Human response to vibration stress in Japanese workers: lessons from our 35-year studies A narrative review

The occupational uses with vibratory tools or vehicles provoked health disorders of users. We reviewed narratively our articles of 35 yr studies and their related literatures, and considered the pathophysiology of the hand-arm vibration disorders. Concerning the risk factors of health impairments in workers with vibratory tools, there are two conflicting schools of the researchers: The peripheral school emphasizes that vibration only makes predominant impairments on hands and arms, showing typically Raynaud’s phenomenon in the fingers. In the systemic school, the health disorders are produced by combination with vibration, noise and working environment, namely vibratory work itself, leading to diversified symptoms and signs in relation to systemic impairments. Our 35 yr studies have evidently supported the systemic school, including disorders of the central and autonomic nervous systems. The genesis is vibratory work itself, including vibration, noise, cold working environment, ergonomic and biodynamic conditions, and emotional stress in work. Because the health disorders yield in the whole body, the following measures would contribute to the prevention of health impairments: the attenuation of vibration and noise generated form vibratory machines and the regulations on operating tool hours. In conclusion, this occupational disease results from systemic impairments due to long-term occupational work with vibratory tools.     

The diagnosis of disorders caused by hand-transmitted vibration: Southampton Workshop 2000

OBJECTIVES: To identify the current state of knowledge, current uncertainties and future needs related to the diagnosis of disorders associated with the use of vibratory hand-held tools. METHOD: An international workshop was convened with invited experts, medical doctors, scientists and engineers familiar with hand-transmitted vibration and the diagnosis of vascular, neurological and musculoskeletal disorders. This paper records the general conclusions from four panel discussions. RESULTS: For the most common vascular disorder (vibration-induced white finger), the principal symptom and sign involves attacks of well-demarcated finger blanching (Raynaud's phenomenon); low finger systolic blood pressure following cooling is indicative of vibration-induced white finger and zero finger systolic blood pressure can confirm an attack of Raynaud's phenomenon. For neurological disorders, some symptoms can exist without detectable signs and some signs can exist without symptoms; numbness and tingling are commonly reported but neurological changes may be present without these symptoms. The pathogenesis of musculoskeletal disorders in users of vibratory tools is not clear; symptoms may include pain that may not be associated with abnormal results in objective tests. For both neurological and musculoskeletal disorders, a thorough neuromuscular and skeletal examination is required; diagnosis must consider the work history and medical history, the results of physical examination and any objective tests in addition to other factors (e.g. age, smoking, alcohol, systemic disorders, medication and neurotoxic agents) that might have contributed to symptoms, signs and test results. CONCLUSIONS: While vibration-induced white finger is caused by vibration, some neurological and musculoskeletal disorders are the result of work with vibratory tools where the separate roles of vibration, repetitive movements, grip and push forces, non-neutral postures and any other ergonomic stressors are often unclear. Such disorders may be more easily identified as being caused by the work rather than by exposure to hand-transmitted vibration per se. A person found to have developed disorders induced by either vibration or the work situation should not be returned to the same vibration exposure or work without any changes expected to lessen the risks.     

A cross sectional epidemiological survey of shipyard workers exposed to hand-arm vibration.

The hand-arm vibration syndrome, widely known as vibration white finger, is a disorder of nerves and blood vessels that occurs in workers exposed to segmental vibration. A cross sectional symptom survey was performed on a sample of workers employed by a large shipyard in the north eastern United States. Random samples were drawn from departments composed of full time dedicated pneumatic grinders, workers with part time exposure to vibration, and other workers not exposed to vibratory tools. Of the 375 workers sampled, 79% responded. The prevalence of white finger symptoms was 71%, 33%, and 6% among the three exposure groups respectively. Similarly, the prevalence of numbness and tingling in the hands and fingers in the three exposure groups was 84%, 50%, and 17%. Workers were classified according to the Stockholm Workshop staging systems for vascular and sensorineural symptom severity. Exposure-response analyses of both vascular and sensorineural stage showed monotonically increasing prevalence of higher disease stages with increasing duration of exposure. Logistic regression analysis, performed to control for potential confounding factors including age and current smoking state, produced highly significant (p less than 0.001) associations between cumulative duration of exposure and prevalence of symptoms. In these analyses smoking state was significantly related to vascular and sensorineural symptoms and age was not. Average latency to onset of symptoms was less than five years of full time equivalent work with vibratory tools. Logistic regression analyses were performed to assess the effect of use of particular work practices on reported symptoms. Further study of this workforce with objective, quantitative measures of peripheral neurological and vascular function is required to characterise the clinical and subclinical effects of vibration exposure.     

A cross sectional epidemiological survey of shipyard workers exposed to hand-arm vibration.

The hand-arm vibration syndrome, widely known as vibration white finger, is a disorder of nerves and blood vessels that occurs in workers exposed to segmental vibration. A cross sectional symptom survey was performed on a sample of workers employed by a large shipyard in the north eastern United States. Random samples were drawn from departments composed of full time dedicated pneumatic grinders, workers with part time exposure to vibration, and other workers not exposed to vibratory tools. Of the 375 workers sampled, 79% responded. The prevalence of white finger symptoms was 71%, 33%, and 6% among the three exposure groups respectively. Similarly, the prevalence of numbness and tingling in the hands and fingers in the three exposure groups was 84%, 50%, and 17%. Workers were classified according to the Stockholm Workshop staging systems for vascular and sensorineural symptom severity. Exposure-response analyses of both vascular and sensorineural stage showed monotonically increasing prevalence of higher disease stages with increasing duration of exposure. Logistic regression analysis, performed to control for potential confounding factors including age and current smoking state, produced highly significant (p less than 0.001) associations between cumulative duration of exposure and prevalence of symptoms. In these analyses smoking state was significantly related to vascular and sensorineural symptoms and age was not. Average latency to onset of symptoms was less than five years of full time equivalent work with vibratory tools. Logistic regression analyses were performed to assess the effect of use of particular work practices on reported symptoms. Further study of this workforce with objective, quantitative measures of peripheral neurological and vascular function is required to characterise the clinical and subclinical effects of vibration exposure.     

Quantitative exposure assessment for shipyard workers exposed to hand-transmitted vibration from a variety of vibration tools

The quantitative exposure to vibration for shipyard workers who have used several kinds of vibratory tools was studied. The dose-response relationship between lifetime exposure dose and hand-arm vibration syndrome also was studied. The study included 344 workers who were exposed to vibration in one shipyard and 53 unexposed workers in the same company. Vibration measurements were made on several vibratory tools according to the international standard, ISO 5349. The actual exposure times for the vibratory tools were measured. Questionnaires for demographics, exposure to vibration, and confounding factors were completed. A lifetime vibration dose was calculated for each worker using job categories, usage pattern of vibratory tools, and the measured vibration acceleration magnitude. Each worker was asked about vascular and neurological symptoms, and symptoms were classified according to the Stockholm workshop scale. The prevalence of vascular and sensorineural symptoms for workers exposed to vibration was 22.7 and 78.2%, which were significantly higher than 0 and 34.0% obtained in the nonexposed workers, respectively. The prevalence and severity of the hand-arm vibration syndrome was increased with an increased lifetime vibration dose. The lifetime vibration dose showed a significant association with both vascular and sensorineural symptoms. In conclusion, the lifetime vibration dose was a useful parameter for quantitative exposure assessment and showed a dose-response relationship between exposure and symptoms when adjusted for confounding factors.     

Quantitative estimation of aesthesiometric thresholds for assessing impaired tactile sensation in workers exposed to vibration

Summary To evaluate the usefulness of aesthesiometric threshold testing in the quantitative assessment of peripheral sensorineural disorders occurring in the hand-arm vibration syndrome, two point discrimination (TPD) and depth sense perception (DSP) thresholds were measured by means of two aesthesiometers in the fingertips of 65 forestry workers exposed to chain saw vibration and 91 healthy males unexposed to local vibration or neurotoxic chemicals. Among the healthy subjects, divided into three age groups, there was no difference in the mean values of TPD and DSP thresholds. Assuming 1.28 or 2 standard deviations above the mean to be the upper limits of normality, in the present study the threshold values for TPD were 2.5 and 3.13 mm, respectively. Using the same assumptions, the normal threshold values for DSP were 0.36 and 0.49 mm. Among the 65 chain saw operators the prevalence of peripheral sensory disturbances was 70.8%. On the basis of the aesthesiometric results obtained for the group of 46 chain sawyers affected with sensorineural symptoms and a control group of 46 manual workers, the specificity of the aesthesiometric testing method was found to range between 93.4 and 100%, while the sensitivity varied from 52.2 to 71.7%. In its predictive value aesthesiometry had a positive accuracy of 84.6–96.0% and a negative accuracy of 42.8–50.0%. Aesthesiometric testing was able to differentiate between normals and vibration workers with sensory disturbances on a group basis (P < 0.001), but due to the high rate of false negatives among vibration exposed patients, it was unsuitable to confirm objectively sensorineural symptoms on an individual basis. We conclude that aesthesiometry may be used in field surveys for epidemiological purposes to assess peripheral sensory disorders in exposed groups at risk.     

人体指端振动觉感觉阈值及其对局部振动病诊断意义的研究

使用丹麦BK振动测量仪器,对60名健康人和97名局部振动病患者的中指指端振动觉阈值进行了测试。振动刺激频率为8、16、31.5、63、125、250、500、1000Hz。结果表明,正常人振动觉阈值与性别和手别无关。在8～250Hz范围内,正常人的振动觉阈值曲线比较平坦。在125Hz处,正常人振动觉最敏感,振动病患者振动觉阈值明显降低。振动觉阈值测定对手臂振动病具有早期诊断意义。推荐右手中指振动觉阈值正常值上限作为局部振动病的一个早期辅助性诊断标准。     

Carbon-dioxide Thermo-saline Springs in the Light of Modern Research

Investigations on the influence of natural Nauheim standing and running effervescent CO₂ thermo-saline baths on the subcutaneous CO₂ and O₂ tension in gas under the skin in rabbits showed a decrease of the CO₂ tension in all experiments. The O₂ tension increased in 50 per cent. of the experiments, in the others it remained unaffected. The results are interpreted as due to an increase in ventilation and an increase in peripheral blood-flow, the peripheral blood-vessels being dilated. Plain water baths of the same temperature and duration did not show this effect on the peripheral circulation, both CO₂ and O₂ tension being decreased after the bath. The relations between these researches and other investigations on the effect of natural thermo-saline baths are discussed as well as the difference between the effect of natural and artificial baths. The special curative properties of fresh natural mineral springs are in some way connected with the composition of the salts as complex compounds and their molecular structure. These complex compounds being decomposed by heat, light or access of air, the special activity is lost. The presence of the salts as complex compounds in fresh natural mineral springs is supposed to be due to the special geological conditions under which these compounds are formed.     

Hand-arm vibration syndrome and upper limb disorders associated with forestry work

BACKGROUND: Occupational exposure to hand-transmitted vibration in forestry workers is associated with an increased risk for vascular, neurological and musculo-skeletal disorders of the upper limbs. OBJECTIVES: To carry out a cross-sectional study of the hand-arm vibration syndrome and soft-tissue disorders of the upper limb in a group of forestry workers employed in the Forestry Service of the Province of Trento (Italy). In the forestry worker group, usage of anti-vibration chain-saws was intermittent over a typical work year (16 weeks/yr, on average). METHODS: To investigate vascular, neurological and musculo-skeletal disorders of the upper limbs, the forestry workers (n=159) and a control group of manual workers, unexposed to hand-transmitted vibration, employed in the same Forestry Service (n=146) underwent a structured medical interview and a complete physical examination. The clinical diagnoses of vibration-induced white finger (VWF) and carpal tunnel syndrome were made according to internationally recognised consensus criteria. Occupational exposure to hand-transmitted vibration was assessed according to the recommendations of the International Standard ISO 5349-1 (2001). RESULTS: The forestry workers showed an increased prevalence of peripheral sensory-neural disturbances (33.3%), musculo-skeletal disorders of the upper limbs (37.7%), and carpal tunnel syndrome (21.4%) compared to those observed in the control group. There was no significant difference in the prevalence ofRaynaud' sphenomenon between the forestry workers (6.3%) and the controls (4.1%). After adjustment for confounding factors (age, body mass index, tobacco and alcohol consumption), a significant association was observed between peripheral neuropathies (peripheral sensory-neural disorders, carpal tunnel syndrome) and several indices of vibration exposure such as 8-hr energy-equivalent frequency-weighted acceleration [A(8) in m/s2 r.m.s.], duration of exposure (years), and lifetime vibration dose (m2/s4 hr). An excess, although not significant, risk for VWF was observed only in the forestry workers with A(8) > or = 4 m/s2 r.m.s.. In the forestry workers, there was no significant association between VWF and sensory-neural disorders, and between VWF and carpal tunnel syndrome. This finding seems to support the hypothesis that the vascular and neurological components of the hand-arm vibration syndrome develop independently of each other. Within the forestry worker group, the variable "years of tool usage" showed the strongest association with peripheral sensory-neural symptoms, carpal tunnel syndrome, and soft-tissue disorders of the upper limbs. It is likely that in the forestry workers the variable "years of tool usage" represents an overall index of duration of exposure to several adverse ergonomic and mechanical risk factors. CONCLUSIONS: The results of this study suggest a tendency for a decrease in the occurrence of VWF among forestry workers, and this finding seems to be associated with the use of anti-vibration chain saws, the reduction of exposure duration, and the improvement of work organization. On the other hand, the forestry workers showed an increase in the occurrence of peripheral sensory neuropathies, carpal tunnel syndrome, and upper-extremity musculo-skeletal disorders. This finding seems to support the view that there is epidemiological evidence for a positive association between exposure to a combination of risk factors (segmental vibration, forcefulness, awkward posture) and the occurrence of soft-tissue disorders of the upper limb in working populations.     

Scleroderma and occupational exposure to hand-transmitted vibration

OBJECTIVES: To determine whether occupational exposure to hand-transmitted vibration is a risk factor for scleroderma (systemic sclerosis, SSc), two case-control studies were conducted in the provinces of Trento and Verona, northeastern Italy. METHODS: In the Trento study, 21 patients with a diagnosis of either systemic or localised scleroderma were recruited from those admitted to all hospitals of the province from 1 January 1976 to 31 December 1991. For each case, two age- and gender-matched controls were selected. In the Verona study, cases included 55 patients diagnosed with SSc and clinically followed at the rheumatology clinic of the local university hospital between 1 January 1997 and 30 June 1999. The controls included 171 subjects frequency-matched by gender and age group. In both studies, all subjects were interviewed by structured questionnaire containing items on personal characteristics, smoking and drinking habits, use of medicines, occupational history and complete medical history. Women were also investigated about silicone implants and cosmetic surgery. Jobs and job tasks involving the use of vibratory tools, with or without concomitant exposure to silica dust in mining and non-mining occupations, were carefully investigated. A minimum criterion of 6 months was required for exposure duration. RESULTS: In the Trento study, men with scleroderma were more likely than controls to have had exposure to hand-transmitted vibration (odds ratio (OR) 1.5, 95% confidence interval (95% CI) 0.1-74.1) or silica dust (OR 5.2, 95% Cl 0.5-74.1), but the association was not significant. The scleroderma patients were miners or stone workers who had operated jackhammers and rock drills. In the Verona study, a greater, although not statistically significant, odds of SSc was observed in men exposed to hand-transmitted vibration (OR 2.4, 95% CI 0.4-14.0) and in women exposed to silica (OR 2.4, 95% Cl 0.4-15.5). The SSc patients with vibration exposure were machinery operators or metal workers who had used grinders and impact wrenches. CONCLUSIONS: Our case-control studies did not show a significant association between scleroderma and hand-transmitted vibration, with or without concomitant exposure to silica dust. Owing to the rarity of the disease and the small number of cases in the present studies, a genetic susceptibility to connective tissue disorders in SSc patients with occupational exposure to hand-transmitted vibration and/or silica cannot be ruled out.     

A study on the contribution of body vibrations to the vibratory sensation induced by high-level, complex low-frequency noise

To investigate the contribution of body vibrations to the vibratory sensation induced by high-level, complex low-frequency noise, we conducted two experiments. In Experiment 1, eight male subjects were exposed to seven types of low-frequency noise stimuli: two pure tones [a 31.5-Hz, 100-dB(SPL) tone and a 50-Hz, 100-dB(SPL) tone] and five complex noises composed of the pure tones. For the complex noise stimuli, the sound pressure level of one tonal component was 100 dB(SPL) and that of another one was either 90, 95, or 100 dB(SPL). Vibration induced on the body surface was measured at five locations, and the correlation with the subjective rating of the vibratory sensation at each site of measurement was examined. In Experiment 2, the correlation between the body surface vibration and the vibratory sensation was similarly examined using seven types of noise stimuli composed of a 25-Hz tone and a 50-Hz tone. In both the experiments, we found that at the chest and the abdomen, the rating of the vibratory sensation was in close correlation with the vibration acceleration level (VAL) of the body surface vibration measured at each corresponding location. This was consistent with our previous results and suggested that at the trunk of the body (the chest and the abdomen), the mechanoreception of body vibrations plays an important role in the experience of the vibratory sensation in persons exposed to high-level low-frequency noise. At the head, however, no close correlation was found between the rating of the vibratory sensation and the VAL of body surface vibration. This suggested that at the head, the perceptual mechanisms of vibration induced by high-level low-frequency noise were different from those in the trunk of the body.     

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

Objectives: 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. Methods: All female workers underwent a medical interview and a complete physical investigation. The clinical diagnoses of Raynauds 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. Results: There was no significant difference in the prevalence of Raynauds 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. Conclusions: 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.     

Outcome of the abduction external rotation test among manual and office workers

Reactions during the Abduction External Rotation (AER) test were studied among 71 platers and 70 assemblers exposed to vibratory tools and manual work and 45 unexposed white collar workers. The frequency of positive neurological reactions was 31% among the platers, 6% among the assemblers, and 16% among the white collar workers. Platers reported the highest fatigue rates in the shoulder regions during the test. A positive association was noted between a pathological AER test and current problems in the neck/scapula or shoulder/upper arm regions, day- or night-time numbness in the hands, tension neck, and carpal tunnel syndrome. Age, length of daily vibration exposure, and vibration acceleration level were also positively associated with a positive AER test outcome. The results indicate that the outcome of the AER test is sensitive to neck and shoulder disorders but also, to some extent, to the carpal tunnel syndrome.     

颈椎保健理疗仪的研制

本文介绍了一种适合治疗各种类型颈椎病的颈椎保健理疗仪。它是由颈椎按摩装置、热疗装置和颈椎牵引装置构成。治疗颈椎病时,先利用颈椎按摩、热疗装置对颈部进行揉捏推拿、振动按摩、热疗;然后利用牵引装置对椎间小关节紊乱、椎间隙狭窄（椎间盘病变）等疾病进行牵引治疗。     

Elbow joint disorders in relation to vibration exposure and age in stone quarry workers

Summary Elbow joint disorders were studied in relation to vibration exposure and age in 74 male stone quarry workers who operated mainly chipping hammers and sometimes rock drills. They were examined for range of active motion in elbow extension and flexion, and by means of radiographs of the elbow joint. Effects of age and vibratory tool operation on the elbow joint were statistically estimated using multiple regression analysis. In the analysis of all subjects, including those aged over 60 years, age was significantly related to the range of motion in extension and to radiographic changes in both elbows, and the duration of vibratory tool operation was associated with the range of right elbow flexion. Among subjects under the age of 60 years, duration of vibratory tool operation showed a significant dose-effect relationship to the range of flexion and radiographic changes in the right elbow, but there was no significant relationship with age. The present results suggest that the operation of chipping hammers and rock drills contributes to elbow joint disordes or osteoarthrosis, even when the effect of age is taken into account. Besides vibration exposure, it may be necessary to consider various loads on the elbow joint such as firmly grasping and pressing the tool against stones with the arm bent at about 90°, and carrying stones.     

Vascular and nerve disorders at exposure to hand-held vibrating tools related to ISO 5349.

The authors present the results of the investigation of peripheral nerves of the hand in a group of 30 glass cutters, 21 metal grinders, 10 blacksmiths and 24 workers who worked with nailers. The measurements of vibrotactile sensitivity were carried out by Vibrometry System Brüel & Kjaer Type 9627. The vibrotactile perception thresholds (VPT) were measured in frequency range from 8 to 500 Hz. The same investigations were carried out in 103 healthy subjects with no previous work-exposure to vibration or shocks. Further electromyographic examination was carried out in all members of exposed groups. The results of measurements VPT have proved reliability and high sensitivity of this method for the early detection of light disorders of peripheral nerves of the hand due to vibration. All the workers also passed investigation of vascular system of fingers. Simultaneously the measurement of vibration and shocks of single types of hand-held tools used by workers was done. The results of measurement have been worked up according to ISO 5349 (1) that enables to determine the beginning of the incidence of disorders of the hands and arms on the base of measured values of vibration and shocks. The results of the vascular system investigation have been compared with the results of the assessment of exposure according to ISO 5349. The conformity has been proved in the case of hand-transmitted vibrations not in the case of shocks.     

卡托普利对接触振动家兔血管内皮活性物质的影响

目的探讨小剂量卡托普利对接触振动家兔血管内皮活性物质的影响及其意义。方法将家兔分为接振对照组、实验组和无接振对照组,实验组与接振对照组分别进行强度10m/s2的接触振动实验。实验组在第11天起给予小剂量卡托普利。于接触振动前、接触振动后10d、20d、30d对各组家兔进行血浆内皮素(ET)和一氧化氮(NO)浓度的测定与分析。结果与接触振动前比较,接触振动20d、30d接振对照组血浆NO浓度显著下降(P<0.01)、ET浓度显著升高;实验组、无接振对照组在接触振动前后血浆NO、ET浓度差异无显著性。结论小剂量卡托普利可通过影响血管内皮活性物质,对接触振动家兔外周血管功能产生一定的保护作用。     

大庆油田钻井工人主要职业病危害因素的调查

目的将传统工艺引起的局部振动与现代化技术引起的噪声2种职业病危害因素进行比对,研究哪种职业病危害因素现今对大庆油田钻井工人健康损害最大,有利于重新分析钻井工人所接触的职业病危害因素,以保护劳动者的利益、防治职业病的发生。方法选工龄2a以上的980名钻井男工为调查对象,平均年龄（30±5）岁,在进行职业健康检查时,按局部振动所规定的体检项目再加上电测听检查,结合现场检测数据,将检查结果进行分析比对。结果钻井工人听力下降人数为80人,占8．16％;振动觉和痛觉改变13人,占1．33％。听力下降检出率明显高于手部末梢循环和（或）手臂神经功能改变检出率。结论噪声比振动对钻井工人的危害大。     

The temporary threshold shift of vibratory sensation induced by composite-band vibration exposure

Eight healthy subjects were exposed to three 1/3 octave-band vibrations (63, 200, and 500 Hz) by hand clasping a vibrated handle in a soundproof and thermoregulated room. The vibratory sensation threshold at 125 Hz was measured before and after the vibration exposure at an exposed fingertip. According to a preceding study, we first determined the relationship between the acceleration of the vibration and the temporary threshold shift of vibratory sensation immediately after the vibratory exposure (TTS_{v, 0}) induced by 1/3 octave-band vibration. We then measured TTS_v after the exposure to a composite vibration composed of two 1/3 octave-band vibrations that might induce an equal magnitude of TTS_{v, 0} on the basis of the above relationship. The TTS_{v, 0} induced by the composite vibration was not larger than the TTS_{v, 0} induced by the component vibrations. This result suggests that the component of the vibration inducing the largest TTS_{v, 0} determines the TTS_{v, 0} by broad-band random vibration.     

Seasonal variation of circulatory and sensory functions during immersion test in cold water

For early diagnosis of vibration syndrome, peripheral circulation and sensory tests after cold water immersion of the upper extremities are being performed widely in Japan. The authors studied the seasonal effect on the immersion test and its influence on diagnosis of vibration syndrome. Eight healthy male subjects, aged from 28 to 39, were examined. The immersion tests were conducted in winter (February), spring (May), summer (August) and autumn (November) in Ube city, Japan (Table 1). The room temperatures were maintained at 10 degrees C, 20 degrees C and 30 degrees C during the tests at each season. As to the exposure-to-cold test, the left hand of subject was immersed in stirred water at 10 degrees C for ten minutes, and the changes of peripheral circulatory function and sensory function were measured. Peripheral circulatory function was assessed by the skin temperature of middle finger and the value of the nail press test on the index finger. Sensory function was assessed by 125 Hz vibratory sense threshold and pain threshold of the middle finger. The finger skin temperature was lower in autumn and winter, followed by spring, and highest in summer. In particular, the finger skin temperature in autumn was lower than that in winter at the condition of room temperature at 30 degrees C, which is considered to be less effected by heat content in the body (Fig. 1, Table 3). The frequency of the appearance of cold induced vasodilation was also lower in autumn than that in winter (Table 2). These findings suggest that the tonus of the vasoconstrictor in the skin vessels of finger is strongest in autumn, followed by winter. It is also suggested that the tonus remains slightly strong in spring and is weakest in summer. Furthermore, the seasonal variations in the value of the nail press test, vibratory sense threshold and pain threshold were observed at some points of measuring time during immersion test (Figs. 2-4). Of these, the variations in the value of the nail press test and vibratory sense threshold were considered to be secondary to the seasonal variation of peripheral circulatory function (Fig.6). The variation in pain threshold was considered to result from paresthesia developing in the lower room temperature at 10 degrees C. The pain of finger during immersion test was also effected by season but the range of variation was not significant (Fig.5).(ABSTRACT TRUNCATED AT 400 WORDS)