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At least 793 records · Page 44Linked to original sources
PubMed2000

Green stink bug Nezara viridula detects differences in amplitude between courtship song vibrations at stem and petiolus.

Green stink bug Nezara viridula courtship songs are transmitted through plants as substrate vibrations. The amplitude of the vibrations is different at different distances from the source of vibration and at different locations on the plant. Amplitudes of the local vibration were measured on stem and petioli of the bean plant (Phaseolus vulgaris) with a Laser-Doppler vibrometer. Differences of the amplitudes of vibration between adjacent points around the nodes were large enough to release differential nerve activities of vibration receptor cells of different legs. There was no correlation between the signal amplitude and the distance from the singing bug, however; the differences in amplitudes of vibrations between the stem and the adjacent petioli of leaves potentially permitted direction finding in the green stink bug males.

Animal Communication↗
PubMed1975

Effects of mechanical vibration on rat plasma calcium, magnesium, phosphate, and xanthine oxidase.

Sprague-Dawley rats were vibrated for 4 min in one of 12 combinations of G levels (+/-2, +/-4, or +/-8 GX) and frequency ranges (12-61, 62-111, 112-161, or 162-211 HZ). The animals were restrained and conscious during vibration. Plasma calcium, magnesium and inorganic phosphate concentrations as well as xanthine oxidase activities were determined for each animal at various times before and after vibration. Vibration at specific G levels induced physiological changes in plasma calcium, magnesium, and xanthine oxidase levels. Plasma inorganic phosphate concentrations appeared to increase with an increase in the displacement of vibration. All of the effects observed occurred within 24 h of vibration treatment. An effect of the frequency of vibration was not observed with any of the parameters examined. Factors involved in performing the experiments also were able to induce certain physiological changes, viz., the level of plasma calcium and xanthine oxidase activity.

Animals↗
PubMed2002

Separation and estimation of muscle spindle and tension receptor populations by vibration of the biceps muscle in the frog.

Frog spinal cord reflex behaviors have been used to test the idea of spinal primitives. We have suggested a significant role for proprioception in regulation of primitives. However the in vivo behavior of spindle and golgi tendon receptors in frogs in response to vibration are not well described and the proportions of these proprioceptors are not established. In this study, we examine the selectivity of muscle vibration in the spinal frog. The aim of the study was (1) to examine how hindlimb muscle spindles and GTO receptors are activated by muscle vibration and (2) to estimate the relative numbers of GTO receptors and spindle afferents in a selected muscle, for comparison with the mammal. Single muscle afferents from the biceps muscle were identified in the dorsal roots. These were tested in response to biceps vibration, intramuscular stimulation and biceps nerve stimulation. Biceps units were categorized into two types: First, spindle afferents which had a high conduction velocity (approximately 20-30 m/s), responded reliably (were entrained 1:1) to muscle vibration, and exhibited distinct pauses to shortening muscle contractions. Second, golgi tendon organ afferents, which had a lower conduction velocity (approximately 10-20 m/s), responded less reliably to muscle vibration at physiologic muscle lengths, but responded more reliably at extended lengths or with background muscle contraction, and exhibited distinct bursts to shortening muscle contractions. Vibration responses of these units were tested with and without muscle curarization. Ensemble (suction electrode) recordings from the dorsal roots were used to provide rough estimates of the proportions of the two muscle afferent types.

Action Potentials↗
PubMed2000

[Effects of local vibration on the levels of plasma endothelin and nitric oxide in rabbits].

In order to explore the effects of local vibration on plasma endothelin(ET) and nitric oxide (NO) and the relations with vibration-induced vascular impairment(VVI), plasma ET and NO levels of rabbits were measured after exposure to different vibration power and different exposure period. The results showed an increasing tendency in plasma ET levels, and a decreasing tendency in plasma NO levels in experiment groups, while lasting vibration exposure and enhancing vibration power. It suggested that local vibration could result in the increasing of plasma ET level and decreasing of plasma NO level, which might be one of the mechanisms of vibration-induced vascular impairment.

Animals↗
PubMed1992

Transfer of tennis racket vibrations onto the human forearm.

One of several factors suspected in the development of lateral epicondylitis, often referred to as tennis elbow, is the impact-induced vibration of the racket-and-arm system at ball contact. Using two miniature accelerometers at the wrist and the elbow of 24 tennis players, the effects of 23 different tennis racket constructions were evaluated in a simulated backhand stroke situation. The influences of body weight, skill level, and tennis racket construction onto the magnitude of vibrations at wrist and elbow were investigated. Amplitudes, integrals, and fourier components were used to characterize arm vibration. More than fourfold reductions in acceleration amplitude and integral were found between wrist and elbow. Off-center as compared with center ball impacts resulted in approximately three times increased acceleration values. Between subjects, body weight as well as skill level were found to influence arm vibration. Compared with proficient players, a group of less skilled subjects demonstrated increased vibration loads on the arm. Between different racket constructions, almost threefold differences in acceleration values could be observed. Increased racket head size as well as a higher resonance frequency of the racket were found to reduce arm vibration. The vibration at the arm after ball impact showed a strong inverse relationship (r = -0.88) with the resonance frequency of tennis rackets.

Acceleration↗
PubMed2004

Blood flow resistance with vibration and its effect on blood cell migration.

The present study investigated the effect of transverse vibration on the hemo-rheological characteristics of blood flow using a newly designed pressure-scanning capillary viscometer. As a transverse vibration was applied, aggregated blood cells become disaggregated. Frequency of vibration was found to be the main parameter causing hemo-rheological changes. For RBC suspension in a non-aggregating medium (Dextran 40), increasing frequency of vibration caused decreased flow resistance. Meanwhile, flow resistance for whole blood increased with frequency of vibration. These seemingly contradictory results could be interpreted without conflict when a comprehensive mechanism of cell migration under vibration is elucidated. The present study confirmed that vibration diminishes RBC aggregation, which triggers two different cell migration mechanisms and subsequently resulted in either increasing or decreasing the flow resistance.

Blood Flow Velocity↗
PubMed2005

Wrist vibration affects the production of finely graded forces.

INTRODUCTION: It is still unclear how central commands and afferent feedback interact to produce finely graded forces. To explore this question, we experimentally degraded afferent responsiveness using wrist vibration. METHODS: Subjects grasped an isometric joystick with their preferred hand and produced forces of different magnitudes and directions according to visually presented vectors. In one condition, the dorsal and palmar sides of the wrist were vibrated at 80 Hz to degrade proprioception; in another condition, the wrist was not vibrated. RESULTS: Response magnitude averaged 2.46 kg of force (kgf) without, and decreased to 1.90 kgf with vibration. The coefficient of magnitude variation was vibration-independent and averaged 0.30 kgf. The directional error of responses and its standard deviation were also vibration-independent, averaging -2.6 degrees and +/-17 degrees, respectively. Subjects' maximum voluntary force was 9.77 kgf without, and decreased to 8.83 kgf with vibration. CONCLUSION: Our findings clearly indicate that afferent feedback plays a role in the production of finely graded forces, probably by facilitating descending motor commands.

Adult↗
PubMed2005

Transmissibility of helicopter vibration in the spines of pilots in flight.

INTRODUCTION: The high incidence of back pain in helicopter pilots (HP) has been attributed to vibration and the in-flight pilot's posture. Helicopter vibration has a peak power at frequencies around 5 Hz, which is within the range that the human upper body presents resonance frequency. This study investigates the transmissibility (TR) of helicopter vibration from the seat to the spine of HP, and the seat resultant vibration (RSV). METHODS: We monitored 12 male HP during flights lasting 2 h on average. Uniaxial accelerometers measured the vibration at the L3 and T1 spinae processes of the pilots, and the helicopter backrest. The vibration at the pilot's seat, measured by triaxial accelerometers, was taken as the reference for the estimation of transmissibility values (TR) to L3, T1, and backrest using the cross-spectral method. TR was considered only for the frequency presenting the maximum power along the seat Z acceleration, and RSV was calculated according to ISO 2631-1. RESULTS: The TR values found for T1 suggest the presence of resonance in the pilot's spine during flight. Most of the HP presented TR within the range reported in the literature, but two of them had higher values at T1. Five flights showed RSV within the "caution zone" for 4-8 h of daily exposure. CONCLUSION: Our findings indicate that cyclic compressive force due to helicopter vibration can potentially increase the load imposed on the spines of pilots during flight. This might explain the incidence of back pain and other injuries to the spines of these professionals.

Acceleration↗
PubMed2005

Vibrations and their applications in sport. A review.

In sport, mechanical vibration is used as a massage tool and/or for training purposes. Two varieties of vibration training (VT) can be distinguished: strength exercises with superimposed vibratory stimulation (VS exercises) and motor tasks performed under whole body vibration (the WBV training). Vibratory massage has been used extensively since the beginning of the 20th century while VT is a relatively new technique. In the research literature, the main subjects addressed have been acute and cumulative effects of VS on flexibility and strength. Marked enhancement effects were obtained in medium-duration stretching and short-duration dynamic strength exercises while prolonged efforts did not show positive impact. The observed effects of vibration depend on various neural facilitatory and inhibitory mechanisms. In comparison to VS exercises, WBV tasks generate more global neuromuscular, metabolic and hormonal responses. WBV training resulted in significant changes in several motor variables, with stretch-shortening cycle tests (such as countermovement jumps, serial high jumps, etc.) being the most sensitive to WBV treatment. Based on available knowledge about proprioceptive spinal reflexes-that feedback from the primary endings of motor spindles produces a stimulatory effect via increased discharge of a-motoneurons, and activation of Golgi tendon organs (GTO) evokes inhibition of muscle action-a hypothesis has been proposed that VT enhances excitatory inflow from muscle spindles to the motorneuron pools and depresses inhibitory impact of GTO due to the accommodation to vibration stimuli. The intensity and duration of vibration used in VT dramatically exceed the standards for occupational vibration established by the International Organization for Standardization.

Exercise↗
PubMed2006

[Magnetic resonance imaging for the wrist joint of the coal miners in vibration department].

OBJECTIVE: To study the magnetic resonance imaging (MRI) in the wrist joint of coal miners who work in excavation and vibration department. METHODS: Forty-three coal miners with the hand-arm vibration disease served as the observation group while 20 workers who were not working in the vibration department acted as the control group. The patients in the observation group were divided into five subgroups according to the time when they received vibration. The regularity of the development of signs and symptoms of MRI was observed and analyzed. RESULTS: The hydroarthrosis was most found in MRI. There were significant difference in hydroarthrosis (chi(2) = 8.80, P < 0.01), osteoporosis and osteomyelitis (chi(2) = 3.91, chi(2) = 5.01, P < 0.05 respectively) between the observation group and the control group. The edema of bone marrow and the avascular necrosis of ossa carpi were found only in the observation group and not found in the control group. The hydroarthrosis and the edema of bone marrow occurred most in the early stage of vibration. The signal in the edema of the bone marrow of the distal end of the radius was decreased in the GE sequence T(2)WI with the specificity. CONCLUSION: (1) Changes in the wrist joint occur in the early stage of the vibration work, and can be found in the MRI. (2) The edema of the bone marrow of the distal end of the radius is of great value in the diagnosis of the hand-arm vibration disease.

Adult↗
PubMed1990

Modulation of cutaneous flexor responses induced in man by vibration-elicited proprioceptive or exteroceptive inputs.

The effects of muscle tendon or skin vibration on the early and late components of polyphasic cutaneous responses elicited in the flexor carpi radialis by electrical stimulation of the radial nerve at the wrist were studied in the human, with all muscles at rest. Both early and late flexor responses were enhanced by flexor vibration and depressed by extensor vibration; facilitation was accompanied by a reduction of latency. Furthermore, when an "antagonist vibration response" was present, inhibition of the flexor reflexes was replaced by a facilitation. Palm skin vibration depressed both components of the flexor reflex, while dorsal or "back-hand" skin vibration induced either a facilitation or an inhibition. In addition, back-hand vibration modified the location of the sensations evoked by electrical stimulation of the nerve. In all cases, vibratory stimulus attenuated the perceived intensity of the electrical stimulus. These observations indicate that proprioceptive or exteroceptive information can modulate the gain of the cutaneous reflex loops in a flexible way, under supraspinal control. These data also suggest a possible impairment of the protective withdrawal reflex under vibratory environmental conditions at rest and eventually in active muscles.

Adaptation, Physiological↗
PubMed1986

Inhibitory effects of combined agonist and antagonist muscle vibration on H-reflex in man.

Vibration alters human sensory motor performance. Changes in the excitability of spinal reflex mechanisms may be responsible for the majority of the observed alterations. We studied the differential effects of vibration locally applied to gastrocnemius soleus and tibialis anterior muscles separately and to both muscles simultaneously. From the results, it is deduced that combined agonist and antagonist muscle vibration may lead to summative interaction between pre- and postsynaptic inhibition at motoneuronal level. Whole-body vibration is taken to mean a combination of synchronous vibrations applied locally and simultaneously to several muscles. The results also demonstrate that the level of inhibition of the H-reflex resulting from the vibration is directly related to the displacement amplitude of the vibration, regardless of the frequency.

Adolescent↗
PubMed1985

[Biogenic amine content of brain sections, blood and adrenals of rabbits exposed to vibration and noise].

Phasic changes of biogenic amines were revealed in brain structures after isolated action of vibration; 15-min vibration increased the content of catecholamines in the hypothalamus and decreased the content of serotonin. 30-min vibration decreased the amount of biogenic amines in the hypothalamus and the cortex. Vibration of a longer duration (1 hr) increased the amount of catecholamines in the brain. After 2-hr vibration the content of catecholamines returned to the control level but the concentration of serotonin still remained above it. Combined action of vibration and noise (2 hrs) decreased the content of catecholamines and increased the amount of serotonin in cerebral structures. Dopamine and serotonin tended to decrease in the blood and adrenals whereas in the urine their amount increased. Multiple combined action of vibration and noise induced the most obvious changes.

Adrenal Glands↗
PubMed1984

[Evaluation of six screening tests for vibration syndrome].

Six primary screening test items (grip strength, skin temperature, Nail-Press test, pain sense, and vibration sense at 125 Hz and at 250 Hz) for the vibration syndrome were assessed for validity and reliability using four measures: correlation with working time in years with vibrating tools; degree of relationship with four major complaints (Raynaud's phenomenon, numbness, coldness, and pain); correlation between two repeated examinations; values of t-test calculated on two groups of workers of comparable age, one having all of the four major complaints and the other having no complaint at all. Both left and right hand scores were used in the analysis with a total of 12 items. As these scores were too heterogeneous to make direct comparison, the screening items were ranked according to the values of the four measures and then the obtained ranks were totalled for each item to establish a further ranking. In this way, the ranks of each screening item were determined. The results indicated that: For validity, pain sense and 250 Hz vibration sense were found to have relatively high validity, followed by 125 Hz vibration sense and grip force. Skin temperature and the Nail-Press test occupied the lowest ranks. For reliability, grip force and 250 Hz vibration sense were highest followed by pain sense. In this case again, skin temperature and the Nail-Press test turned out to belong to the lowest group, which included the 125 Hz vibration sense.(ABSTRACT TRUNCATED AT 250 WORDS)

Evaluation Studies as Topic↗
PubMed1984

Spinal reflex alterations as a function of intensity and frequency of vibration applied to the feet of seated subjects.

Sensorimotor system performance is known to be altered by vibration applied locally to tendons and muscles or to the whole body. The present study is an attempt to determine the influence of vibration amplitude, acceleration, and frequency on the excitability of the motoneurons as evaluated by the amplitude of electrically induced spinal reflex response in man. The results show that a vibration applied to the legs of a seated subject (S) decreased the reflex response. The effect is directly related to the vibration intensity. The reflex amplitude is minimal in the 10-30 Hz range. At constant acceleration, the depressive effect decreased beyond 20-30 Hz while, at constant displacement amplitude, the reflex inhibition was almost constant throughout the frequency range of 20-60 Hz. These observations suggest that the diminution of the reflex response is mainly related to the amplitude of the vibration, regardless of the frequency. The results are interpreted in light of current knowledge of the effect of locally applied vibration on muscle tendons. The marked inhibition observed in the 10-30 Hz range, even with moderate intensity, suggests that particular attention should be devoted to avoid vibration in that frequency range in vehicles in order to prevent alteration of the performance of sensorimotor systems.

Adolescent↗
PubMed1981

Mechanical vibration in neonatal transport.

Mechanical vibration encountered in land transports was assessed objectively through measurement of vertical acceleration experienced by neonates in transit. Vibration was most predominant in the hazardous low frequency range of 3 to 18 Hz. The peak acceleration amplitudes (intermittent thrusts) ranged from 5 to 13 m/sq sec. The root mean square acceleration (averaged vibration) ranged from to 6 m/sq sec. These vibration levels are high when compared with adult vibration tolerance limits, and may jeopardize the safety of the transported infants, particularly in long-distance transports. Further research is needed to understand the possible effects of mechanical vibration in neonates and to define safe vibration thresholds in all modes of transport. Careful-evaluation of vibratory stress and its attenuation in newer designs of transport equipment may be desirable to enhance the safety of the transported infants.

Humans↗
PubMed1981

Effects of whole-body vibrations on sensory motor system performance in man.

The effects of whole body vibration (WBV) were studied on subjects trained to perform on tasks involving blindfolded arm positioning (proprioceptive tasks), tracking of visual targets and control of static and dynamic torques. Subjects were vibrated in a seated position by means of a hydraulic jack. The vibration used (0.1 G at floor level and 18 Hz) was that occasionally encountered on medium-size cruising helicopter. The seat was that of a heliccopter pilot whose foam cushion was 6 cm thick with a density of 26 kg/m3. Systematic past-pointing was observed for both arm flexion and extension. Foot and arm visual tracking precision, as determined by position and velocity errors, increased in both directions. Static and dynamic control, rated by torque holding stability and torque amplitude precision, were also significantly altered compared to pre-stimulus readings. The results are interpreted in relation to current knowledge of the effects of vibration induced at spinal, vestibular, and central nervous system levels. It is concluded that the proprioceptive system through which vibration-induced afferents enter the neurological networks is the common denominator for the observed alterations of the position, velocity, and force controls. Our observations suggest that particular care should be taken in helicopters and other vibrating vehicles to prevent vibration from reaching muscular masses, especially those involved in motor tasks.

Adolescent↗
PubMedDate not supplied

Brain level and synthesis of acetylcholine during exposure to vibration and organic-phosphorus and phenol-derived pesticides.

The experiments were carried out on white rats studying the quantity and synthesis of acetyl-choline in the cerebral cortex and brain stem during exposure to vibration (50 Hz, 2 mm) and noise (80 dB), noise alone, and pesticides, chlorfenwinfos (1.66 mg/kg), DNPP (5.83 mg/kg), and DNBP (6.66 mg/Kg). The pesticides were given separately to resting animals and to animals exposed to vibration and noise, as well as noise alone. Vibration reduced the content and raised the synthesis of acetylcholine only in the cerebral cortex. The effect of exposure to noise included reduced content and increased synthesis of acetylcholine in the brain stem. Chlorfenwinfos, DNPP and DNBP had a similar effect raising the level of acetylcholine in the cortex and brain stem and decreasing the ability of its synthesis. Simultaneous exposure of the rats to the action of pesticides, vibration and noise, or noise alone led to mutual abolishing of the effects produced by each to these factors on the content and ability of acetylcholine synthesis in brain tissue. In the discussion it is suggested that vibration and noise stimulate the cholinergic centres in the brain. A concept of a mechanical action of vibration on the brain tissue is discussed also. Besides that, it was tried to explain the mechanism of action of pesticides on the content of acetylcholine and its synthesis and the mutual abolition of the effects produced by pesticides and those of vibration and noise, and noise alone on the concentration and ability of acetylcholine synthesis in the brain.

2,4-Dinitrophenol↗