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At least 1,621 records · Page 90Linked to original sources
PubMed1999

Effect of paraspinal muscle vibration on position sense of the lumbosacral spine.

STUDY DESIGN: A two-group experimental design with repeated measures on one factor was used. OBJECTIVES: To investigate the role of the muscle spindles of the paraspinal muscles in lumbosacral position sense of healthy individuals. SUMMARY OF BACKGROUND DATA: Muscle spindles are recognized to be important mediators for position and movement sense in peripheral joints, and they are very sensitive to mechanical vibration. However, little is known about their role in the control of lumbosacral spine positioning. METHODS: Twenty-five young individuals with no low back pain were assigned at random to an experimental or control group. Proprioceptive information of the multifidus muscle spindles was distorted in half of the trials in 16 individuals by manually applying vibration (70 Hz, 0.5 mm amplitude) for approximately 5 seconds. The control group (n = 9) only heard the vibrator noise during repositioning of the lumbosacral spine. Repositioning accuracy in the sitting position was estimated by calculating the mean absolute error, constant error, and variable error among six criteria and reproduction sacral tilt angles. RESULTS: Multifidus muscle vibration induced a significant muscle lengthening illusion through which the members of the experimental group undershot the target position (F(1,15) = 30.77, P < 0.0001). The position sense scores of the control group displayed no significant differences across trials (F(1,8) = 0.56, P > 0.05). CONCLUSIONS: The findings suggest that precise muscle spindle input of the paraspinal muscles is essential for accurate positioning of the pelvis and lumbosacral spine in a sitting posture.

Adult↗
PubMed2002

Long-term follow-up study on patients with vibration-induced white finger (VWF).

The prognosis of vibration-induced white finger was investigated with a long follow-up period. From 1975 to 1994, 99 men with hand-arm vibration syndrome who received the annual compulsory examination at San-in Rosai Hospital were followed up for 15 years or longer. Based on the extent of finger-blanching attacks described in the medical records, they were classified according to the vascular stage of the Stockholm workshop scale. In our laboratory, finger systolic blood pressure (FSBP) measurement after finger cooling has been performed since 1989. We compared the stage classification with the results of FSBP measurement after finger cooling in the period 1989-1994. The stage 2 and stage 3 groups showed a significant decrease in FSBP% compared with the stage 0 group. The vascular stage classification based on subjective symptoms in this study was to a certain extent reliable. Although vibration-induced white finger symptoms tended to improve to some extent, 43.2% and 70.4% of patients with stage 2 and stage 3 at first examination, respectively, still suffered from finger blanching attacks after 15 years of observation. Blanching of fingers in advanced stages, especially stage 3, was found to be persistent many years after cessation of vibration exposure.

Blood Circulation↗
PubMed2003

Transmissibility of 15-hertz to 35-hertz vibrations to the human hip and lumbar spine: determining the physiologic feasibility of delivering low-level anabolic mechanical stimuli to skeletal regions at greatest risk of fracture because of osteoporosis.

STUDY DESIGN: Experiments were undertaken to determine the degree to which high-frequency (15-35 Hz) ground-based, whole-body vibration are transmitted to the proximal femur and lumbar vertebrae of the standing human. OBJECTIVES: To establish if extremely low-level (<1 g, where 1 g = earth's gravitational field, or 9.8 ms-2) mechanical stimuli can be efficiently delivered to the axial skeleton of a human. SUMMARY OF BACKGROUND DATA: Vibration is most often considered an etiologic factor in low back pain as well as several other musculoskeletal and neurovestibular complications, but recent in vivo experiments in animals indicates that extremely low-level mechanical signals delivered to bone in the frequency range of 15 to 60 Hz can be strongly anabolic. If these mechanical signals can be effectively and noninvasively transmitted in the standing human to reach those sites of the skeleton at greatest risk of osteoporosis, such as the hip and lumbar spine, then vibration could be used as a unique, nonpharmacologic intervention to prevent or reverse bone loss. MATERIALS AND METHODS: Under sterile conditions and local anesthesia, transcutaneous pins were placed in the spinous process of L4 and the greater trochanter of the femur of six volunteers. Each subject stood on an oscillating platform and data were collected from accelerometers fixed to the pins while a vibration platform provided sinusoidal loading at discrete frequencies from 15 to 35 Hz, with accelerations ranging up to 1 g(peak-peak). RESULTS: With the subjects standing erect, transmissibility at the hip exceeded 100% for loading frequencies less than 20 Hz, indicating a resonance. However, at frequencies more than 25 Hz, transmissibility decreased to approximately 80% at the hip and spine. In relaxed stance, transmissibility decreased to 60%. With 20-degree knee flexion, transmissibility was reduced even further to approximately 30%. A phase-lag reached as high as 70 degrees in the hip and spine signals. CONCLUSIONS: These data indicate that extremely low-level, high-frequency mechanical accelerations are readily transmitted into the lower appendicular and axial skeleton of the standing individual. Considering the anabolic potential of exceedingly low-level mechanical signals in this frequency range, this study represents a key step in the development of a biomechanically based treatment for osteoporosis.

Adult↗
PubMed2004

Using exposure prediction rules for exposure assessment: an example on whole-body vibration in taxi drivers.

BACKGROUND: It is often difficult and expensive to make direct measurements of an individual's occupational or environmental exposures in large epidemiologic studies. METHODS: In this study, we used information collected in validation studies to develop a prediction rule for assessing exposure in a study with no direct measurement. We established a prediction rule through mixed-effect modeling of direct measurement data and information on observable exposure predictors and their interactions. Specifically, we used 383 measures of whole-body vibration from 247 professional taxi drivers and attempted to quantify vibration exposures for individuals in a large study on low back pain. RESULTS: Using the "jackknife method," we found that our prediction rule had an acceptably low relative prediction error of 11% (95% confidence interval-10-12%). Implementing the prediction rule would result in measurement errors independent of low back pain and of all identified and observable predictors of whole-body vibration. We applied the predicted levels to compute each person's daily exposure, and found a strong association between the predicted daily whole-body vibration exposure and prevalence of low back pain. This supported the construct validity of the exposure prediction rule. CONCLUSIONS: The predictive and construct validity of our prediction rule suggests that this general statistical approach can be useful in other occupational settings to improve the quality of exposure assessment.

Adult↗
PubMed2003

Effective intervention with ergonomics, antivibration gloves, and medical surveillance to minimize hand-arm vibration hazards in the workplace.

Medical surveillance was used in the workplace to determine and monitor the level of hand-arm vibration syndrome (HAVS) and carpal tunnel syndrome (CTS) present in workers exposed to upper extremity vibration. Ergonomic intervention in the form of new tools with lower vibration levels and the use of International Standards Organizaiton (ISO) 10819 antivibration gloves were associated with a decrease in the pathologic findings and symptoms in these workers. Workers without such intervention were more likely to show progression of symptoms and findings. These findings suggest that ergonomic intervention can be effective in controlling the workplace hazard of tool vibration.

Arm Injuries↗
PubMed2004

Safe and reliable sound threshold measures with direct vibration of the ossicular chain.

OBJECTIVES: The aim of the study was to evaluate the safety and feasibility of piezoelectric malleus vibration audiometer (MVA), which presents micromechanical vibrations to the umbo membranae tympani. STUDY DESIGN: Phase I study performed in a tertiary referral center (University Hospital). METHODS: The coupling rod of the MVA was moved slowly through the outer ear canal toward the eardrum with a micromanipulator. Coupling was completed when the rod tip touched the umbo membranae tympani. Basic audiologic measures of sound threshold obtained with direct stimulation of the malleus are presented. We used MANOVA (multivariate repeated measures ANOVA) to investigate the repeatability of MVA thresholds from one day to the other and when decoupling and retracting the coupling rod 2 mm off the umbo. We also selected the MANOVA to test for unwanted bone-conduction threshold shifts after MVA application. We assessed normality of the data by quantile-quantile plots of the residuals. RESULTS: Twenty-eight male and 10 female subjects with normal hearing, 22.2 to 34.6 years old (median age, 27.2 yr) underwent an examination. Thirty-six subjects underwent MVA, because 2 of the 38 subjects who volunteered for the study have not undergone the procedure due to the external auditory canal anatomy preventing application of the MVA. The results show that it is possible to safely and reliably measure thresholds of direct vibration of the ossicular chain. Using pure tone audiograms, no pure tone bone- and/or air-conduction threshold shifts occurred after the procedure. None of the subjects reported any other ear-related symptoms such as vertigo, tinnitus, or dizziness. Geometric mean vibratory displacements at threshold ranged from 0.55 nm at 250 Hz to 0.03 nm at 6 kHz. MANOVA demonstrated a repeatability of MVA thresholds. CONCLUSION: Malleus vibration audiometry will not allow exact linkage of actual implantable hearing aid. But the present study demonstrates that MVA can provide an audiometric tool for assessing ossicular function and integrity prior to implantation of an electronic hearing amplifier.

Adult↗
PubMed2005

Aerodynamics of the human larynx during vocal fold vibration.

OBJECTIVES: : The goal of this study was to comprehensively analyze the influence of aerodynamics on laryngeal function. Three specific aspects were considered: 1) a multidimensional comparison of the interaction of subglottic pressure, sound intensity, and fundamental frequency; 2) examination of instantaneous changes in subglottic pressure during each glottic cycle; and 3) determination of the threshold subglottic pressure for vocal fold vibration and its dependence on other aerodynamic factors. STUDY DESIGN: : Prospective study with six healthy individuals without history of voice disorders. METHODS: : The subjects vocalized the vowel sound /i/ with a variety of different intensities, pitch, and sound intensity. Subglottic air pressure, fundamental frequency, sound intensity, and the electroglottography signal were simultaneously measured. RESULTS: : Linear relationships were seen in all subjects between subglottic air pressure and sound intensity, although there were large variations in the slopes of these relationships. Rapid variations in subglottic pressure during each glottic cycle were detected, corresponding to the opening of the vocal folds with each individual vibration. Threshold pressures for vocal fold vibration were dependent primarily on sound intensity and fundamental frequency and tended to be higher at vibration onset than at offset. CONCLUSION: : The larynx responded in a predictable pattern to general aerodynamic forces, but there was tremendous variability in its specific behavior. Fundamental frequency and sound intensity tended to increase with subglottic air pressure, but that relationship was not seen consistently in all subjects. The relationship between subglottic air pressure and sound intensity was usually linear, unlike the exponential relationship seen in previous studies. Subglottic pressure was noted to undergo rapid change with each glottic cycle in some, but not all, subjects and was most strongly affected by average subglottic pressure. Phonation threshold air pressure was influenced by the sound intensity and, to a smaller extent, by the fundamental frequency of the voiced sound.

Adult↗
PubMed2006

Torsional vibrations of circular elastic plates with thickness steps.

This paper presents a theoretical study of torsional vibrations in isotropic elastic plates. The exact solutions for torsional vibrations in circular and annular plates are first reviewed. Then, an approximate method is developed to analyze torsional vibrations of circular plates with thickness steps. The method is based on an approximate plate theory for torsional vibrations derived from the variational principle following Mindlin's series expansion method. Approximate solutions for the zeroth- and first-order torsional modes in the circular plate with one thickness step are presented. It is found that, within a narrow frequency range, the first-order torsional modes can be trapped in the inner region where the thickness exceeds that of the outer region. The mode shapes clearly show that both the displacement and the stress amplitudes decay exponentially away from the thickness step. The existence and the number of the trapped first-order torsional modes in a circular mesa on an infinite plate are determined as functions of the normalized geometric parameters, which may serve as a guide for designing distributed torsional-mode resonators for sensing applications. Comparisons between the theoretical predictions and experimental measurements show close agreements in the resonance frequencies of trapped torsional modes.

Biocompatible Materials↗
PubMed2006

Amplitude modulation drive to rectangular-plate linear ultrasonic motors with vibrators dimensions 8 mm x 2.16 mm X 1 mm.

In this paper, to exploit the contribution from not only the stators but also from other parts of miniature ultrasonic motors, an amplitude modulation drive is proposed to drive a miniature linear ultrasonic motor consisting of two rectangular piezoelectric ceramic plates. Using finite-element software, the first longitudinal and second lateral-bending frequencies of the vibrator are shown to be very close when its dimensions are 8 mm x 2.16 mm x 1 mm. So one single frequency power should be able to drive the motor. However, in practice the motor is found to be hard to move with a single frequency power because of its small vibration amplitudes and big frequency difference between its longitudinal and bending resonance, which is induced by the boundary condition variation. To drive the motor effectively, an amplitude modulation drive is used by superimposing two signals with nearly the same frequencies, around the resonant frequency of the vibrators of the linear motor. When the amplitude modulation frequency is close to the resonant frequency of the vibrator's surroundings, experimental results show that the linear motor can move back and forward with a maximum thrust force (over 0.016 N) and a maximum velocity (over 50 mm/s).

Computer Simulation↗
PubMed1989

Biodynamic behavior of the trunk and the abdomen during whole-body vibration.

Vibration strain may be defined as the sum of all reactions of the human being to vibration exposure. This also includes the biomechanical behavior of particular parts of the body. Knowledge about these reactions is necessary in the field of occupational health and ergonomics. Biomechanical models, experimental methods, and results are presented. It can be shown that under vibration exposure with different conditions (body posture, vibration direction), the body parts are in resonance at varying frequencies, mainly in a low frequency range.

Abdomen↗
PubMed1989

Vasodilatation in human skin induced by low-amplitude high-frequency vibration.

Vasomotor effects in human skin induced by vibration of low amplitude (10-25 microns) and high frequency (150-250 Hz) have been studied by using skin temperature changes as an approximative measure of variations in skin blood flow. In all tested areas of the body surface, including the face, low-amplitude high-frequency vibration regularly induces vasodilatation. The spatial distribution of the temperature changes induced from different sites of stimulation was studied by infrared thermography. The latencies of the temperature changes, determined by thermistor recordings, were found to vary with site of stimulation and stimulus parameters. The increase in temperature to a given stimulus is greater the lower the prevalent skin temperature, i.e. the increase in blood flow is larger the greater the initial vasomotor tone. The results are in accordance with the view that the vasodilatation is due to a reflex inhibition of pre-existent vasomotor tone in the skin by the afferent inflow from vibration-sensitive mechanoreceptors. High-amplitude vibration (100-200 microns), performed in a few comparative experiments, caused vasoconstriction.

Adult↗
PubMed1988

Selective vibration sensing: a new concept for activity-sensing rate-responsive pacing.

A clinically available model of an activity-sensing, rate-responsive pacemaker (Activitrax, Medtronic) utilizes body vibration during exercise as an indicator of the need for a rate increase. Although having the advantage of rapid onset of rate response, this system lacks specificity and the rate response does not closely correlate with the level of exertion. In addition, this pacemaker is susceptible to the effects of extraneous vibration. In this study involving 20 normal subjects fitted with an external Activitrax pacemaker, the rate responses to a variety of exercises were studied and were compared with the corresponding sinus rates. The vibration generated at the level of the pacemaker was also measured by accelerometers in three axes. Only a fair correlation (r = 0.51) was achieved between the pacemaker rate and the sinus rate. The total root mean square value of acceleration in either the anteroposterior or the vertical axes was found to have a better correlation (r = 0.8). As the main accelerations during physical activities were in the lower frequency range (0.1-4 Hz), a low-pass filter was used to reduce the influence of extraneous vibration. Selective sensing of the acceleration level may be usefully implemented in an algorithm for activity pacing.

Adult↗
PubMed1997

Vibration, acceleration, gravitation, and movement: activity controlled rate adaptive pacing during treadmill exercise testing and daily life activities.

Activity-based sensors for rate adaptive pacing have been available for several years and now include several different types: vibration; acceleration; gravitation; and movement. However, a systematic comparison evaluating the relative advantages and disadvantages of these various sensors has received little study. The purpose of the present study was to compare these sensor subtypes using treadmill testing and an outdoor test circuit, which simulated daily life activities and included both uphill and downhill walking. Pacemakers were strapped on the chest of healthy volunteers and connected to one channel of an ambulatory recording device, which also recorded the subject's intrinsic heart rate. The pacemakers were programmed using an initial treadmill test to standardize the rate responsive parameters for each device. Nine different pacemaker models were studied including 3 vibration-based (Elite, Synchrony, Metros), 4 acceleration-based (Relay, Excel, Ergos, Trilogy), 1 gravitational-based (Swing), and 1 movement-based (Sensorithm) device. All devices demonstrated a prompt rate response with casual walking on flat ground. The vibration-, gravitational-, and movement-based pacemakers showed a pronounced rate decline during more strenuous work, e.g., walking uphill. This phenomenon was absent in the accelerometer-based units. In particular, the vibration- and movement-based units showed a higher rate with walking downhill compared to uphill. An optimally tuned rate behavior on the treadmill usually did not provide an optimal rate behavior during daily activities and there was a tendency to overstimulation during low workload. The development of the two newest sensors (gravitational and movement) did not result in an improved performance of rate response behavior. Overall, the accelerometer-based pacemakers simulated or paralleled sinus rate behavior the most closely.

Acceleration↗
PubMed1985

Vibration-induced neuropathy among forestry workers.

The neurological findings of 217 forestry workers were evaluated during a compulsory annual health examination. Vibration detection thresholds were determined for the left hand and foot. The handgrip forces were measured for both hands. A reduction in the vibration detection threshold or handgrip force was not associated with clinical neuropathy. Polyneuropathy was found in 4% of the lumberjacks whereas neuropathy restricted to the arms was found in 7.5% of the lumberjacks. The neuropathic findings were not linked with alcohol consumption but were associated with a history of numbness in the hands and diminished muscle force. The findings support the concept that local vibration can cause neuropathy in the arms, but the mechanism of vibration-induced neuropathy still remains uncertain.

Adult↗
PubMed1990

Vibration sensitivity thresholds: methodological considerations.

Vibration sensitivity thresholds were studied in 12 healthy volunteers using 25, 50, 100 and 250 s-1 stimulus frequencies from an instrument with automated and manual modes ('Vibra Mk II'). For the automated mode, a forced choice principle was adopted. All measurements were performed from both the knuckle of the IInd metacarpophalangeal joint and the medial malleolus on four successive days. In addition, a conventional tuning fork method for vibration sensitivity was applied. The results show high interindividual and intraindividual variation in all measurements. The threshold values measured by the automated system were significantly lower than those by manual system at all frequencies. The largest variation was seen at 250 s-1 and the most uniform values at 100 s-1. There was a clear difference between the values from knuckle and medial malleolus, the values in the foot being lower. There was no learning effect. Clear age-related increase in vibration thresholds was observed. Conventional tuning fork-method showed clear differences in vibration sensitivity between hand and foot, in accordance with computer assisted method. The higher sensitivity of the automated method compared to the manual makes this the method of choice, although further investigations to finish the method and to build up a broader reference material is desirable.

Adult↗
PubMed2006

Effects on leg muscular performance from whole-body vibration exercise: a systematic review.

The purpose of this study was to investigate the effects on leg muscular performance from whole-body vibration exercise. Literature search was performed on the databases Pubmed, Cinahl, ISI web of science (Sci-expanded, SSCI) and Embase (Rehab & Physical Med). Rating of 19 relevant studies was performed (14 on long-term exercise and five on short-term exercise) using a score system for the methodological quality. Several randomized-controlled trial studies of high to moderate quality show similar improvements from long-term regimen on muscular performance in the legs after a period of whole-body vibration exercise. As there were few studies on short-term exercise and as they had no control groups, the same convincing improvements regarding muscular performance were not achieved. Preliminarily, there is strong to moderate evidence that long-term whole-body vibration exercise can have positive effects on the leg muscular performance among untrained people and elderly women. There is no clear evidence for effects on muscular performance after short-term vibration stimuli.

Exercise↗
PubMed1999

In vitro transmission and attenuation of impact vibrations in the distal forelimb.

An in vitro model was developed and validated in vivo to quantify the attenuation of impact vibrations, transmitted through the lower equine forelimb and to assess the effects of horseshoeing on this attenuation. The transsected forelimbs of 13 horses were equipped with custom-made hollow bone screws in the 4 distal bones, on each of which a tri-axial accelerometer could be mounted. The limbs were then preloaded while the impact was simulated by dropping a weight on the steel plate on which the hoof was resting. At the hoof wall, the distal, middle and proximal phalanx and at the metacarpal bone, the shock waves resulting from this impact were quantified. To assess the damping effects of shoeing, measurements were performed with unshod hooves, hooves shod with a normal flat shoe and hooves shod with an equisoft pad and a silicone packing between hoof and pad. The in vitro model was validated by performing in vivo measurements using one horse, and subjecting the limb of this horse to the same in vitro measurements after death. Approximately 67% of the damping of impact vibrations took place at the interface between the hoof wall and the distal phalanx. The attenuation of impact vibrations at the distal and proximal interphalangeal joints was considerably less (both 6%), while at the metacarpophalangeal joint 9% of the amplitude of that at the hoof wall was absorbed, leaving approximately 13% of the initial amplitude at the hoof wall detectable at the metacarpus. Compared to unshod hooves the amplitude at the hoof wall is 15% higher in shod hooves. No differences could be observed between shoe types. At the level of the first phalanx and metacarpus the difference between shod and unshod vanished; it was therefore concluded that, although shoeing might influence the amplitude of impact vibrations at the hoof wall, the effect of shoeing on the amplitude at the level of the metacarpophalangeal joint is minimal.

Animals↗
PubMed1983

Segregation of vibrated powder mixes containing different concentrations of fine potassium chloride and tablet excipients.

The effect of different drug/excipient concentrations on the segregation tendency of three ordered powder mixes was studied. In addition, the influence of vibration frequency on the segregation intensity and mechanisms of segregation was also studied. Differences in content uniformity of the powders were measured by comparing samples from regions at different depths between the upper exposed powder surface and the base of the cylindrical container. Ordered mixes containing recrystallized lactose excipient and fine-particle potassium chloride as a model drug were found to be least susceptible to segregation at most vibration conditions for all potassium chloride concentrations. Dipac excipient/potassium chloride particles were most susceptible to segregation under all test conditions. In general, segregation intensity was most marked in conditions where high potassium chloride concentrations, above 2% w/w, were subjected to low-frequency vibration, below 100 Hz. Segregation mechanisms were considered to be mainly dependent on vibration conditions, although carrier excipient type markedly modified mechanisms and influenced segregation intensity.

Drug Compounding↗