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PubMed1988

The response characteristics of vibration-sensitive saccular fibers in the grassfrog, Rana temporaria.

The response characteristics of saccular nerve fibers in European grassfrogs (Rana temporaria) subjected to dorso-ventral, 10-200 Hz sinusoidal vibrations were studied. Only 4 fibers out of a total of 129 did not respond to the vibrations. 70 fibers had an irregular spontaneous activity of 2-48 spikes/s. These fibers were very vibration-sensitive. The synchronization thresholds at 10-20 Hz varied from below 0.005 to 0.02 cm/s2. In contrast to earlier results, all these fibers had low-pass characteristics (with respect to acceleration) and responded maximally at 10 and 20 Hz. 55 fibers had spontaneous activities from 0-2 spikes/s. These fibers were less sensitive than the fibers with higher spontaneous activity. The spike-rate thresholds varied from about 0.04 to above 1.28 cm/s2, giving a considerable range fractionation. Most of these fibers also had low-pass characteristics with respect to acceleration, but 8 fibers showed band-pass characteristics with maximal synchronizations and spike-rates occurring at 40-80 Hz. At high acceleration levels, most spikes fell within 5-10 degrees of the stimulus cycle. The phase-locking of the saccular fibers is therefore very acute at low frequencies. The phase angles preferred by the fibers at 10 Hz were bimodally distributed with the two peaks about 180 degrees apart. This finding probably reflects the morphological observation that the saccular macula contains two oppositely oriented hair-cell populations. The results also indicate that the actual motion of the otolith relative to the macula is complex. No behavioral role of a vibration receptor has been demonstrated in the grassfrog.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1994

The effect of vibration on back discomfort and serum levels of von Willebrand factor antigen: a preliminary communication.

The von Willebrand factor (vWf) is a complex protein whose release is a marker for endothelial damage; serum levels of its antigen (vWFAg) can be used as a marker for such changes. We measured the levels of back discomfort and vWFAg in 11 subjects following 25-min periods of (1) lying down, (2) sitting upright, (3) vibrating whilst sitting and (4) sitting upright. Back discomfort appeared and vWf levels were significantly increased following sitting upright, compared with lying flat, and increased further following vibration. They fell thereafter with a period of sitting still upright. These results demonstrate that vibration has a significant effect in increasing back discomfort and the serum levels of vWFAg, and it is possible that vibration may induce vascular damage within the spine.

Adult↗
PubMed2004

Tuned vibration absorber for suppression of rest tremor in Parkinson's disease.

A simple approach for the suppression of the tremor associated with Parkinson's disease is presented. The proposed system is a tuned vibration absorber (TVA), which has been very effective in the suppression of vibrations in an experimental model of the human arm with two degrees of freedom. Theoretical and numerical methods were used to study the behaviour of the arm model and to develop an effective tremor reduction approach. Based on these studies, a vibration absorber was designed, tested numerically and fabricated for experimental testing. Experimental investigations indicated that optimum control performance was related to the position of the controller and the excitation frequency. With a distance of 160 mm from the end of forearm, the TVA was found to have the best performance, and, for different tremor frequencies, the vibration of the experimental model was reduced by more than 80%.

Arm↗
PubMed1998

Three-dimensional biomechanical model for simulating the response of the human body to vibration stress.

Several investigations have revealed that long-term exposure to whole-body vibrations can induce low back pain. In analogy to materials handling, the health risk can be assessed if the forces transmitted in the spine during vibration are known. To estimate the forces a biomechanical model has been developed in which the human trunk, neck, head and arms are represented by 16 rigid bodies. An additional body simulates the vibrating seat. The bodies are connected by visco-elastic joint elements, and 56 force elements imitate the trunk and neck muscles. The motion equations are derived by means of the dynamics of systems of rigid bodies, and the motions are simulated in three directions. The frequency-response functions between the accelerations of the seat and the head satisfactorily correspond to data reported in the literature. The spine forces are composed of a static part, due to body posture, and a vibration-induced part. The relation between the oscillating parts of the forces transmitted from seat to pelvis and the spine forces are also described by frequency-response functions. To assess the health risk the simulated spine forces must be compared with the strength of the spine, bearing in mind that this is dependent on the number of load cycles.

Biomechanical Phenomena↗
PubMed2003

[Measurement and interpretation of irregular vocal cord fold vibrations].

BACKGROUND: Irregular vibrations of the vocal folds are regarded as a main reason for the common symptom of hoarseness. With real time resolution, they can only be observed using high speed recording techniques (up to 10,000 images/s). METHOD: During the last years, we have developed a recording device and image processing software dedicated to the extraction of vocal fold motion curves from the image series. Irregular vibrations can be understood by using Hirano's "body-cover-model": one vocal fold is assumed to act as a system of two coupled oscillators (the vocal muscle and the epithelium, coupled by the connective tissue of Reinke's space). RESULTS: By applying this biomechanical two-mass model and inversely solving Bernoulli's equation, the driving parameters of the vibration were computed from the high speed image series in selected cases. These parameters, like the subglottal pressure und the bilateral tension of the vocal muscle cannot, in general, be measured directly. DISCUSSION: From the model, it can be supposed that laryngeal asymmetry (either in mass or tension) is the primary reason causing irregularity. The consequence of asymmetry in the medio-lateral direction are different fundamental frequencies on each side, while asymmetry in the anterior-posterior direction leads to ap-mode vibrations.

Diagnosis, Computer-Assisted↗
PubMed2003

Motion perception during involuntary eye vibration.

Retinal motion caused by reflexive or voluntary eye movements is rarely misinterpreted as object motion, as if the visual system discounted the contribution of these eye movements to retinal motion. Yet, involuntary eye movements caused by mechanical eye vibration is often interpreted as object motion unless the vibration has high frequency, in which case only image blur may be noticed. In these latter conditions, however, a light flickering above the fusion limit is vividly perceived to undergo oscillatory motion over its static surround. We determined the conditions of this phenomenon, showing that the perceived frequency of illusory oscillation equals the difference between flicker frequency and the frequency of vibration of the eyes. This outcome is explained as a result of the low-pass temporal frequency characteristic of vision, which further predicts that the same effect should occur if the flickering light is vibrated and observed with static eyes. This prediction was corroborated empirically. We also determined the minimal amplitude of oscillation required to perceive motion as a function of postural stability and the presence of static references, finding an amplitude threshold of approximately 1 arcmin with postural stability in dim-light conditions, which increases to approximately 2 arcmin with postural instability in the dark.

Eye Movements↗
PubMed2006

Eye movements cannot explain vibration-induced visual motion and motion aftereffect.

Eye movements are thought to account for a number of visual motion illusions involving stationary objects presented against a featureless background or apparent motion of the whole visual field. We tested two different versions of the eye movement account: (a) the retinal slip explanation and (b) the nystagmus-suppression explanation, in particular their ability to account for visual motion experienced during vibration of the neck muscles, and for the visual motion aftereffect following vibration. We vibrated the neck (ventral sternocleidomastoid muscles, bilaterally, or right dorsal muscles) and measured eye movements in conjunction with perceived illusory displacement of an LED presented in complete darkness (N=10). To test the retinal-slip explanation, we compared the direction of slow eye movements to the direction of illusory motion of the visual target. To test the suppression explanation, we estimated the direction of suppressed slow-phase eye movements and compared it to the direction of illusory motion. Two main findings show that neither actual nor suppressed eye movements cause the illusory motion and motion aftereffect. Firstly, eye movements do not reverse direction when the illusory motion reverses after vibration stops. Secondly, there are large individual differences with regards to the direction of eye movements in observers who all experience a similar visual illusion. We conclude that, rather than eye movements, a more global spatial constancy mechanism that takes into account head movement is responsible for the illusion. The results also argue against the notion of a single central signal that determines both perceptual experience and oculomotor behaviour.

Adult↗
PubMed2005

Elastic vibrations in seamless microtubules.

Parameters characterizing elastic properties of microtubules, measured in several recent experiments, reflect an anisotropic character. We describe the microscopic dynamical properties of microtubules using a discrete model based on an appropriate lattice of dimers. Adopting a harmonic approximation for the dimer-dimer interactions and estimating the lattice elastic constants, we make predictions regarding vibration dispersion relations and vibration propagation velocities. Vibration frequencies and velocities are expressed as functions of the elastic constants and of the geometrical characteristics of the microtubules. We show that vibrations which propagate along the protofilament do so significantly faster than those along the helix.

Anisotropy↗
PubMed2002

Diagnostic aspects of vibration-induced white finger.

Vibration-induced white finger (VWF) is a secondary type of Raynaud's phenomenon (RP) caused by exposure to hand-arm vibration. The present review concerns the cold-provoked attack of RP in vasospastic VWF. It concentrates on the most common clinical and laboratory methods used to diagnose RP in vibration-exposed subjects. Some physiological aspects of the attack of RP are mentioned to elucidate the diagnostic principles of the tests. Anamnestic diagnostics by medical interviews and questionnaires as well as cold-provocation tests with detection of finger colour, finger systolic blood pressure (FSP), recovery time of finger skin temperature and recovery time of normal nail colour after nail compression are mentioned. The discriminative capacity and the reproducibility of the tests are discussed. Cold-provocation tests with detection of finger colour or zero FSP during cooling are recommended to be used if an attack of RP has to be registered for diagnostic or medico-legal purposes in individual cases. An abnormal reduction in FSP during cooling makes a history of RP very probable and is a suitable laboratory test for groups of subjects. Both recovery tests may be useful screening tests in field studies of vibration-exposed subject groups.

Cold Temperature↗
PubMed2002

Neurological diagnosis--aspects of quantitative sensory testing methodology in relation to hand-arm vibration syndrome.

OBJECTIVE: The objectives are to summarise the fundamental neurophysiological base for quantitative sensory testing (QST), and to discuss associated methodological and practical aspects necessary to consider with respect to applicability and reliability as a screening or diagnostic aid for vibration-induced sensory neuropathy. RESULTS: QST is the use of psychophysical techniques to measure the intensity of stimuli needed to produce specific sensory perceptions. The physical components are graded stimuli presented to the skin, eye or ear. The psychological component is mental recognition of the physical stimulus. Sensory modalities are named after the subjective feelings elicited, i.e. touch, pressure, vibration, warmth, cold and thermal pain. Since an exposure to vibration may cause symptoms and signs of sensory neuropathy in the hand and arm, the use of QST as an aid for screening and diagnosis has gained an increasing interest. The "Stockholm Workshop" classification scale for sensorineural stages also requires QST. Further, QST has also spread into many other areas, such as in the screening and diagnosis of peripheral neuropathy or polyneuropathy induced by different types of illness, exposure to toxic substances, compression and nerve entrapment. CONCLUSION: QST is in general easy to perform, usually not associated with pain (except thermal pain), suitable for screening and can readily be conducted in the field. QST is, however, known to be susceptible to the effects of multiple covariates and test methodologies. It is thus important that the relative influence on test results from all significant covariates are identified, and to standardise test methodology accordingly before QST can become a reliable and useful tool for diagnostic and screening purposes in the field of vibration-induced sensory neuropathy. The sensitivity, specificity and reliability of different methods for QST for this type of disorder is still very much unknown. Lack of normative values, standardisation of methods and of a "gold standard" for the presence of sensory neuropathy are some reasons.

Arm↗
PubMed2002

Measurement of manipulative dexterity in patients with hand-arm vibration syndrome.

OBJECTIVES: The purpose of the study was to assess quantitative measurements of the manipulative dexterity of patients suffering from hand-transmitted vibration disorder, and to investigate a possible link with impaired tactile perception in their hands. SUBJECTS AND METHODS: The subjects were 30 patients with hand-arm vibration syndrome, 30 office workers and 20 manual laborers of similar ages. Manipulative dexterity was assessed by measuring the performance time of buttoning-unbuttoning a work jacket with five buttons and of picking up and transferring 30 red beans, one by one, with the fingers from one plate to another. Patients were also examined on vibrotactile thresholds at 125 Hz as well as pain thresholds. RESULTS: The buttoning-unbuttoning time and the bean transfer time were significantly prolonged in the patients compared with the worker groups. The patients showed a close correlation between the buttoning-unbuttoning time and the bean transfer time. Performance times did not differ between patients with vibration-induced white finger and those without it. Those times also correlated with the vibrotactile and pain thresholds in the patients. When a cut-off value was set at 2 SDs from the mean performance times of the manual laborers, exceeding the cut-off value was found in 70% of the patients for the button-unbutton test and in 80% of those for the bean transfer test. All patients with moderately or severely increased vibrotactile and pain thresholds exceeded that value in performing the two tasks. CONCLUSION: The present measurements quantitatively showed impaired manipulation in patients with hand-arm vibration syndrome. Such difficulty with manipulation seems to be associated with the impaired tactile sensation in their hands.

Arm↗
PubMed2000

Hormonal responses to whole-body vibration in men.

The aim of this study was to evaluate the acute responses of blood hormone concentrations and neuromuscular performance following whole-body vibration (WBV) treatment. Fourteen male subjects [mean (SD) age 25 (4.6) years] were exposed to vertical sinusoidal WBV, 10 times for 60 s, with 60 s rest between the vibration sets (a rest period lasting 6 min was allowed after 5 vibration sets). Neuromuscular performance tests consisting of counter-movement jumps and maximal dynamic leg presses on a slide machine, performed with an extra load of 160% of the subjects body mass, and with both legs were administered before and immediately after the WBV treatment. The average velocity, acceleration, average force, and power were calculated and the root mean square electromyogram (EMGrms) were recorded from the vastus lateralis and rectus femoris muscles simultaneously during the leg-press measurement. Blood samples were also collected, and plasma concentrations of testosterone (T), growth hormone (GH) and cortisol (C) were measured. The results showed a significant increase in the plasma concentration of T and GH, whereas C levels decreased. An increase in the mechanical power output of the leg extensor muscles was observed together with a reduction in EMGrms activity. Neuromuscular efficiency improved, as indicated by the decrease in the ratio between EMGrms and power. Jumping performance, which was measured using the counter-movement jump test, was also enhanced. Thus, it can be argued that the biological mechanism produced by vibration is similar to the effect produced by explosive power training (jumping and bouncing). The enhancement of explosive power could have been induced by an increase in the synchronisation activity of the motor units, and/or improved co-ordination of the synergistic muscles and increased inhibition of the antagonists. These results suggest that WBV treatment leads to acute responses of hormonal profile and neuromuscular performance. It is therefore likely that the effect of WBV treatment elicited a biological adaptation that is connected to a neural potentiation effect, similar to those reported to occur following resistance and explosive power training. In conclusion, it is suggested that WBV influences proprioceptive feedback mechanisms and specific neural components, leading to an improvement of neuromuscular performance. Moreover, since the hormonal responses, characterised by an increase in T and GH concentration and a decrease in C concentration, and the increase in neuromuscular effectiveness were simultaneous but independent, it is speculated that the two phenomena might have common underlying mechanisms.

Adult↗
PubMed2001

Oxygen uptake during whole-body vibration exercise: comparison with squatting as a slow voluntary movement.

In this study we investigated metabolic power during whole-body vibration exercise (VbX) compared to mild resistance exercise. Specific oxygen consumption (VO2) and subjectively perceived exertion (rating of perceived exertion, RPE; Borg scale) were assessed in 12 young healthy subjects (8 female and 4 male). The outcome parameters were assessed during the last minute of a 3-min exercise bout, which consisted of either (1) simple standing, (2) squatting in cycles of 6 s to 90 degrees knee flexion, and (3) squatting as before with an additional load of 40% of the subject's body weight (35% in females). Exercise types 1-3 were performed with (VbX+) and without (VbX-) platform vibration at a frequency of 26 Hz and an amplitude of 6 mm. Compared to the VbX- condition, the specific VO2 was increased with vibration by 4.5 ml x min(-1) x kg(-1). Likewise, squatting and the additional load were factors that further increased VO2. Corresponding changes were observed in RPE. There was a correlation between VbX- and VbX+ values for exercise types 1-3 (r = 0.90). The correlation coefficient between squat/no-squat values (r = 0.70 without and r = 0.71 with the additional load) was significantly lower than that for VbX-/VbX+. Variation in specific VO2 was significantly higher in the squatting paradigm than with vibration. It is concluded that the increased metabolic power observed in association with VbX is due to muscular activity. It is likely that this muscular activity is easier to control between individuals than is simple squatting.

Adult↗
PubMed2003

Raman spectra and normal coordinate analyses of low-frequency vibrations of oxo-bridged manganese complexes.

The active sites of certain metalloenzymes involved in oxygen metabolism, such as manganese catalase and the oxygen-evolving complex of photosystem II, contain micro -oxo-bridged Mn clusters with ligands that include H(2)O and micro (1,3)-carboxylato bridges provided by protein side chains. In order to understand better the vibrational spectra of such clusters, the low-frequency resonance Raman spectra of a series of structurally characterized Mn-oxo model complexes were examined. The series includes complexes of the type [Mn(2)(O)(OAc)(2)(bpy)(2)(L)(2)] and [Mn(2)(O)(2)(OAc)(bpy)(2)(L)(2)], where bpy=2,2'-bipyridine, OAc=acetate and L=H(2)O or Cl(-). Complexes containing the isotopomers OAc- d(3) and D(2)O, as well as those containing both isotopomers, were also examined. Normal coordinate analyses (NCA) were performed on the various complexes using theGF matrix method. Selected vibrational modes in the 200-600 cm(-1) region were assigned based on the spectra and NCA, which identify vibrational modes arising from the metal-ligand bonds. These results will be useful in interpreting the vibrational spectra obtained from metalloproteins containing Mn-oxo complexes in their active sites.

Crystallization↗
PubMed1980

Labyrinth and neck reflex modification of the tonic vibration reflex in the decerebrate cat.

The interaction between tonic labyrinth or neck reflexes and the tonic vibration reflex acting on the medial head of triceps in the decerebrate cat is described. Medial triceps was isotonically loaded and reflex actions were measured as changes in muscle length. Natural stimulation of the receptors giving rise to tonic labyrinth or neck reflexes can either enhance or diminish the size of a pre-existing tonic vibration reflex. It is also shown that descending activity from either the labyrinth or neck reflex systems can completely suppress the tonic vibration reflex, whereas the tonic vibration reflex was never observed to suppress an established labyrinth or neck reflex.

Animals↗
PubMed1992

Gravitoinertial force level affects the appreciation of limb position during muscle vibration.

Illusory motion and displacement of the restrained forearm can be elicited by vibrating the biceps brachii or triceps brachii muscle. We measured the influence of gravitoinertial force level on these perceptual responses to vibration during parabolic flight maneuvers where normal (1G) and high force (1.8G) background levels alternated with microgravity (0G). Subjects indicated the apparent forearm position of the vibrated arm with the other forearm and also made verbal reports. Biceps brachii vibration induced illusory extension of the forearm and triceps brachii, illusory flexion; these apparent motions and displacements were highly G force-dependent being enhanced at 1.8G and diminished at 0G relative to normal 1G force level. These alterations are discussed in terms of vestibulo-spinal and propriospinal influences on alpha-gamma motoneuronal control of muscle tone and the varying requirements for postural load support in different force backgrounds. Their implications for the control and appreciation of limb movements during exposure to different G force levels are also described.

Arm↗
PubMed1985

Changes in wakefulness during exposure to whole body vibration.

Thirty subjects were exposed to low frequency sinusoidal and random whole body vibration in the vertical direction, 0.3 m/sec2 (rms). Changes in wakefulness during 15 min vibration were compared to changes occurring during corresponding pauses without exposure. Measurements were made on EEG and ECG. Exposure to whole body vibration was found to be correlated with reduction in wakefulness. This effect, verified by an increase of theta and decrease of alpha activity, was greater during sinusoidal than random vibration.

Adult↗
PubMed1984

Some influences of tonic vibration reflexes on the position sense of the contralateral limb.

Mechanically vibrating a skeletal muscle elicits reflex activation of that muscle, a phenomenon which is known as the tonic vibration reflex. We explored in eight individuals how vibration of their right biceps brachii or triceps brachii muscle influenced their ability to point with their left arm to visual targets and to set that arm to particular apparent positions. The position sense of the pointing arm was affected systematically by contralateral vibration with the influence being considerably greater when the biceps brachii rather than the triceps brachii of the contralateral arm was stimulated. This asymmetric effect was related to the different densities of muscle spindle innervation of the biceps brachii and triceps brachii muscles and to their patterns of reflex organization within the spinal cord. The altered position sense of the pointing arm led to errors both for pointing movements with the arm to visual targets and for positioning movements of the arm into specified spatial configurations.

Adult↗