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PubMed1989

Ultrastructural changes of the peripheral nerve induced by vibration: an experimental study.

To investigate the effects of vibration on the peripheral nerves, rabbits were exposed to vibration of 60 cycles/s frequency with 0.35 mm amplitude (acceleration: 51 m/s2) for two hours daily. After 150, 250, 450, and 600 hours vibration, thin sections of the saphenous and median nerves were examined under the electron microscope. Vibration was found to induce the following changes: (1) disruption of the myelin sheath and constriction of the axon, (2) accumulation of vacuoles in the nodal gap and paranodal region, (3) disorganisation of the paranodal end loops and detachment of the paranodal end loops from the axolemma, (4) dilatation of the Schmidt-Lanterman incisures (SLI) and increased density of SLI, and (5) disappearance of neurotubules and neurofilaments in axons. The diameters of myelin sheaths disrupted by vibration varied from 2 to 12 microns. The extent of the myelin disruption is proportional to the vibration dose.

Animals↗

PubMed2003

A vibrator prevents streaming during close-arterial infusion into the kidney.

Close-arterial infusion of test substances allows one to study the responses of a selected vascular bed without inducing confounding systemic effects. Unfortunately, laminar flow patterns within the artery cause streaming of the injected factor, so that distribution within the target organ is not homogeneous. We describe a reliable method of overcoming these problems. Specifically, we attach a vibrator (i-Vibe egg) to the syringe containing the test substance. We showed that, without vibration, infusion of a solution of Evans blue (0.5% wt/vol) results in uneven distribution of the dye in the kidney. Vibration of the syringe during infusion allows for uniform coloration of the kidney surface. There is also functional improvement of drug distribution during vibration. Renal blood flow was measured during intrarenal infusion of phenylephrine (150 microl, 0.05-0.5 microg). Vibration caused a significant leftward shift in the dose-response curve, i.e., the phenylephrine-induced reduction in renal blood flow was enhanced by vibration. This cheap, simple method for ensuring adequate mixing of intra-arterially infused substances will facilitate not only the study of renal function in the rat but also infusion of test and therapeutic substances into other organs.

Animals↗

PubMed1979

Cardiac responses of dogs to nonsynchronous and heart synchronous whole-body vibration.

Changes in cardiac function produced by synchronizing vibration-induced forces with events in the cardiac cycle were compared to those for the nonsynchronous case in eight chronically instrumented, tranquilized dogs. The supine animals received sinusoidal, whole-body vibration (along the spinal +/- Gz axis) at a constant acceleration amplitude (+/- 0.75 G). The vibration frequency (2-3 Hz) was set equal to the paced heart frequency. Synchronization between vibration and cardiac cycles on a beat-by-beat basis produced a specific and sustained cardiovascular response; such a sustained response was not possible with nonsynchronous vibration. With synchronization, relationships could be found and sustained in which changes either exceeded or were below mean nonsynchronous levels, in some cases below previbration values. For the synchronous vs. nonsynchronous states, significant modification of cardiac function was reflected in parameters such as coronary flow (+15% to -34%) and myocardial oxygen consumption (+21% to -51%). Thus, whole-body oscillation acceleration (vibration) is a forcing function that can produce and maintain a particular cardiovascular response.

Animals↗

PubMed1984

Gate mechanism in breathlessness caused by chest wall vibration in humans.

The effects of bilateral alternating out-of-phase vibrations were studied in 10 normal healthy subjects and five asthmatic patients. The second or third intercostal spaces were vibrated during expiration, and the seventh to ninth intercostal spaces were vibrated during inspiration. Most subjects sensed breathlessness during such vibrations, and 100 Hz was most effective. The degree of breathlessness correlated positively with increased respiratory rate. Respiratory rate increased from 14.1 +/- 3.78 (mean +/- SD) to 22.3 +/- 7.14 breaths/min (P less than 0.05) during relatively severe breathlessness and to 20.39 +/- 5.66 breaths/min (P less than 0.05) during less uncomfortable sensation. Slight or negligible breathlessness induced no significant increase in rate (15.33 +/- 4.19 breaths/min). All asthma patients described the sensations during vibration as similar to those during asthma attacks, and their respiratory rates increased 20.7 +/- 11.03% during 100 Hz vibration (P less than 0.01). It is suggested that the uncomfortable sensation of breathlessness may be induced by muscle spindles in the intercostal muscles being activated out of phase with the respiratory cycle. The central mechanism that receives the intercostal afferents may have a certain gate that operates in relation to the sensation of breathlessness.

Adult↗

PubMed2002

Muscle activity damps the soft tissue resonance that occurs in response to pulsed and continuous vibrations.

This study tested the hypotheses that when the excitation frequency of mechanical stimuli to the foot was close to the natural frequency of the soft tissues of the lower extremity, the muscle activity increases 1) the natural frequency and 2) the damping to minimize resonance. Soft tissue vibrations were measured with triaxial accelerometers, and muscle activity was measured by using surface electromyography from the quadriceps, hamstrings, tibialis anterior, and triceps surae groups from 20 subjects. Subjects were presented vibrations while standing on a vibrating platform. Both continuous vibrations and pulsed bursts of vibrations were presented, across the frequency range of 10-65 Hz. Elevated muscle activity and increased damping of vibration power occurred when the frequency of the input was close to the natural frequency of each soft tissue. However, the natural frequency of the soft tissues did not change in a manner that correlated with the frequency of the input. It is suggested that soft tissue damping may be the mechanism by which resonance is minimized at heel strike during running.

Adult↗

PubMed2002

Neck muscle vibration and spatial orientation during stepping in place in humans.

Unilateral long-lasting vibration was applied to the sternomastoid muscle to assess the influence of asymmetric neck proprioceptive input on body orientation during stepping-in-place. Blindfolded subjects performed 3 sequences of 3 trials, each lasting 60 s: control, vibration applied during stepping (VDS), and vibration applied before stepping (VBS). VDS caused clear-cut whole body rotation toward the side opposite to vibration. The body rotated around a vertical axis placed at about arm's length from the body. The rotation did not begin immediately on switching on the vibrator. The delay varied from subject to subject from a few seconds to about 10 s. Once initiated, the angular velocity of rotation was remarkably constant (about 1 degrees /s). In VBS, at the beginning of stepping, subjects rotated for a while as if their neck were still vibrated. At a variable delay, the direction of rotation reversed, and the effects were opposite to those observed during VDS. Under no condition did head rotation, head roll, or lateral body tilt accompany rotation. The results confirm and extend the notion that the neck proprioceptive input plays a major role in body orientation during locomotion. The body rotation does not seem to depend on the same mechanisms that modify the erect posture; rather, the asymmetric neck input would seem to modify the egocentric body-centered coordinate system.

Adult↗

PubMed1994

Vibration-entrained and premovement activity in monkey primary somatosensory cortex.

1. Primary somatosensory cortical (SI) neurons exhibit characteristic activity before the initiation of movements. This premovement activity (PMA) may result from centrally generated as well as from peripheral inputs. We examined PMA for 55 SI neurons (10, 13, 28, and 4 in areas 3a, 3b, 1, and 2, respectively) with activity that was entrained to vibrotactile stimulation (i.e., was temporally correlated with the stimulus). We sought to determine whether the temporal characteristics of vibration-entrained discharges would change throughout the reaction time period, and, if they did, whether these changes might be accounted for by central inputs. 2. Monkeys made wrist flexions and extensions in response to sinusoidal vibration (27, 57, or 127 Hz) of their palms. Vibration remained on until the animal moved at least 5 degrees from the initial hold position. Mean firing rate (MFR), a measure of the level of activity, was derived from the number of spikes per vibratory cycle. The correlation between the vibration and the neuronal firing was described by the mean phase (MP) of the vibratory cycle at which spikes occurred. The degree of entrainment was quantified as synchronicity (Synch), a statistical parameter that could change from 0 for no entrainment to 1 for responses at a constant phase. 3. Premovement MFR increases (activation) and decreases (suppression) were observed. Moreover, two changes in MFR often were observed for the same neuron (2-event PMA). Many MFR shifts, especially the first in the two-event PMA, preceded electromyographic (EMG) onset. The pre-EMG MFR shifts more often had the same sign both for flexion and extension movements rather than having opposite signs. However, with equal frequency, post-EMG PMA events had the same or opposite sign for different movement directions. We suggest that the pre-EMG PMA has an origin different from movement-related peripheral reafference. 4. Premovement activation was accompanied by shifts of MP corresponding to earlier responses to the ongoing vibratory stimulus and by decreases of response Synch. Premovement suppression was not associated with consistent shifts of MP and Synch. We suggest that during premovement activation, asynchronous (uncorrelated with vibration) signals are integrated with the vibratory input. These asynchronous signals may make neurons more likely to discharge and to do so earlier with respect to the vibratory stimulus. The asynchronous component may also disrupt the vibration-entrained activity pattern.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗

PubMedDate not supplied

Separate detection of vocal fold vibration by optoreflectometry: a study of biphonation on excised porcine larynges.

This study describes a novel system allowing the noncontact measurement of vibration of each vocal fold. The system is based on reflectometry, i.e. measurement of light bouncing off a vibrating object. The system works in natural light and is sensitive, compact, and inexpensive. We have used this system for separate and simultaneous detection of the vibration of each vocal fold in excised porcine larynges. Normal conditions of vibration and asymmetry of tension leading to biphonations were studied. Analysis of each vibrating cycle reveals interaction between the vocal folds allowing synchronous vibration despite their physical asymmetry or episodes of period doubling.

Animals↗

PubMed1997

Effect of chest wall vibration on dyspnea during hypercapnia and exercise in chronic obstructive pulmonary disease.

Vibration of chest wall inspiratory muscles during inspiration (in-phase) reduces breathlessness associated with hypercapnia and resistive loading in normal subjects and in patients with chronic obstructive pulmonary disease (COPD) at rest. To evaluate further the effect of chest wall vibration on breathlessness ("breathing discomfort") in patients, we studied 10 subjects 52 to 79 yr of age with severe dyspnea (mean FEV1, 0.75 L, 27% predicted). On a single day, we used two separate stimuli to produce mild to moderate breathlessness (BR): Protocol 1, steady-state hypercapnia; Protocol 2, exercise with a lower extremity ergometer. During each protocol, we applied in-phase chest wall vibration (CW) randomly alternating with one of two controls: deltoid vibration (DV) or no vibration (NV). During hypercapnia, CW significantly reduced BR (DV, 2.9 +/- 2.1; CW, 2.3 +/- 1.4; p < 0.05; NV, 3.3 +/- 2.1; CW, 2.6 +/- 2.0; p < 0.01) without significant changes in ventilation. During exercise, CW did not significantly alter BR relative to controls. These findings may be explained by the effect of vibration on the sense of respiratory effort and/or by improvement of the match between efferent motor commands and afferent information from the respiratory system. The lack of effect during exercise on BR suggests there may be a "therapeutic window" or range of conditions within which CW is effective in reducing dyspnea in patients with COPD.

Aged↗

PubMed1989

Responses of myocardial blood flows to whole-body vibration in the dog.

Experimentally acute exposure to whole-body vibration resulted in changes in myocardial blood flows in the in vivo dog. Regional myocardial blood flows measured by a hydrogen gas clearance method were increased at a vibration frequency of 120 Hz and decreased at 50 Hz. No appreciable changes were found in presence of a beta-adrenergic blocker. The values of plasma cyclic nucleotides were increased at both frequencies of vibration, more at 50 Hz than at 120 Hz. No significant changes were observed in heart rates and arterial pressure during and after vibration load. These findings suggest that increased myocardial blood flows in response to vibration may be related more to the frequency of vibration than to beta-adrenergic actions.

Animals↗

PubMed1998

The role of leukocytes in the pathogenesis of vibration-induced white finger.

Vibration white finger (VWF) is an occupational disorder associated with long-term exposure to hand-transmitted vibration. The condition exhibits features of secondary Raynaud's phenomenon. The etiology is unknown. The aim of this study was to examine the role of leukocyte rheology in the pathogenesis of VWF. Fifty-two male subjects divided into two groups were exposed to controlled acute hand-transmitted vibration. One group consisted of 29 workers who have all had occupational exposure to handheld vibration and all suffered from VWF (mean age 46.9 years, range 22-66). The second group consisted of 23 controls. Venous blood was analyzed from the dorsum of the hand before and after vibration to determine granulocyte deformability, granulocyte morphology, and white blood cell count with differential. There was a subpopulation of hard and poorly deformable granulocytes in the VWF group when compared with controls (p < 0.05). Acute hand-transmitted vibration had no in vitro effect on leukocyte rheology in either group. Leukocyte rheology may play a role in the pathogenesis of microvascular disease and tissue ischemia in VWF, although whether this is a cause or an effect of the disorder is not clear.

Adult↗

PubMed1995

Effect of beat frequency on the velocity of microtubule sliding in reactivated sea urchin sperm flagella under imposed head vibration.

The heads of demembranated spermatozoa of the sea urchin Tripneustes gratilla, reactivated at different concentrations of ATP, were held by suction in the tip of a micropipette and vibrated laterally with respect to the head axis. This imposed vibration resulted in a stable rhythmic beating of the reactivated flagella that was synchronized to the frequency of the micropipette. The reactivated flagella, which in the absence of imposed vibration had an average beat frequency of 39 Hz at 2 mmol l-1 ATP, showed stable beating synchronized to the pipette vibration over a range of 20-70 Hz. Vibration frequencies above 70 Hz caused irregular, asymmetrical beating, while those below 20 Hz induced instability of the beat plane. At ATP concentrations of 10-100 mumol l-1, the range of vibration frequency capable of maintaining stable beating was diminished; an increase in ATP concentration above 2 mmol l-1 had no effect on the range of stable beating. In flagella reactivated at ATP concentrations above 100 mumol l-1, the apparent time-averaged sliding velocity of axonemal microtubules decreased when the imposed frequency was below the undriven flagellar beat frequency, but at higher imposed frequencies it remained constant, with the higher frequency being accompanied by a decrease in bend angle. This maximal sliding velocity at 2 mmol l-1 ATP was close to the sliding velocity in the distal region of live spermatozoa, possibly indicating that it represents an inherent limit in the velocity of active sliding.(ABSTRACT TRUNCATED AT 250 WORDS)

Adenosine Triphosphate↗

PubMed1998

Relation between mechanical stiffness and vibration transmission of fracture callus: an experimental study on rabbit tibia.

It has been suggested that the vibration transmission across a fracture is affected by the stages of healing of the fracture callus. This study aims to correlate the change in vibration transmission with mechanical stiffness of the callus measured by three-point bending. The right tibiae of male, three-month old local albino rabbits were osteotomized and stabilized by intramedullary fixation following open reduction. The intramedullary rods were removed on the 15th, 28th, 42nd and 90th days postoperatively and the tibiae were excised for vibration, three-point bending and bone mineral density analysis by quantitative computerized tomography (QCT). Optimum time for clinical weight bearing was determined by checking the convergence of the vibration parameters of the fractured tibia to those of the unfractured contralateral. The conclusions obtained from curvature analysis, based on vibration experiments, were in considerable correlation (Spearman's rank correlation coefficient r = 0.93, p = 0.003) with the conclusions obtained from the three-point bending test data which reflected the mechanical condition of the bone by direct means. However, no correlation between bone mineral density change and vibration transmission was noted.

Animals↗

PubMed2002

Effects of vibration in inline skating on the Hoffmann reflex, force, and proprioception.

PURPOSE: The objective of this study was to examine the effects of vibrations induced by inline skating on the Hoffmann (H) reflex, maximal voluntary isometric (MVC) force, and ankle proprioception. METHODS: Accelerometers were used to measure the frequencies and amplitudes of the vibrations encountered at the skate and mid-tibia levels. The soleus H reflex was recorded before and after (for 30 min) inline skating for 30 min. Maximal plantarflexor contractions were performed against a strain gauge while EMG was recorded from the soleus and medial gastrocnemius muscles. An ankle position-matching test was carried out to measure proprioception at the ankle. A Modified Borg Scale was used to obtain the appreciation of leg numbness and fatigue during inline skating. RESULTS: The vibrations measured at the skate chassis level had a mean frequency of 141.8 +/- 25.2 Hz and an amplitude of </=5 g. These vibrations were transmitted to the lower limb as measured by a mean frequency of 34.4 +/- 27.7 Hz and an amplitude of </=2 g at the mid-tibia level. The results demonstrate a clear inhibition ( approximately 35%) of the H reflex after skating that persisted for >35 min after skating. A 10% drop in MVC plantarflexor force was observed after inline skating. There was no accompanying change in EMG signal parameters. The ankle proprioception of the subjects decreased after skating, resulting in reproduction errors twice as large as before skating. CONCLUSION: Vibrations encountered during inline skating resulted in modifications of neuromotor functions related to the muscle spindles' primary afferent. These changes may partially be explained by presynaptic inhibition; however, a more plausible mechanism may be a decrease in the Ia afferent transmission induced by the vibration.

Acceleration↗

PubMed2004

Comparing the performance-enhancing effects of squats on a vibration platform with conventional squats in recreationally resistance-trained men.

The purpose of this investigation was to compare the performance-enhancing effects of squats on a vibration platform with conventional squats in recreationally resistance-trained men. The subjects were 14 recreationally resistance-trained men (age, 21-40 years) and the intervention period consisted of 5 weeks. After the initial testing, subjects were randomly assigned to either the "squat whole body vibration" (SWBV) group (n = 7), which performed squats on a vibration platform on a Smith Machine, or the "squat"(S) group (n = 7), which performed conventional squats with no vibrations on a Smith Machine. Testing was performed at the beginning and the end of the study and consisted of 1 repetition maximum (1RM) in squat and maximum jump height in countermovement jump (CMJ). A modified daily undulating periodization program was used during the intervention period in both groups. Both groups trained at the same percentage of 1RM in squats (6-10RM). After the intervention, CMJ performance increased significantly only in the SWBV (p < 0.01), but there was no significant difference between groups in relative jump height increase (p = 0.088). Both groups showed significant increases in 1RM performance in squats (p < 0.01). Although there was a trend toward a greater relative strength increase in the SWBV group, it did not reach a significant level. In conclusion, the preliminary results of this study point toward a tendency of superiority of squats performed on a vibration platform compared with squats without vibrations regarding maximal strength and explosive power as long as the external load is similar in recreationally resistance-trained men.

Adaptation, Physiological↗

PubMed1981

[Vibration disorders in a factory producing concrete pipes and piles (author's transl)].

The investigations were carried out to estimate the actual conditions of exposure and health of workers using impact wrenches and vibrating long iron trowels (Fig. 1) in a factory producing concrete pipes and piles, and the following results were obtained: 1) Vibration acceleration levels of the impact wrenches and the trowels were in excess of the guideline of up to 30 minutes per day proposed by ISO (1979) (Figs. 3 and 4). 2) Daily amounts of time during which workers were exposed to vibration by using tools were roughly calculated to be about 60 minutes per worker. 3) As the results of the special health examinations for 35 workers, 5 cases (14.3%) were diagnosed as vibration disease, 8 cases (22.9%) were suspected of this disease, and white fingers were found in 14.3% of the workers. It was suggested that the protection from vibration and the prevention of vibration disorders are necessary for all factories such that concrete pipes or piles are manufactured by similar processes.

Adult↗

PubMed1982

[Studies of peripheral nerve conduction velocities in vibrating tool operators].

Vibrating tools such as chain-saws, rock-drills, grinders and tie-tampers have been widely used in many kinds of industries in Japan, causing vibration syndrome among the operators. As is well-known, the syndrome includes disorders of the peripheral circulation in the hands, e.g. Raynaud's phenomenon, and of the peripheral and central nervous systems. As the result of preventive countermeasures to the syndrome during the last decade, the picture of the syndrome has been partly changing especially for the patients among the state forestry workers; for example, the prevalence of the peripheral nerve disorders has been relatively increasing compared with that of Raynaud's phenomenon. Peripheral nerve disorders such as numbness, paresthesia and hypesthesia in the upper limbs tend to be usually cumulative and irreversible. The disorders are very important problem of vibration syndrome from the standpoint of treatment and prevention, though there are only a few reports of the study on the disorders using electrophysiological methods. In order to make objectively clear the peripheral nerve disorders, 236 male vibrating tool operators (= Group V) were examined. The following nerve conduction velocities were measured: (1) Maximal motor nerve conduction velocities (MCV) of the median and ulnar nerves in the forearm. (2) Sensory nerve conduction velocities (SCV) of the median and ulnar nerves in the forearm and palm. (3) Residual latency (RL) of the median and ulnar nerves. Besides, working conditions and complaints relevant to vibration syndrome were examined by using questionnaires. MCVs, SCVs and RLs that were outside of mean +/- 2 S.D. of the control group (= Group C), consisting of 30 healthy men, were evaluated as abnormal. The obtained results led to the following conclusions: (1) All MCVs, SCVs and RLs of Group V were significantly less than those of the control group. In Group V, prevalence of the abnormality in each of forearm SCVs was higher than that in each of MCVs of the corresponding nerves. (2) The difference between the median and ulnar SCV in the palm and the respective SCV in the forearm of each subject was significantly greater for Group V than Group C. (Palm-forearm difference) (3) The difference between the forearm and palmar SCV of the ulnar nerve and the respective velocities of the median nerve was statistically greater for Group V than for Group C. (Ulnar-median difference) (4) Ulnar SCV in the palm of Group V was significantly related to the total operating hours of vibrating tools. (5) There was no significant relation between all the nerve conduction velocities and the white finger attack. But a significant relation was noticed between the prevalence of the abnormal values of ulnar SCV in the palm and the peripheral circulatory function score computed from the data of nail press test and cold immersion test.

Adult↗

PubMed1985

[Study of somatosensory evoked response (SER) in patients with occupational vibration disease. Effect on SER induced by load of hot and cold water, and depressing the brachium].

Somatosensory evoked responses (SERs) to mechanical stimulation were recorded in 5 patients with occupational vibration disease and 10 grader drivers, and the results were compared with those obtained from 48 normal subjects. SERs were recorded at room temperature of 20-23 degrees C and after immersing the hand in hot (40 degrees C) or cold (10 degrees C) water for 5 minutes. SERs were also recorded while depressing the brachium and soon thereafter to examine the effect of ischemia. The following results were obtained. In SERs recorded on the finger of patients with occupational vibration disease, it was observed that some peaks of SERs were absent in 6 out of the 10 cases and that peak latency time was abnormally prolonged in 3 out of them. On the other hand, in SERs recorded on the forearm, abnormality was observed in only 1 out of them. In recording SERs in 6 patients with occupational vibration disease after immersing the hands in hot water, it was observed that abnormal SERs became normal in all 6 cases. However, these normalized SERs became abnormal in 5 out of the 6 cases within 25 minutes after removing the hands from hot water. No appreciable change could be observed in SERs recorded after immersing the hands in cold water. Partial absence of SER peaks could be observed in 2 out of 9 grader drivers while depressing the brachium. On the other hand, all SERs in 7 normal cases did not show any abnormality while depressing the brachium. The results suggest the presence of a close relationship between peripheral vascular dysfunction and peripheral somatosensory disturbance in patients with occupational vibration disease. However, it was observed that peripheral vascular dysfunction could not always trigger peripheral neural dysfunction. These findings have led to the conclusion that SERs to mechanical stimulation are more useful in the diagnosis of dysfunction of the peripheral nerve in patients with occupational vibration disease than SERs to electrical stimulation. The findings suggest that immersion in hot water and cold water and depression of the brachium are useful sensory tests for patients with occupational vibration disease and grader drivers.

Adult↗