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PubMed1988

[Effects of local vibration exposure on whole blood viscosity in rats].

To investigate the relationship between vibration hazards and blood viscosity, vibration exposure experiments were conducted. The rat's hind limbs were continuously exposed to local vibration (60 Hz, 5 G) for 4 h. The exposed group showed a slightly lower blood viscosity and plasma fibrinogen in the blood obtained immediately after exposure when compared with the control group. However, in the blood obtained 18 h after exposure, there was no significant difference in the levels of whole blood viscosity and plasma fibrinogen between the exposed group and the control group. Hematocrit was not affected by this exposure. These results indicate that the decrease in the levels of whole blood viscosity induced by local vibration exposure is transient and that some relationship exists between changes of whole blood viscosity and those of plasma fibrinogen.

Animals↗
PubMed1989

The improvement of systolic function of depressed left ventricle by external vibration at diastole.

The left ventricular (LV) incomplete relaxation (IR) has been reported to play an important role in the pathophysiology of the congestive heart failure such as causing higher diastolic pressure and/or impeding the coronary perfusion during diastole. Therefore, using open chest canine preparations (n = 4), we examined 1) whether the minute external vibration during diastole could release IR and 2) what occurred to LV systolic function in this perturbation. LV failure with IR was induced by propranolol administration and, if necessary, by rapid atrial pacing up to 180 beats/min. When we applied a 50 Hz, sinusoidal vibration of 2.1 mm magnitude during diastole to the epicardium of LV with complete relaxation, there was no significant change in the ventricular function. However, the systolic functional improvement (3.8 +/- 1.1 mmHg elevation in LV systolic pressure) was observed when the vibration was applied to LV with IR. We concluded that external vibration at diastole could release IR and would be useful to improve the systolic function of the depressed heart with IR.

Animals↗
PubMed2005

Firmness evaluation of melon using its vibration characteristic and finite element analysis.

The "Huang gua" melons were measured for their physical properties including firmness and static elastic modulus. The vibrational characteristics of fruits and vegetables are governed by their elastic modulus (firmness), mass, and geometry. Therefore, it is possible to evaluate firmness of fruits and vegetables based on their vibrational characteristics. Analysis of the vibration responses of a fruit is suggested for measuring elastic properties (Firmness) non-destructively. The impulse response method is often used to measure firmness of fruits. The fruit was excited using three types of balls (wooden, steel and rubber) and the vibration is detected by an accelerometer. The Instron device was used to measure the static elastic modulus of the inner, middle and outer portions of melon flesh. Finite element (FE) technique was used to determine the optimum excitation location of the chosen measurement sensor and to analyze the mode shape fruits. Four types of mode shapes (torsional or flexural mode shape, first-type, second-type spherical mode and breathing mode shape) were found. Finite element simulation results agreed well with experimental results. Correlation between the firmness and resonant frequency (r2=0.91) and between the resonant frequency and stiffness factor (r2=0.74) existed. The optimum location and suitable direction for excitation and response measurement on the fruit were suggested.

Cucurbitaceae↗
PubMed1985

A pressor response to vibration in conscious rats.

Cardiovascular response in an alerted state induced by vibration was studied in conscious rats by giving a to-and-fro movement to their cages for 30 sec. Cardiac output, superior mesenteric flow, and hindquarter flow were observed with chronically implanted electromagnetic flow probes and arterial pressure with an indwelling catheter. Arterial pressure, heart rate, cardiac output and hindquarter flow increased and superior mesenteric flow decreased with vibration. The increase in heart rate was still present after adrenalectomy, but was abolished by beta-adrenoceptor blockade propranolol. The increase in hindquarter flow was greatly diminished by propranolol or after adrenalectomy, but was still present in adrenalectomized rats after alpha-adrenoceptor blockade phentolamine. The decrease in superior mesenteric flow in vibration was abolished by phentolamine. It was diminished by adrenalectomy. These findings indicate that the cardiovascular response to vibration includes excitation of the cardiac sympathetic nerves, adrenomedullary secretion, and excitation of sympathetic vasoconstrictor fibers and exercise hyperemia in skeletal muscles.

Animals↗
PubMed1994

Effects of upper limb muscle vibration on human voluntary wrist flexion-extension movements.

The effect of upper limb muscle tendon vibration during alternating step flexion-extension movements about the wrist was studied in 6 normal humans. A vibrator was mounted over either the wrist flexor muscle or the elbow flexor and extensor muscles. Vibration was applied either to a single muscle or simultaneously to both muscles during wrist flexion-extension movements. After a period of practice, subjects learned the required movements and were able to make them with their eyes closed. Simultaneous application of subthreshold vibration to the wrist flexor and the elbow extensor or flexor muscles during extension movements produced an undershooting of the required end-movement position. The observed results indicated the pattern of transjoint projections from elbow extensor and flexor muscles to motoneurons supplying wrist extensor and flexor muscles. It is also suggested that those transjoint projections play an important role in coordinated movement of wrist and elbow joints.

Adult↗
PubMed1990

Validity of function tests on the upper extremities in establishing a prognosis in vibration syndrome.

The validity of function tests on the upper extremities as prognostic tools in vibration syndrome was evaluated over a sequence of observation periods. The subjects examined were 672 forest workers using chain saws who had had some complaints and who had shown abnormal findings in the function tests. The function tests consisted of peripheral circulatory and sensory tests, including cold provocation and motor tests of functional capacity in the upper extremities. From the results of testing, 23 variables were selected and examined by multivariate analysis. The four principal components were extracted by principal component analysis, and the factor score of the peripheral circulatory disturbances component was found to be highly correlated with the severity of VWF (Vibration-induced White Finger). The course of VWF and the nail compression test had high standard regression coefficients with the severity of vibration syndrome. The course of finger numbness, pinching power, pain threshold, skin temperature and X-ray findings in the elbow joints had high discriminant function values for the evaluation of the severity of vibration syndrome.

Discriminant Analysis↗
PubMed1997

Influence of local vibration on finger functions of forest workers.

We physically examined of forest workers in the northern part of Fukushima District, Japan. The main purpose of this study was to survey the state of finger functions, especially the differences between the functions of right and left fingers of forest workers. This physical examination was conducted in winter. The items of the physical examination were hand grip strength, finger skin temperature, vibration sensation threshold, nail pressure test of the finger. Subjects were classified into A and B groups on the base of the results of the physical examination. A group is normal or slight disorder, and B group is disorder or illness. Hand grip strength was measured five times at five-second intervals. The decrease ratio of the left hand grip strength was greater than that of the right hand grip strength. Although there were significant differences among each finger of A and B groups, there were no big differences in the skin temperatures of the fingers in each group. Vibration sensation threshold was measured for II, III and IV fingers. The vibration sensation threshold of the index finger was the most sensitive and that of IV finger was the least sensitive. The vibration sensation threshold of the right fingers was more sensitive than that of the left fingers. The reaction times of the nail pressure test of the right fingers were generally faster than those of the left fingers. Forestry workers in Japan become elderly. There are big differences among the physical reactions or strengths of elderly people. Standard values for the measuring items for ageing are needed.

Adult↗
PubMed1998

Whole-body vibration and health effects in the agricultural machinery drivers.

Recently farm mechanization has been widespread and developing rapidly, in particular riding farm machines are increasingly used in paddy fields in Japan. We have no information available on the actual situation regarding whole-body vibration on the seats of these farm machines from the standpoint of labour protection. Measurement and evaluation of whole-body vibration was performed on the seats of popular riding agricultural machineries. Whole-body vibration on the seats of combine harvesters and wheel tractors exceeded exposure limits and the fatigue-decreased proficiency boundary limit of 8 hr and also shortened the reduced comfort boundary limits of ISO 2631 (1985). Some combines, tractors and carieers had only less than one hour exposure duration as compared with the ISO 2631-1 standard (1997). On the other hand a questionnaire was also performed on the subject of agricultural machine operators. Any specific injury or other effects, i.e. low back injuries were not found among the group of operators as compared with those in non-operator farmers. It seems to be difficult to find out the health effects of whole-body vibration itself, because there may be a lot of causes, i.e. working posture, operating heavy materials, in farm working conditions.

Adult↗
PubMed1998

Affected segments of the median nerve detected by fractionated nerve conduction measurement in vibration-induced neuropathy.

Peripheral neuropathy in the hand has often been reported in workers using hand-held vibrating tools. But the affected location in the hand is not clearly demonstrated. To elucidate the impaired segment of the median nerve within the hand, fractionated median sensory nerve conduction velocity (SCV) was measured in the digital, finger-to-palm, palm-to-wrist and wrist-to-elbow segments. Subjects were 56 patients with hand-arm vibration syndrome and 43 healthy controls of similar age. SCV in the digital and the wrist-to-palm segments was significantly slower in the patients than the controls. Slowed SCV in the digital segment was encountered in 36% of the patients, while the slowing in SCV in the wrist-to-palm segment (across the carpal tunnel) was found in 20% of them. The slowing in the digital segment was more frequently encountered in the advanced stage of the Stockholm sensorineural (SN) stage for hand-arm vibration syndrome: 10% in 0SN (no neurological symptoms) while 56% in 3SN (severe stage). The present study has demonstrated that vibration-induced nerve impairments dominantly exist both in the digits and across the carpal tunnel. Careful neurophysiological assessment is important to confirm the impaired location within the hand.

Adult↗
PubMed1998

Health surveillance of forestry workers exposed to hand-arm vibration in Wakayama from 1974 to 1996.

To clarify the trends in the number and the severity of vibration syndrome in Wakayama for these 23 years, the records of the medical examinations for vibration syndrome were analyzed with 4,652 (a total of 9,920) private forestry workers exposed to hand-arm vibration. The number of the subjects who took the medical examinations reached a maximum of 1,242 in 1978. After that, it decreased year by year, but remained at about 300 or less from 1988. There was a corresponding increase in age and the number of years of operating chain saws among the subjects examined. The compensated cases reached a maximum number of 393 cases in 1977, and then a drastic decrease was noted. Year by year there was an increase in the number of cases whose medical examinations revealed no abnormality. The regional occupational health care system including the surveillance card, which has been active since 1975, has probably contributed to the decrease or prevention of occurrence of vibration syndrome in Wakayama.

Adult↗
PubMed1998

Finger skin temperature and laser-Doppler finger blood flow in subjects exposed to hand-arm vibration.

OBJECTIVES: This study was aimed to assess the peripheral circulatory functions of forestry workers exposed to hand-arm vibration, using simultaneous measurements of finger skin temperature (FST) and finger blood flow (FBF). METHODS: The subjects were five men with vibration-induced white finger (VWF), four subjects with numbness in their hands and five exposed controls without any signs or symptoms related to vibration syndrome. Simultaneous measurements of FST and laser-Doppler FBF were performed before, during and following a 10-min recovery period after the hand was immersed in cold water (10 degrees C, 10 min). Partitional measurements of finger blood flows could be made between the capillaries and deeply located vessels using two laser-Doppler flow probes having narrower and wider optic fiber separations. RESULTS: The FST as well as the FBF of the capillary and deeply located vessels during and following the cold immersion test in those with VWF and in the subjects with numbness had a slight increase immediately following the cold immersion and no tendency to be augmented as the time span increased. After the cold immersion test, the control group had significantly greater FST and FBF compared to other groups. Particularly, from the 5th to the 10th min after the cold provocation, the values of FBF of the deeply located vessels in those with VWF were significantly lower than the controls. During the course of observation, the FST had significantly linear relationship with the recorded capillary and deep FBF values, and that was much closely correlated with the deep FBF (i.e., P < 0.01 in each selected condition). The slope of the regression lines in the capillary were steeper and shallow in the deep FBF. CONCLUSIONS: In addition to the measurement of capillary FBF, more detailed and accurate information on the peripheral circulatory functions of vibration-exposed subjects can be obtained by including the assessment of the deep FBF.

Aged↗
PubMed1998

Prediction of TTS for hand intermittent vibration.

Temporary Threshold Shift (TTS) is often used as an indicator of the effect of hand-transmitted vibration on the human body. An experiment for the prediction of TTS in exposure to intermittent vibration was conducted in the present study to examine the exposure equivalent rule, as well as the equations for growth and recovery TTS. It was found that the prediction of TTS obtained here was in good agreement with measured TTS. This estimation procedure for predicting TTS was compared with the notification of the Labor Ministry in Japan, in which control of the operation time and the rest time for hand-vibrating tools was described. The results suggest that the rest time of five minutes for a continuous exposure time of 30 minutes with low-level of vibration tools should be extended to 10 minutes of rest time.

Adult↗
PubMed2002

A study of the hand-arm vibration syndrome in Okinawa, a subtropical area of Japan.

The purpose of this study was to understand the peculiarity of the development of Hand-Arm Vibration Syndrome (HAVS) in a subtropical area of Japan. We analyzed the medical records of 21 subjects reported by the Okinawa Labor Bureau, and tried to determine whether the warm environment has any effect on the severity of HAVS. The mean operating time of vibration tools for all the subjects was over 10,000 hrs. Almost all the subjects from Okinawa had been working only in Okinawa. The presence of Vibration Induced White Fingers (VWF) was markedly smaller in the subjects from Okinawa as compared to those from other prefectures. The results of Cold Water Immersion Tests were similar for all subjects. Ten minutes after the Cold Water Immersion Test, the mean finger skin temperature was about 19 degrees C in all subjects. These findings suggest that not only the operating time of vibration tools but also the warm environment might have an effect on the severity of HAVS. However, the number of subjects in our study was very small. There is the need therefore for further investigations with a larger number of subjects.

Arm↗
PubMed2004

Effect of supplemental tryptophan, vitamin E, and a herbal product on responses by pigs to vibration.

Economic losses related to increased stress during the transport of pigs are well documented. The effects of supplementing of tryptophan (Trp), vitamin E, or a herbal product via feed or drinking water were investigated in terms of effects on stress response in pigs during transport simulation. The study consisted of three analogous experiments. For the testing in each experiment, the pigs (23.5+/-3.2 kg) were allocated to one of two treatments, with and without supplementation of a product. The applied doses were Trp (5 g/L drinking water for 3 d), vitamin E (additional amount of 300 mg/kg feed for 21 d, as-fed basis), and Sedafit (2.5 g/L drinking water for 2 d). Sedafit is a commercial herbal product containing Valeriana officinalis L. and Passiflora incarnata L. as active components. In each experiment of the study, at least 47 pigs were involved, which were treated in groups of 3. The day before transport simulation, a Holter device was attached to the pigs to produce an electrocardiogram during the night (rest values), as well as during vibration in the transport simulator (1.2 Hz, 1 m/s2), where the behavior of the pigs (standing-sitting-lying) was also observed. Samples of saliva (taken before, during, and after [3x] vibration) and blood (taken before and after vibration) were analyzed for cortisol and intermediate metabolites (glucose, lactate, creatine kinase, and nonesterified fatty acids), respectively. Pigs supplemented with Trp tended to spend more time lying down during the second hour of vibration (P < 0.05). Vitamin E decreased the peak heart rate (P < 0.05), ventricular ectopic beats (P < 0.01), and ST elevation (P < 0.10). The supplementation of Sedafit resulted in smaller increases of the investigated heart variables (minimum heart rate, P < 0.05; ventricular ectopic beats, P < 0.05; ST elevation, P < 0.01) during and after stress evocation compared with the control group. None of the tested products influenced the intermediate metabolites; one possible explanation for this finding may be that peak values were reached before the time of bleeding. In conclusion, Trp had a positive behavioral effect in this experiment, and vitamin E and Sedafit mediated an increase in some heart variables, suggesting sedative and antianxiety effects.

Animals↗
PubMed1990

Cardiovascular reflexes in workers exposed to hand-arm vibration.

In the present study autonomic function was observed by measuring cardiovascular reflexes. The quiet breathing test, the deep breathing test and the Valsalva manoeuvre were used. The aim was to study the effects of long-term exposure to hand-arm vibration on the cardiovascular reflexes. The study group included 47 workers (lumberjacks and railroad workers) who were exposed to hand-arm vibration. 36% of the subjects had vibration induced white finger (VWF). Comparisons were also made with 5 primary Raynaud's cases. The changes of the R-R interval in the quiet and deep breathing tests had a significant negative correlation with the ages of the subjects. In all the results there was no evidence that hand-arm vibration could cause autonomic dysfunction in general, but there were signs that it could reduce the autonomic function among workers who are susceptibility to developing white finger reactions. Also, it is possible that the primary Raynaud's cases had reduced cardiovascular reflex responses.

Adult↗
PubMed1990

Vibration stress and the cellular mechanisms in the autonomic nervous system.

The characteristic symptoms of vibration disease, such as Raynaud's phenomenon and palmar superhydrosis, are associated with a sympathetic hyperactivity. This paper discusses the possible sites and mechanisms of the vibration stress-induced facilitation and disinhibition in the sympathetic nervous system, particularly at the levels of the spinal cord and sympathetic ganglion. At the level of the preganglionic neurons, vibration stress may facilitate the activity of the alpha-1 adrenoceptors that mediate the slow excitatory postsynaptic potential and the spike-after depolarization. If the sympathetic hyperactivity is in part due to disinhibition, it could be produced by inhibition of the activity of the alpha-2 adrenoceptors that mediate the slow inhibitory postsynaptic potential in preganglionic neurons. At the level of the ganglion, muscarinic and peptidergic transmission may be facilitated in vibration disease.

Action Potentials↗
PubMed1990

Hormonal responses to cold exposure in subjects with vibration syndrome.

Responses of the autonomic nervous system and the endocrine system to cold exposure were investigated. The subjects were all males, between 41 and 69 years of age. Seventy subjects with the vibration syndrome and vibration-induced white finger (VWF(+) group), 70 subjects with the vibration syndrome without VWF (VWF(-) group) and 70 healthy subjects (control group) were individually matched according to age. The subjects remained in a cold room at 7 C for 30 minutes. Catecholamines, cyclic nucleotides, thyroid hormones, ACTH and cortisol were measured before and during cold exposure. The VWF(+) group and the VWF(-) group had larger % increases of plasma norepinephrine, cyclic AMP, cyclic GMP, T3 and T4 levels than the control group. These findings indicate that the responses of the autonomic nervous system and the thyroid system to cold exposure are greater in the subjects with the vibration syndrome.

Adrenocorticotropic Hormone↗
PubMed2002

Immune responses (CD4 and CD8) to acute vibration stress.

The aim of the experiments was to observe whether or not there is an immune system reaction to vibration stress. Three vibration frequencies were randomly given to 6 male volunteers. The 63 Hz vibration frequency produced a significant decrease in the ratio of CD4 T-cell to CD8 T-cell. This finding suggests that acute vibration stress suppresses the immune system activity in humans body.

Adult↗