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At least 1,207 records · Page 67Linked to original sources
PubMed1999

Effect of whole-body vibration on the low back. A study of tractor-driving farmers in north India.

STUDY DESIGN: A retrospective cohort study of tractor-driving farmers (study group) and non-tractor-driving farmers (control group) matched for age, gender, generic/ethnic group, land-holding, and work routines. OBJECTIVES: To determine, using magnetic resonance imaging and clinical investigations, the effect of whole-body vibrations on the back in tractor-driving farmers. SUMMARY OF BACKGROUND DATA: Low back pain and pathologic changes in the lower backs of tractor drivers have been reported. However, no study with a control group matched for work-related risk factors has been reported. METHODS: Fifty tractor-driving farmers were compared with 50 non-tractor-driving farmers matched for age, gender, ethnic group, land-holding, and work routine. Both groups were interviewed for details of work routine, assets held, family profile, and vibration exposure to assess the influence of these parameters on signs and symptoms of backache. Magnetic resonance imaging was done to assess the effect of exposure on whole-body vibration and degenerative changes in the back. Vibration measurements also were done on tractors to observe the actual severity of the vibrations. RESULTS: Regular work-related backache was more common among tractor-driving farmers (40%) than among non-tractor-driving farmers (18%, P = 0.015). Anthropometric evaluation showed abdominal girth and weight to be significantly higher in tractor-driving farmers (P = 0.006 and 0.046, respectively), whereas while height and arm span were similar between the two groups. Clinical examination for evidence of disc or facet degeneration showed no difference between the two groups. Evaluation of magnetic resonance images of tractor-driving farmers and non-tractor-driving farmers by an orthopedic surgeon, radiologist, and neurosurgeon showed degenerative changes to be similar between the two groups (P > 0.050). CONCLUSIONS: Tractor-driving farmers report backache more often than non-tractor-driving farmers, but no significant objective differences on clinical or magnetic resonance imaging evaluation were found between the two groups.

Adult↗
PubMed2003

The effect of prosthesis design on vibration of the reconstructed ossicular chain: a comparative finite element analysis of four prostheses.

HYPOTHESIS: It was hypothesized that the differences in the bioacoustic performance of ossicular replacement prosthesis designs, and insertion positions, could be quantified using finite element analysis. BACKGROUND: Many designs of prosthesis are available for middle ear surgery. The materials used, and the shape of the implants, differ widely. Advances in computer simulation technologies offer the possibility of replicating the in vivo behavior of the different prostheses. If this can be achieved, insight into the design attributes required for improved biofunctionality may be gained. METHODS: Micro-computed tomography and nuclear magnetic resonance imaging were used to obtain geometric information that was translated into a finite element model of the outer and middle ear. The forced frequency response across the hearing range of the normal middle ear was compared with the middle ear reconstructed with partial and total ossicular replacement prostheses. RESULTS: The amplitude of vibration of the footplate was more similar to that of the normal ear when a Kurz total ossicular replacement prosthesis was implanted than when a Xomed total ossicular replacement prosthesis was implanted. This may be attributed to the latter's titanium link. Partial ossicular replacement prostheses were stiffest and had lower umbo vibrations and higher stapedial footplate vibrations. In all cases but one, the vibration of the prostheses had resonances that caused the vibration of the stapes footplate to be noticeably different from normal. CONCLUSION: The authors confirmed the hypothesis that finite element modeling can be used to predict the differences in the response of ossicular replacement prostheses. This study shows that computer simulation can potentially be used to test or optimize the vibroacoustic characteristics of middle ear implants.

Acoustic Impedance Tests↗
PubMed2006

Is there loss of vibration amplitude across the snap coupling of the bone-anchored hearing aid?

HYPOTHESIS: There is loss of vibration transmission across the snap coupling connecting the Bone-Anchored Hearing Aid transducer to the implanted abutment on the head. BACKGROUND: The only nonrigid part of the Bone-Anchored Hearing Aid system is the connection between the output of the transducer and the abutment. Vibration losses across the coupling have not been previously measured. If a loss is found, a change in design could improve the efficiency of the Bone-Anchored Hearing Aid. This would be very helpful in borderline cases in which the Bone-Anchored Hearing Aid does not have enough power to achieve adequate hearing threshold levels. METHODS: A laser Doppler vibrometer was used to measure vibrations on the output stem and four points on the abutment of the Bone-Anchored Hearing Aid. The Bone-Anchored Hearing Aid was coupled to a dry skull through a plexiglas bite bar screwed to the skull. The impedance load was varied by fixing the skull. A control loose coupling was measured. Five Bone-Anchored Hearing Aid Compacts were measured. RESULTS: There was little loss across the Bone-Anchored Hearing Aid snap coupling. At frequencies above 500 Hz, there was no more than 5-dB loss at any frequency. Changing the impedance load by fixing the skull did not change the loss across the coupling. CONCLUSION: The snap coupling is an efficient means of transmitting vibrations to the skull. There is little loss of vibration attenuation across it. Increases in functional Bone-Anchored Hearing Aid amplification gain cannot be achieved by further optimizing this interface.

Bone Conduction↗
PubMed2003

Ability of the finite element models to predict response of the human spine to sinusoidal vertical vibration.

STUDY DESIGN: The study examined the efficacy of the finite element models of various spinal segments in predicting the vibration response of the human spine. OBJECTIVE: To determine the optimal spinal segment finite element model to understand the effects of vibration on its biomechanics. SUMMARY OF BACKGROUND DATA: Several finite element models (one and two motion segments) have been proposed to look into the effects of vibration on the lumbar spine. However, they cannot be used to predict biomechanical parameters in the lumbar spine in response to whole body vibration. METHODS: A finite element model of the upper body from the head to the sacrum (H-S1) was generated. The H-=S1 model was altered to generate models of one motion segment (L3-L4), two motion segments (L3-L5), and the entire thoracolumbar spine and rib cage (T1-S1). The resonant frequencies of these models and effects of the trunk muscles and gravity were studied. RESULTS: The resonant frequencies decreased with the increase in the number of motion segments. However, the decrease plateaued beyond the T1-S1 segment model. The first resonant frequency in the vertical direction for the H-S1 model was 8.32 Hz. Inclusion of the trunk muscles and the preload of self-weight changed it to 8.91 and 6.82 Hz, respectively. CONCLUSIONS: Both the T1-S1 and H-S1 finite element models were able to predict vibration response of the human spine that closely matched in vivo experimental data reported in the literature.

Biomechanical Phenomena↗
PubMed2006

Output vibration measurements of bone-anchored hearing AIDS.

HYPOTHESIS: Different bone-anchored hearing aids (BAHAs) processors have different output vibration characteristics, which depend on the mechanical load and the volume setting. Responses will differ between live heads and dry or plastic skulls. BACKGROUND: The BAHA is an implantable bone-conduction device. Three different BAHA models are available. Their output vibrations have not been reported using a noncontact method with differing impedance loads, including the BAHA-fitted patient head. METHODS: Using a laser-Doppler vibrometer, vibration responses with sound input of 70- to 80-dB sound pressure level were measured on unloaded BAHAs, a dry skull, a plastic skull, and on the abutments of three live BAHA-fitted patients. Responses at different volume settings and distances from the vibrator were also tested. Frequency responses were calculated for displacement, velocity, and acceleration. RESULTS: Unloaded BAHA accelerations were approximately 30 to 50 dB higher than live-head accelerations. Live-head accelerations were similar to dry skulls in frequencies of more than 500 Hz, but much higher than the plastic skull responses. Live-head responses were more damped. The Cordelle II outperformed the other two processors by approximately 20 dB. The Classic 300 had better low-frequency responses than the Compact. The volume settings had little effect on vibration output overall. Acceleration peak was at approximately 2.5 kHz for all conditions. CONCLUSION: The BAHA processors differ in the output acceleration they can achieve with differing loads. The volume control setting has little impact on accelerations produced for most processors. The live-head responses are similar to the dry skull in frequencies of more than 500 Hz.

Acoustic Stimulation↗
PubMed2004

Short-term effects of whole-body vibration on postural control in unilateral chronic stroke patients: preliminary evidence.

The short-term effects of whole-body vibration as a novel method of somatosensory stimulation on postural control were investigated in 23 chronic stroke patients. While standing on a commercial platform, patients received 30-Hz oscillations at 3 mm of amplitude in the frontal plane. Balance was assessed four times at 45-min intervals with a dual-plate force platform, while quietly standing with the eyes opened and closed and while performing a voluntary weight-shifting task with visual feedback of center-of-pressure movements. Between the second and third assessments, four repetitions of 45-sec whole-body vibrations were given. The results indicated a stable baseline performance from the first to the second assessment for all tasks. After the whole-body vibration, the third assessment demonstrated a reduction in the root mean square (RMS) center-of-pressure velocity in the anteroposterior direction when standing with the eyes closed (P < 0.01), which persisted during the fourth assessment. Furthermore, patients showed an increase in their weight-shifting speed at the third balance assessment (P < 0.05) while their precision remained constant. No adverse effects of whole-body vibration were observed. It is concluded that whole-body vibration may be a promising candidate to improve proprioceptive control of posture in stroke patients.

Chronic Disease↗
PubMed2003

Corticospinal excitability changes following prolonged muscle tendon vibration.

The present experiment addressed the time course of corticospinal excitability changes following interventional muscle tendon vibration. Using transcranial magnetic stimulation, motor evoked potentials of the flexor carpi radialis and extensor carpi radialis brevis muscle were recorded for a period of 60 min after cessation of vibration (80 Hz, 0.5 mm, 30 min) to the distal wrist flexor tendons. A delayed corticospinal excitability increase in both the vibrated and non-vibrated antagonistic muscle was observed, with lasting levels of facilitation for the latter. No changes were observed following interventional cutaneous vibration. These results underscore a facilitatory influence of prolonged Ia-afferent activation on corticospinal excitability. Findings are discussed in light of recent advances in promoting motor recovery after brain injury by somatosensory stimulation.

Adult↗
PubMed2006

The acute effects of different whole body vibration amplitudes on the endocrine system of young healthy men: a preliminary study.

Whole body vibration (WBV) has been suggested as an alternative form of exercise producing adaptive responses similar to that of resistance training. Very limited information is available on the effects of different vibration parameters on anabolic hormones. In this study, we compared the acute effects of different WBV amplitudes on serum testosterone (T) and insulin growth factor-1 (IGF-1). Nine healthy young recreationally active adult males (age 22 +/- 2 years, height 181 +/- 6.3 cm, weight 77.4 +/- 9.5 kg) voluntarily participated in this randomized controlled (cross-over design) study. The subjects performed 20 sets of 1 min each of WBV exercise in the following conditions: Non-vibration condition (control), low amplitude vibration [low (30 Hz, 1.5 mm peak-to-peak amplitude)] and high amplitude vibration [high (30 Hz, 3 mm peak-to-peak amplitude)]. Blood samples were collected before, after 10 sets, at the end (20th set) and after 24 h of the exercise bout. WBV exercise did not produce significant changes in serum T and IGF-1 either with low or high amplitude when compared with the control condition. The results of this study demonstrate that a single session of WBV exposure with a frequency of 30 Hz and amplitudes of 1.5 and 3 mm does not noticeably alter serum T and IGF-1 levels.

Adult↗
PubMed1996

Advantage of monitoring skin vibration as an index of arteriovenous fistular blood flow.

Monitoring of the skin vibration is disturbed little by environmental noise. Therefore, the skin vibration is more relevant than bruit on the skin by means of monitoring the fistular blood flow. Frequency analysis of the skin vibration generated by an internal arteriovenous fistula indicated two peaks of power spectral density (PSD), one in the frequency range of 4-10 Hz and the other from 100-300 Hz. The analysis of the skin vibration generated by an external fistula, however, showed only one peak in the range of 4-10 Hz and a moderate flat PSD level in the range of 100-300 Hz. The PSD level in the range of 100-300 Hz decreased dramatically or disappeared when the fistular blood flow diminshed or ceased. Therefore, the optimal frequency for monitoring skin vibration may be the range of 100-300 Hz.

Arteriovenous Fistula↗
PubMed1997

Hemolysis test of disposable type vibrating flow pump.

The vibrating flow pump (VFP) can generate high frequency oscillated blood flow. Because of the high frequency driving with short stroke volume, the pump system can be small. The disposable type VFP (D-VFP) was developed for use for extracorporeal circulation. The electromagnetic actuator was detached from the vibrating tube, which was newly designed to be a disposable tube with a jellyfish valve. Hemolysis tests of the D-VFP, VFP, centrifugal pump, and roller pump were performed in a mock circulation study using goat blood. Plasma free hemoglobin was measured every 15 min under the same conditions. The plasma free hemoglobin of the D-VFP was 16 mg/dl although that of the VFP was 160 mg/dl at 30 min. The plasma free hemoglobin of the centrifugal pump and roller pump at 30 min were 3 mg/dl and 9 mg/dl, respectively. The hemolysis performance of the D-VFP may be studied further as a result of this study. Two important factors affecting hemolysis development may be the materials of which the vibrating tube is made and heat transmission from the actuator. The D-VFP has a smooth acrylic surface for blood contact compared with the metal surface of old type VFP. The electromagnetic actuator of the VFP surrounded the vibrating tube, so heat from the actuator could be easily transmitted to the blood. Because the D-VFP has a disposable vibrating tube that is detached from the actuator, heat is not readily transmitted to the blood. A mock circulation study of heat transmission was performed using the D-VFP and VFP. Results of the heat transmission study showed that the fluid temperature of the D-VFP was not increased and stayed at room temperature although that of the VFP increased approximately 1 degree C above room temperature. The D-VFP may be a good style for the development of the VFP for use for extracorporeal circulation.

Acrylates↗
PubMed1997

In vitro thrombogenesis study in the Gyro C1E3 for vibration assessment.

To clarify the correlation between vibration and thrombus formation in a centrifugal blood pump, a preliminary simulated thrombus study was conducted for possible detection of thrombus formation inside a pump. Additional in vitro thrombogenesis studies were performed to confirm the results of the preliminary study. The primary data acquisition equipment included an accelerometer (Isotron PE accelerometer, Endevco, San Juan Capistrano, CA, U.S.A.), digitizing oscilloscope (TDS 420, Tektronic, Inc., MA, U.S.A.), and pivot bearing centrifugal pumps. The accelerometer was mounted to the top of the pump casing to sense radial and axial accelerations. For the preliminary study, a piece of Silastic was adhered to each of the 3 common areas of thrombus formation inside the pump. The results provided baseline information to speculate on the possibility of detecting thrombus formation by vibration signal changes. For the next studies, fresh bovine blood was harvested under sterile conditions and with strict avoidance of air contact, adding 1.0 U/ml of heparin. The sterilized test circuit consisted of 3/8 inch tubing (Tygon) and a soft reservoir. During the operating time, the activated clotting time (ACT) was maintained between 150 to 300 s using protamin. A restrictor on the outflow tube maintained the flow rates at about 4.5 L/min. The pumps ran continuously for 6 h. Possible blood clot formation inside the pump was monitored by observing the vibration signal from the device for 6 h. These studies revealed that it was possible to distinguish between an impeller that did not form thrombus and ones that formed fibrogenous thrombus using vibration signal assessment. Vibration assessment is worthwhile as a thrombus monitoring tool for a centrifugal blood pump.

Analysis of Variance↗
PubMed1991

Somatosensory evoked potentials in patients with selective impairment of position sense versus vibration sense.

Ten patients with selective impairment of either position sense or vibration sense were studied with somatosensory evoked potential (SEP). Five patients with spinal cord lesion (three with MS, one with spinal cord tumor and one with spinal cord injury) lost the vibration sense below the iliac crests without impairment of the position sense. However, five patients with cerebral vascular lesions involving thalamus unilaterally showed severe impairment of position sense, though there was no asymmetry as to the vibration sense. In all these cases with spinal and cerebral lesions, SEPs showed abnormalities in the distributions where the position sense was impaired and were not related to the impairment of vibration sense. Our study indicates that SEP is much better correlated with the position sense than with the vibration sense at any lesion level.

Adult↗
PubMed1978

Distortion of mandibular kinesthesia induced by vibration of human jaw muscles.

Kinesthetic experience accompanying vibration of human jaw muscles was investigated in 12 healthy subjects. Vibration of the masseter muscle with the jaw in a 20-mm opened position caused the subjects either to underestimate jaw closing effects or to experience jaw opening movements depending on whether the mandible was free to move or kept in a constant position. During vibration of the depressor muscles with the mandible in its rest position the subjects underestimated an opening movement, but fixation of the mandible caused no illusions of movement. All kinesthetic illusions perceived during vibration corresponded to elongation of the muscles under study beyond their actual length. Distortion of kinesthesia was independent of the amplitude and frequency of vibration and it persisted during anesthesia of the temporomandibular joints and loading of the mandible. It can be concluded that jaw muscle receptors may contribute to mandibular kinesthesia.

Humans↗
PubMed1980

Dissociation of electrical and mechanical activity caused by vibrations in the spontaneously active smooth muscle of the rat portal vein.

The effects of vibrations on the electrical membrane discharge and on the contractile force of the spontaneously active smooth muscle of isolated rat portal vein were studied. The electrical activity was recorded extracellularly and quantitatively related to the mean active force. Sinusoidal vibrations (40 Hz, 2.5--3.0% tissue length peak to peak), applied in the longitudinal direction of the smooth muscle, caused prompt and reversible reduction of active force but neither the pattern of the phasic contractions nor the electrical membrane discharge was altered. The degree of inhibition of mechanical activity increased with vibration amplitude, activity being 50% of control at a vibration amplitude of 12 +/- 4% (mean +/- S.D., n = 8). It is concluded that the induced length changes caused prompt dissociation between electrical membrane discharge and mechanical force development in the vascular smooth muscle. This finding adds support to the previously forwarded hypothesis that vibrations cause inhibition of contracting muscle by direct action on the contractile process.

Animals↗
PubMed1988

Transient increase in insulin-like growth factor I immunoreactivity in rat peripheral nerves exposed to vibrations.

Hind legs of adult rats were exposed to vibrations (81 Hz; amplitude 0.50 mm peak to peak) for 4 h during two consecutive days. The sciatic, tibial and plantar nerves were isolated and processed for immunohistochemical demonstration of IGF-I (insulin-like growth factor I; somatomedin C) immunoreactivity at different time intervals after the vibration exposure. In sham-exposed rats the axons in peripheral nerves showed no or faint IGF-I immunoreactivity while most Schwann cells were negative. Exposure of the hind legs to vibrations induced increased IGF-I immunoreactivity in the Schwann cells, demonstrable at the end of the exposure period and reaching maximal intensity 2-3 days after vibration exposure. Several distended axons similarly showed increased staining. The IGF-I immunoreactivity decreased after 7-10 days to almost the level in the control nerves. The most extensive changes were observed in the plantar nerves. The tibial nerves similarly expressed strongly increased IGF-I immunoreactivity in their Schwann cells. The sciatic nerve showed, however, only slightly to moderately increased staining. Cells in the epineurium of the plantar and, to a limited extent, of the tibial nerves expressed concomitantly increased IGF-I immunoreactivity. We conclude that the transiently increased IGF-I immunoreactivity in peripheral nerves reflects reactive changes caused by vibrations and most prominently expressed by the Schwann cells.

Animals↗
PubMed1969

Presynaptic inhibition of the monosynaptic reflex by vibration.

In cats, the monosynaptic reflex (MSR) elicited from L7 or S1 dorsal roots, or from the tibial nerve (H reflex) was suppressed by vibration at 50-500 c/s of the hind limb with innervation intact. The MSR was not suppressed by selective vibration of cutaneous receptors, and suppression was still observed after the hind limb was skinned. In contrast, the phenomenon disappeared when all muscle nerves were crushed. SUPPRESSION OF THE MSR BY VIBRATION WAS SHOWN TO BE MEDIATED BY PRESYNAPTIC INHIBITION BY THE FOLLOWING METHODS: correlation with onset of the dorsal root potential (DRP) evoked by vibration, and abolition of both DRP and reflex suppression by picrotoxin; demonstration of primary afferent depolarization and normal excitability of motoneurones to direct stimulation. Reasons are given for deducing that the muscle afferent fibres responsible for the presynaptic inhibition induced by vibration are group Ia rather than groups Ib or II, or afferent fibres from Pacinian corpuscles.

Animals↗
PubMed1976

The effect of low amplitude muscle vibration on the discharge of fusimotor neurones in the decerebrate cat.

1. Longitudinal vibration (50-100 mum, 100-300 Hz) has been applied to the triceps surae tendon to examine its effect on the tonic discharges of gastrocnemius medialis fusimotor neurones in the decerebrated cat. 2. For nineteen out of twenty-seven fusimotor neurones vibration consistently caused a small rise in discharge frequency. The remaining eight neurones showed no respose to the vibration which always evoked a considerable discharge in alpha motoneurones. 3. The reflex excitation of fusimotor neurones is attributed to activity in primary endings of muscle spindles since control experiments confirmed that these receptors were powerfully excited by the vibration used whereas secondary endings and Golgi tendon organs remained unaffected. 4. Tonic discharges of fusimotor neurones of unknown destination were also recorded from lumbar 7 and sacral 1 ventral root filaments in decerebrated cats. Of thirty cells, seven were inhibited, five were excited and the remaining eighteen units were unaffected by vibration of the triceps surae. 5. These findings are discussed in relation to the role of muscle stretch receptors in the autogenetic control of fusimotor neurones.

Action Potentials↗
PubMed2002

Acoustic streaming induced by ultrasonic flexural vibrations and associated enhancement of convective heat transfer.

Acoustic streaming induced by ultrasonic flexural vibrations and the associated convection enhancement are investigated. Acoustic streaming pattern, streaming velocity, and associated heat transfer characteristics are experimentally observed. Moreover, analytical analysis based on Nyborg's formulation is performed along with computational fluid dynamics (CFD) simulation using a numerical solver CFX 4.3. Two distinctive acoustic streaming patterns in half-wavelength of the flexural vibrations are observed, which agree well with the theory. However, acoustic streaming velocities obtained from CFD simulation, based on the incompressible flow assumption, exceed the theoretically estimated velocity by a factor ranging from 10 to 100, depending upon the location along the beam. Both CFD simulation and analytical analysis reveal that the acoustic streaming velocity is proportional to the square of the vibration amplitude and the wavelength of the vibrating beam that decreases with the excitation frequency. It is observed that the streaming velocity decreases with the excitation frequency. Also, with an open-ended channel, a substantial increase in streaming velocity is observed from CFD simulations. Using acoustic streaming, a temperature drop of 40 degrees C with a vibration amplitude of 25 microm at 28.4 kHz is experimentally achieved.

Acoustics↗