Energy-equivalent Frequency-weighted Acceleration Research Articles

Effects of expression of calpain mRNA in rabbits exposed to vibration by hind legs

To study the effects of expression of calpain mRNA in rabbits exposed to vibration by hind legs. 32 New Zealand rabbits were randomly divided into a control group and 3 experimental groups according to 4-hour energy-equivalent frequency-weighted acceleration[ahw (4)]: low (4.33 m/s(2)) , moderate (8.67 m/s(2)) and high (17.34 m/s(2)) intensity group to accepted the vibration by hind legs. 45 ds later, brain and skeletal muscle tissue of rabbits were taken to detect the expression of calpain-1 and calpain-2 mRNA by RT-qPCR technique. The relative content of calpain-1 mRNA in the brain tissues in rabbits of low, medium and high intensity group were 8.35±3.75,9.64±4.54,5.10±5.26. While the relative content of calpain-2 mRNA in the brain tissues in rabbits of low, medium and high intensity group were 7.34±4.97,8.50±5.66, 8.16±5.59. Compared with the control group (1.10±0.29, 0.56±0.43) , the expression of calpain-1 and calpain-2 mRNA of the intensity groups showed an significantly increasing trend (P<0.01). In skeletal muscle tissue, the relative content of calpain-1 mRNA were 4.36±2.05, 7.37±4.06, 12.46±6.21.Compared with the control group (0.98±0.59) , the expression of calpain-1 mRNA of experiment groups were significantly higher (P<0.05) .The expression of calpain-2 mRNA of the intensity groups had no significantly difference with the control group (P>0.05). The expression of calpain-1 and calpain-2 mRNA can be promoted by the vibration by the hind legs.

Do exposure limits for hand-transmitted vibration prevent carpal tunnel syndrome?

An apparently high frequency of carpal tunnel syndrome (CTS) among shipyard workers undergoing health surveillance because of exposure to hand-transmitted vibration (HTV) prompted concerns that current regulatory limits on exposure might not protect adequately against the disorder. To explore whether within regulatory limits, higher exposures to HTV predispose to CTS. As part of a retrospective audit, we compared duration and current intensity of exposure to HTV in cases with new-onset CTS and controls matched for age. Conditional logistic regression was used to quantify associations, which were summarized by odds ratios (ORs) and 95% confidence intervals (CIs). There were 23 cases and 55 controls. After adjustment for body mass index and previous diagnosis of diabetes, no clear associations were observed either with duration of exposure to HTV or with current intensity of exposure. Risk was non-significantly elevated in men with ≥30 years' exposure to HTV (OR 1.6), but in the highest category of current exposure [8-h energy-equivalent frequency-weighted acceleration (A8) ≥ 4.0 m/s(2)], risk was lower than that in the reference category (A8 < 2.5 m/s(2)). Moreover, there was a significantly reduced risk of CTS in men with a previous diagnosis of hand-arm vibration syndrome (HAVS) (OR 0.2, 95% CI 0.1-0.9). We found no evidence that below the current limit for A(8) of 5 m/s(2), higher exposures to HTV predispose to CTS. However, care should be taken not to overlook the possibility of treatable CTS when workers with diagnosed HAVS present with new or worsening sensory symptoms in the hand.

A longitudinal study of neck and upper limb musculoskeletal disorders and alternative measures of vibration exposure

To investigate the exposure-response relationships between alternative frequency weightings of hand-transmitted vibration (HTV) and neck and upper limb musculoskeletal disorders (MSDs) in a cohort of HTV workers. In a three-year longitudinal study, the occurrence of neck and upper limb MSDs was investigated in 249 HTV workers and 138 control men. In the HTV workers, MSDs were related to measures of daily vibration exposure expressed in terms of 8-h energy-equivalent frequency-weighted acceleration magnitude [A(8)]. To calculate A(8), the acceleration magnitudes of vibration were weighted by means of four alternative frequency weightings of HTV. The associations between MSDs, individual characteristics, physical work load other than vibration, and psychological strain were also investigated. The occurrence of upper limb MSDs was greater in the HTV workers than in the controls. After adjustment for potential confounders, the occurrence of elbow/forearm and wrist/hand MSDs increased with the increase in vibration exposure. A measure of model selection did not reveal any substantial difference in the performance of the alternative frequency weightings of HTV for the prediction of neck and upper limb MSDs. In the study population, age, hard physical work load, and poor psychological well-being were associated with both neck and upper limb MSDs. In this study, there was evidence for significant exposure-response relationships between HTV exposure and MSDs in the distal sites of the upper limbs. There were no differences in the prediction of neck and upper limb MSDs between measures of daily vibration exposure calculated with alternative frequency weightings of acceleration magnitude.

Measurement and analysis of hand-transmitted vibration of vibration tools in workplace for automobile casting and assembly

To investigate the features of hand-transmitted vibration of common vibration tools in the workplace for automobile casting and assembly. From September to October, 2014, measurement and spectral analysis were performed for 16 typical hand tools(including percussion drill, pneumatic wrench, grinding machine, internal grinder, and arc welding machine) in 6 workplaces for automobile casting and assembly according to ISO 5349-1-2001 Mechanical vibration-Measurement and evaluation of human exposure to hand-transmitted vibration-part 1: General requirements and ISO 5349-2-2001 Mechanical vibration-Measurement and evaluation of human exposure to hand-transmitted vibration-Part 2: Practical guidance for measurement in the workplace. The vibration acceleration waveforms of shearing machine, arc welding machine, and pneumatic wrench were mainly impact wave and random wave, while those of internal grinder, angle grinder, percussion drill, and grinding machine were mainly long-and short-period waves. The daily exposure duration to vibration of electric wrench, pneumatic wrench, shearing machine, percussion drill, and internal grinder was about 150 minutes, while that of plasma cutting machine, angle grinder, grinding machine, bench grinder, and arc welding machine was about 400 minutes. The range of vibration total value(ahv) was as follows: pneumatic wrench 0.30~11.04 m/s(2), grinding wheel 1.61~8.97 m/s(2), internal grinder 1.46~8.70 m/s(2), percussion drill 11.10~14.50 m/s(2), and arc welding machine 0.21~2.18 m/s(2). The workers engaged in cleaning had the longest daily exposure duration to vibration, and the effective value of 8-hour energy-equivalent frequency-weighted acceleration for them[A(8)] was 8.03 m/s(2), while this value for workers engaged in assembly was 4.78 m/s(2). The frequency spectrogram with an 1/3-time frequency interval showed that grinding machine, angle grinder, and percussion drill had a high vibration acceleration, and the vibration limit curve was recommended for those with a frequency higher than 400 min/d. The workers who are engaged in cleaning, grinding, and a few positions of assembly and use grinding machine, angle grinder, internal grinder, and percussion drill are exposed to vibrations with a high vibration acceleration and at a high position of the frequency spectrum. The hand-transmitted vibration in the positions of cutting, polishing, and cleaning in automobile casting has great harm, and the harm caused by pneumatic wrench in automobile assembly should be taken seriously.

Relationships of neurosensory disorders and reduced work ability to alternative frequency weightings of hand-transmitted vibration.

This cohort study aims to compare the performance of alternative frequency weightings of hand-transmitted vibration (HTV) for the assessment of the exposure-response relationships for neurosensory disorders and reduced work ability among HTV-exposed workers. In a 3-year follow up study, the occurrence of neurosensory symptoms and reduced work ability, and the response to quantitative sensory testing (grip force, manipulative dexterity, touch sensation) were investigated in 249 HTV-exposed workers and 138 healthy controls. Among the HTV-exposed workers, the sensory outcomes were related to measures of daily vibration exposure expressed in terms of 8-hour energy-equivalent frequency-weighted acceleration magnitude [A(8)]. To calculate A(8), the acceleration magnitudes of vibration were weighted by means of four alternative frequency weightings of HTV. The occurrence of neurosensory symptoms, reduced work ability, and abnormalities of sensory tests was greater among the HTV-exposed workers than the controls. Among the HTV-exposed workers, the deterioration of neurosensory outcomes and the reduction of work ability increased on par with the measures of vibration exposure. Exposure-response models revealed that the four alternative frequency weightings of HTV provided the same predictions for the probability of finger numbness among the exposed workers (observed 36% versus predicted 32%). The findings of this study revealed significant dose-response relationships between measures of vibration exposure, sensory disorders, and reduced work ability among the HTV-exposed workers. There were no differences in the prediction of finger numbness between measures of vibration exposure calculated with alternative frequency weightings of HTV.

A cohort study of sciatic pain and measures of internal spinal load in professional drivers

In a prospective cohort study of 537 male professional drivers, the occurrence of sciatic pain showed stronger associations with measures of internal lumbar load expressed in terms of daily compressive dose, Sed (MPa), and risk factor, R (non-dimensional), according to ISO/WD 2631-5 (2013), than with measures of daily vibration exposure calculated as either 8-h energy-equivalent frequency-weighted acceleration (ms− 2 r.m.s.) or vibration dose value (ms− 1.75) according to the EU Directive on mechanical vibration (2002). Herniated lumbar disc, previous lumbar trauma and physical work load were also powerful predictors of the occurrence of sciatic pain over time. Psychosocial work environment was poorly associated with sciatic pain. The boundary values of risk factor (R) for low and high probabilities of adverse health effects on the lumbar spine, as proposed by international standard ISO/WD 2631-5 (2013), tend to underestimate the health risk in professional drivers.

A Longitudinal Study of Low Back Pain and Daily Vibration Exposure in Professional Drivers

The aim of this study was to investigate the relation between low back pain (LBP) outcomes and measures of daily exposure to whole-body vibration (WBV) in professional drivers. In a study population of 202 male drivers, who were not affected with LBP at the initial survey, LBP in terms of duration, intensity, and disability was investigated over a two-year follow-up period. Vibration measurements were made on representative samples of machines and vehicles. The following measures of daily WBV exposure were obtained: (i) 8-h energy-equivalent frequency-weighted acceleration (highest axis), A(8)(max) in ms(-2) r.m.s.; (ii) A(8)(sum) (root-sum-of-squares) in ms(-2) r.m.s.; (iii) Vibration Dose Value (highest axis), VDV(max) in ms(-1.75); (iv) VDV(sum) (root-sum-of-quads) in ms(-1.75). The cumulative incidence of LBP over the follow-up period was 38.6%. The incidence of high pain intensity and severe disability was 16.8 and 14.4%, respectively. After adjustment for several confounders, VDV(max) or VDV(sum) gave better predictions of LBP outcomes over time than A(8)(max) or A(8)(sum), respectively. Poor predictions were obtained with A(8)(max), which is the currently preferred measure of daily WBV exposure in European countries. In multivariate data analysis, physical work load was a significant predictor of LBP outcomes over the follow-up period. Perceived psychosocial work environment was not associated with LBP.

Vibrotactile Perception and Effects of Short-Term Exposure to Hand-Arm Vibration

This study clarifies whether the established frequency weighting procedure for evaluating exposure to hand-transmitted vibration can effectively evaluate the temporary changes in vibrotactile perception thresholds due to pre-exposure to vibration. In addition, this study investigates the relationship between changes of the vibrotactile perception thresholds and the normalized energy-equivalent frequency-weighted acceleration. The fingers of 10 healthy subjects, five male and five female, were exposed to vibration under 16 conditions with a combination of different frequencies, intensities, and exposure times. The vibration frequencies were 31.5 and 125 Hz and exposure lasted between 2 and 16 min. According to International Organization for Standardization (ISO) 5349-1, the energy-equivalent frequency-weighted acceleration for the experimental time of 16 min is 2.5 or 5.0 m s(-2) root-mean-square, corresponding to a 8-h equivalent acceleration, A(8), of approximately 0.5 and 0.9 m s(-2), respectively. A measure of the vibrotactile perception thresholds was conducted before the different exposures to vibration. Immediately after the vibration exposure, the acute effect was measured continuously on the exposed index finger for the first 75 s, followed by 30 s of measures every minute for a maximum of 10 min. If the subject's thresholds had not recovered, the measures continued for a maximum of 30 min with measurements taken every 5 min. Pre-exposure to vibration significantly influenced vibrotactile thresholds. This study concludes that the influence on the thresholds depends on the frequency of the vibration stimuli. Increased equivalent frequency-weighted acceleration resulted in a significant change in threshold, but the thresholds were unaffected when changes in the vibration magnitude were expressed as the frequency-weighted acceleration or the unweighted acceleration. Moreover, the frequency of the pre-vibration exposure significantly influenced (up to 25 min after exposure) recovery time of the vibrotactile thresholds. This study shows that the frequency weighting procedure in ISO 5349-1 is unable to predict the produced acute changes in the vibrotactile perception. Moreover, the results imply that the calculation of the 'energy-equivalent' frequency-weighted acceleration does not reflect the acute changes of the vibration perception thresholds due to pre-exposure to vibration. Furthermore, when testing for the vibrotactile thresholds, exposure to vibration on the day of a test might influence the results. Until further knowledge is obtained, the previous practice of 3 h avoidance of vibration exposure before assessment is recommended.

Cervical HIVD Related to Long-Term Whole Body Vibration and Awkward Posture

Background: The relationship between whole body vibration and awkward neck posture to cervical herniated intervertebral disc (HIVD) has been rarely reported. In this report, we present the case of an overhead crane operator, that had no known history of neck injury, but had long-term exposure to whole body vibration and improper neck posture, who developed cervical HIVD, which raises concerns over the possibility of occupational causation. Case: A patient, operating an overhead crane since Dec 26 th 1986, began to suffer from a neck pain and developed cervical HIVD in 1998. He had been frequently treated in an outpatient clinic, but the symptom was not improve. Eventually, he got HIVD surgery in Sep 6 th 2007, and then the symptom was relieved. There were 4 groups and 3 shift system in the patient’s overhead crane operation. He worked eight hours a day and 5 days a week. Actual crane work time was about 6 hours a day. The crane was located at 20 meters above the work field so that the crane operator had to look downward and the neck was bent by more than 20˚ for nearly the entire working day. Daily vibration exposure was expressed in terms of an 8-hour energy-equivalent frequency-weighted acceleration magnitude (A(8)) and vibration dose value (VDV). The daily A(8) was measured to be 0.23 ㎧² and the daily VDV was 7.4 ㎧ 1.75 . Although these levels were below the action level recommended by the International Organization for Standardization (ISO) and European Commission (EC), it cannot be ignored that whole body vibration in addition to an awkward neck posture may be related to an increased risk for neck disease. A long-term awkward posture can adversely impact the prevalence of neck disease. In addition, occupational exposure to whole body vibration along with an awkward neck posture seems to exacerbate these effects. Conclusion: An overhead crane operator may have acquired cervical HIVD due to an occupational causation. Therefore, to elucidate the causal relationship of an improper neck posture and whole body vibration to neck diseases, further investigations need to be conducted for lager sample of overhead crane operators that were exposed to a long-term awkward neck posture and whole body vibration.

Associations between work-related factors and the carpal tunnel syndrome—a systematic review

The aim of this study was to make a quantitative assessment of the exposure-response relationships between work-related physical and psychosocial factors and the occurrence of carpal tunnel syndrome (CTS) in occupational populations. A systematic review of the literature was conducted on the associations of type of work, physical load factors, and psychosocial aspects at work to the occurrence of CTS. The associations between work factors and CTS were expressed in quantitative measures, namely, odds ratios (OR) or relative risks. Jobs with the highest risk of CTS included work in the meat- and fish-processing industry, forestry work with chain saws, and electronic assembly work (OR 76.5, 21.3, and 11.4, respectively). The occurrence of CTS was associated with high levels of hand-arm vibration, prolonged work with a flexed or extended wrist, high requirements for hand force, high repetitiveness, and their combination. No association was found between any psychosocial risk factor and CTS. Contradictory findings were reported for associations between computer work and CTS. This review provides consistent indications that CTS is associated with an average hand force requirement of >4 kg, repetitiveness at work (cycle time 50% of cycle time performing the same movements), and a daily 8-hour energy-equivalent frequency-weighted acceleration of 3.9 m/s2.

An epidemiological study of low back pain in professional drivers

The prevalence of low back pain (LBP) was investigated in 598 Italian professional drivers exposed to whole-body vibration (WBV) and ergonomic risk factors (drivers of earth moving machines, fork-lift truck drivers, truck drivers, bus drivers). The control group consisted of a small sample of 30 fire inspectors not exposed to WBV. Personal, occupational and health histories were collected by means of a structured questionnaire. Vibration measurements were performed on representative samples of the machines and vehicles used by the driver groups. From the vibration magnitudes and exposure durations, alternative measures of vibration dose were estimated for each subject. Daily vibration exposure, expressed in terms of 8-h energy-equivalent frequency-weighted acceleration, A(8), averaged 0.28–0.61 (range 0.10–1.18) m s −2 rms in the driver groups. Duration of exposure to WBV ranged between 1 and 41 years. The 7-day and 12-month prevalence of LBP was greater in the driver groups than in the controls. In the professional drivers, the occurrence of 12-month LBP, high intensity of LBP (Von Korff pain scale score ⩾5), and LBP disability (Roland & Morris disability scale score ⩾12) significantly increased with increasing cumulative vibration exposure. Even though several alternative measures of vibration exposure were associated with LBP outcomes, nevertheless a more regular trend of association with LBP was found for vibration dose expressed as ∑ a vit i (m s −2 h), in which the frequency-weighted acceleration, a v , and lifetime exposure duration, t, were given equal weight. In multivariate data analysis, individual characteristics (e.g. age, body mass index) and a physical load index (derived from combining manual materials handling and awkward postures) were significantly associated with LBP outcomes, while psychosocial work factors (e.g. job decision, job support) showed a marginal relation to LBP. This study tends to confirm that professional driving in industry is associated with an increased risk of work-related LBP. Exposure to WBV and physical loading factors at work are important components of the multifactorial origin of LBP in professional drivers.

Work-related disorders of the upper limb in female workers using orbital sanders

To investigate the prevalence of vascular, neurological and musculoskeletal disorders of the upper limb in a group of female workers performing either mechanical or hand sanding in the furniture industry (n=100) and in a control group of female office workers (n=100). A further aim was to study the possible adverse effects of exposure to a combination of vibration and ergonomic risk factors in female workers. All female workers underwent a medical interview and a complete physical investigation. The clinical diagnoses of Raynaud's phenomenon and carpal tunnel syndrome (CTS) were made according to international consensus criteria. Hand-transmitted vibration from orbital sanders was measured according to International Organization for Standardization (ISO) recommendations. Daily vibration exposure was assessed in terms of 8-h energy-equivalent frequency-weighted acceleration [A(8)] according to the European Directive on physical agents. Ergonomic load on the upper limbs was estimated by means of strain index methodology. There was no significant difference in the prevalence of Raynaud's phenomenon between the furniture workers (4%) and the controls (8%). The prevalence of CTS, peripheral sensorineural disturbances (after exclusion of CTS cases) and upper-limb musculoskeletal complaints was significantly greater in the furniture workers than in the controls. CTS was clinically diagnosed in 19% of the furniture workers and 8% of the controls. A log-binomial regression analysis showed that the occurrence of soft-tissue disorders of the upper limb increased significantly with the increase of both daily vibration exposure and the strain index score. It was estimated that the risk for CTS increased by a factor of 1.30 (95% CI 1.11-1.53) for each unit of increase in A(8) (ms(-2)), and by 1.09 (95% CI 1.02-1.15) for each unit of increase in the strain index score. Even though the cross-sectional design of this epidemiological study does not allow aetiological considerations, our findings suggest a significant association between occupational use of vibratory tools and soft-tissue disorders in the upper limbs of female workers. Quantitative estimation of vibration exposure and ergonomic stress showed that these physical risk factors seem to contribute in a multiplicative way to the occurrence of chronic nerve and musculoskeletal disorders in female workers operating hand-held vibrating tools in the furniture industry.

Acute effects of continuous and intermittent vibration on finger circulation

To compare the acute response of finger circulation to continuous and intermittent vibration having the same total duration of vibration exposure and the same energy-equivalent acceleration magnitude. Finger blood flow (FBF) was measured in the middle and little fingers of both hands of ten healthy men. Finger skin temperature (FST) was measured in the middle right finger. With a static load of 10 N, the middle finger of the right hand was exposed to 125 Hz at 44 m s(-2) root mean square (r.m.s.) in five conditions: (1). 30 min continuous exposure, (2). two periods of 15 min, separated by a 15 min period with no vibration, (3). four periods of 7.5 min, separated by 7.5 min periods with no vibration, (4). eight periods of 3.75 min, separated by 3.75 min periods with no vibration, (5). 16 periods of 1.88 min, separated by 1.88 min periods with no vibration. All five exposures correspond to an 8 h energy-equivalent frequency-weighted acceleration magnitude of 1.4 m s(-2) r.m.s. according to International Standard ISO 5349-1 (2001). Finger circulation was measured in all four digits before the application of vibration and at fixed intervals during vibration exposure and during a 45 min recovery period. The FST did not change during vibration exposure, whereas all vibration conditions produced significant reductions in FBF of the vibrated finger when compared with the pre-exposure FBF. During vibration exposure, the vibration caused a similar degree of vasoconstriction in the vibrated finger without evidence of cumulative effects during intermittent exposure. After the end of exposure to 30 min of continuous vibration there was a progressive decrease in the FBF, whereas there was no statistically significant reduction following exposure to intermittent vibration. For the vibration stimuli investigated (exposure durations varying from 1.88 min to 30 min, with rest periods varying from 1.88 min to 15 min), the reduction of FBF during exposure was the same for continuous and intermittent vibration. The after effect of vibration was greater following the continuous vibration exposure. Although some evidence from this study is consistent with the notion that intermittent vibration has a less severe effect than continuous vibration, this evidence is not yet conclusive.

Vibration-induced white finger and cold response of digital arterial vessels in occupational groups with various patterns of exposure to hand-transmitted vibration.

This study investigated the relation between vibration exposure, the prevalence of white fingers, and the cold response of digital arterial vessels in workers using vibrating tools. The change in finger systolic blood pressure (FSBP) at 15 and 10 degrees C as the percentage of the pressure at 30 degrees C (FSBP%) was measured in 455 healthy referents and 822 workers exposed to hand-transmitted vibration. Exposure to hand-transmitted vibration was assessed in terms of 8-hour energy-equivalent frequency-weighted acceleration [A(8)] and total operating time with vibrating tools. The prevalence of white fingers was 1.1% for the referents and ranged from 9.0% to 51.6% for the vibration-exposed groups. The estimated mean value of A(8) ranged between 1.6 (referents) and 8.3 (quarry drillers) m/s2. After adjustment for age, smoking, and drinking habits, the FSBP% was significantly lower in the vibration-exposed groups than in the reference group. Groupwise, the FSBP%(10 degrees) was inversely related to the prevalence of white fingers, the estimated A(8), and total operating time. With FSBP%(10 degrees) <70% or <60% as the lower normal limit, the sensitivity of the cold test varied from 86% to 100%, with a specificity of 90% to 94%, and a positive predictive value of 68% to 74%. FSBP measurement during cold provocation is a useful laboratory test for white fingers. A quantitative relationship between cold-induced digital arterial hyperresponsiveness and occupational exposure to hand-transmitted vibration was suggested.

Assessment of hand-arm vibration exposure among traffic police motorcyclists

The aims of this study were (1) to evaluate subjective symptoms in the hand-arm system of all traffic police motorcyclists of a city located in the central part of Japan and (2) to assess their hand-arm vibration exposure associated with traffic police motorcycle riding. The study population consisted of 119 motorcycling traffic policemen and 49 male controls. By means of a questionnaire, information on the occupational history and the presence of subjective symptoms in the hand-arm system of all subjects was obtained. Vibration was measured on the handlebars of the representative motorcycles and on the hands of the riders. The 4- and 8-h energy-equivalent frequency-weighted acceleration as well as the lifetime vibration dose were calculated for all police motorcyclists. The prevalence of finger blanching in the traffic police motorcyclists was 4.2%, but none of the controls had this symptom. The rates of finger numbness (19.3%), finger stiffness (16.0%), shoulder pain (13.4%), and shoulder stiffness (45.4%) were significantly higher among police motorcyclists as compared with controls. The root-mean-square (rms) frequency-weighted acceleration on the handlebars of police motorcycles was in the range of 2.2-4.9 m/s2 rms. The computed 4- and 8-h energy-equivalent frequency-weighted acceleration values were 2.8-4.5 and 2.0-3.2 m/s2 rms, respectively. A pattern of increasing percentage prevalence with increasing cumulative vibration dose was noticed. The subjects with a lifetime vibration dose of more than 20.1 m2 h3 s-4 (in scale) showed significantly higher prevalence rates for symptoms in the fingers and shoulders as compared with the control group. As occupational vibration exposure of traffic police motorcyclists might be considered a risk factor for the development of symptoms in the hand-arm system of the riders, its evaluation and control is needed for prevention methodology evolution.

Occupational musculoskeletal disorders in the neck and upper limbs of forestry workers exposed to hand-arm vibration.

An epidemiologic and clinical study of neck and upper limb musculoskeletal disorders was carried out on 65 vibration-exposed forestry operators using chain-saws and 31 comparable control subjects (maintenance workers) performing manual activity and not exposed to vibration. Upper limb function was evaluated by measuring finger and wrist circumference size, maximal hand grip strength and range of motion manoeuvres in both the controls and the exposed workers. Vibration from two chain-saws was measured, and vibration exposure for each forestry worker was assessed in terms of 4 h energy-equivalent frequency-weighted acceleration according to ISO 5349. Job analysis indicated a slight excess risk of upper extremity cumulative trauma disorders (CTDs) in the forestry operators compared with the control workers. After adjustment for age and body constitution, significantly higher prevalence rates of persistent upper limb pain, muscle-tendon syndromes and carpal tunnel syndrome were observed among the forestry workers than among the controls. In the forestry operators, the occurrence of upper limb musculoskeletal disorders increased with increasing vibration exposure. Upper limb function was found to be impaired in the forestry workers compared with the controls. Vibration exposure was significantly related to increased finger circumference size, diminished muscle force and reduced joint function. Even though it is difficult to establish the relative importance of vibration and ergonomic factors in the aetiology of CTDs, nevertheless the results of this study indicate that musculoskeletal impairment to the upper limbs was more severe in the forestry operators than in the controls who did solely manual work. This finding and the observed dose-effect relationships suggest that vibration stress is an important contributor to the development of musculoskeletal disorders in workers using hand-held vibrating tools.

Vibration Exposure, Vibration-Induced White Finger and Digital Arterial Tone in Chain Saw Operators

In a group of 65 Italian forestry operators using chain saws, the overall prevalence of vibration-induced white finger (VWF) was found to be 29.2%. The occurrence of VWF was higher in the chain sawyers who had operated non-antivibration (non-A/V) as well as A/V saws (46.4%) than in those with experience limited to A/V saws (16.2%). The latency time before VWF averaged 9.4 yr (SD 6.8). The mean value of the four-hour energy-equivalent frequency-weighted acceleration [(ah,w)eq(4)] was 7.2 m/s2 (SD 1.2). On the basis of the known VWF prevalence and of [(ah,w)eq(4)], a latent period before VWF of 7.1 yr was expected according to ISO 5349. The measurement of finger systolic pressure (FSP) at 15°C and 10°C by plethysmographic technique showed that the chain sawyers affected with VWF experienced a more intense digital vasospasm than a group of comparable controls and the chain sawyers without VWF. The sensitivity of the method to detect vibration-induced digital arterial hyper-responsiveness to cold was 84.2% and the specificity was 100%. The findings of this study showed a good agreement between the expected and observed latency times before VWF, even though the ISO dose-effect relationship seems to overestimate slightly the risk. The results of the cold test indicated that the measurement of FSP during local cooling is an accurate laboratory method to diagnose objectively Raynaud's phenomenon of occupational origin.