of lung tissue were collected 1, 3, 5, 7, 14 and 28 d after injection. RT-PCR method was used to analyze the gene expression of TGF-beta(1) in lung tissue of silica-treated mice.</p><p><b>RESULTS</b>The expression of TGF-beta(1) gene in lung tissue elevated from the 3rd day (1.20 +/- 0.15) and the peak value was on the 7th day (1.74 +/- 0.19). Then the expression decreased from the 14th to 28th day. But there was still higher than control until the 28th day.</p><p><b>CONCLUSION</b>TGF-beta(1) may play an important role in silica-induced pulmonary fibrosis.</p>