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At least 649 records · Page 36Linked to original sources
PubMed1984

An empirical note on attaining a spatial target after distorting the initial conditions of movement via muscle vibration.

Can one's limb be accurately positioned to a spatial location without a veridical estimate of the initial conditions of movement? The experiment reported here examined this question by distorting perception of a limb's starting position via muscle vibration. Subjects executed rapid flexion movements under no-vibration, contralateral arm vibration, and ipsilateral arm vibration conditions. Vibration was applied to the biceps for 10 sec prior to the start of a reproduction movement. The results showed that vibration on the ipsilateral arm caused a significant increase in reproduction error, relative to the no-vibration and contralateral-vibration conditions. This finding provides additional evidence that accurate knowledge about the initial conditions of movement is a necessary component in positioning a limb.

Journal Article↗
PubMed1994

EFFECT OF MECHANICAL VIBRATION ON ACTIVE TENSION IN THE LONGITUDINAL RETRACTOR MUSCLE OF A SEA CUCUMBER STICHOPUS JAPONICUS

1. The effect of mechanical vibration on active tension in an echinoderm somatic smooth muscle was studied using the longitudinal retractor muscle (LRM) of a sea cucumber Stichopus japonicus. 2. The steady contracture tension in LRM fibres maximally activated with 10(-3) mol l-1 acetylcholine (ACh) was reduced by vibrations (peak-to-peak amplitude, 0.5­2.5 % of l0, where l0 is the slack length of the muscle; frequency, 5­100 Hz). The extent of reduction of active contracture tension increased with increasing amplitude of vibration, but it did not change appreciably with increasing frequency of vibration. 3. The steady contracture tension in LRM fibres submaximally activated with 10(-5) mol l-1 ACh was more markedly reduced by vibrations than was that in maximally activated fibres. 4. The vibration-induced reduction of active contracture tension disappeared when temperature was lowered from 20­23 to 0 °C. 5. The development of contracture tension in LRM fibres activated with ACh was not affected by mechanical vibration. 6. These results are discussed in connection with the vibration-induced decrease in the rate of breakage of the actin­myosin linkages responsible for isometric force generation.

Journal Article↗
PubMed1990

[Effects of an increase or decrease in the middle ear pressure on tympanic membrane vibrations (experimental study by holographic interferometry)].

The effects of positive and negative pressure in the middle ear on tympanic membrane (TM) vibrations were studied in twenty canine temporal bones by holographic interferometry. The displacement of the TM was measured by moiré topography. 1) When pressure was applied to the tympanic cavity, the curvature of the TM became small under negative pressure and large under positive pressure, with the displacement being greater under positive pressure. 2) Without pressure load, the vibration pattern below 2 kHz was simple and there were peak displacement regions in the posterior and anterior parts of the membrane and the peaks occurred approximately halfway along the manubrium. The TM vibrations showed sectional patterns, above 3 kHz in the posterior and above 4 kHz in the anterior. The amplitude of the anterior peak was larger than that of the mallear tip, but smaller than that of the posterior. 3) At frequencies below 2 kHz, the vibration pattern was not affected by negative pressure load. At frequencies of 3 kHz or higher, the sectional patterns changed into the simpler patterns and the sectional vibrations diminished as the pressure increased. 4) Below 2 kHz, the TM amplitude decreased with increasing negative pressure. Above 3 kH, the amplitude showed an initial increase but decreased at higher negative pressure loading. With the amplitude of the mallear tip, the same tendency was observed. The resonance frequency shifted to a higher frequency range with pressure loading. 5) Under positive pressure, the vibration pattern remained unchanged below 2 kHz, and above 3 kH, sectional vibrations changed to the simple vibrations.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed2000

Vibration does not improve results of the canalith repositioning procedure.

OBJECTIVE: To determine whether, in patients with benign paroxysmal positional vertigo (BPPV), the canalith repositioning procedure performed with vibration applied over the mastoid bone of the affected ear is more effective in resolving the symptoms and preventing recurrence of BPPV than the procedure performed without vibration. DESIGN: Retrospective case review. SETTING: Tertiary referral center. PATIENTS: Ninety-four patients diagnosed as having BPPV involving the posterior semicircular canal. INTERVENTIONS: Patients were assigned to one of 2 treatment groups: the canalith repositioning procedure with vibration (n=44) and with no vibration (n=50). MAIN OUTCOME MEASURES: Effectiveness of treatment was determined through clinical reevaluation or reported through a telephone interview 1 week after treatment. Intensity of symptoms was quantified on a scale of 1 to 3 (mild, moderate, or severe); effectiveness of treatment was categorized on a scale of 1 to 4 (cure, much better, better, or no change). Rate of recurrence was determined through later clinical reevaluation or a telephone interview. RESULTS: At 1 week, 57 of the 94 patients were cured and 16 were much better, providing a 78% overall success rate. There was no significant difference in effectiveness of the treatment or the frequency of reoccurrence of BPPV between the vibration and no-vibration groups as determined from the Kaplan-Meier product-limit method and log-rank test. Rate of recurrence was 47% at a maximum follow-up of 5.25 years. CONCLUSIONS: Our results suggest that, while the canalith repositioning procedure is effective in the treatment of BPPV, vibration applied during the maneuver does not significantly affect short-term or long-term outcomes.

Adult↗
PubMed2005

Evidence for frequency-dependent arterial damage in vibrated rat tails.

The effects of single 4-hr bouts of continuous 30, 60, 120, and 800 Hz tail vibration (49 m/sec2, root mean squared) were compared to assess frequency-amplitude-related structural damage of the ventral caudal artery. Amplitudes were 3.9, 0.98, 0.24, and 0.0055 mm, respectively. Vibrated, sham-vibrated, and normal arteries were processed for light and electron microscopy. The Curry rat tail model of hand-arm vibration (Curry et al. Muscle Nerve 2002;25:527-534) proved well-suited for testing multiple frequencies. NFATc3 immunostaining, an early marker of cell damage, increased in smooth muscle and endothelial cells after 30, 60, and 120 Hz but not 800 Hz. Increased vacuolization, which is indicative of smooth muscle contraction, occurred for all frequencies except 800 Hz. Vacuoles increased in both endothelial and smooth muscle cells after 60 and 120 Hz. Only 30 Hz showed pronounced smooth muscle cell vacuolization along the internal and external elastic membranes, suggesting stretch-mediated contraction from the large amplitude shear stress. Discontinuities in toluidine blue staining of the internal elastic membrane (IEM) increased for all frequencies, indicating vibration-induced structural weakening of this structure. Patches of missing IEM and overlying endothelium occurred in approximately 5% of arteries after 60, 120, and 800 Hz. The pattern of damage after 800 Hz suggests that the IEM is disrupted because it resonates at this frequency. Vibration acceleration stress and smooth muscle contraction appear to be the major contributors to arterial damage. The pattern of vibration-induced arterial damage of smooth muscle and endothelial cells is frequency-amplitude-dependent.

Animals↗
PubMed1989

Different effects of mechanical vibration on bone ingrowth into porous hydroxyapatite and fracture healing in a rabbit model.

The effects of mechanical vibration on bone ingrowth into porous hydroxyapatite implants and fracture healing were examined radiographically, histomorphometrically, and biomechanically in a rabbit model. Fifty-three female NZW rabbits were used in this study. These rabbits were divided into four separate studies to assess the effects of 20 and 60 min of vibration/day in both implant and osteotomy models as compared with the respective non-vibrated controls. For the implant model, coral hydroxyapatite goniopora rods were implanted bilaterally into tibiae and for the osteotomy model, bilateral fibulae were osteotomized. A resonant frequency of 25 Hz mechanical vibration was used. After periods of 2, 3, 4, and 6 weeks of vibration, the rabbits were killed and examined. For the implant model, there was no significant difference between control, 20, or 60 min of vibration/day with respect to the rate or amount of new bone ingrowth. For the fracture model, 60 min of vibration/day produced a significantly larger callus as compared with the non-vibrated controls (p less than 0.05), whereas 20 min of vibration/day did not. Although biomechanical testing demonstrated a general trend for increased strength in the vibrated animals, it failed to reach significance. These results suggest that the mechanical vibration used in the present study had a beneficial effect on callus volume, possibly due to the stimulation of secondary bone healing processes, but does not appear to promote bone ingrowth into a porous hydroxyapatite implant.

Animals↗
PubMed1993

Assessment of central, peripheral, and autonomic nervous system functions in vibrating tool operators: neuroelectrophysiological studies.

To evaluate the effects of vibrating tool operation (i.e., combined stressors of local vibration, noise, cold climate, and heavy work) on the central, peripheral, and autonomic nervous systems, the short-latency somatosensory and brain stem auditory evoked potentials (SSEP and BAEP), the distribution of sensory median nerve conduction velocities (DCV), conventional median nerve conduction velocities (NCV), and the electrocardiographic R-R interval variability (CVRR) were measured in three groups of male vibrating tool operators and age-matched male healthy adults. Two components of the CVRR reflecting parasympathetic activity (C-CVRSA) and sympathetic activity (C-CVMWSA) were also examined. In the first group of vibrating tool operators (15 chain saw operators), all parameters of DCV (V10-V90 velocities) and sensory and motor nerve conduction velocities of NCV were significantly slowed. All peak latencies of SSEP were significantly prolonged, while no significant differences were found in the interpeak latencies of SSEP. The N9 peak latency of SSEP was significantly related to total working days. In the second group of the operators (12 chain saw and 8 brush saw operators), the I-V interpeak and V peak latencies of BAEP were significantly prolonged in the 12 chain saw operators; the I-V interpeak latency of BAEP was significantly correlated with the working years in the 8 brush saw operators. In the third group of vibrating tool operators, i.e., 13 operators with a history of vibration-induced white finger (VWF group) and 11 operators without VWF (non-VWF group), both the CVRR and C-CVRSA were significantly reduced in the VWF group; only the CVRR was significantly reduced in the non-VWF group. Similarly, the faster velocities of DCV (V70, V80, and V90 velocities) were significantly slowed in both the VWF and non-VWF groups. In conclusion, it is suggested that vibrating tool operation affects the faster sensory and motor nerve fibers, the parasympathetic activity, and the auditory pathway from the acoustic nerve to the brain stem.

Adult↗
PubMed1995

Effects of developmental methylmercury exposure or lifetime lead exposure on vibration sensitivity function in monkeys.

Paresthesias are a frequently reported symptom of methylmercury exposure in adults, while peripheral neuropathy has long been known to result from high-level lead exposure. Despite this, no objective determination of somatosensory function has been performed in either humans or animals for either toxicant. Somatosensory function was assessed following developmental methylmercury exposure or lifetime lead exposure in monkeys (Macaca fascicularis) by determination of sensitivity to vibration applied to the fingertip. Vibration thresholds were determined over a number of frequencies, from 25 to 250 Hz, by means of a behavioral procedure. The underside of the tip of the monkey's middle finger was precisely positioned over a blunt probe attached to a vibrator. The monkey signaled detection of the vibration by breaking contact with a stainless steel bar with the free hand. At each of the five frequencies tested, the amplitude of the vibration was manipulated systematically to determine the monkey's threshold of detection. Four of five monkeys dosed with methylmercury from birth to 7 years of age, with blood mercury levels during dosing of 0.8-1.1 micrograms/g, exhibited elevated thresholds when tested at 18 years of age. Two monkeys dosed in utero through 4 years of age, with blood mercury levels of 0.35 micrograms/g during dosing, were impaired when tested at 15 years of age, while two monkeys with histories of blood mercury levels of 0.70 were relatively unimpaired. Lifetime exposure to lead resulting in stable blood lead levels of 20-25 micrograms/dl resulted in elevated vibration sensitivity only at the highest frequency in all four individuals tested. However, only two of six individuals with high lead levels (60-130 micrograms/dl) exhibited impairment. These results represent severe impairment in methylmercury-exposed monkeys 11 years after cessation of dosing and extend previous research documenting visual and auditory impairment in these monkeys. While effects of lifetime lead exposure on vibration sensitivity observed in the present study are suggestive, there is clearly a need for further research.

Animals↗
PubMed1996

Responses of motor cortical cells to short trains of vibration.

The response discharges of precentral motor cortical cells to brief trains of vibration applied to the tendon of biceps brachii were analyzed in two alert but passive monkeys. The activity of 20 phasic-tonic and 6 tonic cells was analyzed. All had functional linkages with flexor muscles during a preceding flexion task and responded to passive movement of the elbow. Taking as a reference the stereotyped reflex response in the stretched muscle, the effect of changes in the amplitude of a constant frequency vibration (4 vibrations at 58 Hz) was quantified statistically in peristimulus histograms of the cortical cell discharges. All cells were transiently influenced by low vibration amplitudes. Most responses (71%) were excitatory and occurred at a mean latency of 24 ms, which is consistent with cells activated by input from stretch receptors. Excitatory, reproducible responses to the lowest vibration amplitudes were more frequent in phasic-tonic than in pure tonic cells. Large-amplitude vibrations always excited the motor cortical cells. The sign of the responses to vibration matched that to passive elbow movements for most cells. These findings show that elbow-related motor cortical cells are very sensitive to proprioceptive input from primary spindle afferents.

Animals↗
PubMed1996

High-frequency vibratory sensitive neurons in monkey primary somatosensory cortex: entrained and nonentrained responses to vibration during the performance of vibratory-cued hand movements.

The activity of high-frequency vibratory sensitive (HFVS) neurons was recorded in monkey primary somatosensory cortex (SI) while animals performed wrist flexions and extensions in response to 57-Hz or 127-Hz palmar vibration. HFVS neurons were distinguished by their exquisite responsiveness to the higher frequency vibration (127 Hz). These neurons probably received input from Pacinian afferents. Systematic selection of HFVS neurons was made using K-means cluster analysis of neuronal firing rates during stimulating at 127 Hz and 57 Hz. HFVS neurons constituted approximately 4% of all recorded cells and more frequently were found in areas 3b, 1, and 2 (approximately 5% of total in each area) than in area 3a (approximately 1%). Using circular-statistics analyses for nonuniformity of discharges over the vibratory cycle, HFVS neurons were split into two groups of vibration-entrained neurons (E1 and E2 neurons) and one group of nonentrained neurons (NE neurons). E1 neurons were entrained to vibration at both 127 Hz and 57 Hz, whereas E2 neurons were entrained only at one of these vibratory frequencies. Vibration-entrained neurons often exhibited multimodal distributions of interspike intervals (ISIs), with the modes at multiples of the period of vibration. In addition, for these neurons, ISI clusters in joint interval plots commonly had diagonal orientations that were indicative of negative serial correlations of the ISIs, a feature of extrinsically driven rhythmic activity. HFVS neurons located in areas 3a, 3b, and 1 responded to vibration onset at shorter latencies (16.5 +/- 1.6, 19.8 +/- 5.9, and 21.4 +/- 6.4 ms, respectively, during 127-Hz stimulation) than those located in area 2 (35.6 +/- 13.8 ms). These observations are consistent with a scheme in which HFVS area 2 neurons receive their inputs from more anterior areas of SI. Moreover, entrained neurons exhibited shorter response latencies than nonentrained neurons. During 127-Hz stimulation, response latencies were 17.3 +/- 3.0, 17.5 +/- 2.6, and 25.7 +/- 6.4 ms for E1, E2, and NE neurons, respectively, located in areas 3a, 3b, and 1. Thus, entrained and nonentrained HFVS neurons may belong to different hierarchical stages of information processing.

Analysis of Variance↗
PubMed1992

The effects of wrist muscle vibration on human voluntary elbow flexion-extension movements.

The effect of forearm muscle tendon vibration during alternating step flexion-extension movements about the elbow was studied in normal humans. In one experiment, a vibrator was mounted over either the forearm flexor or the extensor muscle. In a second experiment, a vibrator was mounted over either the forearm muscle or the biceps muscle. In both experiments, vibration was applied either to a single muscle or simultaneously to both muscles during elbow flexion-extension movements. After a period of practice, subjects learned the required movements and were able to make them with their eyes closed. Application of vibration to the forearm and the biceps muscle during extension movements produced an undershoot of the required end-movement position. Moreover, application of high-frequency vibration (100 Hz) to the forearm extensor and flexor muscle produced an overshoot of the required end-movement position. The observed results are consistent with vibration induced activation of muscle spindle receptors not only in the lengthening muscle during movement but also in the forearm muscles. It is suggested that the pattern of distribution of muscle spindle afferent from the forearm muscle onto alpha-motoneurons of muscles acting at the elbow has played an important role of alternating step flexion-extension movements.

Elbow↗
PubMed1981

The effects of muscle vibration on the attainment of intended final position during voluntary human arm movements.

Muscle tendon vibration was applied during voluntary step-tracking arm target-movements performed by normal human subjects. Vibration (freq. = 120 Hz) was applied over either the biceps or triceps tendons. During non-visually guided (eyes closed) trials, vibration of the muscle antagonistic to the movement being performed resulted in an undershoot of the required target. Thus, biceps vibration produced an undershoot of the extension target and triceps vibration an undershoot of the flexion target. The same effect occurred if the vibration was applied continuously over several movements or only during the course of individual movements. In contrast, vibration of the muscle acting as the prime mover had no effect on the correct attainment of the required target. It is suggested that the central nervous system may monitor muscle afferent activity of the lengthening (antagonist) muscle during simple, step movements.

Arm↗
PubMed1984

Acute effects of shock-type vibration transmitted to the hand-arm system.

The aim of the project was to find out whether shock-type vibration of hand-tools compared to non-impulsive vibration has stronger acute effects on the hand-arm system and therefore needs a stricter evaluation from the occupational health point of view in comparison with the requirements of the Draft International Standard ISO-DIS 5349. Under laboratory conditions, subjects were exposed to simulated vibration of hand-tools (grinder, chain saw, hammer-drill, pneumatic hammer, rivet hammer and nailer). The following evaluation criteria were used: biomechanical transmissibility of the hand-arm system (wrist, elbow joint, shoulder joint); muscle-activity (m. flexor carpi ulnaris, m. biceps, m. triceps); peripheral circulation (skin temperature) and subjective perception (comparison of intensity of standard and test vibrations). The results show no significant difference in acute effects on the hand-arm system between impulsive and non-impulsive type vibrations of the hand-tools tested with respect to the chosen vibration level, short-time exposure (up to 8 min) and evaluation criteria. In summary, therefore, it may be concluded that for the evaluation of shock-type vibration of the hand-tools tested, it is justified to use the existing Draft International Standard ISO-DIS 5349.

Adult↗
PubMed1981

Temporary threshold shift of vibratory sensation after clasping a vibrating handle.

The temporary threshold shift of vibratory sensation (TTSv) at 125 Hz after clasping a vibrating handle was investigated in relationship to four influencing factors: discrete frequency and acceleration of the vibration exposed to, the grip in clasping a handle and the time after exposure. Clasping the vibrating handle resulted in significantly larger TTSv than shown in clasping a non-vibrating handle. The TTSv after exposure to the 250 Hz vibration was significantly the largest in all frequencies at equal acceleration. The TTSv recovered exponentially as time elapsed after exposure. The TTSv also increased proportionally to the power of acceleration at each frequency and grip force. The larger grip force resulted in a significantly larger TTSv. A general form of regression equation of TTSv involving the four factors was established. The prediction equations obtained confirmed that a frequency around 200 Hz induced the largest TTSv among vibrations with equal acceleration and around 240 Hz among vibrations with equal velocity.

Adult↗
PubMed1996

Different acute effects of single-axis and multi-axis hand-arm vibration.

Under laboratory conditions the effects of single-axis and multi-axis hand-arm vibration exposure on several strain parameters were tested in up to 20 male subjects. As parameters of these acute effects, the biodynamic vibration behavior of the hand-arm system, the electrical activity of the most affected muscle groups, the skin temperature, the vibration sensitivity of the fingertips, and the subjective vibration sensation were measured. When comparing simulated three-axis vibration exposure with single-axis vibration exposure, synergistic effects in the form of an increasing reaction could be found. It could be proven that the vector sum of the frequency-weighted acceleration in the three axes represents the acute effects better than does the weighted acceleration in the main axis alone. This summation has to take into account the relatively lower effects of vibration in the x- or y-direction compared with the z-direction. On the basis of the experimental results a new proposal for frequency weighting of the three different axes and an energetic summation procedure are derived. Application of this knowledge in the International Standard ISO 5349 is proposed.

Adolescent↗
PubMed1991

Autonomic and peripheral nervous system dysfunction in workers exposed to hand-arm vibration: a study of R-R interval variability and distribution of nerve conduction velocities.

To assess the effects of vibrating-tool operation on the autonomic and peripheral nervous system, we measured the variability in the electrocardiographic R-R interval (CVRR) and the distribution of nerve conduction velocities (DCV) in 24 men who were vibrating-tool operators and in 17 healthy adult men (control group). Of the 24 tool operators, 13 had a history of vibration-induced white finger [VWF(+) group] and 11 had no such history [VWF(-) group]. Two components of CVRR, i.e. C-CVRSA and C-CVMWSA, which have been considered to reflect parasympathetic and sympathetic activities, respectively, were also examined. Both the CVRR and the C-CVRSA in the VWF(+) group and the CVRR in the VWF(-) group were found to be significantly depressed as compared with the control values; moreover, a significant difference in the C-CVRSA was observed between the VWF(+) group and the VWF(-) group. The faster DCVs and the sensory median nerve conduction velocity were significantly slowed in the VWF(+) and VWF(-) groups. The C-CVMWSA was significantly correlated with most of the DCV parameters and with the median nerve conduction velocities in all 24 vibrating-tool operators. These data suggest that operation of vibrating tools, which involves exposure to combined stressors of local vibration, heavy work, climate, and noise, affects both the faster myelinated nerve-fiber activity and the parasympathetic activity; the sympathetic activity at rest in workers exposed to hand-arm vibration may be related to depression of peripheral nerve conduction.

Adult↗
PubMed1985

Time dependence and non-linearity of the impedance of the human hand-arm system while exposed to intense vibration.

The object of the investigation was to find out possible non-linearities and dependencies of the impedance of the hand-arm-system on the exposure time. The measurements were made on four male test persons, with the vibrations being introduced parallel to the forearm axis and in a standing position with the arms stretched. The vibration accelerations were between 11 m/s2 and 36 m/s2, and the measuring handle had a weight of only 48 g. The impedance decreases in dependence on time at maximum spanning force without pressing force. After 1 min of exposure time, values of about 55% are reached at 40 Hz and values of about 80% at 20 Hz. The impedance with pressing force of 100 N without spanning force increases with time, most distinctly at 25 Hz. No influence of the vibration intensity could be seen. The compression-tension quotient was introduced as characteristic for the non-linearity. It is dependent on the frequency, the vibration acceleration and, with large vibration accelerations, also on the exposure time. The quotient is 1 ... 1.5 at vibration accelerations up to 10 m/s2, and 3 ... 4 at vibration accelerations up to 36 m/s2 and after 3 to 5 min exposure time.

Arm↗
PubMed1990

Responses of sympathetic nervous system to cold exposure in vibration syndrome subjects and age-matched healthy controls.

Plasma norepinephrine and epinephrine in vibration syndrome subjects and age-matched healthy controls were measured for the purpose of estimating the responsibility of the sympathetic nervous system to cold exposure. In preliminary experiment, it was confirmed that cold air exposure of the whole body was more suitable than one-hand immersion in cold water. In the main experiment, 195 subjects were examined. Sixty-five subjects had vibration syndrome with vibration-induced white finger (VWF + group) and 65 subjects had vibration syndrome without VWF (VWF- group) and 65 controls had no symptoms (control group). In the three groups, plasma norepinephrine levels increased during cold air exposure of whole body at 7 degrees +/- 1.5 degrees C. Blood pressure increased and skin temperature decreased during cold exposure. Percent increase of norepinephrine in the VWF+ group was the highest while that in VWF- group followed and that in the control group was the lowest. This whole-body response of the sympathetic nervous system to cold conditions reflected the VWF which are characteristic symptoms of vibration syndrome. Excluding the effects of shivering and a cold feeling under cold conditions, it was confirmed that the sympathetic nervous system in vibration syndrome is activated more than in the controls. These results suggest that vibration exposure to hand and arm affects the sympathetic nervous system.

Adult↗