Frequency-dependent effects of vibration on physiological systems: experiments with animals and other human surrogates

The effects of whole-body vibration therapy on immune and brain functioning: current insights in the underlying cellular and molecular mechanisms

Whole-body vibration (WBV) therapy is a way of passive exercise in which subjects are exposed to mild and well-controlled mechanical vibrations through a vibrating platform. For a long time, studies have focused on the effects and applications of WBV to enhance musculoskeletal performance in athletes and patients suffering from musculoskeletal disorders. Recent evidence points toward the positive effect of WBV on the brain and its therapeutic potential in brain disorders. Research being done in the field gradually reveals cellular and molecular mechanisms underlying WBV affecting the body and brain. Particularly, the influence of WBV on immune and brain function is a growing field that warrants an up-to-date and integrated review. Immune function is closely intertwined with brain functioning and plays a significant role in various brain disorders. Dysregulation of the immune response is linked to conditions such as neuroinflammation, neurodegenerative diseases, and mood disorders, highlighting the crucial connection between the immune system and the brain. This review aims to explore the impact of WBV on the cellular and molecular pathways involved in immune and brain functions. Understanding the effects of WBV at a cellular and molecular level will aid in optimizing WBV protocols to improve its therapeutic potential for brain disorders.

Intervention Hypothesis for Training with Whole-Body Vibration to Improve Physical Fitness Levels: An Umbrella Review

Whole-body vibration (WBV) is a training modality, and it seems to be a safe and efficient exercise especially to improve different aspects of physical fitness in different populations. The protocols for WBV are still not standardized. The difficulty in comparing the data confuses the real efficacy of this instrument. Consequently, the objective of this umbrella review is to analyze the protocols previously adopted and eventually to propose a standard operating procedure for WBV training. Systematic review and meta-analysis of randomized controlled trials on WBV were searched on the electronic databases PubMed, Web of Science, and Scopus until 18 March 2024. A quality assessment of the studies included has been performed. A total of 20 studies were included in this umbrella review and frequency, magnitude, and amplitude intensity data were recorded. Detailed information about the protocols (static or dynamic exercises, barefoot or with shoes, intensity duration, weekly frequency, and vibration characteristics) was also collected. WBV presents widely different protocols. Consequently, a standard operating procedure has not been proposed for WBV training. A hypothesis of intervention was instead written in which parameters for frequency, amplitude, acceleration, and training mode were proposed.

Evaluation of Vibration as an Extrinsic Variable in In Vivo Research

Vibration is inherent in research animal facilities due to the mechanical systems and practices required for animal care and use. Ample evidence indicates that vibration can change behavior and physiology in multiple species, potentially altering the results of research studies. Although one cannot eliminate environmental vibration, its control is important in research animal environments to decrease the possibility of introducing a research variable due to vibration effects. To assess the potential for a vibration source to alter experimental results and variability, one must understand the principles of vibration, its likely sources, and control methods. The literature regarding the effects of vibration, as it applies in a practical sense, can be challenging to interpret because the vibration frequencies tested to date have often not been within or near the most sensitive ranges of the species being tested. Some previous studies have used unrealistic vibration magnitudes and provided insufficient detail to duplicate or build upon conclusions. Standardization is essential for research examining the effects of vibration on animals to validate knowledge of this extrinsic variable in animal research and identify ways to mitigate the variable in research facilities.

Relation of digital arterial dysfunction to alternative frequency weightings of hand-transmitted vibration

This study compared the relative performance of alternative frequency weightings of hand-transmitted vibration (HTV) to predict the extent of cold-induced vasoconstriction in the digital arteries of HTV workers. The cold response of digital arteries was related to measures of daily vibration exposure expressed in terms of r.m.s. acceleration magnitude normalised to an 8-h day, frequency weighted according to either the frequency weighting Wh defined in international standard ISO 5349-1:2001 (Ah(8) in ms-2 r.m.s.) or the hand-arm vascular frequency weighting Wp proposed in the ISO Technical Report 18570:2007 (Ap(8) in ms-2 r.m.s.). The measure of daily vibration exposure constructed with the frequency weighting Wp (Ap(8)) was a better predictor of the cold response of the digital arteries in the HTV workers than the metric derived from the conventional ISO frequency weighting Wh (Ah(8)). This finding suggests that a measure of daily vibration exposure constructed with the vascular weighting Wp, which gives more weight to intermediate- and high-frequency vibration (31.5-250 Hz), performed better for the prediction of cold induced digital arterial hyperresponsiveness than that obtained with the frequency weighting Wh recommended in ISO 5349-1 which gives more importance to lower frequency vibration (≤16 Hz).

Applied Force Alters Sensorineural and Peripheral Vascular Function in a Rat Model of Hand-Arm Vibration Syndrome

OBJECTIVE

This study described the effects of applied force (grip) on vascular and sensorineural function in an animal model of hand-arm vibration syndrome (HAVS).

METHODS

Rat tails were exposed to 0, 2, or 4 N of applied force 4 hr/d for 10 days. Blood flow and sensitivity to transcutaneous electrical stimulation and pressure were measured.

RESULTS

Applied force increased blood flow but reduced measures of arterial plasticity. Animals exposed to force tended to be more sensitive to 250-Hz electrical stimulation and pressure applied to the tail.

CONCLUSIONS

Effects of applied force on blood flow and sensation are different than those of vibration. Studies examining co-exposures to force and vibration will provide data that can be used to determine how these factors affect risk of workers developing vascular and sensorineural dysfunction (ie, HAVS).

Quantification of mechanical behavior of rat tail under compression

BACKGORUND

The development of vibration-induced finger disorders is likely associated with combined static and dynamic responses of the fingers to vibration exposure. To study the mechanism of the disorders, a new rat-tail model has been established to mimic the finger vibration and pressure exposures. However, the mechanical behavior of the tail during compression needs to be better understood to improve the model and its applications.

OBJECTIVE

To investigate the static and time-dependent force responses of the rat tail during compression.

METHODS

Compression tests were conducted on Sprague-Dawley cadaver rat tails using a micromechanical system at three deformation velocities and three deformation magnitudes. Contact-width and the time-histories of force and deformation were measured. Additionally, force-relaxation tests were conducted and a Prony series was used to model the force-relaxation behavior of the tail.

RESULTS

The rat tails' force-deformation and stiffness-deformation relationships were strongly nonlinear and time-dependent. Force/stiffness increased with an increase in deformation and deformation velocity. The time-dependent force-relaxation characteristics of the tails can be well described using a Prony series.

CONCULSIONS

We successfully quantified the static and time-dependent force responses of rat tails under compression. The identified mechanical behavior of the tail can help improve the rat-tail model and its applications.

A novel rat-tail model for studying human finger vibration health effects

It has been hypothesized that the biodynamic responses of the human finger tissues to vibration are among the major stimuli that cause vibration health effects. Furthermore, the finger contact pressure can alter these effects. It is difficult to test these hypotheses using human subjects or existing animal models. The objective of this study was to develop a new rat-tail vibration model to investigate the combined effects of vibration and contact pressure and to identify their relationships with the biodynamic responses. Physically, the new exposure system was developed by adding a loading device to an existing rat-tail model. An analytical model of the rat-tail exposure system was proposed and used to formulate the methods for quantifying the biodynamic responses. A series of tests with six tails dissected from rat cadavers were conducted to test and evaluate the new model. The experimental and modeling results demonstrate that the new model behaves as predicted. Unlike the previous model, the vibration strain and stress of the rat tail does not depend primarily on the vibration response of the tail itself but on that of the loading device. This makes it possible to quantify and control the biodynamic responses conveniently and reliably by measuring the loading device response. This study also identified the basic characteristics of the tail biodynamic responses in the exposure system, which can be used to help design the experiments for studying vibration biological effects.

Cryoglobulins and cold agglutinins for hand arm vibration syndrome

BACKGROUND

Hand arm vibration syndrome (HAVS) is a condition caused by hand transmitted vibration from the use of hand-held vibrating tools or workpieces. The disease affects the vascular, neurological and musculoskeletal systems. The vascular component of HAVS is a form of secondary Raynaud's phenomenon. Other causes of disease must be excluded before attributing the cause to hand transmitted vibration.

AIMS

To evaluate the prevalence, and utility of testing for, cryoglobulins and cold agglutinins in patients with HAVS symptoms.

METHODS

A retrospective cohort study of 1183 patients referred for HAVS clinical assessment at St. Michael's Hospital, Toronto, Canada, between 2014 and 2020. The standard operating procedure at the clinic includes a detailed clinical and exposure history, physical examination, objective investigations and blood tests. Data were retrieved from patient chart review and laboratory investigation results for all cases with cryoglobulin and cold agglutinin testing.

RESULTS

A total of 1183 patients had a serum cryoglobulin measurement. Eleven patients (1%) were positive. Seven positive results were 'low titre' (1% positive) and the other four results were 2%, 6%, 9% and 18%. The patient with a 9% positive cryoglobulin titre had previously diagnosed Sjögren's syndrome. There were no positive cold agglutinin tests in the 795 patients tested.

CONCLUSIONS

Routine testing for cryoglobulins and cold agglutinins in patients with HAVS symptoms is not recommended because test positivity rates are negligible. Testing may be considered if the clinical history or routine blood investigations suggest evidence of underlying cryoglobulinaemia or cold agglutinin disease.

Effects of whole-body vibration on reproductive physiology in a rat model of whole-body vibration

Findings from epidemiological studies suggest that occupational exposure to whole-body vibration (WBV) may increase the risk of miscarriage and contribute to a reduction in fertility rates in both men and women. However, workers exposed to WBV may also be exposed to other risk factors that contribute to reproductive dysfunction. The goal of this experiment was to examine the effects of WBV on reproductive physiology in a rat model. Male and female rats were exposed to WBV at the resonant frequency of the torso (31.5 Hz, 0.3 g amplitude) for 4 hr/day for 10 days. WBV exposure resulted in a significant reduction in number of developing follicles, and decrease in circulating estradiol concentrations, ovarian luteinizing hormone receptor protein levels, and marked changes in transcript levels for several factors involved in follicular development, cell cycle, and steroidogenesis. In males, WBV resulted in a significant reduction in spermatids and circulating prolactin levels, elevation in number of males having higher circulating testosterone concentrations, and marked alterations in levels of transcripts associated with oxidative stress, inflammation, and factors involved in regulating the cell cycle. Based upon these findings data indicate that occupational exposure to WBV contributes to adverse alterations in reproductive physiology in both genders that may lead to reduction in fertility.

A Multiscale Approach for Predicting Certain Effects of Hand-Transmitted Vibration on Finger Arteries

Prolonged exposure to strong hand-arm vibrations can lead to vascular disorders such as Vibration White Finger (VWF). We modeled the onset of this peripheral vascular disease in two steps. The first consists in assessing the reduction in shearing forces exerted by the blood on the walls of the arteries (Wall Shear Stress—WSS) during exposure to vibrations. An acute but repeated reduction in WSS can lead to arterial stenosis characteristic of VWF. The second step is devoted to using a numerical mechano-biological model to predict this stenosis as a function of WSS. WSS is reduced by a factor of 3 during exposure to vibration of 40 m·s−2. This reduction is independent of the frequency of excitation between 31 Hz and 400 Hz. WSS decreases logarithmically when the amplitude of the vibration increases. The mechano-biological model simulated arterial stenosis of 30% for an employee exposed for 4 h a day for 10 years. This model also highlighted the chronic accumulation of matrix metalloproteinase 2. By considering daily exposure and the vibratory level, we can calculate the degree of stenosis, thus that of the disease for chronic exposure to vibrations.

VISTATM: Visual Impairment Subtle Touch AidTM - a range detection and feedback system for sightless navigation

We devised a low-tech, low-cost, robust, and minimally obtrusive navigational travelling aid to be paired with and bolster standard white cane use for people with visual impairments. The device combines ultrasonic range detection with proportional vibrational output. The navigational aid was devised using a sensing belt equipped with independent ultrasonic sensors for distance measurements. Sensors were mounted using adjustable mobile clips to allow for user variability. The sensing belt was connected to a stimulation belt affixed to the ribcage. The stimulation belt used vibrating motors with vibration proportional to the distance between the belt wearer and surrounding obstacles sensed by corresponding ultrasonic sensors. The device was validated through preliminary testing on blindfolded, but fully sighted, persons and one blind person (all authors) in navigating a novel environment without supplemental aid. Testing sessions varied from 45 to 90 min. In preliminary tests, the devised ultrasonic-sensor-belt and vibration-actuator-equipped belt combination was capable of informing users of surrounding obstacles in real-time while navigating a hallway with several turns.

Exposure to Hand-Arm Vibration in the Australian Workforce

OBJECTIVE

To estimate the prevalence of hand-arm vibration (HAV) in Australian workplaces.

METHODS

The Australian Workplace Exposure Survey (AWES)-Hearing was a cross-sectional telephone survey of Australian workers conducted in 2016-2017. Respondents were asked about the time spent using tools or performing tasks known to be associated with HAV during their most recent working day. We created a library of HAV magnitude levels for each tool/task and estimated each worker's daily HAV exposure level using standard formulae. We categorized each worker as to whether they exceeded the daily occupational limits of 2.5 and 5.0 m/s2. Results were extrapolated to the Australian working population using a raked weighting method.

RESULTS

In our sample of 4991 workers, 5.4% of men and 0.7% of women exceeded the HAV action limit of 2.5 m/s2 on their most recent working day. We estimate that 3.8% of the Australian workforce exceeds the HAV limit of 2.5 m/s2 and 0.8% exceeds the 5 m/s2 limit. Men were more likely to exceed the HAV limits than women, as were those with trade qualifications, and those who worked in remote locations. Workers in the construction, farming, and automobile industries had the highest prevalence of HAV exposure. Tool groups that contributed to higher exposure levels included: compactors, rollers, and tampers; power hammers and jackhammers; and underground mining equipment.

CONCLUSIONS

HAV is common in the Australian working population. Given the health risks associated with this exposure, reduction strategies and interventions should be developed, with engineering controls as the starting point for exposure reduction strategies.

Local vibration induced vascular pathological structural changes and abnormal levels of vascular damage indicators

BACKGROUND

The vascular component of the hand-arm-vibration syndrome (HAVS) is often characterized by vibration-induced white fingers (VWF). Active substances secreted by the vascular endothelial cells (VEC) maintain a dynamic balance but damage to the blood vessels may occur when the equilibrium is altered, thus forming an important pathological basis for VWF. This study was aimed at investigating vascular damage indicators as a basis for an early detection of disorders caused by vibration, using the rat tail model.

METHODS AND RESULTS

Experiments were conducted using a control group of rats not exposed to vibration while two exposed groups having different exposure durations of 7 and 14 days were randomly formed. Following exposure, the structural changes of tail tissue samples in anesthetized rats were observed. Enzyme-linked immunosorbent assay (ELISA) was used for analyzing four vascular damage indicators myosin regulatory light chain (MLC2), endothelin-1 (ET-1), vinculin (VCL) and 5-hydroxytryptamine (5-HT) in tail blood samples. We found that both vascular smooth muscle and endothelial cells displayed changes in morphology characterized by vacuolization and swelling in the vibration-exposed group. The levels of vascular damage indicators were altered under the vibration.

CONCLUSION

The degree of vascular pathology increased with the longer duration exposure. Furthermore, the levels of MLC2, ET-1 and 5-HT in rat plasma were associated with vascular injury caused by local vibration.

A Review of Hand-Arm Vibration Studies Conducted by US NIOSH since 2000

Studies on hand-transmitted vibration exposure, biodynamic responses, and biological effects were conducted by researchers at the Health Effects Laboratory Division (HELD) of the National Institute for Occupational Safety and Health (NIOSH) during the last 20 years. These studies are systematically reviewed in this report, along with the identification of areas where additional research is needed. The majority of the studies cover the following aspects: (i) the methods and techniques for measuring hand-transmitted vibration exposure; (ii) vibration biodynamics of the hand-arm system and the quantification of vibration exposure; (iii) biological effects of hand-transmitted vibration exposure; (iv) measurements of vibration-induced health effects; (iv) quantification of influencing biomechanical effects; and (v) intervention methods and technologies for controlling hand-transmitted vibration exposure. The major findings of the studies are summarized and discussed.

Vibration Exposure Safety Guidelines for Surgeons Using Power-Assisted Liposuction (PAL)

BACKGROUND

As power-assisted liposuction (PAL) gains in popularity, plastic surgeons operating these devices experience occupational exposure to hand-transmitted vibration, which can result in hand-arm vibration syndrome, a debilitating neurovasculopathy.

OBJECTIVES

The objective of the study was to determine vibration exposure from the utilization of a PAL device during surgery to generate recommendations for safe use.

METHODS

Vibration emission of a commonly utilized PAL system (MicroAire-650, Surgical Instruments, Charlottesville, VA) was examined employing a vibration data logger under both controlled laboratory conditions and during 13 typical liposuction cases. Data were analyzed and compared with established safety limits of vibration exposure.

RESULTS

The experiments demonstrated a mean vibration magnitude of typical liposuction surgeries to be 5.69 ± 0.77 m/s2 (range, 4.59-6.27 m/s2), which is significantly higher than the manufacturer declared value of 3.77 m/s2. Cannula size was shown to be the most significant contributor to vibration magnitude, with larger cannulas causing more vibration transmission.

CONCLUSIONS

These results indicate that recommendations must be made to prevent undue occupational exposure to vibration from PAL. The MicroAire-650 can generally be safely utilized for less than 1.5 h/d. At exposure levels >1.5 h/d, there is increased risk of developing vibration-related injuries, and vibration-reducing strategies should be implemented. At exposure levels >6 h/d, the safety limit is exceeded and there is significantly increased risk of developing hand-arm vibration syndrome and vibration exposure should be halted.

LEVEL OF EVIDENCE: 4

Infrared Thermography as a Method of Verification in Raynaud's Phenomenon

Raynaud's phenomenon (RP) is characterized by the episodic whitening of the fingers upon exposure to cold. A recently described thermographic algorithm was proposed as a diagnostic replacement of the currently applied finger systolic pressure (FSP) test. The aim of the study was to evaluate the performance of the thermographic algorithm when applied in patients suspected of having RP. Forty-three patients were examined using thermographic imaging after local cooling of the hands in water of 10 °C for 1 min. The thermographic algorithm was applied to predict the probability of RP. The performance of the algorithm was evaluated with different cut-off levels. A new algorithm was proposed based on patients from the target population. The performance of the tested algorithm was noninferior to the FSP test, when a cut-off level of 0.05 was applied, yielding a sensitivity and specificity of 69% and 58%, respectively. The accuracy was 66%. The FSP test had a sensitivity and specificity of 77% and 37%, respectively, and the accuracy was 59%. The thermographic method proved useful for detecting RP and was able to replace the FSP test as a diagnostic test. The alternative algorithm revealed that other thermographic variables were more predictive of the target population, but this should be verified in future patients.

Vibrotactile sensitivity testing for occupational and disease-induce peripheral neuropathies

The International Standard Organization (ISO) standard 13091-1 describes methods and procedures for performing the vibrotactile perception threshold (VPT) testing to diagnose changes in tactile sensory function associated with occupational exposures. However, the VPT test also has been used in the diagnosis of peripheral neuropathies associated with a number of disorders. This review examines the VPT test, variations in procedures that have been used, as well as disorders and diseases in which this test has been reliable for the detection of sensory changes. Mechanisms potentially underlying the changes in VPTs are also discussed along with procedural and subject/patient factors that may affect the interpretation of test results. Based upon the review of the literature, there are also suggestions for where additional research might improve the administration of this test, depending upon the subject/patient population and interpretation of data.

Biological effects of inhaled hydraulic fracturing sand dust. VI. Cardiovascular effects

Hydraulic fracturing is used to access oil and natural gas reserves. This process involves the high-pressure injection of fluid to fracture shale. Fracking fluid contains approximately 95% water, chemicals and 4.5% fracking sand. Workers may be exposed to fracking sand dust (FSD) during the manipulation of the sand, and negative health consequences could occur if FSD is inhaled. In the absence of any information about its potential toxicity, a comprehensive rat animal model study (see Fedan et al., 2020) was designed to investigate the bioactivities of several FSDs in comparison to MIN-U-SIL® 5, a respirable α-quartz reference dust used in previous animal models of silicosis, in several organ systems. The goal of this study was to assess the effects of inhalation of one FSD, i.e., FSD 8, on factors and tissues that affect cardiovascular function. Male rats were exposed to 10 or 30 mg/m³ FSD (6 h/d for 4 d) by whole body inhalation, with measurements made 1, 7 or 27 d post-exposure. One day following exposure to 10 mg/m³ FSD the sensitivity to phenylephrine-induced vasoconstriction in tail arteries in vitro was increased. FSD exposure at both doses resulted in decreases in heart rate (HR), HR variability, and blood pressure in vivo. FSD induced changes in hydrogen peroxide concentrations and transcript levels for pro-inflammatory factors in heart tissues. In kidney, expression of proteins indicative of injury and remodeling was reduced after FSD exposure. When analyzed using regression analysis, changes in proteins involved in repair and remodeling were correlated. Thus, it appears that inhalation of FSD does have some prolonged effects on cardiovascular, and, possibly, renal function. The findings also provide information regarding potential mechanisms that may lead to these changes, and biomarkers that could be examined to monitor physiological changes that could be indicative of impending cardiovascular dysfunction.

Can Blood Flow be Used to Monitor Changes in Peripheral Vascular Function That Occur in Response to Segmental Vibration Exposure?

OBJECTIVES

Laser Doppler blood flow measurements have been used for diagnosis or detection of peripheral vascular dysfunction. This study used a rat tail model of vibration-induced vascular injury to determine how laser Doppler measurements were affected by acute and repeated exposures to vibration, and to identify changes in the Doppler signal that were associated with the exposure.

METHODS

Blood flow was measured immediately after a single exposure to vibration, or before vibration exposure on days 1, 5, 10, 15, and 20 of a 20 days exposure.

RESULTS

After a single exposure to vibration, average tail blood flow was reduced. With 20 days of exposure, there was a reduction in the amplitude of the arterial pulse on days 10 to 20 in vibrated rats and days 15 to 20 in control rats.

CONCLUSIONS

More detailed statistical analyses of laser Doppler data may be needed to identify early changes in peripheral circulation after exposure to vibration.

Sound and Vibration as Research Variables in Terrestrial Vertebrate Models

Sound and vibration have been shown to alter animal behavior and induce physiological changes as well as to cause effects at the cellular and molecular level. For these reasons, both environmental factors have a considerable potential to alter research outcomes when the outcome of the study is dependent on the animal existing in a normal or predictable biological state. Determining the specific levels of sound or vibration that will alter research is complex, as species will respond to different frequencies and have varying frequencies where they are most sensitive. In consideration of the potential of these factors to alter research, a thorough review of the literature and the conditions that likely exist in the research facility should occur specific to each research study. This review will summarize the fundamental physical properties of sound and vibration in relation to deriving maximal level standards, consider the sources of exposure, review the effects on animals, and discuss means by which the adverse effects of these factors can be mitigated.

Bioinspired Fluffy Fabric with In Situ Grown Carbon Nanotubes for Ultrasensitive Wearable Airflow Sensor

Recently, electronic skin and smart textiles have attracted considerable attention. Flexible sensors, as a kind of indispensable components of flexible electronics, have been extensively studied. However, wearable airflow sensors capable of monitoring the environment airflow in real time are rarely reported. Herein, by mimicking the spider's fluff, an ultrasensitive and flexible all-textile airflow sensor based on fabric with in situ grown carbon nanotubes (CNTs) is developed. The fabric decorated with fluffy-like CNTs possesses exceptionally large contact area, endowing the airflow sensor with superior properties including ultralow detection limit (≈0.05 m s^-1 ), multiangle airflow differential response (0°-90°), and fast response time (≈1.3 s). Besides, the fluffy fabric airflow sensor can be combined with a pristine fabric airflow sensor to realize highly sensitive detection in a wide airflow range (0.05-7.0 m s^-1 ). Its potential applications including transmitting information according to Morse code by blowing the sensors, monitoring increasing and decreasing airflow velocity, and alerting blind people walking outside about potential hazard induced by nearby fast-moving objects are demonstrated. Furthermore, the airflow sensor can be directly integrated into clothing as stylish designs without sacrificing comfortness. It is believed that the ultrasensitive all-textile airflow sensor holds great promise for applications in smart textiles and wearable electronics.

Frequency-dependent changes in mitochondrial number and generation of reactive oxygen species in a rat model of vibration-induced injury

Regular use of vibrating hand tools results in cold-induced vasoconstriction, finger blanching, and a reduction in tactile sensitivity and manual dexterity. Depending upon the length and frequency, vibration induces regeneration, or dysfunction and apoptosis, inflammation and an increase in reactive oxygen species (ROS) levels. These changes may be associated with mitochondria, this study examined the effects of vibration on total and functional mitochondria number. Male rats were exposed to restraint or tail vibration at 62.5, 125, or 250 Hz. The frequency-dependent effects of vibration on mitochondrial number and generation of oxidative stress were examined. After 10 days of exposure at 125 Hz, ventral tail arteries (VTA) were constricted and there was an increase in mitochondrial number and intensity of ROS staining. In the skin, the influence of vibration on arterioles displayed a similar but insignificant response in VTA. There was also a reduction in the number of small nerves with exposure to vibration at 250 Hz, and a reduction in mitochondrial number in nerves in restrained and all vibrated conditions. There was a significant rise in the size of the sensory receptors with vibration at 125 Hz, and an elevation in ROS levels. Based upon these results, mitochondria number and activity are affected by vibration, especially at frequencies at or near resonance. The influence of vibration on the vascular system may either be adaptive or maladaptive. However, the effects on cutaneous nerves might be a precursor to loss of innervation and sensory function noted in workers exposed to vibration.

Nociceptor Interleukin 33 Receptor/ST2 Signaling in Vibration-Induced Muscle Pain in the Rat

Occupational exposure to mechanical vibration can produce the hand-arm vibration syndrome (HAVS), whose most disabling symptom is persistent muscle pain. Unfortunately, the pathophysiology of HAVS pain is still poorly understood, precluding the development of mechanism-based therapies. Since interleukin 33 (IL-33) is essential for inflammation and recovery that follows skeletal muscle injury, we explored its role in muscle pain in a model of HAVS, in adult male rats. Concomitant to mechanical hyperalgesia, an increase in IL-33 in the ipsilateral gastrocnemius muscle was observed 24 hours after vibration. A similar hyperalgesia was produced by intramuscular injection of recombinant rat IL-33 (rrIL-33, 10-300 ng). Intrathecal administration of an oligodeoxynucleotide antisense to IL-33R/ST2 mRNA decreased the expression of ST2 in DRG and attenuated both rrIL-33 and vibration-induced mechanical hyperalgesia. Together these data support the suggestion that IL-33 plays a central role in vibration-induced muscle pain by action, at least in part, on skeletal muscle nociceptors. PERSPECTIVE: Our findings provide evidence of the contribution of IL-33, acting on its canonical receptor, in nociceptors, to muscle pain induced by ergonomic vibration. This suggests that targeting IL-33/ST2 signaling may be a useful strategy for the treatment of muscle pain in HAVS.

The Peculiarities of Remodelling Muscle Tissue of Rats Under the Vibration Influence

Study of the influence of vibration oscillations of different frequency, amplitude and vibration acceleration on the structural and functional state and mechanisms of muscle tissue remodelling. An experimental study was conducted on sexually mature male rats. The rats of the four experimental groups were subjected to vertical vibration oscillations of 15, 25, 50 and 75 Hz, respectively. It has been established that pathological changes in muscle tissue in the form of different variants of damage and remodelling tend to increase, which correlates with the frequency of vibration, amplitude and vibration acceleration level, as in the 2nd group, where the maximum permissible vibration levels did not exceed the established allowable norms, and in other groups of animals, where the permissible levels of total vibration were exceeded. By increasing vibration acceleration for more than 1.25 m/s2 (0.13 g, frequency more than 25 Hz and amplitude of 2 mm), severe damages are observed in the form of alterative changes of muscle fibres with the disappearance of transverse strain, homogenization of sarcoplasm, fragmentation with dissociation fibres on separate beams, partial and subtotal myocytolysis, and necrosis of separate fibres. Inflammation is rapidly increasing with the increase in the frequency of vibration and the level of vibration acceleration for more than 5.0 m/s2 (0.51 g).

Improvements in Pain, Well-being, Arterial Pressure, and Lower Limb Volume Following Andullation Therapy in Healthy and Unhealthy Humans

Our aim was to test the effects of Andullation therapy on pain threshold, pain perception, feeling of well-being, arterial pressure, and leg volume in healthy and unhealthy patients. We used a multidirectional vibration (frequency range: 5-40 Hz; peak-to-peak amplitude: 2-8 mm; acceleration: 0.4-2 m/s2) in an undulatory way through the surface of the body when the patient was in contact with a mattress ("andullation"). The vibes traveled from the heel to the head in a random fashion while the participants (N = 50) were lying on the mattress. We measured the pain threshold using an algometer; pain perception and well-being through a visual analog scale (VAS); arterial pressure with an electronic sphygmomanometer; and leg volume with Kuhnke's technique. Measurements were made just before the first andullation session and after the fifth andullation session. Every participant received andullation sessions of 30 min a day for 5 consecutive days. The patients' pain threshold significantly (P < .001) increased by 34.48% and 25.79% in the lumbar and trapezius zones, respectively, after 5 sessions of therapy. The subjective perception of pain decreased by 52.3% and the feeling of well-being increased by 45.1%. The systolic and diastolic pressures significantly (P < .001) decreased by 6.44 and 4.68 mm Hg on average, respectively. Leg volume significantly decreased (P < .01) by 64.39 mL after the fifth andullation session. Despite not including a control group in our study, the andullation intervention showed an improvement in pain, well-being, arterial pressure, and lower limb volume in the studied population.

Acute Vibration Induces Peripheral Nerve Sensitization in a Rat Tail Model: Possible Role of Oxidative Stress and Inflammation

Prolonged occupational exposure to hand-held vibrating tools leads to pain and reductions in tactile sensitivity, grip strength and manual dexterity. The goal of the current study was to use a rat-tail vibration model to determine how vibration frequency influences factors related to nerve injury and dysfunction. Rats were exposed to restraint, or restraint plus tail vibration at 62.5 Hz or 250 Hz. Nerve function was assessed using the current perception threshold (CPT) test. Exposure to vibration at 62.5 and 250 Hz, resulted in a reduction in the CPT at 2000 and 250-Hz electrical stimulation (i.e. increased Aβ and Aδ, nerve fiber sensitivity). Vibration exposure at 250 Hz also resulted in an increased sensitivity of C-fibers to electrical stimulation and thermal nociception. These changes in nerve fiber sensitivity were associated with increased expression of interleukin (IL)-1β and tumor necrosis factor (TNF)-α in ventral tail nerves, and increases in circulating concentrations of IL-1 β in rats exposed to 250-Hz vibration. There was an increase in glutathione, but no changes in other measures of oxidative activity in the peripheral nerve. However, measures of oxidative stress were increased in the dorsal root ganglia (DRG). These changes in pro-inflammatory factors and markers of oxidative stress in the peripheral nerve and DRG were associated with inflammation, and reductions in myelin basic protein and post-synaptic density protein (PSD)-95 gene expression, suggesting that vibration-induced changes in sensory function may be the result of changes at the exposed nerve, the DRG and/or the spinal cord.

Assessment of structural and functional condition of rats bone tissue under the influence of various parameters of vibration

Whole body vibration involves the exposure of the entire human body to direct contact with environmental vibration. Chronic mechanical vibrations, combined with the physical attributes of the human body, can amplify the incoming energy and present the potential for negative health effects. Vibration exposure can, thus, result in adverse health effects such as spinal injuries, abdominal neurological and cardiovascular disorders. These can manifest indirectly as an accident causal factor. The aim of our research is to study the impact of vibration fluctuations of different frequencies on the structural and functional condition and mechanisms of bone remodelling. An experimental study was, therefore, conducted on mature male rats. For assessment of bone metabolism in the venous blood of rats, osteocalcin level was determined, while fragments of rats’ lumbar vertebrae were subsequently taken for histologic examination. Our work revealed that with the increase of vibration frequency, an increase of osteocalcin level in the blood of experimental animals comes about. Moreover, we noted after terminating vibration fluctuations on the 56th day of the experiment, osteocalcin levels are gradually reduced. In addition, in the course of histological study of specimens of lumbar vertebrae bone tissue, even as early as of the 28th day of the experiment, evidences of acute impairment of the bone tissue and initial signs of its remodelling are clearly traced. Indeed, on the 56th day, the remodelling processes represented by enhanced regeneration in the zone of the cartilage plate, increased in proliferation activity. We also saw hyperplasia of chondrocytes, hypertrophy of the respective zones of cartilage tissue, zones of forming immature bone tissue on the areas of previous damage, focal replacement fibrosis and angiomatosis. Hence, with increasing vibratory acceleration of 0,5 g, the rate of bone metabolism grows, osteoblast activation processes are accelerated and the impairment of collagen and calcium loss is increased. All this leads subsequently to the occurrence of osteoporosis.

Risk assessment of vascular disorders by a supplementary hand-arm vascular weighting of hand-transmitted vibration

PURPOSE

To provide an updated epidemiological validation for a supplementary method for assessing the risk of vascular disorders from hand-transmitted vibration.

METHODS

The occurrence of vibration-induced white finger (VWF) in the vibration-exposed workers of the Italian cohort of the EU VIBRISKS study was related to measures of daily vibration exposure expressed in terms of r.m.s. acceleration magnitude normalised to an 8-h day, frequency weighted according to either the frequency weighting W_h defined in international standard ISO 5349-1:2001 [A_h(8) in ms^- 2] or the hand-arm vascular frequency weighting W_p proposed in the ISO technical report (TR) 18570:2017 [A_p(8) in ms^- 2]. To estimate a threshold value for vascular hand-arm vibration risk, the W_p-weighted vibration exposure value E_p,d (in ms^- 1.5) was calculated according to the ISO/TR document. The difference in the predictions of VWF between the exposure measures calculated with the frequency weightings W_h or W_p was investigated by means of logistic modelling.

RESULTS

Measures of daily vibration exposure constructed with the frequency weighting W_p [A_p(8) and E_p,d], which gives more importance to intermediate- and high-frequency vibration, were better predictors of the occurrence of VWF in the vibration-exposed workers than the metric derived from the conventional ISO frequency weighting W_h [A_h(8)]. There was some epidemiological evidence for a threshold value of E_p,d for the onset of VWF in the vibration-exposed workers.

CONCLUSIONS

Measures of daily vibration exposure evaluated with the vascular weighting W_p performed better for the predictions of VWF than those obtained with the frequency weighting W_h recommended in ISO 5349-1.

Systemic Effects of Segmental Vibration in an Animal Model of Hand-Arm Vibration Syndrome

OBJECTIVE

Epidemiology suggests that occupational exposure to hand-transmitted (segmental) vibration has local and systemic effects. This study used an animal model of segmental vibration to characterize the systemic effects of vibration.

METHODS

Male Sprague Dawley rats were exposed to tail vibration for 10 days. Genes indicative of inflammation, oxidative stress, and cell cycle, along were measured in the heart, kidney, prostate, and liver.

RESULTS

Vibration increased oxidative stress and pro-inflammatory gene expression, and decreased anti-oxidant enzymes in heart tissue. In the prostate and liver, vibration resulted in changes in the expression of pro-inflammatory factors and genes involved in cell cycle regulation.

CONCLUSIONS

These changes are consistent with epidemiological studies suggesting that segmental vibration has systemic effects. These effects may be mediated by changes in autonomic nervous system function, and/or inflammation and oxidative stress.

Vibration in mice: A review of comparative effects and use in translational research

Sound pressure waves surround individuals in everyday life and are perceived by animals and humans primarily through sound or vibration. When sound pressure waves traverse through a solid medium, vibration will result. Vibration has long been considered an unwanted variable in animal research and may confound scientific endeavors using animals. Understanding the characteristics of vibration is required to determine whether effects in animals are likely to be therapeutic or result in adverse biological effects. The eighth edition of the "Guide for the Care and Use of Laboratory Animals" highlights the importance of considering vibration and its effects on animals in the research setting, but knowledge of the level of vibration for eliciting these effects was unknown. The literature provides information regarding therapeutic use of vibration in humans, but the range of conditions to be of therapeutic benefit is varied and without clarity. Understanding the characteristics of vibration (eg, frequency and magnitude) necessary to cause various effects will ultimately assist in the evaluation of this environmental factor and its role on a number of potential therapeutic regimens for use in humans. This paper will review the principles of vibration, sources within a research setting, comparative physiological effects in various species, and the relative potential use of vibration in the mouse as a translational research model.

Health effects associated with occupational exposure to hand-arm or whole body vibration

Workers in a number of different occupational sectors are exposed to workplace vibration on a daily basis. This exposure may arise through the use of powered-hand tools or hand-transmitted vibration (HTV). Workers might also be exposed to whole body vibration (WBV) by driving delivery vehicles, earth moving equipment, or through use of tools that generate vibration at low dominant frequencies and high amplitudes, such as jackhammers. Occupational exposure to vibration has been associated with an increased risk of musculoskeletal pain in the back, neck, hands, shoulders, and hips. Occupational exposure may also contribute to the development of peripheral and cardiovascular disorders and gastrointestinal problems. In addition, there are more recent data suggesting that occupational exposure to vibration may enhance the risk of developing certain cancers. The aim of this review is to provide an assessment of the occupations where exposure to vibration is most prevalent, and a description of the adverse health effects associated with occupational exposure to vibration. This review will examine (1) various experimental methods used to measure and describe the characteristics of vibration generated by various tools and vehicles, (2) the etiology of vibration-induced disorders, and (3) how these data were employed to assess and improve intervention strategies and equipment that reduces the transmission of vibration to the body. Finally, there is a discussion of the research gaps that need to be investigated to further reduction in the incidence of vibration-induced illnesses and injuries.

Contact area affects frequency-dependent responses to vibration in the peripheral vascular and sensorineural systems

Repetitive exposure to hand-transmitted vibration is associated with development of peripheral vascular and sensorineural dysfunctions. These disorders and symptoms associated with it are referred to as hand-arm vibration syndrome (HAVS). Although the symptoms of the disorder have been well characterized, the etiology and contribution of various exposure factors to development of the dysfunctions are not well understood. Previous studies performed using a rat-tail model of vibration demonstrated that vascular and peripheral nervous system adverse effects of vibration are frequency-dependent, with vibration frequencies at or near the resonant frequency producing the most severe injury. However, in these investigations, the amplitude of the exposed tissue was greater than amplitude typically noted in human fingers. To determine how contact with vibrating source and amplitude of the biodynamic response of the tissue affects the risk of injury occurring, this study compared the influence of frequency using different levels of restraint to assess how maintaining contact of the tail with vibrating source affects the transmission of vibration. Data demonstrated that for the most part, increasing the contact of the tail with the platform by restraining it with additional straps resulted in an enhancement in transmission of vibration signal and elevation in factors associated with vascular and peripheral nerve injury. In addition, there were also frequency-dependent effects, with exposure at 250 Hz generating greater effects than vibration at 62.5 Hz. These observations are consistent with studies in humans demonstrating that greater contact and exposure to frequencies near the resonant frequency pose the highest risk for generating peripheral vascular and sensorineural dysfunction.

A two scale modeling and computational framework for vibration-induced Raynaud syndrome

Hand-Arm Vibration syndrome (HAVS), usually caused by long-term use of hand-held power tools, can in certain manifestations alter the peripheral blood circulation in the hand-arm region. HAVS typically occurs after exposure to cold, causing an abnormally strong vasoconstriction of blood vessels. A pathoanatomical mechanism suggests that a reduction of the lumen of the blood vessels in VWF (Vibration White Finger) subjects, due to either hypertrophy or thickening of the vessel wall, may be at the origin of the disease. However, the direct and indirect effects of the load of the hand-held tools on the structure of blood vessels remain controversial:.one hypothesis is the mechanical action of vibration on the local acral dysregulation and/or on the vessel histomorphological modifications. Another hypothesis is the participation of the sympathetic nervous system to this dysregulation. In this paper, we assume the modifications as mechanobiological growth and the load-effect relationship may be interpreted as directly or indirectly induced. This work is the first attempt to model the effect of vibration through soft tissues onto the distal capillaries, addressing the double paradigm of multi space-time scales, i.e. low period vibration versus high time constant of the growth phenomenon as well as vibrations propagating in the macroscopic tissue including the microscopic capillary structures subjected to a pathological microstructural evolution. The objective is to lay down the theoretical basis of growth modeling for the small distal artery, with the ability to predict the geometrical and structural changes of the arterial walls caused by vibration exposure. We adopt the key idea of splitting the problem into one global vibration problem at the macroscopic scale and one local growth problem at the micro level. The macroscopic hyperelastic viscous dynamic model of the fingertip cross-section is validated by fitting experimental data. It is then used in steady-state vibration conditions to predict the mechanical fields in the close vicinity of capillaries. The space scale transfer from macroscopic to microscopic levels is ensured by considering a representative volume element (RVE) embedding a single capillary in its center. The vibrations emitted by the hand held power tool are next linked to the capillary growth through the adopted biomechanical growth model at the capillary level. The obtained results show that vibrations induce an increase of the thickness of the capillary's wall, thereby confirming the scenario of vibrations induced reduction of the lumen of blood vessels.

Effect of the gel elasticity of model skin matrices on the distance/depth-dependent transmission of vibration energy supplied from a cosmetic vibrator

OBJECTIVE

The purpose of this study was to determine how the energies supplied from a cosmetic vibrator are deeply or far transferred into organs and tissues, and how these depths or distances are influenced by tissue elasticity.

METHODS

External vibration energy was applied to model skin surfaces through a facial cleansing vibrator, and we measured a distance- and depth-dependent energy that was transferred to model skin matrices. As model skin matrices, we synthesized hard and soft poly(dimethylsiloxane) (PDMS) gels, as well as hydrogels with a modulus of 2.63 MPa, 0.33 MPa and 21 kPa, respectively, mostly representing those of skin and other organs. The transfer of vibration energy was measured either by increasing the separation distances or by increasing the depth from the vibrator.

RESULTS

The energies were transmitted deeper into the hard PDMS than into the soft PDMS and hydrogel matrices. This finding implies that the vibration forces influence a larger area of the gel matrices when the gels are more elastic (or rigid). There were no appreciable differences between the soft PDMS and hydrogel matrices. However, the absorbed energies were more concentrated in the area closest to the vibrator with decreasing elasticity of the matrix. Softer materials absorbed most of the supplied energy around the point of the vibrator. In contrast, harder materials scattered the external energy over a broad area.

CONCLUSIONS

The current results are the first report in estimating how the external energy is deeply or distantly transferred into a model skins depending on the elastic moduli of the models skins. In doing so, the results would be potentially useful in predicting the health of cells, tissues and organs exposed to various stimuli.

Transcriptional Pathways Altered in Response to Vibration in a Model of Hand-Arm Vibration Syndrome

OBJECTIVE

The aim of this study was to use an established model of vibration-induced injury to assess frequency-dependent changes in transcript expression in skin, artery, and nerve tissues.

METHODS

Transcript expression in tissues from control and vibration-exposed rats (4 h/day for 10 days at 62.5, 125, or 250 Hz; 49 m/s, rms) was measured. Transcripts affected by vibration were used in bioinformatics analyses to identify molecular- and disease-related pathways associated with exposure to vibration.

RESULTS

Analyses revealed that cancer-related pathways showed frequency-dependent changes in activation or inhibition. Most notably, the breast-related cancer-1 pathway was affected. Other pathways associated with breast cancer type 1 susceptibility protein related signaling, or associated with cancer and cell cycle/cell survivability were also affected.

CONCLUSION

Occupational exposure to vibration may result in DNA damage and alterations in cell signaling pathways that have significant effects on cellular division.

The effects of impact vibration on peripheral blood vessels and nerves

Research regarding the risk of developing hand-arm vibration syndrome after exposure to impact vibration has produced conflicting results. This study used an established animal model of vibration-induced dysfunction to determine how exposure to impact vibration affects peripheral blood vessels and nerves. The tails of male rats were exposed to a single bout of impact vibration (15 min exposure, at a dominant frequency of 30 Hz and an unweighted acceleration of approximately 345 m/s(2)) generated by a riveting hammer. Responsiveness of the ventral tail artery to adrenoreceptor-mediated vasoconstriction and acetylcholine-mediated re-dilation was measured ex vivo. Ventral tail nerves and nerve endings in the skin were assessed using morphological and immunohistochemical techniques. Impact vibration did not alter vascular responsiveness to any factors or affect trunk nerves. However, 4 days following exposure there was an increase in protein-gene product (PGP) 9.5 staining around hair follicles. A single exposure to impact vibration, with the exposure characteristics described above, affects peripheral nerves but not blood vessels.