Vibrotactile Perception Thresholds Research Articles

Residual Shift of Vibrotactile Perception Thresholds Following Repeated Hand-Arm Vibration Exposure: Screening Parameter for Early Signs of Neurosensory Disorders

Background: The purpose of this study was to validate the applicability of a new screening parameter of VPTW defined as the difference between the ascending and descending thresholds of vibrotactile perception to evaluation of the increasing risk of the neurological components of hand-arm vibration syndrome (HAVS) for repeated exposure to hand-arm vibration (HAV). Methods: Thirty subjects—10 old exposed (G1), 10 old non-exposed (G2), and 10 young non-exposed subjects (G3)—were required to carry out three 3 min grip tasks with exposure to two intensities of HAV at 10 min intervals. Vibration perception measurements, each of which lasted 90 s, were performed at 5 min intervals at the right index finger. Results: VPTWs calculated from pairs of the vibrotactile ascending and descending thresholds at the fingertips were not significantly affected by repeated HAV exposure. Moreover, the VPTWs measured for non-exposed subjects were almost invariant regardless of the subjects’ age or the time elapsed after repeated exposure to HAV. Residual TTSs at 125 Hz gradually recovered in all subject groups under both HAV exposure conditions. The residual TTSs of non-exposed subject groups significantly increased as the number of iterations of HAV exposure increased. Conclusions: VPTWs measured after exposure to repeated HAV are invariant and independent of the individual neurosensory characteristics of the fingertips, which supports the hypothesis that VPTWs can be used as a screening parameter to detect potential patients only with neurosensory components observed as early signs of HAVS.

Vibrotactile Perception Thresholds following Short-Term Exposure to Hand–Arm Vibration: Application for Identifying Potential Workers at Risk of Neurosensory Disorders

Background: The aim of this study was to propose and validate a novel indicator that characterizes the potential effects of exposure to hand–arm vibration (HAV) and evaluates the increasing risk of neurosensory components of hand–arm vibration syndrome (HAVS). The author focused on a quantity calculated from ascending and descending thresholds and residual shifts in vibrotactile perception thresholds (VPTs) observed at the fingertips in the recovery process after exposure to HAV. Methods: Thirty subjects—10 old exposed (G1), 10 old non-exposed (G2), and 10 young non-exposed subjects (G3)—were required to perform a series of grip tasks with exposure to two intensities of HAV, which was followed by 90 s of vibration perception measurements at the tip of each subject’s right index finger. Vibrotactile perception was measured every 5 min for 30 min. Results: Mean differences between ascending and descending thresholds (VPTWs) for G2 and G3 remained nearly unchanged over time after exposure to HAV. In contrast, the mean VPTWs for G1 gradually increased over time after exposure to HAV. The mean VPTWs for G1 were always larger than those for G2 and G3. TTS recovery was observed at 125 Hz under both of the HAV exposure conditions in each group. TTSs of nearly zero were observed for the low-HAV condition in G3. TTS recovery after exposure to HAV was not observed at 31.5 Hz in any of the subject groups. Regardless of elapsed time, the mean TTSs for G2 and G3 were smaller than those for G1. Negative TTS values showing a lower TTS than the baseline were sometimes observed for the low-HAV condition in G3. Conclusions: VPTWs can be a screening parameter that detects potential patients with only neurosensory components observed as an early sign of HAVS.

Vibrotactile sense might improve over time in paediatric subjects with type 1 diabetes-A mid-term follow-up using multifrequency vibrometry.

Impaired vibrotactile sense, mirroring diabetic peripheral neuropathy, is present among children and adolescents with type 1 diabetes. This study aims to re-examine the vibrotactile sense of paediatric type 1 diabetes subjects in order to evaluate any alterations in the vibrotactile sense over time. A VibroSense Meter I device was used to determine the vibrotactile perception thresholds (VPTs) for seven frequencies from the pulp of index and little fingers and for five frequencies from metatarsal heads one and five on the sole of the foot, of 37 children and adolescents with type 1 diabetes, previously examined in a larger cohort. Subjects were followed up after a median time of 30months. Z-scores of VPTs were calculated using previously collected normative data. Vibrotactile perception thresholds improved over time at low frequencies (especially 16Hz) on the foot, while not being statistically significant different on the rest of the frequencies, either on hand or foot. VPTs were not correlated with HbA1c. A mid-term follow-up of vibrotactile sense in paediatric subjects with type 1 diabetes shows a conceivable normalization of previously impaired vibrotactile sense on some frequencies on the foot, indicating that vibrotactile sense might fluctuate over time.

An Investigation of the Effects of Drill Operator Posture on Vibration Exposure and Temporary Threshold Shift of Vibrotactile Perception Threshold

The present study involved performing an experiment to clarify whether vibration measurement values on the tool handle, in accordance with ISO 5349-1, can assess risk from workplace environments. The study investigated the relationship between the vibration magnitude of a hand-held electric drill with different operating postures. The experiment included the determination of the participant’s temporary threshold shift (TTS) of vibrotactile perception threshold (VPT) at the tip of the index finger. The experimental hypothesis was that the vibration measurement values on the tool handle, in accordance with the ISO 5349-1 standard, include the effect of posture on the vibration measurements obtained despite the variation in posture and test participants. The hand-transmitted vibration (HTV) was applied using a hand-held electric drill applied to a pre-cast concrete paving slab substrate (600 × 600 × 50 mm, 55 MPa) using a 10 mm diameter masonry drill bit (without hammer action). The tool was operated using the right hand on twelve male subjects with three working postures (n = 36). Vibration was measured in three orthogonal directions according to the international standard ISO 5349-1 procedure. Vibration magnitudes were expressed as root-mean-square (r.m.s.) acceleration, frequency-weighted using the Wh frequency weighting. Clause 4.3 states that the characterisation of the vibration exposure is assessed from the acceleration of the surface in contact with the hand as the primary quantity. The experimental results indicate that the TTS following vibration exposure is not related to the measured vibration magnitude on the tool handle. Therefore, the automatic inclusion of posture and test participant variation is not proven. The results suggest that the vibration measurement values on the tool handle do not predict the TTS after hand-transmitted vibration in varying posture across the test participants. The research concludes that tool handle vibration measurement, in accordance with ISO 5349-1, does not properly assess the potential hazard from authentic workplace tool usage conditions of varying postures.

Vibrotactile perception in Dupuytren disease

Purpose Dupuytren disease (DD) has been associated with enlarged Pacinian corpuscles (PCs) and with PCs having a greater number of lamellae. Based on these associations, we hypothesized that subjects with DD would have altered sensitivity to high-frequency vibrations and that the changes would be more prominent at 250 Hz, where healthy subjects demonstrate the highest sensitivity. Methods A novel device was created to deliver vibrations of specific frequencies and amplitudes to the fingers and palm. Using a Psi-marginal adaptive algorithm, vibrotactile perception thresholds (VPTs) were determined in 36 subjects with DD and 74 subjects without DD. Experiments were performed at 250 Hz and 500 Hz at the fingertip and palm. The VPTs were statistically analyzed with respect to disease status, age, gender, location tested, and frequency tested. Results We found that VPT increases with age, which agrees with findings by others. Women showed greater sensitivity (i.e. lower VPT) than men. Men exhibited lower sensitivity in DD versus healthy subjects, but the results were not statistically significant. In subjects with DD presenting unilaterally, the unaffected hand was more sensitive than the affected hand, in particular for a 250 Hz stimulus applied to the finger. Conclusions The data on vibration sensitivity obtained from a large group of subjects with and without DD present interesting trends that may serve as a useful reference to future DD researchers. Understanding additional symptoms of DD may facilitate development of novel diagnostic or prognostic protocols.

Determination of hand-transmitted vibration risk on the human

ObjectiveThe purpose of this paper is to examine the effectiveness of the proposed consideration for hand-transmitted vibration measurement on the human. MethodTo obtain the temporary threshold shift (TTS) in the fingertip vibrotactile perception threshold, the vibrotactile perception thresholds were measured before and after the subjects were exposed to hand-transmitted vibration from the hand-held tool. The vibration magnitude has been measured by using conventional vibration measurement on the tool and by using the proposed consideration vibration on the human simultaneously. ResultsThe proposed hand-transmitted vibration measurement on the subject was proportional with increasing TTS. In contrast the data from conventional vibration measurement on the tool shows a relatively constant vibration level while TTS increases within a subject group. ConclusionThe proposed measurement method of hand-transmitted vibration on the subject captures at least some of the effects of factors relating to the human interaction with the tool identified within Annex D of the ISO 5349-1 standard. The effectiveness of the proposed hand-transmitted vibration measurement consideration on the human for improved understanding of tool vibration exposure has been shown.

Associations between anthropometric factors and peripheral neuropathy defined by vibrotactile perception threshold among industrial vibrating tool operators in Japan.

The effect of anthropometric factors on the fingertip vibrotactile perception threshold (VPT) of industrial vibrating tool operators (IVTOs) is not well known. The purpose of this study was to investigate the associations between anthropometric factors and fingertip VPT. We included for analysis two groups of IVTOs: Group 1, predominantly forestry workers (n=325); and Group 2, public servants (n=68). These IVTOs regularly received medical examinations to evaluate hand-arm vibration syndrome. In the examination, measurements of their fingertip VPTs were taken before and after cold-water immersion (10 minutes at 10°C for Group 1 and 5 minutes at 12°C for Group 2). Their body height and weight were measured to calculate the body mass index (BMI). The presence of peripheral neuropathy (PN) was defined as a VPT ≥17.5 dB at 10 minutes after finishing immersion. In the univariate analysis, weight and BMI were associated with a decreased risk of PN in both Groups 1 and 2. The negative association between BMI and PN remained in the multivariate analysis consistently, but weight reached marginal significance only in the multivariate analysis without BMI in both the groups. Age was positively associated with PN consistently in Group 1 but not in Group 2. Years exposed to vibration showed positive association with PN only in the univariate analysis of Group 1. Among IVTOs, factors reflecting body heat production, such as weight and BMI, were associated with a decreased risk of VPT-defined PN, regardless of the task engaged.

The Association of Sensory Responsiveness with Somatic Symptoms and Illness Anxiety

Somatoform Disorders or Somatic Symptom and Related Disorders are a major public health problem.The pathophysiology underlying these disorders is not yet understood. The aim of this study was to explore if sensory responsiveness could contribute to a better understanding of pathophysiological mechanisms underlying two key symptoms of Somatoform Disorders, namely somatic symptoms and illness anxiety. We measured vibrotactile perception thresholds with the HVLab Perception Meter and examined their association with somatic symptoms, illness anxiety and trait anxiety. A sample of 205 volunteers participated in the study. Sensory responsiveness was neither associated with somatic symptoms (β = -0.01; 95% confidence interval (CI), -0.37, 0.39) nor trait anxiety (β = -0.07; 95% CI, -0.30, 0.07). However, lower vibrotactile perception thresholds were associated with increased scores of the overall illness anxiety scale (β = -0.65; 95% CI, -1.21, -0.14) and its constituent subscale disease conviction (β = -2.07; 95% CI, -3.94, -0.43). Our results suggest that increased sensory responsiveness is associated with illness anxiety and hence should be examined further as potential target within the etiopathology of somatoform disorders.

Relation between vibrotactile perception thresholds and reductions in finger blood flow induced by vibration of the hand at frequencies in the range 8-250 Hz.

This study investigated how the vasoconstriction induced by vibration depends on the frequency of vibration when the vibration magnitude is defined by individual thresholds for perceiving vibration [i.e. sensation levels (SL)]. Fourteen healthy subjects attended the laboratory on seven occasions: for six vibration frequencies (8, 16, 31.5, 63, 125, or 250 Hz) and a static control condition. Finger blood flow (FBF) was measured in the middle fingers of both hands at 30-second intervals during five successive periods: (i) no force or vibration, (ii) 2-N force, no vibration, (iii) 2-N force, vibration, (iv) 2-N force, no vibration, (v) no force or vibration. During period (iii), vibration was applied to the right thenar eminence via a 6-mm diameter probe during ten successive 3-min periods as the vibration magnitude increased in ten steps (-10 to +40 dB SL). With vibration at 63, 125, and 250 Hz, there was vasoconstriction on both hands when the vibration magnitude reached 10 dB SL. With vibration at 8, 16, and 31.5 Hz, there was no significant vasoconstriction until the vibration reached 25 dB SL. At all frequencies, there was greater vasoconstriction with greater magnitudes of vibration. It is concluded that at the higher frequencies (63, 125, and 250 Hz), the Pacinian channel mediates vibrotactile sensations near threshold and vasoconstriction occurs when vibration is perceptible. At lower frequencies (8, 16, and 31.5 Hz), the Pacinian channel does not mediate sensations near threshold and vasoconstriction commences at greater magnitudes when the Pacinian channel is activated.

Neurosensory sequelae assessed by thermal and vibrotactile perception thresholds after local cold injury

BackgroundLocal freezing cold injuries are common in the north and sequelae to cold injury can persist many years. Quantitative sensory testing (QST) can be used to assess neurosensory symptoms but has previously not been used on cold injury patients.ObjectiveTo evaluate neurosensory sequelae after local freezing cold injury by thermal and vibrotactile perception thresholds and by symptom descriptions.DesignFifteen patients with a local freezing cold injury in the hands or feet, acquired during military training, were studied with QST by assessment of vibrotactile (VPT), warmth (WPT) and cold (CPT) perception thresholds 4 months post-injury. In addition, a follow-up questionnaire, focusing on neurovascular symptoms, was completed 4 months and 4 years post-injury.ResultsQST demonstrated abnormal findings in one or both affected hands for VPT in 6 patients, for WPT in 4 patients and for CPT in 1 patient. In the feet, QST was abnormal for VPT in one or both affected feet in 8 patients, for WPT in 6 patients and for CPT in 4 patients. Freezing cold injury related symptoms, e.g. pain/discomfort when exposed to cold, cold sensation and white fingers were common at 4 months and persisted 4 years after the initial injury.ConclusionsNeurosensory sequelae after local freezing cold injury, in terms of abnormal thermal and/or vibration perception thresholds, may last at least 4 months after the initial injury. Symptoms such as pain/discomfort at cold exposure, cold sensations and white fingers may persist at least 4 years after the initial injury.

A cross sectional study on hand-arm vibration syndrome among a group of tree fellers in a tropical environment.

This study aimed to explore the clinical characteristics of hand arm vibration syndrome (HAVS) in a group of tree fellers in a tropical environment. We examined all tree fellers and selected control subjects in a logging camp of central Sarawak for vibration exposure and presence of HAVS symptoms utilizing vibrotactile perception threshold test (VPT) and cold water provocation test (CWP). None of the subjects reported white finger. The tree fellers reported significantly higher prevalence of finger coldness as compared to the control subjects (OR=10.32, 95%CI=1.21–87.94). A lower finger skin temperature, longer fingernail capillary return time and higher VPT were observed among the tree fellers as compared to the control subjects in all fingers (effect size >0.5). The VPT following CWP of the tree fellers was significantly higher (repeated measures ANOVA p=0.002, partial η2=0.196) than the control subject. The A (8) level was associated with finger tingling, numbness and dullness (effect size=0.983) and finger coldness (effect size=0.524) among the tree fellers. Finger coldness and finger tingling, numbness and dullness are important symptoms for HAVS in tropical environment that may indicate vascular and neurological damage due to hand-transmitted vibration exposure.

A Comparison of Hand‐arm Vibration Syndrome between Malaysian and Japanese Workers

The aim of this study was to investigate the clinical characteristics of HAVS in a tropical environment in comparison with a temperate environment. We conducted a series medical examinations among the forestry, construction and automobile industry workers in Malaysia adopting the compulsory medical examination procedure used by Wakayama Medical University for Japanese vibratory tools workers. We matched the duration of vibration exposure and compared our results against the Japanese workers. We also compared the results of the Malaysian tree fellers against a group of symptomatic Japanese tree fellers diagnosed with HAVS. Malaysian subjects reported a similar prevalence of finger tingling, numbness and dullness (Malaysian=25.0%, Japanese=21.5%, p=0.444) but had a lower finger skin temperature (FST) and higher vibrotactile perception threshold (VPT) values as compared with the Japanese workers. No white finger was reported in Malaysian subjects. The FST and VPT of the Malaysian tree fellers were at least as bad as the Japanese tree fellers despite a shorter duration (mean difference=20.12 years, 95%CI=14.50, 25.40) of vibration exposure. Although the vascular disorder does not manifest clinically in the tropical environment, the severity of HAVS can be as bad as in the temperate environment with predominantly neurological disorder. Hence, it is essential to formulate national legislation for the control of the occupational vibration exposure.

Normative data for neuromuscular assessment of the hand–arm vibration syndrome and its retrospective applications in Korean male workers

The purpose of this study was to describe normative data for the neuromuscular assessments of the hand-arm vibration syndrome (HAVS) in Korean. Data for the vibrotactile perception threshold (VPT) at three frequencies (31.5, 125, and 250 Hz), the hand grip strength (HGS), the finger pinch strength (FPS), the finger tapping test, and the Purdue pegboard tests were collected from 120 male office workers aged 30-59 years with no prior history of regular use of handheld vibrating tools. The collected data were compared with the results of a similar study of shipbuilding workers in order to investigate the diagnostic utility of clinical test for HAVS. The mean VPT values indicate that no significant differences were observed between the dominant and non-dominant hands or between the index and little fingers. The age group of 30s was highly sensitive to vibration input with a peak in sensitivity at 125 Hz among all age groups. In neuromuscular performance, dominant hands are usually more accurate, dexterous, and functionally quicker than non-dominant hands. The index finger was superior to the little finger in the finger tapping counts (p < 0.05). Also, FPS was greater in the index finger than in the middle finger (p < 0.05). The HGS of dominant hands was significantly stronger than that of non-dominant hands (p < 0.05). When the normative data were compared with the data of shipyard workers exposed to vibration, there were statistically significant differences in VPT and neuromuscular functions. The current data can be used to evaluate HAVS in Korean male workers. Age is an important factor for VPT.

Dose–response relationship between hand-transmitted vibration and hand-arm vibration syndrome in a tropical environment

ObjectivesThe dose–response relationship for hand-transmitted vibration has been investigated extensively in temperate environments. Since the clinical features of hand-arm vibration syndrome (HAVS) differ between the temperate and tropical environment, we...

Effect of individual finger skin temperature on vibrotactile perception threshold

In healthy people, the vibrotactile perception threshold (VPT) at fingertips depends on a given measurement method and on individual characteristics such as age, gender and finger skin temperature. The aim of the study was to compare the VPT values in 2 groups of healthy subjects with different finger skin temperature. The study group comprised 56 males and 76 females, who formed pairs matched with respect to age, gender and body mass index (BMI) but differing in terms of finger skin temperature at pre-launch testing. The finger skin temperature of less than 29°C indicated the subjects with "cold hands" and that of more than 29°C, the subjects with "warm hands". The measuring system made use of P8 pallesthesiometer (EMSON-MAT, Poland) and the measurement procedure was in compliance with the ISO 13091-1:2001 standard. VPT measurements were performed for the index, middle and ring fingers of both hands at the frequencies of 4 Hz, 25 Hz, 31.5 Hz, 63 Hz, 125 Hz and 250 Hz. The findings of the study revealed that the mean VPTs among the subjects with "cold hands" were significantly higher than the corresponding values among the subjects with "warm hands". The type of individual peripheral thermoregulation should be considered when assessing the VPT and determining its reference values.

Quantitative neurosensory findings, symptoms and signs in young vibration exposed workers

BackgroundLong-term exposure to hand-held vibrating tools may cause the hand arm vibration syndrome (HAVS) including vibration induced white fingers and sensorineural symptoms. The aim was to study early neurosensory effects by quantitative vibrotactile and monofilament tests in young workers with hand-held vibration exposure.MethodsThis cross-sectional study consisted of 142 young, male machine shop and construction workers with hand-held exposure to vibrating tools. They were compared with 41 non-vibration exposed subjects of the same age-group. All participants passed a structured interview, answered several questionnaires and had a physical examination including the determination of vibrotactile perception thresholds (VPTs) at two frequencies (31.5 and 125 Hz) and Semmes Weinstein’s Monofilament test.ResultsIn the vibration exposed group 8% of the workers reported episodes of tingling sensations and 10% numbness in their fingers. Approximately 5–10% of the exposed population displayed abnormal results on monofilament tests. The vibrotactile testing showed significantly increased VPTs for 125 Hz in dig II bilaterally (right hand, p = 0.01; left hand, p = 0.024) in the vibration exposed group.A multiple regression analysis (VPT - dependent variable; age, height, examiner and five different vibration dose calculations – predictor variables) in dig II bilaterally showed rather low R2-values. None of the explanatory variables including five separately calculated vibration doses were included in the models, neither for the total vibration exposed group, nor for the highest exposed quartile.A logistic multiple regression analysis (result of monofilament testing - dependent variable; age, height, examiner and five vibration dose calculations – predictor variables) of the results of monofilament testing in dig II bilaterally gave a similar outcome. None of the independent variables including five calculated vibration doses were included in the models neither for the total exposed group nor for the highest exposed quartile.ConclusionIn spite of the fairly short vibration exposure, a tendency to raised VPTs as well as pathologic monofilament test results was observed. Thus, early neurophysiologic symptoms and signs of vibration exposure may appear after short-term exposure also in young workers.

Research on Simultaneous Impact of Hand–Arm and Whole-Body Vibration

This article presents the results of laboratory tests on the combined effect of whole-body vibration (WBV) and hand–arm vibration (HAV). The reactions of subjects exposed to various combinations of vibration were recorded. The vibrotactile perception threshold (VPT) test identified changes caused by exposure to vibration. Ten male subjects met the criteria of the study. There were 4 series of tests: a reference test and tests after exposure to HAV, WBV, and after simultaneous exposure to HAV and WBV. An analysis of the results (6000 ascending and descending VPTs) showed that the changes in VPTs were greatest after simultaneous exposure to both kinds of vibration. The increase in VPT, for all stimulus frequencies, was then higher than after exposure to HAV or WBV only.

The Characteristics of Vibrotactile Perception Threshold among Shipyard Workers in a Tropical Environment

The objectives of this study are to determine the prevalence of hand-arm vibration syndrome (HAVS) and the characteristics of the vibrotactile perception threshold (VPT) among users of hand-held vibrating tools working in a tropical environment. A cross sectional study was done among 47 shipyard workers using instruments and a questionnaire to determine HAVS related symptoms. The vibration acceleration magnitude was determined using a Human Vibration Meter (Maestro). A P8 Pallesthesiometer (EMSON-MAT, Poland) was used to determine the VPT of index and little finger at frequencies of 31.5 Hz and 125 Hz. The mean reference threshold shift was determined from the reference threshold shift derived from the VPT value. The results show a moderate prevalence of HAVS (49%) among the shipyard workers. They were exposed to the same high intensity level of HAVS (mean = 4.19 ± 1.94 m/s(2)) from the use of vibrating hand-held tools. The VPT values were found to be higher for both fingers and both frequencies (index, 31.5 Hz = 110.91 ± 7.36 dB, 125 Hz = 117.0 ± 10.25 dB; little, 31.5 Hz = 110.70 ± 6.75 dB, 125 Hz = 117.71 ± 10.25 dB) compared to the normal healthy population with a mean threshold shift of between 9.20 to 10.61 decibels. The frequency of 31.5 Hz had a higher percentage of positive mean reference threshold shift (index finger=93.6%, little finger=100%) compared to 125 Hz (index finger=85.1%, little finger=78.7%). In conclusion, the prevalence of HAVS was lower than those working in a cold environment; however, all workers had a higher mean VPT value compared to the normal population with all those reported as having HAVS showing a positive mean reference threshold shift of VPT value.

Reductions in finger blood flow in men and women induced by 125-Hz vibration: association with vibration perception thresholds

Vibration of one hand reduces blood flow in the exposed hand and in the contralateral hand not exposed to vibration, but the mechanisms involved are not understood. This study investigated whether vibration-induced reductions in finger blood flow are associated with vibrotactile perception thresholds mediated by the Pacinian channel and considered sex differences in both vibration thresholds and vibration-induced changes in digital circulation. With force and vibration applied to the thenar eminence of the right hand, finger blood flow and finger skin temperature were measured in the middle fingers of both hands at 30-s intervals during seven successive 4-min periods: 1) pre-exposure with no force or vibration, 2) pre-exposure with force, 3) vibration 1, 4) rest with force, 5) vibration 2, 6) postexposure with force, and 7) recovery with no force or vibration. A 2-N force was applied during periods 2-6 and 125-Hz vibration at 0.5 and 1.5 ms(-2) root mean square (r.m.s.; unweighted) was applied during periods 3 and 5, respectively. Vibrotactile thresholds were measured at the thenar eminence of right hand using the same force, contact conditions, and vibration frequency. When the vibration magnitude was greater than individual vibration thresholds, changes in finger blood flow were correlated with thresholds (with both 0.5 and 1.5 ms(-2) r.m.s. vibration): subjects with lower thresholds showed greater reductions in finger blood flow. Women had lower vibrotactile thresholds and showed greater vibration-induced reductions in finger blood flow. It is concluded that mechanoreceptors responsible for mediating vibration perception are involved in the vascular response to vibration.

Vibrotactile perception thresholds at the sole of the foot: Effects of contact force and probe indentation

When using vibrotactile thresholds to investigate neuropathy in the fingers, the indentation of a vibrating probe, and the force applied to a static surround around a vibrating probe, affect thresholds. This study was designed to investigate the effects on vibrotactile perception thresholds at the sole of the foot of probe indentation (i.e. height of a vibrating probe relative to a static surround) and the force applied to the static surround. Thresholds at 20Hz (expected to be mediated by the NP I channel) and at 160Hz (expected to be mediated by the Pacinian channel) were obtained at the hallux (i.e. greater toe) and the ball of the foot on 14 healthy subjects. In one condition, the height of the vibrating probe was varied to 0, 1, 2, 3, and 4mm above a static surround with 4-N force applied to the surround. In a second condition, the force applied to the surround was varied to 1, 2, 3, 4, 5, and 6N while using a probe height of 1mm. Thresholds at 20Hz decreased with increasing probe height from 0 to 1mm but showed no significant variation between 2, 3, and 4mm at either the hallux or the ball of the foot. Thresholds at 160Hz decreased with increasing probe height from 0 to 4mm at both the hallux and the ball of the foot. Thresholds at 20Hz obtained with 1-N surround force were higher than thresholds obtained with 2N, but there was no significant difference with surround forces from 2 to 6N at either the hallux or the ball of the foot. Thresholds at 160Hz were unaffected by variations in surround force at the ball of the foot but tended to decrease with increasing force at the hallux. It is concluded that a vibrating probe flush with a static surround, and a surround force in the range 2–4N, are appropriate when measuring vibrotactile thresholds at the hallux and the ball of the foot with a 6-mm diameter contactor and a 2-mm gap to the static surround.