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The effectiveness of vibration-reducing (VR) gloves is conventionally assessed based on the vibration transmissibility of the gloves. This study proposed a method for analyzing and assessing the effectiveness of VR gloves based on how gloves affect the vibration power absorption (VPA) of the hand&ndash, arm system and its distribution. A model of the entire tool&ndash, handle&ndash, glove&ndash, hand&ndash, arm system was used to predict the VPA distributed in the glove and across the substructures of the hand&ndash, arm system. The ratio of the gloved-VPA and ungloved-VPA in each group of system substructures was calculated and used to quantify VR glove effectiveness, which was termed the VPA-based glove vibration transmissibility in this study. The VPA-based transmissibility values were compared with those determined using to-the-hand and on-the-hand methods. Three types of gloves (ordinary work glove, gel VR glove, and air bubble VR glove) were considered in the modeling analyses. This study made the following findings: the total VPA-based transmissibility spectrum exhibits some similarities with those determined using the other two methods, the VPA-based transmissibility for the wrist&ndash, forearm&ndash, elbow substructures is identical to that for the upper&ndash, arm&ndash, shoulder substructures in the model used in this study, each of them is equal to the square of the glove vibration transmissibility determined using the on-the-wrist method or on-the-upper-arm method, the other substructure-specific VPA-based transmissibility spectra exhibit some unique features, the effectiveness of a glove for reducing the overall VPA in the hand&ndash, arm system depends on the glove effectiveness for absorbing the vibration energy, which seems to be associated primarily with the glove cushioning materials, the glove may also help protect the fingers or hand by redistributing the VPA across the hand substructures, this redistribution seems to be primarily associated with the glove structural properties, especially the tightness of fit for the glove.

The objective of this study is to characterize the vibration responses of a handheld workpiece and the hand–arm system, which is an important step toward identifying and developing effective methods and technologies for controlling the vibration exposures to workers performing the grinding of handheld workpieces. This study established a method for measuring the vibration responses of the entire workpiece–hand–arm system; the vibration exposure of a worker holding and pressing a typical workpiece against a sanding belt or grinding wheel in order to shape the workpiece was simulated. This method was applied to measure the apparent mass and vibration transmissibility of the system under two different feed forces (15 N and 30 N) and six simulated grinding interfaces with different stiffness values. A major resonance was observed in each transmissibility spectrum of the workpiece, which was correlated with the major resonance of the impedance of the entire system. This resonant frequency depended primarily on the workpiece mass and the grinding interface stiffness, but the hand–arm system could substantially affect the resonance magnitude. The feed force also significantly affected the resonance frequency and magnitude. While increasing the feed force increased the overall vibration transmissibility on the hand–arm system, the transmissibility with respect to the workpiece was not significantly affected by the interface conditions. The implications of the results are discussed.

The objective of this study was to develop a convenient and reliable adapter method for testing and evaluating vibration-reducing (VR) gloves and VR materials at the fingers. The general requirements and technical specifications for the design of the new adapter were based on our previous studies of hand-held adapters for vibration measurement and a conceptual model of the fingers-adapter-glove-handle system developed in this study. Two thicknesses (2 mm and 3 mm) of the adapter beam were fabricated using a 3-D printer. Each adapter is a thin beam equipped with a miniature tri-axial accelerometer (1.1 g) mounted at its center, with a total weight ≤ 2.2 g. To measure glove vibration transmissibility, the adapter is held with two gloved fingers; a finger is positioned on each side of the accelerometer. Each end of the adapter beam is slotted between the glove material and the finger. A series of experiments was conducted to evaluate this two-fingers-held adapter method by measuring the transmissibility of typical VR gloves and a sample VR material. The experimental results indicate that the major resonant frequency of the lightweight adapter on the VR material (≥800 Hz) is much higher than the resonant frequencies of the gloved fingers grasping a cylindrical handle (≤300 Hz). The experimental results were repeatable across the test treatments. The basic characteristics of the measured glove vibration transmissibility are consistent with the theoretical predictions based on the biodynamics of the gloved fingers-hand-arm system. The results suggest that VR glove fingers can effectively reduce only high-frequency vibration, and VR effectiveness can be increased by reducing the finger contact force. This study also demonstrated that the finger adapter method can be combined with the palm adapter method prescribed in the standardized glove test, which can double the test efficiency without substantially increasing the expense of the test.

Prolonged and intensive vibration exposures during the grinding of handheld workpieces may cause hand-arm vibration syndrome. The objectives of this study are to develop an on-the-hand method for evaluating vibration-reducing (VR) gloves, and to determine whether VR gloves can significantly reduce the vibration exposures. A worker holding and pressing a typical workpiece (golf club head) against a grinding wheel or belt in order to shape the workpiece was simulated, and the input vibration and those on the workpiece and hand-arm system were measured. Ten human subjects participated in the experiment. The results demonstrate that VR gloves significantly reduced the vibrations at the palm, hand dorsum, and wrist. The grinding interface condition and hand feed force did not substantially affect glove effectiveness. The use of gloves slightly increased the workpiece resonant response, but the resonant response did not significantly affect glove effectiveness. This study concluded that the use of VR gloves can help control vibration exposures of workers performing grinding of handheld workpieces.

The objective of this study was to develop a vibration model of a grinding machine-workpiece-hand-arm system. A lumped-parameter model structure of the system was proposed, and its major parameters were determined using the mechanical impedance measured at the grinding point of a typical workpiece (golf club head) held by two hands and referenced to the vibration transmissibility spectra measured at the wrist and on the upper arm of human subjects. The model reasonably predicted the vibration transmissibility spectra measured on the club head and the driving-point response function when the grinding contact stiffness was below a certain value. This suggests that the model is acceptable not only to enhance the understanding of the system responses, but also to explore some engineering methods for controlling vibration exposures during the grinding process. The identified model parameters reveal that the major resonance of the handheld workpiece depends primarily on its mass and grinding contact stiffness. The feed force applied in the grinding process can substantially affect the grinding contact stiffness; as a result, it can significantly influence the resonance. Vibration-reducing gloves can marginally increase the workpiece resonance, but these gloves can reduce some vibration transmitted to the hand-arm system. This study also clarified an important mechanism for the prediction errors of linear human vibration models, which is useful to further improve human vibration modeling.

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.

Some powered hand tools can generate significant vibration at frequencies below 25 Hz. It is not clear whether such vibration can be effectively transmitted to the upper arm, shoulder, neck, and head and cause adverse effects in these substructures. The objective of this study is to investigate the vibration transmission from the human hands to these substructures. Eight human subjects participated in the experiment, which was conducted on a 1-D vibration test system. Unlike many vibration transmission studies, both the right and left hand-arm systems were simultaneously exposed to the vibration to simulate a working posture in the experiment. A laser vibrometer and three accelerometers were used to measure the vibration transmitted to the substructures. The apparent mass at the palm of each hand was also measured to help in understanding the transmitted vibration and biodynamic response. This study found that the upper arm resonance frequency was 7–12 Hz, the shoulder resonance was 7–9 Hz, and the back and neck resonances were 6–7 Hz. The responses were affected by the hand-arm posture, applied hand force, and vibration magnitude. The transmissibility measured on the upper arm had a trend similar to that of the apparent mass measured at the palm in their major resonant frequency ranges. The implications of the results are discussed. Relevance to industry Musculoskeletal disorders (MSDs) of the shoulder and neck are important issues among many workers. Many of these workers use heavy-duty powered hand tools. The combined mechanical loads and vibration exposures are among the major factors contributing to the development of MSDs. The vibration characteristics of the body segments examined in this study can be used to help understand MSDs and to help develop more effective intervention methods.

BACKGROUND: Fingers-transmitted vibration can cause vibration-induced white finger. The effectiveness of vibrationreducing (VR) gloves for reducing hand transmitted vibration to the fingers has not been sufficiently examined. OBJECTIVE:The objective of this study is to examine tool-specific performance of VR gloves for reducing finger-transmitted vibrations in three orthogonal directions (3D) from powered hand tools. METHODS: A transfer function method was used to estimate the tool-specific effectiveness of four typical VR gloves. The transfer functions of the VR glove fingers in three directions were either measured in this study or during a previous study using a 3D laser vibrometer. More than seventy vibration spectra of various tools or machines were used in the estimations. RESULTS: When assessed based on frequency-weighted acceleration, the gloves provided little vibration reduction. In some cases, the gloves amplified the vibration by more than 10%, especially the neoprene glove. However, the neoprene glove did the best when the assessment was based on unweighted acceleration. The neoprene glove was able to reduce the vibration by 10% or more of the unweighted vibration for 27 out of the 79 tools. If the dominant vibration of a tool handle or workpiece was in the shear direction relative to the fingers, as observed in the operation of needle scalers, hammer chisels, and bucking bars, the gloves did not reduce the vibration but increased it. CONCLUSIONS: This study confirmed that the effectiveness for reducing vibration varied with the gloves and the vibration reduction of each glove depended on tool, vibration direction to the fingers, and finger location. VR gloves, including certified anti-vibration gloves do not provide much vibration reduction when judged based on frequency-weighted acceleration. However, some of the VR gloves can provide more than 10% reduction of the unweighted vibration for some tools or workpieces. Tools and gloves can be matched for better effectiveness for protecting the fingers.

The objective of this study is to identify effective engineering methods for controlling handheld workpiece vibration during grinding processes. Prolonged and intensive exposures to such vibration can cause hand-arm vibration syndrome among workers performing workpiece grinding, but how to effectively control these exposures remains an important issue. This study developed a methodology for performing their analyses and evaluations based on a model of the entire grinding machine-workpiece-hand-arm system. The model can simulate the vibration responses of a workpiece held in the worker's hands and pressed against a grinding wheel in order to shape the workpiece in the major frequency range of concern (6.3–1600 Hz). The methodology was evaluated using available experimental data. The results suggest that the methodology is acceptable for these analyses and evaluations. The results also suggest that the workpiece vibration resulting from the machine vibration generally depends on two mechanisms or pathways: (1) the direct vibration transmission from the grinding machine; and (2) the indirect transmission that depends on both the machine vibration transmission to the workpiece and the interface excitation transformation to the workpiece vibration. The methodology was applied to explore and/or analyze various engineering methods for controlling workpiece vibrations. The modeling results suggest that while these intervention methods have different advantages and limitations, some of their combinations can effectively reduce the vibration exposures of grinding workers. These findings can be used as guidance for selecting and developing more effective technologies to control handheld workpiece vibration exposures.

Percussive riveting is the primary process for attaching the outer sheet metal “skins” of an aircraft to its airframe. Workers using manually-operated riveting tools (riveting hammers and rivet bucking bars) are exposed to significant levels of hand-transmitted vibration (HTV) and are at risk of developing components of hand-arm vibration syndrome (HAVS). To protect workers, employers can assess and select riveting tools that produce reduced HTV exposures. Researchers at the National Institute for Occupational Safety & Health (NIOSH) have developed a laboratory-based apparatus and methodology to evaluate the vibrations of rivet bucking bars. Using this simulated riveting approach, this study investigated the effects of feed force on the vibrations of several typical rivet bucking bars and that transmitted to the bucking bar operator's wrist. Five bucking bar models were assessed under three levels of feed force. The study results demonstrate that the feed force can be a major influencing factor on bucking bar vibrations. Similar feed force effects were observed at the bucking bar operator's wrist. This study also shows that different bucking bar designs will respond differently to variations in feed force. Some bucking bar designs may offer reduced vibration exposures to the bar operator's fingers while providing little attenuation of wrist acceleration. Knowledge of how rivet bucking bar models respond to riveting hammer vibrations can be important for making informed bucking bar selections. The study results indicate that, to help in the appropriate selection of bucking bars, candidate bar models should be evaluated at multiple feed force levels. The results also indicate that the bucking bar model, feed force level, or the bucking bar operator have no meaningful effects on the vibration excitation (riveting hammer), which further suggests that the test apparatus proposed by NIOSH researchers meets the basic requirements for a stable vibration source in laboratory-based bucking bar vibration assessments. This study provides relevant information that can be used to help develop a standardized laboratory-based bucking bar evaluation methodology and to help in the selection of appropriate bucking bars for various workplace riveting applications. Relevance to Industry Because the feed force level can affect HTV exposures to bucking bar operators, the feed force required for specific riveting operations should be an important consideration when selecting bucking bar models. This study provides useful information about bucking bar responses to riveting hammer vibrations; this knowledge can improve bucking bar selections.

The hand coordinate systems for measuring vibration exposures and biodynamic responses have been standardized, but they are not actually used in many studies. This contradicts the purpose of the standardization. The objectives of this study were to identify the major sources of this problem, and to help define or identify better coordinate systems for the standardization. This study systematically reviewed the principles and definition methods, and evaluated typical hand coordinate systems. This study confirms that, as accelerometers remain the major technology for vibration measurement, it is reasonable to standardize two types of coordinate systems: a tool-based basicentric (BC) system and an anatomically based biodynamic (BD) system. However, these coordinate systems are not well defined in the current standard. Definition of the standard BC system is confusing, and it can be interpreted differently; as a result, it has been inconsistently applied in various standards and studies. The standard hand BD system is defined using the orientation of the third metacarpal bone. It is neither convenient nor defined based on important biological or biodynamic features. This explains why it is rarely used in practice. To resolve these inconsistencies and deficiencies, we proposed a revised method for defining the realistic handle BC system and an alternative method for defining the hand BD system. A fingertip-based BD system for measuring the principal grip force is also proposed based on an important feature of the grip force confirmed in this study.

The objective of this study is to evaluate an adapter method for measuring the vibration on the human arms. Four instrumented adapters with different weights were used to measure the vibration transmitted to the wrist, forearm, and upper arm of each subject. Each adapter was attached at each location on the subjects using an elastic cloth wrap. Two laser vibrometers were also used to measure the transmitted vibration at each location to evaluate the validity of the adapter method. The apparent mass at the palm of the hand along the forearm direction was also measured to enhance the evaluation. This study found that the adapter and laser-measured transmissibility spectra were comparable with some systematic differences. While increasing the adapter mass reduced the resonant frequency at the measurement location, increasing the tightness of the adapter attachment increased the resonant frequency. However, the use of lightweight (≤15 g) adapters under medium attachment tightness did not change the basic trends of the transmissibility spectrum. The resonant features observed in the transmissibility spectra were also correlated with those observed in the apparent mass spectra. Because the local coordinate systems of the adapters may be significantly misaligned relative to the global coordinates of the vibration test systems, large errors were observed for the adapter-measured transmissibility in some individual orthogonal directions. This study, however, also demonstrated that the misalignment issue can be resolved by either using the total vibration transmissibility or by measuring the misalignment angles to correct the errors. Therefore, the adapter method is acceptable for understanding the basic characteristics of the vibration transmission in the human arms, and the adapter-measured data are acceptable for approximately modeling the system.

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.Hand-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.

Contact interactions between the hand and handle, such as the contact surface softness and contact surface curvature, will affect both physical effort and musculoskeletal fatigue, thereby the comfort and safety of power tool operations. Previous models of hand gripping can be categorized into two groups: multi-body dynamic models and finite element (FE) models. The goal of the current study is to develop a hybrid FE hand gripping model, which combines the features of conventional FE models and multi-body dynamic models. The proposed model is applied to simulate hand-gripping on a cylindrical handle with covering materials of different softness levels. The model included three finger segments (distal, middle, and proximal phalanxes), three finger joints (the distal interphalangeal (DIP), proximal interphalangeal (PIP), and metacarpophalangeal (MCP) joint), and major anatomical substructures. The model was driven by joint moments, which are the net effects of all passive and active muscular forces acting about the joints. The finger model was first calibrated by using experimental data of human subject tests, and then applied to investigate the effects of surface softness on contact interactions between a finger and a cylindrical handle. Our results show that the maximal compressive stress and strain in the soft tissues of the fingers can be effectively reduced by reducing the stiffness of the covering material.

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. Relevance to industry Prolonged, intensive exposure to hand-transmitted vibration can cause hand-arm vibration syndrome. Vibration-reducing gloves have been used as an alternative approach to reduce the vibration exposure. However, their effectiveness for reducing finger-transmitted vibrations remains unclear. This study enhanced the understanding of the glove effects on finger vibration and provided useful information on the effectiveness of typical VR gloves at reducing the vibration transmitted to the fingers. The new results and knowledge can be used to help select appropriate gloves for the operations of powered hand tools, to help perform risk assessment of the vibration exposure, and to help design better VR gloves.

The use of a handheld adapter equipped with a tri-axial accelerometer is the most convenient and efficient approach for measuring vibration exposure at the hand-tool interface, especially when the adapter is incorporated into a miniature handheld or wrist-strapped dosimeter. To help optimize the adapter approach, the specific aims of this study are to identify and understand the major sources and mechanisms of measurement errors and uncertainties associated with using these adapters, and to explore their improvements. Five representative adapter models were selected and used in the experiment. Five human subjects served as operators in the experiment on a hand-arm vibration test system. The results of this study confirm that many of the handheld adapters can produce substantial overestimations of vibration exposure, and measurement errors can significantly vary with tool, adapter model, mounting position, mounting orientation, and subject. Major problems with this approach include unavoidable influence of the hand dynamic motion on the adapter, unstable attachment, insufficient attachment contact force, and inappropriate adapter structure. However, the results of this study also suggest that measurement errors can be substantially reduced if the design and use of an adapter can be systematically optimized toward minimizing the combined effects of the identified factors. Some potential methods for improving the design and use of the adapters are also proposed and discussed.

Vibration-reducing (VR) gloves are commonly used as a means to help control exposures to hand-transmitted vibrations generated by powered hand tools. The objective of this study was to characterise the vibration transmissibility spectra and frequency-weighted vibration transmissibility of VR gloves at the palm of the hand in three orthogonal directions. Seven adult males participated in the evaluation of seven glove models using a three-dimensional hand-arm vibration test system. Three levels of hand coupling force were applied in the experiment. This study found that, in general, VR gloves are most effective at reducing vibrations transmitted to the palm along the forearm direction. Gloves that are found to be superior at reducing vibrations in the forearm direction may not be more effective in the other directions when compared with other VR gloves. This casts doubts on the validity of the standardised glove screening test. Practitioner Summary: This study used human subjects to measure three-dimensional vibration transmissibility of vibration-reducing gloves at the palm and identified their vibration attenuation characteristics. This study found the gloves to be most effective at reducing vibrations along the forearm direction. These gloves did not effectively attenuate vibration along the handle axial direction.

The objectives of this study were to develop models of the hand-arm system in the three orthogonal directions (xh, yh , and zh ) and to enhance the understanding of the hand vibration dynamics. A four-degrees-of-freedom (DOF) model and 5-DOF model were used in the simulation for each direction. The driving-point mechanical impedances distributed at the fingers and palm of the hand reported in a previous study were used to determine the parameters of the models. The 5-DOF models were generally superior to the 4-DOF models for the simulation. Hence, as examples of applications, the 5-DOF models were used to predict the transmissibility of a vibration-reducing glove and the vibration transmissibility on the major substructures of the hand-arm system. The model-predicted results were also compared with the experimental data reported in two other recent studies. Some reasonable agreements were observed in the comparisons, which provided some validation of the developed models. This study concluded that the 5-DOF models are acceptable for helping to design and analyze vibrating tools and anti-vibration devices. This study also confirmed that the 5-DOF model in the zh direction is acceptable for a coarse estimation of the biodynamic responses distributed throughout the major substructures of the hand-arm system. Some interesting phenomena observed in the experimental study of the biodynamic responses in the three directions were also explained in this study.

It is known that the vibration characteristics of the fingers and hand and the level of grip action interacts when operating a power tool. In the current study, we developed a hybrid finger model to simulate the vibrations of the hand–finger system when gripping a vibrating handle covered with soft materials. The hybrid finger model combines the characteristics of conventional finite element (FE) models, multi-body musculoskeletal models, and lumped mass models. The distal, middle, and proximal finger segments were constructed using FE models, the finger segments were connected via three flexible joint linkages (i.e., distal interphalangeal joint (DIP), proximal interphalangeal joint (PIP), and metacarpophalangeal (MCP) joint), and the MCP joint was connected to the ground and handle via lumped parameter elements. The effects of the active muscle forces were accounted for via the joint moments. The bone, nail, and hard connective tissues were assumed to be linearly elastic whereas the soft tissues, which include the skin and subcutaneous tissues, were considered as hyperelastic and viscoelastic. The general trends of the model predictions agree well with the previous experimental measurements in that the resonant frequency increased from proximal to the middle and to the distal finger segments for the same grip force, that the resonant frequency tends to increase with increasing grip force for the same finger segment, especially for the distal segment, and that the magnitude of vibration transmissibility tends to increase with increasing grip force, especially for the proximal segment. The advantage of the proposed model over the traditional vibration models is that it can predict the local vibration behavior of the finger to a tissue level, while taking into account the effects of the active musculoskeletal force, the effects of the contact conditions on vibrations, the global vibration characteristics.

While simulations of the measured biodynamic responses of the whole human body or body segments to vibration are conventionally interpreted as summaries of biodynamic measurements, and the resulting models are considered quantitative, this study looked at these simulations from a different angle: model calibration. The specific aims of this study are to review and clarify the theoretical basis for model calibration, to help formulate the criteria for calibration validation, and to help appropriately select and apply calibration methods. In addition to established vibration theory, a novel theorem of mechanical vibration is also used to enhance the understanding of the mathematical and physical principles of the calibration. Based on this enhanced understanding, a set of criteria was proposed and used to systematically examine the calibration methods. Besides theoretical analyses, a numerical testing method is also used in the examination. This study identified the basic requirements for each calibration method to obtain a unique calibration solution. This study also confirmed that the solution becomes more robust if more than sufficient calibration references are provided. Practically, however, as more references are used, more inconsistencies can arise among the measured data for representing the biodynamic properties. To help account for the relative reliabilities of the references, a baseline weighting scheme is proposed. The analyses suggest that the best choice of calibration method depends on the modeling purpose, the model structure, and the availability and reliability of representative reference data.

The Jamar handle dynamometer is the most commonly used instrument for measuring grip strength. However, the grip strength applied on a cylindrical handle may not exhibit the same handle size relationship as that observed with the Jamar handle. Direct comparison studies are required to clearly identify the major differences between the two dynamometer styles. This study utilized a recent grip dynamometer design along with the Jamar dynamometer to further examine these relationships. The objective of this study was to compare how changes in grip size affects grip strength measured with each dynamometer style. Results confirm that handle size significantly affects the applied grip strength measured with both types of grip dynamometer. The handle size effect is more pronounced with the Jamar handle, especially at the small handle diameter/span. The highest grip force components observed with the cylindrical handles were found at the fingertips. The Jamar grip dynamometer may not adequately reflect the fingertip forces at the low and middle spans because the fingertips are not applied in the force measurement plane of the Jamar handle. Therefore, the Jamar dynamometer may not adequately capture changes in the fingertip forces under different grip spans. Relevance to Industry: It is important to properly characterize grip strength used in occupational settings in order to optimize tool and machine handle designs. The Jamar dynamometer may not be appropriate for assessing cylindrical or near-cylindrical handles that are found on the majority of tools and machines. The grip strength measured with the cylindrical dynamometer used in this study can be used to help optimize handle designs.

The objective of this study is to investigate the basic characteristics of the three axis mechanical impedances distributed at the fingers and palm of the hand subjected to vibrations along three orthogonal directions (xh, yh, and zh). Seven subjects participated in the experiment on a novel three-dimensional (3-D) hand–arm vibration test system equipped with a 3-D instrumented handle. The total impedance of the entire hand–arm system was obtained by performing a sum of the distributed impedances. Two major resonances were observed in the impedance data in each direction. For the hand forces (30 N grip and 50 N push) and body postures applied in this study, the first resonance was in the range of 20–40 Hz, and it was primarily observed in the impedance at the palm. The second resonance was generally observed in the impedance at the fingers, while the resonance frequency varied greatly with the subject and vibration direction, ranging from 100 to 200 Hz in the xh direction, 60 to 120 Hz in the yh direction, and 160 to 300 Hz in the zh direction. The impedance at the palm was greater than that at the fingers below a certain frequency in the range of 50–100 Hz, depending on the vibration direction. At higher frequencies, however, the impedance magnitude at the fingers either approached or exceeded that at the palm. The impedance in the zh direction was generally higher than those in the other directions, but it became comparable with that in the xh direction at frequencies above 250 Hz, while the impedance in the yh direction was the lowest. The frequency dependencies of the vibration power absorptions for the entire hand–arm system in the three directions were different, but their basic trends were similar to that of the frequency weighting defined in the current ISO standard. The implications of the results are discussed.

The objective of this study is to propose a theory on the biodynamic frequency weighting for studying hand-transmitted vibration exposures and vibration-induced effects. We hypothesize that the development of a vibration effect is the result of two consecutive but synergistic processes: biodynamic responses to input vibration and biological responses to the biomechanical stimuli resulting from the biodynamic responses. Hence, we further hypothesize that the frequency-dependency (W) of the effect generally includes two components: a biodynamic frequency weighting (W1) and a biological frequency weighting (W2), or W=W1• W2. These hypotheses are consistent with the stress and strain analysis theory and methods widely used in structural dynamics and biomechanics. The factorization may make it easier to study the complex frequency-dependency using different approaches: the biodynamic frequency weighting depends on the passive physical response of the system to vibration, and it can thus be determined by examining the biodynamic response of the system using various engineering methods; on the other hand, the biological frequency weighting depends on the biological mechanisms of the effects, and it can be investigated by studying the psychophysical, physiological, and pathological responses. To help test these hypotheses, this study reviewed and further developed methods to derive the finger biodynamic frequency weighting. As a result, preliminary finger biodynamic frequency weightings are proposed. The implications of the proposed theory and the preliminary biodynamic frequency weightings are also discussed.

To improve the reliability of the anti-vibration (AV) glove test defined in the current standard, a revised version of the standard has been proposed. However, the revised method has not been fully tested and sufficiently evaluated, and it is unknown whether it is practically feasible and convenient to implement the standard. To help achieve the objective of the revision, the specific aims of this study are to examine the rationale behind the major revisions of the standard and to evaluate the major technical aspects of the revised method through an experiment. Five human subjects participated in the experiment for the evaluation. Fifteen gloves with anti-vibration features were used in the experiment. To help evaluate the AV glove criteria, the effects of the glove on the grip strength were also examined. While this study failed to realize the constant-velocity spectrum proposed in the original revision, the glove vibration transmissibility values measured with a new spectrum proposed in the current study were very similar to those measured with the M and H spectra defined in the current standard, which suggests the new spectrum can greatly simplify the test without changing the original test results, and it should be adopted in the further revision of the standard. The results of this study also strongly support the proposed major revisions in the instrumentation and test procedures. Coincidently, the glove that reduced the grip strength the least was also the one that reduced the most vibration, which suggests that the negative and positive effects of the glove can be balanced in its design. While the subject is identified as a major influencing factor, this study proposed a novel approach – the use of a reference glove in the test to minimize the inter-subject and inter-laboratory variations. Based on the results of this study, some other further revisions in the test procedures, evaluation methods, and AV glove criteria were also proposed and discussed. Relevance to industry Anti-vibration gloves have been used as an alternative approach to reduce hand-transmitted vibration exposure. A standard is required to conduct a reliable screening test to help select appropriate anti-vibration gloves. This study can significantly help improve the current standard on the test. The results of this study can also be directly used to help select appropriate AV gloves.

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 industry Prolonged, 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.

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.

The major objectives of this study were to establish an alternative method for measuring the effects of gloves on the grip strength applied to cylindrical handles and to quantify the strength reduction due to the use of typical anti-vibration (AV) gloves. Different from previous studies that measure the grip force in a specific plane, the alternative method measures the total contact force normal to a cylindrical handle; the total grip strength is defined as the total contact force measured when a subject applies a power grip to the handle with his/her maximum voluntary contraction (MVC) effort. Two instrumented cylindrical handles (30 and 40 mm) were used in this study. Ten subjects participated in the experiment. Four types of AV gloves and two types of non-AV gloves were used in the experiment. Compared with bare-handed trials, each of the four anti-vibration gloves reduced the grip strength by more than 29%, regardless of handle size. One of the non-AV gloves also largely reduced the grip strength (≥25%) whereas the grip strength reduction of the other one was less than 10%. The gloves also influenced the grip force distribution pattern around the circumference of the cylindrical handles. The results suggest that the thickness of a glove is one of the major factors associated with these effects. Relevance to industry Glove use is generally recommended to keep the hands warm and dry and to protect them from many other hazards, provided this is consistent with safe and effective tool operation. However, a user of thicker, stiffer gloves, such as some AV gloves, could be trading one health risk for another. Knowledge of the effects of gloves on grip strength can help workers, managers, and safety professionals make informed decisions about glove selection and use in the workplace. This knowledge may also lead to work glove improvements.

The major objective of this study is to develop a modeling method for estimating the biodynamic responses distributed at the fingers and the palm of the hand based on the total driving-point mechanical impedance of the entire hand–arm system. A five degrees-of-freedom (DOF) model with a set of constraints proposed in this study was used in the estimation. Three sets of mechanical impedance data measured at the fingers and palm of the hand were used to examine the validity of the proposed method. The estimated response distributed at the palm was consistent with the measured data even when the real part of the impedance alone was used in the modeling (coefficient of correlation, r2 ≥ 0.902). Better agreements between the estimated and measured responses were obtained (r2 ≥ 0.929) when the magnitude and phase of the total impedance or the magnitude alone were used in the modeling estimation. In each case, the estimated response distributed at the fingers was also reliably correlated with the experimental data (r2 ≥ 0.726) but it was not as consistent with the experimental data as that distributed at the palm. The applications of the proposed method were also demonstrated using five other sets of reported experimental data. This study also demonstrated that the modeling method may also be used to assess the quality of the experimental data in some cases. As a special application of the acceptable data identified in this study, this study also defined a 2-DOF model for the construction of a hand–arm simulator for tool tests. The results of this study and the proposed modeling method are expected to contribute to the revision of ISO 10068 (1998).

The interaction between the handle and operator’s hand affects the comfort and safety of tool and machine operations. In most of the previous studies, the investigators considered only the normal contact forces. The effect of friction on the joint moments in fingers has not been analyzed. Furthermore, the observed contact forces have not been linked to the internal musculoskeletal loading in the previous experimental studies. In the current study, we proposed a universal model of a hand to evaluate the joint moments in the fingers during grasping tasks. The hand model was developed on the platform of the commercial software package AnyBody. Only four fingers (index, long, ring, and little finger) were included in the model. The anatomical structure of each finger is comprised of four phalanges (distal, middle, proximal, and metacarpal phalange). The simulations were performed using an inverse dynamics technique. The joint angles and the normal contact forces on each finger section reported by previous researchers were used as inputs, while the joint moments of each finger were predicted. The predicted trends of the dependence of the distal interphalangeal (DIP) and proximal interphalangeal (PIP) joint moments on the cylinder diameter agree with those of the contact forces on the fingers observed in the previous experimental study. Our results show that the DIP and PIP joint moments reach their maximums at a cylinder diameter of about 31 mm, which is consistent with the trend of the finger contact forces measured in the experiments. The proposed approach will be useful for simulating musculoskeletal loading in the hand for occupational activities, thereby optimizing tool-handle design.

Vibration-induced biodynamic responses (BR) of the human hand–arm system measured with subjects participating in an experiment are usually arithmetically averaged and used to represent their mean response. The mean BR data reported from different studies are further arithmetically averaged to form the reference mean response for standardization and other applications. The objectives of this study are to clarify whether such a response-based averaging process could significantly misrepresent the characteristics of the original responses, and to identify an appropriate derivation method. The arithmetically averaged response was directly compared with the response derived from a property-based method proposed in this study. Two sets of reported mechanical impedance data measured at the fingers and the palms of the hands were used to derive the models required for the comparison. This study found that the response-based arithmetic averaging could generate some systematic errors. The range of the subjects’ natural frequencies in each resonance mode, the mode damping ratio, and the number of subjects participating in the experiment are among the major factors influencing the level of the errors. An effective and practical approach for reducing the potential for error is to increase the number of subjects in the BR measurement. On the other hand, the property-based derivation method can be generally used to obtain the representative response, but it is less efficient than the response-based derivation method.

The objective of this study is to enhance the understanding of the hand grip force applied to a cylindrical handle and to develop a new dynamometer for measuring maximum grip force or grip strength. Specifically, a 40 mm instrumented cylindrical handle with six measuring arms was developed. A theoretical model was proposed and used to analyze the principle of the measurement. Human test subjects were used in conducting two sets of experiments to evaluate the handle and to assess the measurement method. This study confirmed that some friction force exists in the grip-only action, but its level is not comparable with the normal force. This study also found that the friction force can stabilize the grip action and marginally increase the grip strength. No reliable correlation between the grip strengths measured with the 40 mm cylindrical handle and Jamar handle with a 47.6 mm span was observed. This suggests that grip strength measured with Jamar handle may not be reliably applicable to the design and risk assessment of some tools or machines with cylindrical handles. In contrast, the cylindrical handle proved to be able to determine the overall grip strength for a subject, as well as show the grip force distribution around the circumference of the handle. The handle is accurate with less than 4% error, and it demonstrates that the measurement is independent of the loading position along the handle. Therefore, this study concluded that this new dynamometer is suitable for measuring grip strength with sufficient precision.

The primary objectives of the current study are to enhance the understanding of the mechanisms of the anti-vibration gloves and to evaluate the methods for assessing their vibration isolation effectiveness through developing a mechanical-equivalent model of the glove-hand–arm system. The model is developed based on the measured driving-point mechanical impedances distributed at the fingers and the palm of the hand with and without a glove. Six subjects participated in the experiments with two types of anti-vibration gloves (air-bladder glove and gel-filled glove) for measuring the required impedance data. The proposed model is applied to predict the effectiveness of the glove in terms of vibration transmitted to the fingers-glove and palm-glove interfaces, the finger bones, and the wrist. The results show that the gloves could provide some attenuation of the palm-transmitted vibration at frequencies above the fundamental resonant frequency of the gloved hand–arm system, but only little reduction in the finger vibration below the dominant finger resonant frequency. The present standardized methodology based upon the transmissibility measurement at the palm alone would thus be inappropriate for characterizing the overall reduction of the vibration exposure by a glove. Moreover, the palm adapter could introduce some measurement errors because of its mass and misalignment effects and its interference with the glove-palm coupling relationship. Therefore, the standardized method may only be used for general screening tests. On the basis of the model results, several potential improvements in the current standardized methodologies for evaluations of gloves and glove material are proposed and discussed. The proposed model may also serve as a useful tool for further developments of anti-vibration gloves and other anti-vibration devices.

Reliable experimental data of the driving-point biodynamic response (DPBR) of the hand–arm system are required to develop better biodynamic models for several important applications. The objectives of this study are to enhance the understanding of mechanisms of errors induced via the dynamics of instrumented handles and to identify a relatively more reliable method for DPBR measurement. A model of the handle–hand–arm system was developed and applied to examine various measurement methods. Both analytical and finite element methods were used to perform the examinations. This study found that the handle dynamic response could cause an uneven vibration distribution on its structures, especially at high frequencies (⩾500 Hz), and hand coupling on the handle could influence the distribution characteristics. Whereas the uneven distribution itself could directly result in measurement error, the hand coupling-induced vibration changes could cause errors in tare mass cancellation. The essential reason for both types of error is that the acceleration measured at one point on the handle may not be the same as that distributed at other locations. Because the cap measurement method that separately measures the DPBRs distributed at the fingers and palm can minimize both types of error, it is the best one among the methods examined in this study. The theory developed in this study can be used to help select, develop, and improve the measurement method for a specific application.

In this study it was hypothesized that the vibration-induced injuries or disorders in a substructure of human hand–arm system are primarily associated with the vibration power absorption distributed in that substructure. As the first step to test this hypothesis, the major objective of this study is to develop a method for analyzing the vibration power flow and the distribution of vibration power absorptions in the major substructures (fingers, palm–hand–wrist, forearm and upper arm, and shoulder) of the system exposed to hand-transmitted vibration. A five-degrees-of-freedom model of the system incorporating finger- as well as palm-side driving points was applied for the analysis. The mechanical impedance data measured at the two driving points under four different hand actions involving 50 N grip-only, 15 N grip and 35 N push, 30 N grip and 45 N push, and 50 N grip and 50 N push, were used to identify the model parameters. The vibration power absorption distributed in the substructures were evaluated using vibration spectra measured on many tools. The frequency weightings of the distributed vibration power absorptions were derived and compared with the weighting defined in ISO 5349-1 (2001). This study found that vibration power absorption is primarily distributed in the arm and shoulder when operating low-frequency tools such as rammers, while a high concentration of vibration power absorption in the fingers and hand is observed when operating high-frequency tools, such as grinders. The vibration power absorption distributed in palm–wrist and arm is well correlated with the ISO-weighted acceleration, while the finger vibration power absorption is highly correlated with unweighted acceleration. The finger vibration power absorption-based frequency weighting suggested that exposure to vibration in the frequency range of 16–500 Hz could pose higher risks of developing finger disorders. The results support the use of the frequency weighting specified in the current standard for assessing risks of developing disorders in the palm–wrist–arm substructures. The standardized weighting, however, could overestimate low-frequency effects but greatly underestimate high-frequency effects on the development of finger disorders. The results are further discussed to show that the trends observed in the vibration power absorptions distributed in the substructures are consistent with some major findings of various physiological and epidemiological studies, which provides a support to the hypothesis of this study.

The grip force applied to a cylindrical handle is a function of the measurement reference axis. So far, however, no attempt has been made to fully describe the exact form of this function. The objectives of this study were to examine some fundamental characteristics of grip forces and to explore the basic pattern of the grip force function. Twenty subjects (10 males and 10 females) participated in the experiment. The subjects alternately used their left and right hands to apply maximum grip forces and medium grip forces (about 40% of maximum) to a 30 mm handle. A flexible pressure sensor mat was used to measure the grip pressure. The pressure was integrated with respect to different measurement axes; this resulted in the grip force function. This study found that every gripping action produces maximum and minimum force axes; these axes are separated by about 90 degrees . The maximum force is correlated with the minimum force, but the former is generally about 1.42 times the latter. The principal grip direction is about 78 degrees from the z(h)-axis of the hand biodynamic coordinate system defined in ISO 8727 [ISO 8727. Mechanical vibration and shock - human exposure - biodynamic coordinate systems. Geneva, Switzerland: International Organization for Standardization; 1997]. More interestingly, each of the 160 sets of experimental data reasonably fit this study's proposed elliptical model. The implications of the findings are discussed.

Comprehensive assessments of health risks associated with the operation of vibratory tools should include evaluations of hand–tool coupling forces. The use of hand-force instrumentation in field applications can be difficult and expensive. A previous study (McDowell, T.W., Wiker, S.F., Dong, R.G., Welcome, D.E., Schopper, A.W., 2006. Evaluation of psychometric estimates of vibratory hand–tool grip and push forces. International Journal of Industrial Ergonomics 36(2), 119–128.) examined various combinations of handle vibration frequencies and grip and push force levels upon one's ability to recall those forces using psychophysical methods. The results of that study were promising. The present study is a follow-up experiment that further investigated the potential for using psychophysical force-recall methods to estimate grip and push forces when operating powered hand tools. In this experiment, 20 subjects (10 male, 10 female) grasped and pushed an instrumented handle for 45 s at one of three force levels while it vibrated sinusoidally at one of four frequencies (16, 31.5, 63, or 125 Hz) or with no vibration. Unlike the first study, two levels of vibration magnitude were examined along with gender differences. This study further clarifies relationships between vibration exposure characteristics and their effects on grip and push force-recall performance. Vibration exposure conditions and other influential factors can be accounted for in enhanced force-recall methodologies that can be incorporated into a variety of workplace exposure assessment applications. Relevance to industry Workers who are repeatedly exposed to intense hand-transmitted vibration are at risk of developing health problems. To better assess these health risks, hand–tool coupling forces should be evaluated. A refined psychophysical force-recall technique may be a practical alternative to expensive or fragile instrumentation. Before such a method is proposed for laboratory or field applications, an understanding of vibration effects upon force-recall performance must first be explored.

Mechanical arm systems are commonly used to support powered hand tools to alleviate ergonomic stressors related to the development of workplace musculoskeletal disorders. However, the use of these systems can increase exposure times to other potentially harmful agents such as hand-transmitted vibration. To examine how these tool support systems affect tool vibration, the primary objectives of this study were to characterize the vibration emissions of typical portable pneumatic grinders used for surface grinding with and without a mechanical arm support system at a workplace and to estimate the potential risk of the increased vibration exposure time afforded by the use of these mechanical arm systems. This study also developed a laboratory-based simulated grinding task based on the ISO 28927-1 (2009) standard for assessing grinder vibrations; the simulated grinding vibrations were compared with those measured during actual workplace grinder operations. The results of this study demonstrate that use of the mechanical arm may provide a health benefit by reducing the forces required to lift and maneuver the tools and by decreasing hand-transmitted vibration exposure. However, the arm does not substantially change the basic characteristics of grinder vibration spectra. The mechanical arm reduced the average frequency-weighted acceleration by about 24% in the workplace and by about 7% in the laboratory. Because use of the mechanical arm system can increase daily time-on-task by 50% or more, the use of such systems may actually increase daily time-weighted hand-transmitted vibration exposures in some cases. The laboratory acceleration measurements were substantially lower than the workplace measurements, and the laboratory tool rankings based on acceleration were considerably different than those from the workplace. Thus, it is doubtful that ISO 28927-1 is useful for estimating workplace grinder vibration exposures or for predicting workplace grinder acceleration rank orders.

Tool grip and push forces are important determinants of health risk associated with operation of powered hand tools. In the field, use of sophisticated hand-force instrumentation can be impractical. This study investigated the potential for using psychophysical force recall methods to estimate grip and push forces when operating vibratory hand tools. This study examined various combinations of handle vibration and grip and push force exposures upon one's ability to recall those forces using psychophysical methods. Twelve male subjects grasped and pushed an instrumented handle for 45 s at one of three levels of force while it vibrated sinusoidally at one of five frequencies (0, 12.5, 40, 125, or 250 Hz). We examined the effects of post-exertion rest periods of 10 and 20 s upon force recall performance, and day-to-day test-retest reliability. Results showed vibration frequency and force level differentially influenced grip and push force recall accuracy. Subjects characteristically overestimated grip and push forces; especially during vibration exposures of 40 and 125 Hz. The magnitude of the overestimations increased as target force levels decreased. Test–retest correlations were reasonably strong. Relevance to industry Operators of powered hand tools are at risk of developing health problems associated with repeated forceful actions and exposure to intense hand-transmitted vibration. To better assess health risks, hand-tool coupling forces should be quantified. Psychophysical force recall techniques may permit assessment of these forces without the need for expensive or fragile instrumentation. An understanding of the effects of vibration and force level upon force recall accuracy and reliability must first be explored before such methods are proposed for research or field assessments.

The objectives of this study are to derive the frequency weighting from three vibration power absorption (VPA) methods (finger VPA, palm VPA, and total or hand VPA), and to explore whether these energy methods are better than the currently accepted acceleration method. To calculate the VPA weightings, the mechanical impedance of eight subjects exposed to a broadband random vibration spectrum in the z h -axis using 18 combinations of hand couplings and applied forces was measured. The VPA weightings were compared with the frequency weighting specified in ISO 5349-1 [2001. Mechanical Vibration—Measurement and Evaluation of Human Exposure to Hand-Transmitted Vibration—Part 1: General Requirements. International Organization for Standardization, Geneva, Switzerland]. This study found that the hand and palm VPA weightings are very similar to the ISO weighting but the finger VPA weighting for the combined grip and push action is much higher than the ISO weighting at frequencies higher than 25 Hz. Therefore, this study predicted that the total power absorption of the entire hand–arm system is likely to be correlated with psychophysical response or subjective sensation. However, if the ISO weighting method cannot yield good predictions of the vibration-induced disorders in the fingers and hand, the hand and palm energy methods are unlikely to yield significantly better predictions. The finger VPA is a vibration measure between unweighted and ISO weighted accelerations. The palm VPA method may have some value for studying the disorders in the wrist–arm system.

Anti-vibration gloves are increasingly being used as personal protective equipment to help reduce the hazards of hand-transmitted vibration. A vibration transfer function method for estimating the tool-specific performance of anti-vibration gloves has been proposed to help select appropriate gloves for particular tools and to assess the potential risks posed by tool vibration. This study evaluates the validity of the method by comparing the predicted vibration transmissibility with the measured value. Two typical vibration-attenuating gloves (air-bladder and visco-elastic material gloves) were used in the study. Two series of experiments were performed for the evaluation. In the first series, the isolation efficiency of selected anti-vibration gloves was evaluated in the laboratory under synthesized handle vibration spectra of six different tools. The second series of tests involved the measurement of the glove transmissibility, while operating two different pneumatic chipping hammers. The results of the study show reasonably good agreements between the predicted and measured acceleration transmissibility values of the candidate gloves. It is thus concluded that the transfer function method provides a reasonably good estimate of vibration attenuation performance of gloves for specific tools.

A comprehensive understanding of the complex biodynamic response of the human fingers–hand–arm system may help researchers determine the causation of injuries arising from hand-transmitted vibration. This study theoretically demonstrates that the mechanical impedance (MI) in a hand power grip, as a measure of the biodynamic response of the system, can be divided into finger MI and palm MI. A methodology is developed to measure them separately and to investigate their distribution characteristics. This study involves 6 adult male subjects, constant-velocity sinusoidal excitations at 10 different discrete frequencies (16, 25, 40, 63, 100, 160, 250, 400, 630, 1000 Hz), and three different hand–handle coupling conditions. Our results suggest that at low frequencies (⩽40 Hz), the palm MI is substantially higher than the finger MI; the majority of the hand MI remains distributed at the palm up to 100 Hz; and at frequencies higher than 160 Hz, the finger MI is comparable to or higher than the palm MI. Furthermore, at frequencies equal to or above 100 Hz, the finger MI is practically independent of the palm–handle coupling conditions. Knowledge of the MI distribution pattern may increase the understanding of vibration transmission to the hand and aid in the development of effective isolation devices.

Anti-vibration gloves are widely used to help minimize hand–arm vibration exposure. In this study, an alternative method is proposed to assess the vibration isolation effectiveness of these gloves using the biodynamic responses of the bare- and gloved-hand–arm system exposed to vibration. The laboratory experiments were performed with a total of five human subjects using a typical anti-vibration air bladder glove subjected to a broad-band random vibration spectrum in conjunction with a specially designed instrumented handle. The measured data were analyzed to derive the biodynamic responses of the bare as well as gloved human hand–arm system in terms of the apparent mass and the mechanical impedance. The two biodynamic responses were applied to estimate the vibration isolation effectiveness of the glove. The validity of the proposed concept was examined by comparing the estimated vibration transmissibility magnitudes of the glove with those obtained using a palm adapter method. The comparison of the results suggests that the proposed method offers a good alternative for estimating glove vibration transmissibility. The measured data and the proposed method based upon the biodynamic responses were further used to investigate the effect of the palm adapter on the vibration transmissibility of the glove. The results suggest that the presence of the palm adapter between the subject's palm and the glove may not alter the basic trends in the transmissibility response, but it would affect the transmissibility magnitudes in the middle- and high-frequency ranges. A distinct advantage of the proposed method is that it eliminates the use of an adapter in assessing the vibration isolation effectiveness of the gloves.