Tool-specific performance of vibration-reducing gloves for attenuating palm-transmitted vibrations in three orthogonal directions

Vibration-reducing (VR) gloves have been increasingly used to help reduce vibration exposure, but it remains unclear how effective these gloves are. The purpose of this study was to estimate tool-specific performances of VR gloves for reducing the vibrations transmitted to the palm of the hand in three orthogonal directions (3-D) in an attempt to assess glove effectiveness and aid in the appropriate selection of these gloves. Four typical VR gloves were considered in this study, two of which can be classified as anti-vibration (AV) gloves according to the current AV glove test standard. The average transmissibility spectrum of each glove in each direction was synthesized based on spectra measured in this study and other spectra collected from reported studies. More than seventy vibration spectra of various tools or machines were considered in the estimations, which were also measured in this study or collected from reported studies. The glove performance assessments were based on the percent reduction of frequency-weighted acceleration as is required in the current standard for assessing the risk of vibration exposures. The estimated tool-specific vibration reductions of the gloves indicate that the VR gloves could slightly reduce (<5%) or marginally amplify (<10%) the vibrations generated from low-frequency (<25 Hz) tools or those vibrating primarily along the axis of the tool handle. With other tools, the VR gloves could reduce palm-transmitted vibrations in the range of 5%–58%, primarily depending on the specific tool and its vibration spectra in the three directions. The two AV gloves were not more effective than the other gloves with some of the tools considered in this study. The implications of the results are discussed.Relevance to industryHand-transmitted vibration exposure may cause hand-arm vibration syndrome. Vibration-reducing gloves are considered as an alternative approach to reduce the vibration exposure. This study provides useful information on the effectiveness of the gloves when used with many tools for reducing the vibration transmitted to the palm in three directions. The results can aid in the appropriate selection and use of these gloves.     

The effects of vibration-reducing gloves on finger vibration

Vibration-reducing (VR) gloves have been used to reduce the hand-transmitted vibration exposures from machines and powered hand tools but their effectiveness remains unclear, especially for finger protection. The objectives of this study are to determine whether VR gloves can attenuate the vibration transmitted to the fingers and to enhance the understanding of the mechanisms of how these gloves work. Seven adult male subjects participated in the experiment. The fixed factors evaluated include hand force (four levels), glove condition (gel-filled, air bladder, no gloves), and location of the finger vibration measurement. A 3-D laser vibrometer was used to measure the vibrations on the fingers with and without wearing a glove on a 3-D hand-arm vibration test system. This study finds that the effect of VR gloves on the finger vibration depends on not only the gloves but also their influence on the distribution of the finger contact stiffness and the grip effort. As a result, the gloves increase the vibration in the fingertip area but marginally reduce the vibration in the proximal area at some frequencies below 100 Hz. On average, the gloves reduce the vibration of the entire fingers by less than 3% at frequencies below 80 Hz but increase at frequencies from 80 to 400 Hz. At higher frequencies, the gel-filled glove is more effective at reducing the finger vibration than the air bladder-filled glove. The implications of these findings are discussed.     

A methodology for integrated performance analyses of vibration reducing gloves

This study proposes a methodology for evaluating the integrated performance of vibration reducing (VR) gloves considering four measures. These include manual dexterity, distributed palm and fingers vibration transmission and grip strength preservation, which generally pose conflicting design requirements. The weights for the conflicting performance measures are identified for the given work conditions, classified according to the frequency ranges of predominant tool handle vibration (low and high), as defined in ISO-10819 together with the assembly/disassembly tasks. An index of weighted measures is formulated for identifying the most desirable VR glove for the given work condition. The results showed the greatest weighting for the fingers vibration response for high-frequency vibration spectra. Higher weightings for palm vibration and muscles' activity, were obtained for low-frequency vibration spectra, while the weighting for manual dexterity increased when coupled with manual tasks. An integrated performance index is identified and applied to rank nine different VR gloves and a conventional glove with known individual performance measures for identifying the most desirable glove. The vibration reducing gloves included: five gloves with gel vibration isolation materials, denoted as gel1, …, gel5; two gloves with air bladder vibration isolation material, denoted as air1 and air2; one hybrid glove comprising air pocket vibration isolation material in the palm region and gel in the fingers regions, denoted as hybrid; and a rubber glove. The gel2, air2 and hybrid gloves, made of air bladder or viscoelastic gels, showed superior integrated performance for high- and low-frequency vibration spectra among the ten alternatives. The fabric and rubber gloves revealed best integrated performance for the multiple tasks in conjunction with the low-frequency vibration spectrum.     

The transmission of vibration through gloves: effects of push force,vibration magnitude and inter-subject variability

The extent to which a glove modifies the risks from hand-transmitted vibration is quantified in ISO 10819:1996 by a measure of glove transmissibility determined with one vibration magnitude, one contact force with a handle and only three subjects. This study was designed to investigate systematically the vibration transmissibility of four ‘anti-vibration’ gloves over the frequency range 16–1600 Hz with 12 subjects, at six magnitudes of vibration (0.25–8.0 ms^?2 r.m.s.) and with six push forces (5 N to 80 N). The four gloves showed different transmissibility characteristics that were not greatly affected by vibration magnitude but highly dependent on push force. In all conditions, the variability in transmissibility between subjects was as great as the variability between gloves. It is concluded that a standardised test of glove dynamic performance should include a wide range of hands and a range of forces representative of those occurring in work with vibratory tools.

Statement of Relevance: The transmission of vibration through anti-vibration gloves is highly dependent on the push force between the hand and a handle and also highly dependent on the hand that is inside the glove. The influence of neither factor is well reflected in ISO 10819:1996, the current standard for anti-vibration gloves.     

The transmission of vibration through gloves: effects of push force, vibration magnitude and inter-subject variability

The extent to which a glove modifies the risks from hand-transmitted vibration is quantified in ISO 10819:1996 by a measure of glove transmissibility determined with one vibration magnitude, one contact force with a handle and only three subjects. This study was designed to investigate systematically the vibration transmissibility of four 'anti-vibration' gloves over the frequency range 16-1600 Hz with 12 subjects, at six magnitudes of vibration (0.25-8.0 ms(-2) r.m.s.) and with six push forces (5 N to 80 N). The four gloves showed different transmissibility characteristics that were not greatly affected by vibration magnitude but highly dependent on push force. In all conditions, the variability in transmissibility between subjects was as great as the variability between gloves. It is concluded that a standardised test of glove dynamic performance should include a wide range of hands and a range of forces representative of those occurring in work with vibratory tools. STATEMENT OF RELEVANCE: The transmission of vibration through anti-vibration gloves is highly dependent on the push force between the hand and a handle and also highly dependent on the hand that is inside the glove. The influence of neither factor is well reflected in ISO 10819:1996, the current standard for anti-vibration gloves.     

Transmission of vibration through glove materials: effects of contact force

This study investigated effects of applied force on the apparent mass of the hand, the dynamic stiffness of glove materials and the transmission of vibration through gloves to the hand. For 10 subjects, 3 glove materials and 3 contact forces, apparent masses and glove transmissibilities were measured at the palm and at a finger at frequencies in the range 5–300 Hz. The dynamic stiffnesses of the materials were also measured. With increasing force, the dynamic stiffnesses of the materials increased, the apparent mass at the palm increased at frequencies greater than the resonance and the apparent mass at the finger increased at low frequencies. The effects of force on transmissibilities therefore differed between materials and depended on vibration frequency, but changes in apparent mass and dynamic stiffness had predictable effects on material transmissibility. Depending on the glove material, the transmission of vibration through a glove can be increased or decreased when increasing the applied force.

Practitioner summary: Increasing the contact force (i.e. push force or grip force) can increase or decrease the transmission of vibration through a glove. The vibration transmissibilities of gloves should be assessed with a range of contact forces to understand their likely influence on the exposure of the hand and fingers to vibration.     

Transmission of vibration through gloves: effects of material thickness

It might be assumed that increasing the thickness of a glove would reduce the vibration transmitted to the hand. Three material samples from an anti-vibration glove were stacked to produce three thicknesses: 6.4, 12.8 and 19.2 mm. The dynamic stiffnesses of all three thicknesses, the apparent mass at the palm and the finger and the transmission of vibration to the palm and finger were measured. At frequencies from 20 to 350 Hz, the material reduced vibration at the palm but increased vibration at the finger. Increased thickness reduced vibration at the palm but increased vibration at the finger. The measured transmissibilities could be predicted from the material dynamic stiffness and the apparent mass of the palm and finger. Reducing the dynamic stiffness of glove material may increase or decrease the transmission of vibration, depending on the material, the frequency of vibration and the location of measurement (palm or finger).

Practitioner Summary: Transmission of vibration through gloves depends on the dynamic response of the hand and the dynamic stiffness of glove material, which depends on material thickness. Measuring the transmission of vibration through gloves to the palm of the hand gives a misleading indication of the transmission of vibration to the fingers.     

An examination of the vibration transmissibility of the hand-arm system in three orthogonal directions

The objective of this study is to enhance the understanding of the vibration transmission in the hand-arm system in three orthogonal directions (X, Y, and Z). For the first time, the transmitted vibrations distributed on the entire hand-arm system exposed in the three orthogonal directions via a 3-D vibration test system were measured using a 3-D laser vibrometer. Seven adult male subjects participated in the experiment. This study confirms that the vibration transmissibility generally decreased with the increase in distance from the hand and it varied with the vibration direction. Specifically, to the upper arm and shoulder, only moderate vibration transmission was measured in the test frequency range (16 to 500 Hz), and virtually no transmission was measured in the frequency range higher than 50 Hz. The resonance vibration on the forearm was primarily in the range of 16–30 Hz with the peak amplitude of approximately 1.5 times of the input vibration amplitude. The major resonance on the dorsal surfaces of the hand and wrist occurred at around 30–40 Hz and, in the Y direction, with peak amplitude of more than 2.5 times of the input amplitude. At higher than 50 Hz, vibration transmission was effectively limited to the hand and fingers. A major finger resonance was observed at around 100 Hz in the X and Y directions and around 200 Hz in the Z direction. In the fingers, the resonance magnitude in the Z direction was generally the lowest, and the resonance magnitude in the Y direction was generally the highest with the resonance amplitude of 3 times the input vibration, which was similar to the transmissibility at the wrist and hand dorsum. The implications of the results are discussed.Relevance to industryProlonged, intensive exposure to hand-transmitted vibration could result in hand-arm vibration syndrome. While the syndrome's precise mechanisms remain unclear, the characterization of the vibration transmissibility of the system in the three orthogonal dimensions performed in this study can help understand the syndrome and help develop improved frequency weightings for assessing the risk of the exposure for developing various components of the syndrome.     

A new methodology for measuring the vibration transmission from handle to finger whilst gripping

The transmission of vibration from hand-held tools via work gloves and into the operators' hands can be affected by several factors such as glove material properties, tool vibration conditions, grip force, and temperature. The primary aim of this study is to develop a new methodology to measure and evaluate vibration transmissibility for a human finger in contact with different materials, whilst measuring and controlling the grip force. The study presented here used a new bespoke lab-based apparatus for assessing vibration transmissibility that includes a generic handle instrumented for vibration and grip force measurements. The handle is freely suspended and can be excited at a range of real-world vibration conditions whilst being gripped by a human subject. The study conducted a frequency response function (FRF) of the handle using an instrumented hammer to ensure that the handle system was resonance free at the important frequency range for glove research, as outlined in ISO 10819: 1996: 2013, and also investigated how glove material properties and design affect the tool vibration transmission into the index finger (Almagirby et al. 2015). The FRF results obtained at each of six positions shows that the dynamic system of the handle has three resonance frequencies in the low frequency range (2, 11 and 17 Hz) and indicated that no resonances were displayed up to a frequency of about 550 Hz. No significant vibration attenuation was shown at frequencies lower than 150 Hz. The two materials cut from the gloves that were labelled as anti-vibration gloves (AV) indicated resonance at frequencies of 150 and 160 Hz. However, the non-glove material that did not meet the requirements for AV gloves showed resonance at 250 Hz. The attenuation for the three materials was found at frequencies of 315 Hz and 400 Hz. The level and position of the true resonance frequencies were found to vary between samples and individual subjects.     

Effect of coating over the handle of a drill machine on vibration transmissibility

This study was to see the effect of different coatings on the handle of hand-held drilling machines. Out of five different handles chosen for this study, including one handle uncoated. Root mean square (rms) values of the vibration levels (acceleration) were recorded at the surface of handle and wrist of the operators. Results showed that maximum vibrations were reduced by coating of handle coated with rubber sheet and Rexene (H4) followed by handle coated with cotton sandwiched between jeans cloth (H5). Equivalent vibrations transmitted through coating of handles coated with sponge and velvet (H2) and jute and cotton (H3) were of almost same magnitude and these two coated handles were able to reduce least vibration transmitted. Transmissibility of vibrations along dominant (Z) direction was analyzed using ANOVA. Results showed that coating on handles significantly affected vibration transmitted in Z direction. Vibration transmissibility ratios were found to be 0.354, 0.571, 0.408, 0.4326, and 0.3555 for handles H1, H2, H3, H4 and H5 respectively.     

The vibration transmissibility and driving-point biodynamic response of the hand exposed to vibration normal to the palm

Prolonged, intensive exposure to vibrations from palm and orbital sanders could cause finger disorders. They are likely to be associated with the biodynamic responses of the fingers. Although the biodynamic responses of the hand-arm system have been studied by many researchers, the detailed biodynamic responses distributed in the hand substructures have not been sufficiently understood. To advance the knowledge in this aspect and to aid in the development of improved finite element models of the substructures, this study simultaneously measured the overall driving-point biodynamic response and the distribution of vibration transmissibility at the fingers and back of the hand exposed to a flat plate vibration (as an approximate simulation of the operations of the palm and orbital sanders) and examined the relationship between these two measures of biodynamic responses. Ten subjects (five males and five females) participated in the experiment. A scanning laser vibrometer was used to measure the distributed vibration. This study confirmed that the distributed hand responses generally varied with locations on each finger, vibration frequencies, and applied hand force. Two major resonances were observed in the vibration transmissibility. At the first resonance, the transmitted vibrations at different locations were more or less in phase; hence, this resonance was also observed in the driving-point biodynamic response that measures the overall biodynamic response of the system. The second resonance was observed at the fingers. Because this resonant frequency varied greatly among the fingers and the specific segments of each finger, it is difficult to identify this resonance in the driving-point biodynamic response. The implications of the findings for further model developments and applications are discussed.

Relevance to industry

This study enhanced the understanding of the biodynamic responses of the fingers and hand exposed to vibrations on a contact surface with a large effective radius such as that found on palm and orbital sanders. The results can also be used to develop and/or validate models of the substructures of the hand-arm system, which can be further used to help design and analyze these tools and associated anti-vibration devices. The results may also be applicable to help develop location-specific frequency weightings to assess the risks of the finger vibration exposure.     

Effect of protective gloves on hand movement: an exploratory study

This exploratory study was conducted to determine whether wearing protective gloves limits the range of motion that the hand can complete. The kinematic motion of the hand/wrist/forearm of two participants was analysed during the performance of two tasks typical of pesticide applicators. High-speed cinematography was used to collect data which were then digitized and combined to produce three-dimensional data. Graphs of the transformed data showed that in comparison with the barehanded state, the protective glove decreased the abduction/adduction and supination/pronation ranges that the hand could complete. Extension/flexion did not appear to be affected. Overall, kinematic motion of the hand appeared to decrease while wearing protective gloves.     

Short and longer duration effects of protective gloves on hand performance capabilities and subjective assessments in a screw-driving task

The study investigated short and longer duration effects of gloves on hand performance capabilities (muscle activity, dexterity, touch sensitivity, finger pinch and forearm torque strength) and subjective assessments of discomfort and ease of manipulation when performing a light assembly task. The independent variables were hand condition with four levels (wearing cotton, nylon or nitrile gloves as well as barehanded) and point of time within the 2 h duration of the task (with measurements taken at 0, 30, 60, 90 and 120 min). Participants worked with a screwdriver to fit two components together using screws. Wearing gloves significantly increased the muscle activity, pinch strength and discomfort but reduced the dexterity and touch sensitivity. There was also a significant effect of task time on the muscle activity, dexterity, forearm torque strength and touch sensitivity, which indicates that the duration of the task should be an important consideration in glove evaluation studies and in the selection of work gloves.

Statement of Relevance:It is important to evaluate the effects of gloves on hand performance capabilities in a working context so that job demands can be taken into account and the most appropriate type of glove be chosen for each task. This study gives recommendations regarding the evaluation and use of gloves for screw-driving tasks.     

Short and longer duration effects of protective gloves on hand performance capabilities and subjective assessments in a screw-driving task

The study investigated short and longer duration effects of gloves on hand performance capabilities (muscle activity, dexterity, touch sensitivity, finger pinch and forearm torque strength) and subjective assessments of discomfort and ease of manipulation when performing a light assembly task. The independent variables were hand condition with four levels (wearing cotton, nylon or nitrile gloves as well as barehanded) and point of time within the 2 h duration of the task (with measurements taken at 0, 30, 60, 90 and 120 min). Participants worked with a screwdriver to fit two components together using screws. Wearing gloves significantly increased the muscle activity, pinch strength and discomfort but reduced the dexterity and touch sensitivity. There was also a significant effect of task time on the muscle activity, dexterity, forearm torque strength and touch sensitivity, which indicates that the duration of the task should be an important consideration in glove evaluation studies and in the selection of work gloves. STATEMENT OF RELEVANCE: It is important to evaluate the effects of gloves on hand performance capabilities in a working context so that job demands can be taken into account and the most appropriate type of glove be chosen for each task. This study gives recommendations regarding the evaluation and use of gloves for screw-driving tasks.     

The relationships between hand coupling force and vibration biodynamic responses of the hand-arm system

This study conducted two series of experiments to investigate the relationships between hand coupling force and biodynamic responses of the hand–arm system. In the first experiment, the vibration transmissibility on the system was measured as a continuous function of grip force while the hand was subjected to discrete sinusoidal excitations. In the second experiment, the biodynamic responses of the system subjected to a broadband random vibration were measured under five levels of grip forces and a combination of grip and push forces. This study found that the transmissibility at each given frequency increased with the increase in the grip force before reaching a maximum level. The transmissibility then tended to plateau or decrease when the grip force was further increased. This threshold force increased with an increase in the vibration frequency. These relationships remained the same for both types of vibrations. The implications of the experimental results are discussed.

Practitioner Summary: Shocks and vibrations transmitted to the hand–arm system may cause injuries and disorders of the system. How to take hand coupling force into account in the risk assessment of vibration exposure remains an important issue for further studies. This study is designed and conducted to help resolve this issue.     

Methodology for evaluating gloves in relation to the effects on hand performance capabilities: a literature review

The present study was conducted to review the literature on the methods that have been considered appropriate for evaluation of the effects of gloves on different aspects of hand performance, to make recommendations for the testing and assessment of gloves, and to identify where further research is needed to improve the evaluation protocols. Eighty-five papers meeting the criteria for inclusion were reviewed. Many studies show that gloves may have negative effects on manual dexterity, tactile sensitivity, handgrip strength, muscle activity and fatigue and comfort, while further research is needed to determine glove effects on pinch strength, forearm torque strength and range of finger and wrist movements. The review also highlights several methodological issues (including consideration of both task type and duration of glove use by workers, guidance on the selection and allocation of suitable glove(s) for particular tasks/jobs, and glove design features) that need to be considered in future research.

Practitioner Summary: The relevant literature on the effects of protective gloves on different aspects of hand performance was reviewed to make recommendations for the testing and assessment of gloves, and to improve evaluation protocols. The review highlights research areas and methodological issues that need to be considered in future research.     

Safety performance of gloves using the pressure tolerance of the hand

Two prototype gloves have been designed and developed at the University of Nebraska-Lincoln. The aim of this study was to evaluate the safety performance of the developed gloves. An experiment was conducted to assess the discomfort threshold level at 12 zones on the palmar surface of the hand for five hand conditions--bare hand, single glove, double glove and two prototype gloves. Prototype I consisted of a glove with an extra layer of glove material applied selectively to critical areas of the hand; while prototype II had up to four layers applied to critical areas. This design increases protection in critical areas without increasing bulk, provides performances comparable with single glove, and improves grip strength. The study was conducted using an algometer device to apply pressure to each of the 12 zones, for all hand conditions. The results indicated that for pressure tolerance, prototype II had the highest pressure-discomfort threshold, while prototype I had a threshold similar to the double layer glove. Pressure discomfort tolerance threshold is greatly increased by the use of gloves, and pressure-discomfort thresholds are raised by 25-65%. The two prototype gloves, although much less bulkier than the double glove, have pressure thresholds that are equal to or superior to that of a double glove. The algometer can be used to assess the safety of glove from mechanical trauma. Hence, the generalizability of the results is somewhat restricted. However, the method of selective protection, without compromising performance appears to be promising and is worth pursuing by glove designers.     

Safety performance of gloves using the pressure tolerance of the hand

Two prototype gloves have been designed and developed at the University of Nebraska-Lincoln. The aim of this study was to evaluate the safety performance of the developed gloves. An experiment was conducted to assess the discomfort threshold level at 12 zones on the palmar surface of the hand for five hand conditions — bare hand, single glove, double glove and two prototype gloves. Prototype I consisted of a glove with an extra layer of glove material applied selectively to critical areas of the hand; while prototype II had up to four layers applied to critical areas. This design increases protection in critical areas without increasing bulk, provides performances comparable with single glove, and improves grip strength. The study was conducted using an algometer device to apply pressure to each of the 12 zones, for all hand conditions. The results indicated that for pressure tolerance, prototype II had the highest pressure-discomfort threshold, while prototype I had a threshold similar to the double layer glove. Pressure discomfort tolerance threshold is greatly increased by the use of gloves, and pressure— discomfort thresholds are raised by 25–65%. The two prototype gloves, although much less bulkier than the double glove, have pressure thresholds that are equal to or superior to that of a double glove. The algometer can be used to assess the safety of glove from mechanical trauma. Hence, the generalizability of the results is somewhat restricted. However, the method of selective protection, without compromising performance appears to be promising and is worth pursuing by glove designers.     

Distributed vibration power absorption of the human hand-arm system in different postures coupled with vibrating handle and power tools

This study presents vibration power absorption (VPA) of different hand-arm substructures in the bent-arm and extended arm postures excited by broadband random and power tool vibrations. VPAs are estimated using biomechanical models of the hand-arm system derived from both the driving-point mechanical impedance and distributed vibration transmissibility. VPAs due to the vibrations of selected hand-held power tools are also estimated. The results show that distributed VPAs of the arms are greater below 25 Hz than those of the hand (fingers and palm) for both postures, while the hand VPAs are greater above 100 Hz, although the values are smaller than those below 25 Hz. The power absorbed during the extended arm posture is about 2.5 times greater than the power absorbed with the bent-arm posture for similar hand forces and vibration magnitude. Similar trends are observed in distributed VPAs due to broadband random as well as typical tool excitations, while the VPA due to tool vibration revealed peaks near the operating frequencies of the power tools and their harmonics. Furthermore, the percentage of power absorbed in different hand-arm substructures was dependent on the operating speed of the power tools, the higher the operating speed the higher the power absorbed in the hand and vice versa. The results showed relatively lower VPA values in the fingers and palm in the 60–160 Hz range than those obtained for the arms in the 5–16 Hz range. The study revealed the need for different frequency weightings for assessment of potential injury risk of different hand-arm substructures.Relevance to industryOperators of hand-held power tools are exposed to hand-transmitted vibration and the associated potential injuries. This study showed that the extended arm posture should be avoided when operating hand-held power tools because large vibration power is absorbed in the human hand-arm system, which may cause hand-arm injury.     

Preliminary results of hand arm vibration (HAV) exposures of chipping hammer operators in tropical weather: Analysis of exposures and protective gloves

Objectives of this study are to analyze the HAV exposures of chipping hammer operators from field measurements and to investigate the potential of various types of gloves in reducing the exposures. HAV exposures of twelve male operators were measured at four different operating conditions: bare hand, wearing normal workman gloves, wearing heavy workman gloves and wearing vibration reducing gloves. From the measurements, 8 h exposure values were determined and assessed against standards. The total vibration values were determined and effectiveness in vibration attenuation by gloves was compared. It was found that all most all operators, HAV exposure levels exceeded the exposure action value (EAV) and about 83% of the operators exceeded the exposure limit values (ELV). A reduction in the total vibration magnitude was observed with protective gloves: 8.3% with normal workman gloves, 14.6% with heavy workman gloves and 40% with vibration-reducing gloves. To confirm the effectiveness of the vibration reducing gloves, further field investigations are required with simultaneous measurements by considering parameters affecting HAV (i.e., hand forces and postures).