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PubMed2006

Acute effects of whole-body vibration on muscle activity, strength, and power.

The purpose of this study was to investigate the effects of a single bout of whole-body vibration on isometric squat (IS) and countermovement jump (CMJ) performance. Nine moderately resistance-trained men were tested for peak force (PF) during the IS and jump height (JH) and peak power (PP) during the CMJ. Average integrated electromyography (IEMG) was measured from the vastus medialis, vastus lateralis, and biceps femoris muscles. Subjects performed the 2 treatment conditions, vibration or sham, in a randomized order. Subjects were tested for baseline performance variables in both the IS and CMJ, and were exposed to either a 30-second bout of whole-body vibration or sham intervention. Subjects were tested immediately following the vibration or sham treatment, as well as 5, 15, and 30 minutes posttreatment. Whole-body vibration resulted in a significantly higher (p < or = 0.05) JH during the CMJ immediately following vibration, as compared with the sham condition. No significant differences were observed in CMJ PP; PF during IS or IEMG of the vastus medialis, vastus lateralis, or biceps femoris during the CMJ; or IS between vibration and sham treatments. Whole-body vibration may be a potential warm-up procedure for increasing vertical JH. Future research is warranted addressing the influence of various protocols of whole-body vibration (i.e., duration, amplitude, frequency) on athletic performance.

Adult↗
PubMed2005

Comparison of the apparent mass of the seated human measured using random and sinusoidal vibration.

Exposure to whole-body vibration is generally accepted as being a risk factor for low back pain and therefore exposure to vibration should be minimised. The results of previous laboratory based research investigating the biomechanical response of the seated human to vibration has been used to develop models that can be used within tools that are capable of predicting the response of seats. Several studies in the literature have reported apparent masses of seated human subjects whilst exposed to either random or sinusoidal vibration. Although these studies have shown similar trends, there have been no systematic comparisons of apparent mass for the same subjects exposed to random and sinusoidal vibration. This paper reports a study where twelve male subjects were exposed to random whole-body vibration at 1.0 m/s2 r.m.s. and to sinusoidal vibration at 1, 2, 4, 8, 16 and 32 Hz. The modulus of the apparent masses were nominally identical when measured using random or sinusoidal vibration. The phase of the apparent masses were similar at 1, 2 and 4 Hz, when measured using random or sinusoidal vibration, but showed consistent differences at 8, 16 and 32 Hz. As the results between experiments using different waveforms are similar, models derived from experimental work based on one type of stimulus could be applied in scenarios involving the other type of stimulus.

Acceleration↗
PubMed2005

Necessary research for standardization of subjective scaling of whole-body vibration.

Researches into the relationship between the physical quantity of vibration and the subjectively perceived quantity become important in designs for the vibration environment. Subjective experimental methods to obtain the relationship between the physical quantity of vibration and the subjectively perceived quantity are different depending on the design objectives which consider the human sense of vibration characteristic. In this review, the following are outlined: (i) fundamental methods for obtaining the design objectives for vibration environments; (ii) reported findings on the physical quantity of vibration environments and the human characteristics of sense vibration; and (iii) problems with and limits of the ISO 2631-1 standard, which defines the subjective response of the ride comfort in public transportation. Finally, the directions of research into the subjective experimental methods for obtaining design objectives in the vibration environment considering of the human characteristics of sense vibration are described.

Equipment Safety↗
PubMed2005

Multi-body dynamics modelling of seated human body under exposure to whole-body vibration.

In vehicle systems occupational drivers might expose themselves to vibration for a long time. This may cause illness of the spine such as chronic lumbago or low back pain. Therefore, it is necessary to evaluate the influence of vibration to the spinal column and to make up appropriate guidelines or counter plans. In ISO2631-1 or ISO2631-5 assessment of vibration effects to human in the view of adverse-health effect was already presented. However, it is necessary to carry out further research to understand the effect of vibration to human body to examine their validity and to prepare for the future revision. This paper shows the detail measurement of human response to vibration, and the modelling of the seated human body for the assessment of the vibration risk. The vibration transmissibilities from the seat surface to the spinal column and to the head are measured during the exposure to vertical excitation. The modal paramters of seated subject are extracted in order to understand the dominant natural modes. For the evaluation of adverse-health effect the multi-body modelling of the spinal column is introduced. A simplified model having 10 DOFs is counstructed so that the transmissibilities of the model fit to those of experiment. The transient response analysis is illustrated when a half-sine input is applied. The relative displacements of vertebrae are evaluated, which can be a basis for the assessment of vibration risk. It is suggested that the multi-body dynamic model is used to evaluate the vibration effect to the spinal column for seated subjects.

Biomechanical Phenomena↗
PubMed2005

The European vibration directive.

The European Union adopted a Directive in 2002 on minimum requirements for the health and safety of workers exposed to vibration. This is known as the Physical Agents (Vibration) Directive. It builds on existing general employers' duties to manage risks to health and safety, and introduces exposure action and limit values for both hand-arm vibration and whole-body vibration, setting minimum standards for the control of vibration risks across Europe. New Regulations on Vibration at Work will be introduced in Great Britain on 6 July 2005 to implement the Directive. These Regulations should serve to strengthen the continuing work of the Health and Safety Executive (HSE) to reduce exposures to hand-arm vibration in British industry. Implementation of the Directive for whole-body vibration presents a different challenge and the HSE is currently preparing appropriate guidance to accompany the Regulations. This will form part of an holistic approach to back pain in professional drivers, setting vibration in context with other risk factors, particularly postural concerns and manual handling operations.

European Union↗
PubMed2005

Influence of supplemental magnesium, tryptophan, vitamin C, and vitamin E on stress responses of pigs to vibration.

Our objectives were to investigate and compare the effects of supplemental Mg, Trp, vitamin E (vit E), and vitamin C (vit C) on stress responses of pigs undergoing transport simulation. In this study, 126 pigs (25.1 +/- 4.4 kg BW) were allocated to one of the six following treatments: 1) negative control (no supplementation); 2) positive control (i.m. injection with 0.5 mg of carazolol/20 kg BW 12 h before vibration, beta-blocker); 3) Trp (additional amount of 6 g/kg of feed for 5 d, as-fed basis); 4) Mg (3 g/L drinking water for 2 d); 5) vit E (additional amount of 150 mg/kg of feed for 21 d, as-fed basis); 6) or vit C (additional amount of 300 mg/kg of feed for 21 d, as-fed basis). Pigs were treated in groups of three, and each treatment was replicated seven times. Feed and water intake were not different among treatments. Heart rate variables (mean, peak, and minimum heart rate, ventricular ectopic beats, and ST elevation of Channels A and B) and heart rate variability were registered from the night before vibration. Pigs were subjected to vibration in a transport simulator (8 Hz, 3 m/s) for 2 h and allowed to recover for 2 h. Generally, the positive control pigs had the lowest heart rate values (mean, peak, minimum heart rate, ST elevation of Channel A; P < 0.05), whereas Mg and Trp decreased ventricular ectopic beats and ST elevation of Channel B, respectively. The effect of vit C and E as vagal stimulators was clearly visible, whereas carazolol and Mg clearly blocked the sympathetic pathways of the autonomic nervous system. During vibration, the negative control pigs lay the least, and Mg pigs the most (P < 0.05). Salivary cortisol concentrations (taken before and after vibration and after recovery) showed that vit E pigs produced the least cortisol during stress periods. Intermediary metabolites (glucose, lactate, creatine kinase, and NEFA) were analyzed in plasma from blood taken before and after vibration. At the two sampling points, the vit E and Mg pigs had the lowest NEFA concentrations (P < 0.05), and the vit E pigs also had the lowest lactate concentrations before vibration. Urine samples were collected before and after vibration to determine catecholamine concentrations; only negative control pigs had an increase (P = 0.04) in epinephrine concentration, despite large individual variation. In general, these results indicate that the supplementation of Trp, Mg, vit E, or vit C improved coping ability of pigs during vibration comparison with the negative control treatment. A muscular injection of carazolol influenced only the heart rate variables.

Adaptation, Psychological↗
PubMed1989

Frequency dependence of the suppressive effects of vibration on atherosclerosis in the rabbit.

Whole-body vibration suppresses the development of atherosclerosis in the rabbit (Oki and Matoba, 1987). The present study was designed to clarify whether the effect of vibration on atherosclerosis depends on the frequency of vibration. Longitudinal vibrations at a frequency of 30 or 60 Hz was applied to 12 New Zealand white rabbits for 12 weeks. The gradual decrease in body weight and blood hematocrit in the vibration groups with time were parallel to the changes in the controls. The rate of increase in serum lipid concentrations induced by a cholesterol-rich diet was significantly suppressed in the vibration groups, as compared to the controls. This may be due to the vibration and not the diet. The aortic wall was thinner at 60 Hz than at 30 Hz, whereas the ratios of trace metals (Ca/Mg and Zn/Cu) in the aortic tissues were smaller at 30 Hz. The area of plaque formation in the intima was smaller at 60 Hz than at 30 Hz (p less than 0.05). Thus, the suppressive effect of vibration on the development of atherosclerosis in the aorta may be greater at a frequency of 60 Hz than at 30 Hz. Vibration may play an important role in lipid metabolism.

Animals↗
PubMed2000

Adverse effects of whole-body vibration on gastric motility.

To investigate the response of gastric motility to whole-body vibration (WBV) exposure, electrogastrography (EGG) and gastric manometry were performed in 10 healthy male volunteers. Sinusoidal vertical vibration of three different frequencies (4 Hz, 8 Hz, and 16 Hz) with a constant vibration magnitude of 1.0 ms-2 (rms.) was randomly given to the subject seated on the platform of a vibrator for 10 min. Exposure to vibration of 4 and 8 Hz decreased the amplitude of EGG wave and of the power spectrum corresponding to a slow wave component at fasting state. Food intake (solid meal 80 g, 135 cm3, 400 kcal) enhanced gastric motility showing about 2.5-fold in the power spectrum, of which response modes during and after vibration exposure were similar to those at fasting state. The periodical manometric change around one cpm was observed during vibration exposure under the condition of food intake. Short-term exposure to WBV led to a suppression of the activity of gastric smooth muscles and affect contraction wave. These responses may result from resonance of vibration frequency as a mechanical factor and stomach contents, and increase regulation of neurohumoral factors due to vibration stress.

Action Potentials↗
PubMed1997

Short-term effect of hand-arm vibration exposure on tactile sensitivity and manual skill.

OBJECTIVES: The present study investigated whether the impairment of tactile sensitivity after exposure to vibration disturbs the motor control of precision handling and, if so, whether it can result in an increased risk of injury during or after tasks involving the use of vibrating tools. METHODS: Twelve men were manually exposed to vibration from an electric sander for 30 min. Cutaneous sensitivity was quantified to measuring the pressure perception threshold and vibration perception threshold (125 Hz) on the pulp of the second finger. Manipulative skill was evaluated by grip-lift movements and the Purdue pegboard test. RESULTS: The vibration perception threshold increased very significantly from 94.0 dB (0.06 m/s2) before the vibration exposure to 127.5 dB (3.2 m/s2) immediately after the exposure. The pressure perception threshold tended to increase after vibration exposure, although not significantly, but manipulative skill was not altered. CONCLUSIONS: Change in vibration perception threshold was not associated with a significant increase in the pressure perception threshold or a perturbation of manual skill. Therefore, in conditions similar to those of our experiment, the safety of a precision task does not appear to be reduced after such vibration exposure.

Adult↗
PubMed2003

Dependence of palmar sweating response and central nervous system activity on the frequency of whole-body vibration.

OBJECTIVES: This study was carried out to determine the effects of the frequency of whole-body vibration on palmar sweating response and the activity of the central sympathetic nervous system. METHODS: Palmar sweating volume was measured on the right palm of six healthy men before and during 3 minutes of exposure to sinusoidal whole-body vibration at three different frequencies (16, 31.5, and 63 Hz). The whole-body vibration had a frequency-weighted, root mean square (rms) acceleration magnitude of 2.0 m/s2. As the index of the activated central sympathetic nervous system, saliva level of 3-methoxy-4-hydroxyphenylglycol (MHPG) was analyzed before and immediately after each vibration exposure. RESULTS: Each vibration frequency induced a palmar sweating response, that of 31.5 Hz being the largest. However, no significant difference was found between the three vibration conditions. Saliva MHPG increased in all the vibration exposures, and the largest change was observed at 31.5 Hz, the difference being significant. CONCLUSIONS: Acute exposure to whole-body vibration induced a palmar sweating response and activated the central sympathetic nervous system. The effects on the central nervous system were found to be dependent on the frequency of the vibration.

Adult↗
PubMed2005

Effect of impulse vibration on red blood cells in vitro.

OBJECTIVES: This study was carried out to evaluate the damage induced in red blood cells by exposure to impulse vibration. METHODS: The peak accelerations of impulse vibration included 50, 100, 200, 250 and 300 x 10(3) km/s2. A blood sample was put in a container filled with heparin so that there was no space inside. For each peak acceleration the exposure durations of 10, 20, and 30 minutes were used. The repetition rate of the impulses was 1 cycle per second (1 cycle/s). After the vibration exposure, the percentage of damaged red blood cells was calculated. Then the red blood cells were studied microscopically. RESULTS: Each vibration caused damage to red blood cells with all durations. The higher the peak acceleration and the longer the exposure duration, the more the damage to the red blood cells. Of the five impulse vibration levels with the three exposure durations, the largest damage was done by the vibration exposure with a peak acceleration of 300 km/s2 for 30 minutes with a mean value of 76.7% for the damaged cells, followed by the exposure with a peak acceleration of 300 km/s2 for 20 minutes with 55.5% of the cells being damaged. For exposure for 20 and 30 minutes, the vibration with peak accelerations of higher than 200 km/s2 provoked damage to red blood cells out of proportion to those with peak accelerations lower than 200 km/s2. CONCLUSIONS: Impulse vibration was shown in vitro to cause damage to red blood cells. It is suggested that the damage of red blood cells depends on both the peak acceleration and exposure duration of impulse vibration.

Erythrocytes↗
PubMedDate not supplied

Frequency analysis of commercially available vibrators.

The tonic vibration reflex -- elicitation of a muscle contraction by mechanical vibration -- is a well documented physiological phenomenon of particular relevance to physiotherapy. Among the critical features pertaining to the effectiveness of its use in clinical practice are the mechanical attributes of the vibrator used to elicit the reflex. Because physiological responses differ with vibrations of varying frequency and amplitude, it is necessary to measure these characteristics before a commercial vibrator is used therapeutically: Facilities and equipment for performing such tests are, however, not readily available to physiotherapists. The purpose of this study, therefore, was to measure and compare frequencies of a variety of commercially available vibrators under varying load conditions and over time. Vibrators from major Canadian retail outlets and manufacturers were obtained and, through the use of both mechanical and optical methods, a total of 19 models were frequency-calibrated. The results of the study permit discussion related to the suitability and reliability of each model and provide specific guidance to physiotherapy departments in the selection of appropriate therapeutic vibrators. The results also indicate that the mode of application, such as strapping the apparatus to the patient rather than having the operator hold it in her hand, affects the frequency in some models. The data related to frequency measurements, gained through this study, should enable therapists to make more effective use of commercially available vibrators in motor reeducation.

Canada↗
PubMed1976

[An epidemiologic study on vibration hazards among workers at the state forests in Kyushu (author's transl)].

There are only very few reports of epidemiologic analysis on vibration hazards among the workers at the state forests of Japan since 1970. It was necessary to perform investigations on the state of vibration hazards anew, through some labor hygienic policies on the prevention of the hazards, such as regulation of the time of using vibrating tools, had been executed to some extent since 1970. From the data of physical check-ups of 861 chain saw users of 24 District Forestry Offices in Kumamoto, Miyazaki and Kagoshima Prefectures in the south of Kyushu, the transition of vibration hazards was studied by using the incidence and prevalence of Raynaud's phenomenon and paresthesia of the fingers as indices. From the yearly transition of the hazards, a tendency was observed of increasing patients with vibration syndrome during the period from 1962 to 1970 when countermeasures on vibration hazards were not sufficient. However, since 1970 the occurrence of Raynaud's Phenomenon has shown a tendency to decrease among the workers with short history of using chain saw and the occurrence of paresthesia of the fingers as indices. From the yearly transition of the hazards, a tendency was observed of increasing patients with vibration syndrome during the period from 1962 to 1970 when countermeasures on vibration hazards were not sufficient. However, since 1970 the occurrence of Raynaud's Phenomenon has shown a tendency to decrease among the workers with short history of using chain saw and the occurrence of paresthesia of the fingers to increase among those with long history. The results are suggestive of making clear the pathophysiology of vibration hazards.

Fingers↗
PubMed2001

[The role of vibration in pathology of hearing].

Vibration is now considered as one of the most common environmental traumatic factors. The energy absorbed may exert a pathological effect on all bodily tissues and organs, although the consequences of exposure to vibration do not present a uniform clinical picture. Because all machines and vibrating tools also produce noise, the combined effect of both factors is usually examined. In the professional literature, an opinion predominates that vibration exerts only a week, additional traumatic influence on the hearing organ. This opinion is contrary to reports on vibration-related hearing impairments observed in workers of various branches of industry. In the past, the studies of harmful effects of vibration with the participation of volunteers were seldom and short-term. Experiments on laboratory animals were carried out on species with different sensibility of the hearing organ, and exposure to vibration was most frequently accompanied by noise. Nevertheless, they usually confirmed the presence of vibration-related changes in the inner ear, mostly in the hair cells. Moreover, there have been several reports on post-vibratory pathological changes not only in the inner, but also in other parts of the ear. All these findings indicate that the role of vibration in the pathology of the hearing organ is still underestimated and not fully elucidated.

Hearing Disorders↗
PubMed1970

An effect of weightlessness following exposure to vibration.

Vibration of germinating wheat seedlings at the levels experienced during the launch of the NASA Biosatellite II increases the frequency of developmental arrest in seedling organs. Severe vibrations lasted approximately 30 sec in two stages. Power spectral density was greatest at frequencies around 15-16 and 19-22 Hz on the entire vehicle. Vibration forces reaching the affected parts of individual seedlings could not be measured. One or more seedling organs may be expected to be absent in 11% of selected Earth-grown wheat plants. If subjected to simulated launch vibration between 12 and 27 hr after the start of germination, the number of abnormal plants rises to 21.6%. Lateral roots are most affected by vibration at this age. Seedlings which went into orbital weightlessness aboard Biosatellite II, or were grown for several days on a horizontal clinostat after vibration, showed only 5.3% abnormalities. Simulated weightlessness on the clinostat without prior vibration did not alter the number of abnormal plants. It is suggested that growth in weightlessness following exposure to vibration permits more extensive repair of injury produced by vibration than does growth in Earth's gravity.

Acceleration↗
PubMed2002

[Monitoring arterial hypertension in workers in professions exposed to vibration hazards (results of a 15-year study)].

AIM: To follow up for 15 years prevalence of arterial hypertension (AH) in workers exposed to vibration, to study AH course and possible correction in long-term vibration exposure. MATERIAL AND METHODS: The survey covered 1232 males aged 25-59 years exposed to vibration at their working places for 1 to 30 years (test group) and 1163 males matched for age but not exposed to vibration (control group). Active primary and secondary prevention of AH and annual population control for 10 years were performed in the test group. The control group was followed up outpatiently without active intervention. Final screening was conducted 5 years after completion of the program of AH prophylaxis. RESULTS: Among workers exposed to vibration AH prevalence was similar to that in the controls and tended to reduction in the process of preventive treatment. However, after the end of prophylactic measures AH incidence rate returned to the baseline level. In workers at risk of vibration aftereffects conversion of normal arterial pressure to hypertension was observed more frequently than in unexposed patients. This requires active prophylactic intervention. CONCLUSION: Long-term exposure to moderate and high frequency vibration is an AH risk factor. Incidence rate of AH increases with longer exposure to vibration. Compared to controls, aged workers exposed to vibration have AH much more frequently.

Adult↗
PubMed2002

[Effects of individual features on the measurement of vibration perception thresholds: standard setting for healthy people].

The thresholds of vibration perception in healthy people may differ significantly depending on individual and constitutional features: age, weight, height, race and gender, and also on various addictions like smoking or alcohol abuse. These variables have not as yet been analyzed in setting Polish standards of vibration perception thresholds used for therapeutical and certification purposes. The aim of the study was to develop a model that could render it possible to assess the normative values of vibration perception, taking account of individual features. The study covered 187 healthy persons free from exposure to vibration. Two methods were used to determine vibration perception thresholds: the standard Polish method and the method based on the ISO 13091-1/2001 standard. The methods differed in the technical parameters (contact force of vibrating probe 1.2 N and 0.1; probe diameter 12 and 5 mm-standard method and the method according to ISO, respectively), the presentation of stimuli (ascending method versus von: Bekesy method) and their frequencies. Vibration perception thresholds were significantly influenced by age (within the range of 63-250 Hz-standard method; 4-250 Hz-method according to ISO), body mass (full range of frequencies--standard method; 4-125-method according to ISO) and height (single frequencies--both methods). A model for determining vibration perception thresholds, taking account of age, height and body mass of study subjects, was developed. The results of the study show that individual and constitutional features should be taken into consideration when interpreting the results of the vibration perception examinations conducted for the purpose of occupational disease certification.

Adult↗
PubMed2005

Sensitivity and specificity of mastoid vibration test in detection of effects of vestibular neuritis.

Aim of this study was to determine sensitivity and specificity of the mastoid vibration test in patients who had suffered an attack of vestibular neuritis. Results were compared with the caloric test and two bedside tests of vestibular function (head shaking test and head thrust test). Results are reported in 28 patients who had a residual vestibular deficit 6 months after acute neuritis and in 25 healthy subjects. Mastoid vibration nystagmus was evoked in 21 patients but not in controls. In these patients, mastoid vibration test had a sensitivity of 75% and specificity of 100%. Since one patient had inverted mastoid vibration nystagmus, specificity of identification on the pathological side was 95%. Sensitivity of the test increased with increasing severity of the vestibular lesion. Indeed, mastoid vibration nystagmus was induced in 93% of patients with caloric paralysis and in 58% of those with caloric paresis. Nystagmus could usually be modulated or elicited by stimulation of either mastoid. In the few patients in whom mastoid vibration nystagmus was elicited only from one side, or when there was a clear difference in intensity of the nystagmus induced on the two sides, the stimulated side was more often the affected side. Four patients still showed spontaneous nystagmus. The caloric test was abnormal in 26/28 patients (93%) with paralysis in 16 and paresis in 12; 71% of patients had a head shaking induced nystagmus: 64% had an asymmetrical response in head thrust test. In conclusion, mastoid vibration test was overall more sensitive than head thrust test. Mastoid vibration test was slightly less sensitive than head shaking test in patients with severe residual deficit and more sensitive in patients with partial deficit. Mastoid vibration test, a valid, low cost clinical screening test for rapid detection of asymmetrical vestibular function, does not cause patient discomfort. It is suggested that this test be included in the diagnostic workup of all patients with suspected vestibular dysfunction.

Acute Disease↗