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At least 433 records · Page 24Linked to original sources
PubMed1999

Support stability influences postural responses to muscle vibration in humans.

We studied the effect of support stability on postural responses to the vibration of Achilles tendons and of neck dorsal muscles in healthy humans. For this purpose we compared postural responses on a rigid floor and on 6 cm high rocking supports (see-saws) of different curvatures (different radii: 30, 60 and 120 cm). The subject stood with eyes closed, the centre of the feet coincided with the centre of the see-saw. We recorded platform tilt, horizontal displacements of the upper body, ankle joint angle and activity of ankle joint muscles. On the rocking platform subjects maintained balance in a sagittal direction by making see-saw rotations placing the support under the body's centre of gravity. Equilibrium maintenance requires that the torque in the ankle joint increases during forward body displacements, as on the rigid floor, and be accompanied by a plantar flexion (not by a dorsiflexion) in the ankle joint. The directional dependence of vibration-induced reactions on the see-saw was the same (relative to space) as on the rigid floor: backward body displacement during Achilles tendon vibration and forward body displacement during neck muscle vibration. A decrease of support stability (with a decrease of the radius from 120 to 30 cm) diminished significantly the effect of Achilles tendon vibration and to a lesser extent the effect of neck muscle vibration. In contrast, the increase of platform stability by hand contact with a stable external object gave rise to prominent body sway in response to Achilles tendon vibration. Neck muscle vibration on the movable support provoked a quick initial forward body sway. This initial quick response was absent during vibration of the Achilles tendons. We conclude that postural responses to muscle vibration reflect the participation of different muscles in posture control and depend on the support properties. Support instability changes the role of proprioceptive information and the state of the system of equilibrium maintenance.

Achilles Tendon↗
PubMed1997

Proprioceptive control of wrist movements in Parkinson's disease. Reduced muscle vibration-induced errors.

The effects upon the trajectories of practised slow (approximately 9 degrees/s) voluntary wrist-extension movements of applying vibration to the tendon of an antagonist muscle (flexor carpi radialis) during the course of the movement have been studied in patients with idiopathic Parkinson's disease and age-matched healthy individuals. In both patient and control groups, flexor vibration elicited undershooting of wrist-extension movements. Wrist extensor and flexor surface EMG recordings indicated that, in patients and controls, such undershooting resulted principally from sustained reductions in extensor (prime mover) activity. Small vibration reflexes were commonly elicited in the wrist flexors which, in both Parkinson's disease and healthy subjects, were usually otherwise virtually quiescent during these slow extension movements. The amplitudes of such vibration reflexes did not differ systematically between patient and control groups and appeared inadequate to have exerted an appreciable braking action upon the extension trajectories. However, the extent of vibration-induced undershooting was, on average, significantly less in the Parkinson's disease group. In a subgroup of patients with asymmetrical parkinsonism the effects of antagonist vibration upon wrist movements of the more and less affected limb were compared. The degree of vibration-induced undershooting was significantly smaller on the more affected side. This finding suggests that disturbed proprioceptive guidance of voluntary movements in Parkinson's disease is related to the severity of clinical motor deficits. A small number Parkinson's disease patients were studied 'ON' and 'OFF' their routine anti-parkinsonian medication. A non-significant tendency was found for vibration-induced errors to be less marked in the 'OFF' state. In a separate series of experiments, under isometric conditions, vibration-induced EMG changes were recorded whilst subjects attempted to maintain a steady (15% maximum) voluntary wrist extensor effort. Results in control subjects suggested that prolonged flexor vibration produced significant tonic reflex reciprocal inhibition of the extensor muscles. However, the strength of reflex inhibition appeared sufficient to account for only a small fraction of the undershooting observed during the movement tasks. Thus, our results are consistent with the existence of an abnormality of higher-level proprioceptive integration in Parkinson's disease in which there is a mismatch of sensory (proprioceptive) and motor (corollary discharge) information.

Aged↗
PubMed2001

Quantum chemical study of agonist-receptor vibrational interactions for activation of the glutamate receptor.

To understand the mechanism of activation of a receptor by its agonist, the excitation and relaxation processes of the vibrational states of the receptor should be examined. As a first approach to this problem, we calculated the normal vibrational modes of agonists (glutamate and kainate) and an antagonist (6-cyano-7-nitroquinoxaline-2,3-dione: CNQX) of the glutamate receptor, and then investigated the vibrational interactions between kainate and the binding site of glutamate receptor subunit GluR2 by use of a semiempirical molecular orbital method (MOPAC2000-PM3). We found that two local vibrational modes of kainate, which were also observed in glutamate but not in CNQX, interacted through hydrogen bonds with the vibrational modes of GluR2: (i) the bending vibration of the amine group of kainate, interacting with the stretching vibration of the carboxyl group of Glu705 of GluR2, and (ii) the symmetric stretching vibration of the carboxyl group of kainate, interacting with the bending vibration of the guanidinium group of Arg485. We also found collective modes with low frequency at the binding site of GluR2 in the kainate-bound state. The vibrational energy supplied by an agonist may flow from the high-frequency local modes to the low-frequency collective modes in a receptor, resulting in receptor activation.

6-Cyano-7-nitroquinoxaline-2,3-dione↗
PubMed1997

Vibrational force alters mRNA expression in osteoblasts.

Serum-deprived mouse osteoblastic (MC3T3E1) cells were subjected to a vibrational force modeled by NASA to simulate a space shuttle launch (7.83 G rms). The mRNA levels for eight genes were investigated to determine the effect of vibrational force on mRNA expression. The mRNA levels of two growth-related protooncogenes, c-fos and c-myc, were up-regulated significantly within 30 min after vibration, whereas those of osteocalcin as well as transforming growth factor-beta1 were decreased significantly within 3 h after vibration. No changes were detected in the levels of beta-actin, histone H4, or cytoplasmic phospholipase A2 after vibration. No basal levels of cyclooxygenase-2 expression were detected. In addition, the extracellular concentrations of prostaglandin E2 (PGE2), a potent autocrine/paracrine growth factor in bone, were not significantly altered after vibration most likely due to the serum deprivation state of the osteoblasts. In comparison with the gravitational launch profile, vibrational-induced changes in gene expression were greater both in magnitude and number of genes activated. Taken together, these data suggest that the changes in mRNA expression are due to a direct mechanical effect of the vibrational force on the osteoblast cells and not to changes in the local PGE2 concentrations. The finding that launch forces induce gene expression is of utmost importance since many of the biological experiments do not dampen vibrational loads on experimental samples. This lack of dampening of vibrational forces may partially explain why 1-G onboard controls sometimes do not reflect 1-G ground controls. These data may also suggest that scientists use extra ground controls that are exposed to launch forces, have these forces dampened on launched samples, or use facilities such as Biorack that provide an onboard 1-G centrufuge in order to control for space shuttle launch forces.

Animals↗
PubMed1994

Effects of whole body vibration on dorsal root ganglion neurons. Changes in neuronal nuclei.

STUDY DESIGN: This blinded, histomorphometric analysis compared neuronal nuclei from lumbar dorsal root ganglia from three groups of rabbits: normal controls, immobilized controls, and an experimental group exposed to daily, whole body vibration. OBJECTIVES: To identify ultrastructural changes in dorsal root ganglion neurons consistent with, and capable of producing, neuropeptide changes previously documented in vibration-exposed animals. METHODS: Normal adult rabbits were exposed to modulated whole body vibration at a frequency and amplitude previously shown to produce changes in dorsal root ganglion neuropeptides. Lumbar ganglia from control and vibrated rabbits were fixed, stained, and studied under transmission electron microscopy. One-thousand-two-hundred cells were sampled, and 190 appropriately sectioned cells were analyzed. SUMMARY OF BACKGROUND DATA: Epidemiologic studies have suggested a strong correlation between vibration and back pain. Previous studies have shown that short-term exposure to whole body vibration alters the normal neuropeptide profile seen in dorsal root ganglion neurons. RESULTS: Nuclear clefting was increased 39% in vibrated nuclei relative to controls, and nuclear pores were increased 46% in areas of clefting compared with adjacent nonclefted segments and controls (P < .001). Mitochondria, rough endoplasmic reticulum, and free ribosomes crowded the cleft spaces of vibrated cells, and the normal perinuclear clear space was lost. Mitochondrial and lysosomal volumes were significantly increased in vibrated cells. CONCLUSIONS: These ultrastructural changes, generated by a physiologically valid vibration stimulus, provide an anatomic link between the clinical observation of increased back pain and the biochemical alterations involving pain-related neuropeptides.

Animals↗
PubMed1979

Tremor in the tension developed isometrically by soleus during the tonic vibration reflex in the decerebrate cat.

1. Irregularities in the development of tension during the tonic vibration reflex of the soleus muscle of the decerebrate cat have been analysed into their frequency components. The reflex was recorded isometrically and elicited by longitudinal vibration, normally at 150 Hz. The amplitude of vibration was set so as to elicit a maximal reflex response, suggesting 1:1 driving of the majority of the Ia afferents at the frequency of vibration. 2. The resulting power spectrum regularly showed a well marked tremor peak separated by a trough from any slow irregularities. The predominant frequency of this tremor varied from 4 to 11 Hz in different preparations, with a mean of 7.4 Hz; on average, frequencies within 1.7 Hz on either side contained over half the power of the predominant frequency. Altering the frequency of vibration did not alter the distribution of tremor frequencies. 3. The root mean square value of the tension irregularities, over the range 4-14 Hz, varied from 12 to 110 mN in different preparations (median value, 23 mN); this was superimposed on mean active reflex tensions varying from 2 to 10 N. 4. The 'tremor' due to a single motor unit was estimated from spectral analysis of tetanic contractions of the whole muscle and decreased with increasing frequency of activation. Comparison of the single unit values with the tremor seen during vibration in the same preparations showed that equivalent amounts of tremor to the latter could typically have been produced by the continued synchronous contraction of about five 'average' motor units firing at the predominant tremor frequency. 5. When a tonic stretch reflex was present its tremor frequencies did not differ consistently from those of the tonic vibration reflex. On average, the tremor was smaller for the stretch reflex than for the tonic vibration reflex; the difference was usually slight and might have been related to the stretch refex tension being smaller. 6. Evidence was obtained that the tremor was not due to any insecurity of 1:1 driving of the Ia afferents by the vibration. First, the tremor did not increase when the amplitude of vibration was decreased sufficiently to ensure that the degree of 1:1 driving must have been reduced. Secondly, the introduction of a comparable 'artificial tremor' by sinusoidally oscillating the muscle at low frequency did not produce the e.m.g. response that would have been expected if the applied 'tremor' had been modulating the firing of the Ia or any other group of afferents. 7. It is concluded that the observed tremor cannot be attributed to 'oscillation in the stretch reflex arc', though without prejudice to the role of this mechanism under other conditions and especially when the recording is not isometric. However, the genesis of the tremor has not been established and much of it might result simply from the chance synchronization of motor units that are firing below their tetanic fusion frequency.

Action Potentials↗
PubMed1981

The kinetics of post-vibration tension recovery of the isolated rat portal vein.

1. The kinetics of post-vibration tension recovery have been examined during electrical, noradrenaline or KCl stimulation of the isolated rat portal vein. 2. Inhibition of isometric contractions produced by a combination of noradrenaline (20 microM) and KCl (53 mM) by longitudinal, 100 Hz sinusoidal vibration increased with increasing vibration amplitude up to a maximum of 78.7% of the active tension. This inhibition was little affected by a decrease in temperature from 37 to 25 degrees C. Recovery of tension after the end of vibration was complete and took place exponentially. The time constant for this recovery was little affected by changes in vibration amplitude, but increased from 1.72 +/- 0.09 to 4.35 +/- 0.33 sec, for large amplitude vibrations, when the temperature was lowered from 37 to 25 degrees C. 3. The increase in isometric tension during 50 Hz a.c. electrical field stimulation was exponential, apart from a minor initial activation component, and took place with a time constant of 1.25 +/- 0.17 sec. Neither delaying nor interrupting development of this contraction with inhibitory vibration altered the time constant for this exponential increase in tension. There was no correlation between the time constant and the maximum active tension achieved after vibration was stopped. 4. Post-vibration tension recovery during electrical, noradrenaline (20 microM) or KCl (120-130 mM) stimulation was independent of the nature of the stimulus at comparable times of stimulation, but the time constant increased during exposures of more than 10 sec to either noradrenaline or KCl. With noradrenaline, the increase was from 1.45 +/- 0.10 sec after 50 sec of stimulation to 2.24 +/- 0.16 sec after 336 sec of stimulation (P less than 0.0005). Such an increase in the time constant may reflect slower cycling of cross-bridges with an improvement in the efficiency by which contraction is maintained. 5. The kinetics of post-vibration tension recovery were those of a monomolecular or, as is more likely, a pseudo-monomolecular chemical reaction. A cross-bridge attachment model based on such a reaction has been used to interpret the observations.

Animals↗
PubMed1990

Proprioceptive guidance of human voluntary wrist movements studied using muscle vibration.

1. The alterations in voluntary wrist extension and flexion movement trajectories induced by application of vibration to the tendon of flexor carpi radialis throughout the course of the movement, together with the associated EMG patterns, have been studied in normal human subjects. Both extension and flexion movements were routinely of a target amplitude of 30 deg and made against a torque load of 0.32 N m. Flexor tendon vibration consistently produced undershooting of voluntary extension movements. In contrast, voluntary flexion movements were relatively unaffected. 2. The degree of vibration-induced undershooting of 1 s voluntary extension movements was graded according to the amplitude (0.75, 1.0 and 1.5 mm) of flexor tendon vibration. 3. As flexor vibration was initiated progressively later (at greater angular thresholds) during the course of 1 s voluntary extension movements, and the period of vibration was proportionately reduced, so the degree of vibration-induced undershooting showed a corresponding decline. 4. Varying the torque loads (0.32, 0.65 and 0.97 N m) against which 1 s extension movements were made, and thereby the strength of voluntary extensor contraction, produced no systematic changes in the degree of flexor vibration-induced undershooting. 5. Analysis of EMG patterns recorded from wrist flexor and extensor muscles indicated that vibration-induced undershooting of extension movements resulted largely from a reduction in activity in the prime-mover rather than increased antagonist activity. The earliest reductions in extensor EMG commenced some 40 ms after the onset of vibration, i.e. well before voluntary reaction time; these initial responses were considered to be 'automatic' in nature. 6. These results support the view that the central nervous system utilizes proprioceptive information in the continuous regulation of moderately slow voluntary wrist movements. Proprioceptive sensory input from the passively lengthening antagonist muscle, presumably arising mainly from muscle spindle I a afferents, appears to be particularly important and to act mainly in the reciprocal control of the prime-mover.

Adult↗
PubMed1992

Does vibration cause poststenotic dilatation in vivo and influence atherogenesis in cholesterol-fed rabbits?

Arterial post-stenotic dilatation (PSD) is a fusiform swelling immediately down-stream to a stenosis. It is characterized by the presence of turbulent blood flow and wall vibration which has been claimed by others to be causal by producing structural weakening. We tested the hypothesis that vibration causes PSD in vivo by attaching electromagnetic and pneumatic vibrators to the aortic wall in chronic rabbits. We also observed whether mechanical vibration of the aorta in vivo influenced the distribution of oil-red-O lesions during one percent dietary cholesterol feeding. Low mass vibration gauges were developed to measure the vibration. Electromechanical vibrators having a ceramic magnet slug within a coil supplied with 50 Hz were glued to the aorta of chronic rabbits and the vibration maintained for an average of 8 weeks. Despite greater amounts of energy imparted to the wall there was no dilatation or difference in oil-red-O staining from the controls. Five weeks vibration at 100 Hz and an amplitude equal to the normal diameter pulse also produced no dilatation. We conclude that vibration does not cause PSD in vivo and suggest that its cause is likely to involve the vascular muscle stimulated by the effect of turbulent flow on the endothelium.

Animals↗
PubMed1979

Development of noise and vibration ride comfort criteria.

A laboratory investigation was directed at the development of criteria for the prediction of ride quality in a noise-vibration environment. The stimuli for the study consisted of octave bands of noise centered at 500 and 2000 Hz and vertical floor vibrations composed of either 5 Hz sinusoidal vibration, or random vibrations centered at 5 Hz and with a 5 Hz bandwidth. The noise stimuli were presented at A-weighted sound pressure levels ranging from ambient to 95 dB and the vibration and acceleration levels ranging from 0.02--0.13 grms. Results indicated that the total subjective discomfort response could be divided into two subjective components. One component consisted of subjective discomfort to vibration and was found to be a linear function of vibration acceleration level. The other component consisted of discomfort due to noise which varied logarithmically with noise level (power relationship). However, the magnitude of the noise discomfort component was dependent upon the level of vibration present in the combined environment. Based on the experimental results, a model of subjective discomfort that accounted for the interdependence of noise and vibration was developed. The model was then used to develop a set of criteria (constant discomfort) curves that illustrate the basic design tradeoffs available between noise and vibration.

Adult↗
PubMed2005

Prolonged muscle vibration increases stretch reflex amplitude, motor unit discharge rate, and force fluctuations in a hand muscle.

The purpose of this study was to compare the influence of prolonged vibration of a hand muscle on the amplitude of the stretch reflex, motor unit discharge rate, and force fluctuations during steady, submaximal contractions. Thirty-two young adults performed 10 isometric contractions at a constant force (5.0 +/- 2.3% of maximal force) with the first dorsal interosseus muscle. Each contraction was held steady for 10 s, and then stretch reflexes were evoked. Subsequently, 20 subjects had vibration applied to the relaxed muscle for 30 min, and 12 subjects received no vibration. The muscle vibration induced a tonic vibration reflex. The intervention (vibration or no vibration) was followed by 2 sets of 10 constant-force contractions with applied stretches (After and Recovery trials). The mean electromyogram amplitude of the short-latency component of the stretch reflex increased by 33% during the After trials (P < 0.01) and by 38% during the Recovery trials (P < 0.01). The standard deviation of force during the steady contractions increased by 21% during the After trials (P < 0.05) and by 28% during the Recovery trials (P < 0.01). The discharge rate of motor units increased from 10.3 +/- 2.7 pulses/s (pps) before vibration to 12.2 +/- 3.1 pps (P < 0.01) during the After trials and to 11.9 +/- 2.6 pps during the Recovery trials (P < 0.01). There was no change in force fluctuations or stretch reflex magnitude for the subjects in the Control group. The results indicate that prolonged vibration increased the short-latency component of the stretch reflex, the discharge rate of motor units, and the fluctuations in force during contractions by a hand muscle. These adjustments were necessary to achieve the target force due to the vibration-induced decrease in the force capacity of the muscle.

Adolescent↗
PubMed1986

Differential effects of low-frequency depression, vibration-induced inhibition, and posttetanic potentiation on H-reflexes and tendon jerks in the human soleus muscle.

A comparison was made between the effects of repetition rate, muscle vibration, and tetanic stimulation of the tibial nerve on H-reflexes and tendon (T) jerks elicited in the relaxed soleus muscle of normal human. H- and T-reflexes with electromyographic (EMG) potentials of equivalent amplitude were elicited alternately in the same leg to ensure identical experimental conditions. H- and T-reflexes of identical EMG amplitude showed isometric twitch tensions of identical amplitude and time course. H- and T-reflexes were elicited at different repetition rates ranging from once every 6 s to 2/s. H-reflexes showed a significantly stronger low-frequency depression than T-reflexes. Inhibition of H- and T-reflexes was induced by 2-min vibration at 100 Hz of ankle extensors, ankle flexors, or knee flexors. Vibration of ankle extensors and flexors induced a stronger inhibition than vibration of knee flexors. In all three conditions, inhibition of H-reflexes was stronger than inhibition of T-reflexes. The difference was relatively greater during vibration of ankle extensors and flexors than during vibration of knee flexors. When tested together, the effects of low-frequency depression and vibration-induced inhibition of H- and T-reflexes were found to be independent if reflex amplitudes were expressed as a percentage of the control reflex amplitude. The cessation of vibration of ankle extensors was followed by a gradual recovery of H-reflexes from inhibition. On the contrary, T-reflexes showed a marked potentiation. Such postvibratory effects were generally not observed following vibration of ankle or knee flexors. When postvibratory effects were tested during low-frequency depression, percent postvibratory depression of H-reflexes and percent postvibratory potentiation of T-reflexes were found to be independent of the degree of low-frequency depression. Tetanic stimulation of the tibial nerve for 20 s at 200 Hz resulted in posttetanic potentiation (PTP) of H- and T-reflexes, the former being stronger than the latter. The extent of the changes in H- and T-reflex EMG amplitudes, due to changes in repetition rate, vibration, or tetanic stimulation, was generally inversely related to the intensity of the electrical or mechanical reflex stimuli. The observed discrepancies between the induced changes in H- and T-reflex amplitudes are interpreted in terms of the differences in afferent inputs between the two reflexes that were suggested by Burke and his colleagues (9-11).(ABSTRACT TRUNCATED AT 400 WORDS)

Adolescent↗
PubMed2000

Response of the canine inspiratory intercostal muscles to chest wall vibration.

High-frequency mechanical vibration of the rib cage reduces dyspnea, but the effect of this procedure on the respiratory muscles is largely unknown. In the present studies, we have initially assessed the electrical and mechanical response to vibration (40 Hz) of the canine parasternal and external intercostal muscles (third interspace) during hyperventilation-induced apnea. When the vibrator was applied to the segment investigated, prominent external intercostal activity was recorded in the seven animals studied, whereas low-amplitude parasternal intercostal activity was recorded in only four animals. Similarly, when the vibrator was applied to more rostral and more caudal interspaces, activity was recorded commonly from the external intercostal but only occasionally from the parasternal. The two muscles, however, showed similar changes in length. We next examined the response to vibration of the muscles in seven spontaneously breathing animals. Vibrating the rib cage during inspiration (in-phase) had no effect on parasternal intercostal inspiratory activity but induced a marked increase in neural drive to the external intercostals. For the animal group, peak external intercostal activity during the control, nonvibrated breaths averaged (mean +/- SE) 43.1 +/- 3.7% of the activity recorded during the vibrated breaths (p < 0.001). External intercostal activity during vibration also occurred earlier at the onset of inspiration and commonly carried on after the cessation of parasternal intercostal activity. Yet tidal volume was unchanged. Vibrating the rib cage during expiration (out-of-phase) did not elicit any parasternal or external intercostal activity in six animals. These observations thus indicate that the external intercostals, with their larger spindle density, are much more sensitive to chest wall vibration than the parasternal intercostals. They also suggest that the impact of this procedure on the mechanical behavior of the respiratory system is relatively small.

Animals↗
PubMed2006

Vibration exercise makes your muscles and bones stronger: fact or fiction?

Vibration transmitted to the whole body or part of it has been extensively studied in relation to the risks to the health and safety of workers. These studies have highlighted the particular danger of lower-back morbidity and spinal trauma arising after prolonged exposure to vibration. However, short-term exposure to whole-body vibration (WBV) or the use of vibrating dumbbells can have beneficial effects on the musculoskeletal system. As a consequence of this encouraging work, many manufacturers have developed exercise devices characterized by vibrating plates transmitting vibration to the whole body and vibrating dumbbells. Preliminary results seem to recommend WBV exercise as a therapeutic alternative for preventing/reversing sarcopenia and possibly osteoporosis. However, there is a paucity of well designed studies in the elderly. In particular, there is a lack of understanding of the physiological mechanisms involved in the adaptive responses to vibration exposure, and of the most appropriate vibration parameters to be used in order to maximize gains and improve safety. The effectiveness of this novel exercise modality on musculoskeletal structures is examined in this review. The physiological mechanisms involved in the adaptive responses to vibration exercise are discussed and suggestions for future studies are made.

Exercise Therapy↗
PubMed1986

[The labor of freight-container tractor drivers and low back pain. Correlation with whole-body vibration exposure].

In order to determine the causal factors of low back pain (LBP) which prevails among freight-container tractor drivers, vibration measurements of the seat of ten freight-container tractors and one heavy truck, a survey on the daily working hours of 240 tractor drivers for a month, and a time study of work on 28 person-days were conducted. Vibration measurement was made under routine conditions on paved public roads for 40 km under laden and unladen conditions. For the evaluation of vibration exposure, ISO 2631 was used. With the freight-container tractors, the mean vibration levels were high in X and Z directions, particularly in X direction. In the heavy truck, the vibration level was consistently higher in Z direction. According to the evaluation made by ISO 2631, the X component of the vibration was found to be serious. The magnitude of the vibration level was greatly influenced by the condition of the road surface with bridges tending to produce a high level of vibration. Vibration levels of the new model tractors were not necessarily always lower than that of the old models. It was estimated from the foregoing results and the time study that in more than 90% of the drivers the daily exposure time (i.e. driving hours) exceeded the allowable exposure time of fatigue-decreased proficiency boundary (FDP), and in about one-third of the drivers the allowable exposure time of exposure limit (EL) was exceeded. These results suggest that long exposure to severe vibration during work is one of the possible causal factors of LBP of freight-container drivers.

Automobile Driving↗
PubMed1991

[An experimental study on transmission of hand-arm vibration on the body of users].

Vibration forced into the hand-arm system was observed on the body surface during work with chain saw and under loading experiments by electrodynamic shaker in the laboratory, and factors related to transmission over joints were investigated using pig elbow joints constructed with ulna, radius and humerus. Vibration was measured according to IS 5349 and JIS C1511 between 8 and 1,000 Hz in vibration frequency. Vibration on the bone of pig foreleg conducted without attenuating its amplitude from the peripheral side to the central side between 8 and 1,000 Hz. On the other hand, vibration transmitted over joints damped its amplitude in higher frequency components rather than in lower frequency between 8 and 1,000 Hz. The decreasing ratio of transmitted vibration over joint was changed by the resonance of the soft tissues between the bones constructing the joint. The attenuation changed with the elastic modulus of the soft tissues. The peak frequency was considered to be the resonance because of the physical mass and elasticity. The harder the joint was tied, the stronger became the transmission, because the resonance moved to higher frequencies with increase in elastic modulus. In the loading test from the electrodynamic shaker to the hand-arm system of man, vibration on the soft tissues was transmitted on its surface as wave motion, when the vibration was observed over the skin on the soft tissues. Vibration reduced its amplitude at every joints especially above 100 Hz. The shape of the vibration attenuation curves varied according to the frequency and components of the chain saws.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1998

Evaluation of whole-body road traffic vibration in building.

Level fluctuating vibration has been evaluated by the cumulative index L10, but some investigators suggest that the L10 cannot represent an adverse comment on vibration. In order to clarify the compliant, various factors involving vibration need to be analysed together by statistical methods, for instance factor analysis or quantum theory. The authors investigated the relationship between an evaluation index and human sensation of vibration in a subjective experiment in a wooden house. The subjects were exposed to vertical road traffic vibration reproduced with an electrodynamic vibrator placed near the house. The range of vibration levels at surfaces in contact with the subjects were from 50dB to 70dB in root mean square of frequency weighted acceleration level, i.e. the vibration level. Numbers assigned by the subjects and evaluation indices of the vibration level were analysed by applying the Stevens power law. The results showed that L10 or Leq (55) could become an effective index for the assessment of subjective perception of level fluctuating vibration in a wooden house.

Acceleration↗
PubMed1990

[Holographic observation of the tympanic membrane vibration after stapes fixation].

Sclerosis of auditory ossicle was experimentally induced by fixation of the stapes, and its effect on the tympanic membrane vibration was examined using fresh 10 canine temporal bones by means of holographic interferometry. By changing the sound pressure (from 90 to 110dB) and the frequency (from 250Hz to 8kHz) in steps, vibration of the membrane was induced in a free field. At each frequency, the vibration of the membrane was photographed by the time averaged method using He-Ne laser. A small hole was created in the tympanic bulla and the stapes was fixed with an adhesive (Alon Alpha), followed by closure of the hole. Before stapes fixation, the posterior part of the membrane showed a simple vibration pattern, forming cocentric interference circles at frequencies from 250Hz to 2kHz. At 3kHz, segmental vibration began to be noted, and complex segmental vibration was seen at frequencies 4.5 and 6kHz. The vibration after stapes fixation became simpler at frequencies over 3kHz, accompanied by decrease in the number of segmental vibrations. Vibration amplitude in the posterior part of the membrane decreased from 250Hz to 3kHz, while it increased at frequencies over 4kHz. In the anterior part of the membrane, the amplitude decreased at frequencies under 2kHz, remained unchanged at 3kHz and increased at frequencies over 4kHz after stapes fixation. In the tip of the manubrium mallei, the amplitude decreased at frequencies under 3kHz and increased at frequencies over 4kHz. Thus, a shift of peak vibration to high sound region was observed after stapes fixation at every part of tympanic membrane.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗