Biomedical subjects

M Parnianpour

Publications and source records attributed to M Parnianpour.

At least 19 recordsLinked to original sources

PubMed2003

Subject-specific compressive tolerance estimates.

Spinal load models have become an increasingly valuable tool for the evaluation of the stress placed on the spine. In order to get an accurate representation of these spinal loads, they must be compared to known tolerance values. Bone mineral content and density of the lumbar spine of 23 males and 21 females was measured using a dual energy x-ray absorptiometry. Compression tolerance values were predicted by previously published studies based upon bone mineral levels. Anthropometric measurements were recorded and related to the compression tolerance values through the use of multivariate linear regression techniques. Compression tolerance values based on the bone mineral content or density explains more of the individual variability than solely age-based estimates. Several anthropometric variable regression models were developed that resulted in moderate to good predictive power (R(2) = 0.62 to 0.81). The current study describes a useful alternative to traditional tolerance estimates that accounts for individual differences requiring non-invasive and time-efficient procedures.

Absorptiometry, Photon↗

PubMed2002

Muscle force evaluation and the role of posture in human lumbar spine under compression.

Using two nonlinear finite element models of the lumbar spine, the concept of optimal posture is explored by minimizing the segmental sagittal moments required for the equilibrium of the passive lumbar spine under a total of 2800 N axial compression while varying the pelvic tilt and lumbar lordosis. The redundant active-passive system is subsequently solved for this posture using a novel kinematics-based muscle calculation algorithm along with minimization approach. Some flattening in the lumbar spine substantially reduces the required moments and internal passive shear forces under 2800 N axial compression force. Small muscle forces are calculated for this optimal posture. The role of flattening in the lumbar lordosis and posterior pelvic tilt in diminishing the lumbar muscle activities in neutral postures is demonstrated. Without such changes in posture, the required moments probably exceed the moment-generating capability of local lumbar muscles. Consideration of such active-passive synergy and lack of its restriction may prove crucial in many activities. Moreover, a kinematics-based algorithm is proposed for the solution of spinal redundancy that fully accounts for the existing passive-active synergy while simultaneously satisfying all kinematics and equilibrium conditions along the length of the spine.

Biomechanical Phenomena↗

PubMed2001

Range of motion and lordosis of the lumbar spine: reliability of measurement and normative values.

STUDY DESIGN: Repeated measures for intratester reliability were performed. OBJECTIVES: To investigate the intratester reliability of a new measurement technique that evaluates lumbar range of motion in three planes using a pelvic restraint device, and to examine the reliability of lumbar lordosis measurement by inclinometer technique. Preliminary normative data on lumbar range of motion and lumbar lordosis were collected for comparison with the findings of previous studies. SUMMARY OF BACKGROUND DATA: Various noninvasive measurement methods have been developed for recording lumbar range of motion. However, pelvic movement was not effectively restricted during the use of these measurement techniques. The use of the pelvic restraint device to measure lumbar range of motion has not been investigated previously. Very few studies have investigated the reliability of quantifying lumbar lordosis by the inclinometer technique. METHODS: Normative values were measured in 35 healthy men, and 12 of these subjects were included for the reliability study. Pelvic motion was limited by the pelvic restraint device during lumbar range of motion measurement in standing. An inclinometer was used for evaluation of lumbar flexion, extension, lateral flexion, and lumbar lordosis, whereas a lumbar rotameter was used to measure axial rotation. RESULTS: Good intratester reliability was shown in the lumbar range of motion and lordosis measurement. Most of the intraclass correlation coefficient and Pearson's r values (accompanied with nonsignificant paired t tests) were greater than 0.9, and most of the intrasubject coefficients of variation were less than 10%. The values of lumbar range of motion in three planes and lumbar lordosis found in the current study were comparable with those from most of the previous studies on these measurements in the normal population. CONCLUSIONS: Inclinometer and lumbar rotameter measurements with the use of a pelvic restraint device are reliable for measuring lumbar spine range of motion. Use of the inclinometer technique to record lumbar lordosis also is a reliable measure.

Adult↗

PubMed2001

Functional roles of abdominal and back muscles during isometric axial rotation of the trunk.

Electromyographic (EMG) studies have shown that a large number of trunk muscles are recruited during axial rotation. The functional roles of these trunk muscles in axial rotation are multiple and have not been well investigated. In addition, there is no information on the coupling torque at different exertion levels during axial rotation. The aim of the study was to investigate the functional roles of rectus abdominis, external oblique, internal oblique, latissimus dorsi, iliocostalis lumborum and multifidus during isometric right and left axial rotation at 100%, 70%, 50% and 30% maximum voluntary contractions (MVC) in a standing position. The coupling torques in sagittal and coronal planes were measured during axial rotation to examine the coupling nature of torque at different levels of exertions. Results showed that the coupled sagittal torque switches from nil to flexion at maximum exertion of axial rotation. Generally, higher EMG activities were shown at higher exertion levels for all the trunk muscles. Significant differences in activity between the right and left axial rotation exertions were demonstrated in external oblique, internal oblique, latissimus dorsi and iliocostalis lumborum while no difference was shown in rectus abdominis and multifidus. These results demonstrated the different functional roles of trunk muscles during axial rotation. This is important considering that the abdominal and back muscles not only produce torque but also maintain the spinal posture and stability during axial rotation exertions. The changing coupling torque direction in the sagittal plane when submaximal to maximal exertions were compared may indicate the complex nature of the kinetic coupling of trunk muscles.

Abdominal Muscles↗

PubMed2000

Impairment magnification during dynamic trunk motions.

STUDY DESIGN: An examination of a group of patients with low back disorder and a group of healthy (asymptomatic) individuals asked to produce trunk motions under sincere and insincere experimental conditions. Trunk motion components were examined to determine which combination of motion components could best distinguish between sincere and insincere efforts. OBJECTIVE: To determine whether examination of trunk motion components could be used to identify impairment magnification during unresisted repeated bending tasks. SUMMARY OF BACKGROUND DATA: Trunk motion measures can be used to assess and "benchmark" the status of the low back. However, these measures typically are clinically useful only if the individual is producing an effort that does not magnify the impairment during the functional evaluation. This study addressed the issue of impairment magnification during the production of free dynamic trunk motion. METHODS: The trunk motion characteristics of 100 healthy individuals and 100 patients with chronic low back disorders were documented. All participants were asked to produce the trunk motions in two different types of conditions. In the one experimental condition, they were asked to produce sincere trunk motions. In the other experimental condition they were asked to pretend either that they were experiencing low back pain (the asymptomatic group) or that their pain was worse than it actually was (group with low back pain). RESULTS: A combination of trunk motion measures was able to distinguish well between the conditions. Sensitivity and specificity for the asymptomatic group were 92%, whereas they were 75% for the group with low back pain. Overall, sensitivity and specificity were 81.5% for all the participants combined. CONCLUSIONS: These results indicate that motion measures can be used to help assess impairment magnification during functional trunk motion testing. These measures can provide a means by which to scrutinize the quality of quantitative measures indicating the extent of a low back disorder. These objective motion measures also can be used to complement other subjective observational methods for the assessment of impairment.

Acceleration↗

PubMed2000

Viscoelastic finite-element analysis of a lumbar motion segment in combined compression and sagittal flexion. Effect of loading rate.

STUDY DESIGN: A study using a validated viscoelastic finite-element model of a L2-L3 motion segment to identify the load sharing among the passive elements at different loading rates. OBJECTIVE: To enhance understanding concerning the role of the loading rate (i.e., speed of lifting and lowering during manual material handling tasks) on the load sharing and safety margin of spinal structures. SUMMARY OF BACKGROUND DATA: Industrial epidemiologic studies have shown that jobs requiring a higher speed of trunk motion contribute to a higher risk of industrial low back disorders. Consideration of the dynamic loading characteristics, such as lifting at different speeds, requires modeling of the viscoelastic behavior of passive tissues. Detailed systematic analysis of loading rate effects has been lacking in the literature. METHODS: Complex flexion movement was simulated by applying compression and shear loads at the top of the upper vertebra while its sagittal flexion angle was prescribed without constraining any translations. The lower vertebra was fixed at the bottom. The load reached its maximum values of 2000 N compression and 200 N anterior shear while L2 was flexed to 10 degrees of flexion in the three different durations of 0.3, 1, and 3 seconds to represent fast, medium, and slow movements, respectively. The resisted bending moment, gross load-displacement response of the motion segment, forces in facet joints and ligaments, stresses and strains in anulus fibrosus, and intradiscal pressure were compared across different rates. RESULTS: The distribution of stress and strain was markedly affected by the loading rate. The higher loading rate increased the peak intradiscal pressure (12.4%), bending moment (20.7%), total ligament forces (11.4%), posterior longitudinal ligament stress (15.7%), and anulus fiber stress at the posterolateral innermost region (17.9%), despite the 15.4% reduction in their strain. CONCLUSIONS: Consideration of the time-dependent material properties of passive elements is essential to improving understanding of motion segment responses to dynamic loading conditions. Higher loading rate markedly reduces the safety margin of passive spinal elements. When the dynamic tolerance limits of tissues are available, the results provide bases for the guidelines of safe dynamic activities in clinics or industry.

Elasticity↗

PubMed2000

Comparison of methods for the calculation of energy storage and return in a dynamic elastic response prosthesis.

The standard method used to calculate the ankle joint power contains deficiencies when applied to dynamic elastic response prosthetic feet. The standard model, using rotational power and inverse dynamics, assumes a fixed joint center and cannot account for energy storage, dissipation, and return. This study compared the standard method with new analysis models. First, assumptions of inverse dynamics were avoided by directly measuring ankle forces and moments. Second, the ankle center of rotation was corrected by including translational power terms. Analysis with below-knee amputees revealed that the conventional method overestimates ankle forces and moments as well as prosthesis energy storage and return. Results for efficiency of energy return were varied. Large differences between models indicate the standard method may have serious inadequacies in the analysis of certain prosthetic feet. This research is the first application of the new models to prosthetic feet, and suggests the need for additional research in gait analysis with energy-storing prostheses.

Ankle Joint↗

PubMed2000

Load-bearing and stress analysis of the human spine under a novel wrapping compression loading.

OBJECTIVE: To examine biomechanics of the human spine under a novel compression loading that follows the curvature of the spine.Design. The detailed response of the spine is predicted and compared under various types of compression loading at different postures. BACKGROUND: The posture and loading configuration could be so adjusted as to increase load-bearing capacity and stability of the spine in compression while minimizing the muscle activity and risk of tissue injury. METHODS: The nonlinear finite element formulation of wrapping elements sliding over solid body edges is developed and used to study the load-bearing capacity of simplified beam-rigid body thoracolumbar (T1-S1) and lumbosacral (L1-S1) spines under a wrapping compression force. The load-bearing and stress analysis of a detailed model of the lumbar spine, L1-S1, is also investigated under five wrapping loads resulting in differential compression forces at various levels. Follower load at L1, axially fixed compression at L1, and combined axially fixed compression and moments load are also considered for comparison. For the detailed model, the effect of changes in the position of wrapping elements and in the lumbar curvature on results are considered. RESULTS: The idealized wrapping loading stiffens the spine, allowing it to carry very large compression loads without hypermobility. It diminishes local segmental shear forces and moments as well as tissue stresses. CONCLUSIONS: In comparison to fixed axial compression, the compression loading by wrapping elements that follow the spinal curvatures increases the load-bearing capacity in compression and provides a greater margin of safety against both instability and tissue injury. Relevance These findings suggest a plausible mechanism in which postural changes and muscle activation patterns could be exploited to yield a loading configuration somewhat similar to that of the wrapping loading, i.e., the net reaction force at various levels passes through discs nearly normal to their mid-height plane. To alleviate hypermobility in compression, the wrapping loading could also allow for the application of meaningful compression loads in experimental as well as model studies of the multi-segmental spinal biomechanics.

Aged↗

PubMed2000

Wavelet and short-time Fourier transform analysis of electromyography for detection of back muscle fatigue.

Measurement of the time-varying characteristics of the frequency content of trunk muscle electromyography is a method to quantify the amount of fatigue endured by workers during industrial tasks, as well as a tool that may guide the training and rehabilitation of healthy and injured workers. Quantification of the change of signal power within specific frequency ranges may shed greater insight into the fatigue process. Sixteen healthy male subjects performed isometric trunk extension at 70% of their maximum voluntary contraction. Surface electromyography from medial and lateral erector spinae, and latissimus dorsi locations were processed using the short-time Fourier transform (STFT) and wavelet transform. Linear regression quantified the time rate of change of median frequency as well as frequency specific STFT filter and wavelet scale measures. The median frequency from the short-time Fourier transform declined by 22 Hz/min from an initial value of 77 Hz on average. The wavelet and STFT filter measures demonstrated this decline to be caused by a reduction in 209-349 Hz signal power in addition to an increase in 7-88 Hz signal power. A significant reduction in median frequency and significant elevation in 13-22 Hz wavelet signal component was detected in about 90% of the cases, indicating their use for detecting and quantifying fatigue.

Adult↗

PubMed2000

A well-posed, embedded constraint representation of joint moments from kinesiological measurements.

Joint moment estimation using the traditional inverse dynamics analysis presents two challenging problems, which limit its reliability. First, the quality of the computed moments depends directly on unreliable estimates of the segment accelerations obtained numerically by differentiating noisy marker measurements. Second, the representation of joint moments from combined video and force plate measurements belongs to a class of ill-posed problems, which does not possess a unique solution. This paper presents a well-posed representation derived from an embedded constraint equation. The proposed method, referred to as the embedded constraint representation (ECR), provides unique moment estimates, which satisfy all measurement constraints and boundary conditions and require fewer acceleration components than the traditional inverse dynamics method. Specifically, for an n-segment open chain planar system, the ECR requires n-3 acceleration components as compared to 3(n-1) components required by the traditional (from ground up) inverse dynamics analysis. Based on a simulated experiment using a simple three-segment model, the precision of the ECR is evaluated at different noise levels and compared to the traditional inverse dynamics technique. At the lowest noise levels, the inverse dynamics method is up to 50 percent more accurate while at the highest noise levels the ECR method is up to 100 percent more accurate. The ECR results over the entire range of noise levels reveals an average improvement on the order 20 percent in estimating the moments distal to the force plate and no significant improvement in estimating moments proximal to the force plate. The new method is particularly advantageous in a combined video, force plate, and accelerometery sensing strategy.

Algorithms↗

PubMed1999

The quantification of low back disorder using motion measures. Methodology and validation.

STUDY DESIGN: Trunk angular motion features were used as a means to quantify the extent of a low back disorder in healthy people and patients with chronic low back disorders. OBJECTIVE: To refine and validate a previously reported means of quantifying the extent of a low back disorder. SUMMARY AND BACKGROUND: Many assessment tools of low back disorder are subjective. A quantitative assessment tool would facilitate the tracking of the recovery and help document the appropriateness of treatments. METHODS: The trunk motion characteristics of 374 healthy people and 335 patients with chronic low back disorders of varying severity were documented as they flexed and extended their trunks in five different planes of motion. The trunk motion features were normalized as a function of age and gender. Four classification techniques were used to assess the ability of the quantitative motion measure to identify those with and without low back disorders. In addition, 31 patients were observed longitudinally to determine whether the motion measures agreed with observed changes in back pain symptoms. RESULTS: The quantitative trunk motion measure distinguished between people with low back disorders and healthy people between 88% and 94% of the time, depending on which classification system was used. Sensitivity and specificity varied between 83% and 97%. The quantitative measure also showed promise as a means to distinguish between muscle-based and structure-based low back disorders. Prospective findings indicated that the quantification system agreed well with clinical observations of progress. CONCLUSIONS: The quantification of trunk motion can serve as a measure of the extent of a low back disorder. When considered along with other clinical information, the ability to assess and treat low back disorders is enhanced.

Adult↗

PubMed1999

Wavelet analysis of electromyography for back muscle fatigue detection during isokinetic constant-torque exertions.

STUDY DESIGN: An investigation of the effects of human trunk extensor muscle fatigue on the temporal change in frequency content of the electromyogram as quantified using the Fourier and wavelet transforms during the performance of repetitive dynamic trunk extension. OBJECTIVE: To evaluate whether alterations in the Fourier and wavelet transform measures were consistent with a shift of the signal power to lower frequencies, and to determine which measures were more highly correlated with the decline in maximal trunk extension torque. SUMMARY OF BACKGROUND DATA: Objective assessment of trunk muscle fatigue is likely to play a more important role in the rehabilitation and prevention of low back injuries, given the association between lack of trunk muscle endurance and acquisition of low back pain. Validation of new methods designed to quantify the level of fatigue using the surface electromyogram is necessary before these techniques can be used in industrial rehabilitation settings. The wavelet transform is a recent development in the signal processing of electromyograms that shows promise as a method for assessment of fatigue. METHODS: Trunk muscle electromyograms obtained from study participants performing repetitive isokinetic trunk extension endurance tests were analyzed using the wavelet and the traditional Fourier methods. Trunk extension torque was controlled at 35% and 70% of the participants' maximal voluntary contraction while they exerted at 5 and 10 repetitions per minute. The decline in maximal trunk extension torque was measured once per minute. Linear regression quantified the rate of change in Fourier and wavelet measures caused by fatigue, whereas Pearson's correlation coefficient determined their association with the decline in maximum torque. RESULTS: Changes in the characteristics of the electromyogram were consistent with a shift to lower frequencies: The signal power at higher frequencies was reduced, whereas the power at lower frequencies was elevated. The amount of change was dependent on the task conditions (exertion level and repetition rate). The wavelet-based measures demonstrated as strong an association with the decline in maximal torque output as the Fourier-based measures. CONCLUSIONS: This study demonstrates that assessment of trunk muscle fatigue during isokinetic movementis possible using both Fourier and wavelet measurements. However, the methods were not as likely to change significantly during lower rates of exertion. These methods, when implemented in a controlled setting, may be used to document the rehabilitation process and guide preventive exercise training.

Adult↗

PubMed1999

Preliminary investigation of the lateral postural stability of spinal cord-injured individuals subjected to dynamic perturbations.

STUDY DESIGN: A study of the impact of spinal cord injury (SCI) on seated balance was conducted by comparing the results obtained from experiments with able-bodied and SCI subjects. OBJECTIVES: The purpose of this preliminary study was to examine the lateral postural stability of seated individuals with SCI in a dynamic environment. SETTING: Experiments were conducted at the Cleveland Clinic Foundation in Cleveland, Ohio. METHODS: Controlled perturbations were applied to each subject, seated in a wheelchair, through the use of a servo-controlled tilt platform. The platform was rotated so as to create disturbances similar in nature to those experienced in the frontal plane during left turns in a vehicle. Four quadriplegic, four paraplegic, and five able-bodied subjects participated in this study. Kinematic information and center of pressure (COP) movement were recorded. RESULTS: None of the spinal cord-injured subjects was able to maintain his stability when exposed to the stronger perturbations, while all of the able-bodied subjects stayed upright for all of the trials. On an individual basis, injury level was not always indicative of balance. However, regression results suggest a correlation between ability to perform static leaning and dynamic balance (P<0.001). CONCLUSIONS: SCI subjects lost stability under dynamic conditions even though they were stable in the static situation. Initial results also raise some questions about where and when external support may be needed. Information of this nature could help to guide the design of new lateral supports with improved client acceptance.

Adult↗

PubMed1999

Determination of the effect of lift characteristics on dynamic performance profiles during manual materials handling tasks.

In any quantitative gait or occupational biomechanics investigation, the quantification of the different kinematic, kinetic, and electromyographic parameters is essential towards assessment of functional capacity and development of a biomechanical profile of the task demands. In the current study, the authors presented a methodology for using inferential statistics to evaluate the effect of lift characteristics on phase-dependent and phase-independent variability in performance. Using a database of kinematic and kinetic profiles obtained from a manual lifting study, the phase-dependent effects of lift characteristics: box mass (load), mode (technique of lift), and speed (frequency of lift) were investigated through the use of analysis of variance (ANOVA) techniques, which recognize the vectorial constitution of the profiles. In addition, the Karhunen-Loeve Expansion (KLE) feature extraction method was used for representing the lifting patterns of measured joint angular position, velocity, acceleration, and net muscular torque profiles obtained from a 2-D biomechanical lifting model in order to study the phase-independent effects. In comparison to traditional descriptive statistical analyses currently used in various occupational biomechanics experimental investigations, this method allows the significant information content of the time varying signal to be captured, enhancing the sensitivity of subsequent hypothesis testing procedures. The application of this technique to MMH investigations allows identification of the lift characteristics that dominate the variability of task demands, hence aiding in the design and assessment of ergonomic solutions.

Biomechanical Phenomena↗

PubMed1999

Feature extraction and quantification of the variability of dynamic performance profiles due to the different sagittal lift characteristics.

Investigation of manual material handling (MMH) tasks, such as lifting, requires the quantification of the various kinematic and kinetic parameters of performance for assessment of the functional capacity and/or task demand profiles. Traditional statistical descriptive analyses usually involve computing the summary statistics (maximum, minimum, mean, and/or range) of the resulting performance parameters over the cycle duration (i.e., lifting/lowering cycle). Consequently, the significant information content of the time-varying signals is diminished, limiting the sensitivity of subsequent hypothesis testing procedures. The present study developed a methodology for representing and quantifying performance data variability of the kinematic and kinetic motion profiles due to the different lift characteristics (load, mode, and speed) during MMH tasks while capturing the temporal characteristics. Using a database of motion profiles from a manual lifting experiment, the Karhunen-Loeve Expansion (KLE) feature extraction technique was shown to be quite effective for representing the various motion profiles. The number of basis vectors (eigenvectors) and corresponding coefficients needed for accurate representation were substantially smaller than the original data set, resulting in data compression. Moreover, the effects of lift characteristics were investigated using analysis of variance techniques that recognize the vectorial constitution of the waveforms. The application of these techniques will enable the quantification of highly phasic profiles and enhance the ability to document the effect of intervening measures such as educational or physical training/exercise on the kinematic and kinetic patterns of performance. Additionally, the differential influence of lift characteristics on the variability of performance during different phases of lifting and lowering provides added resolution in the analysis of MMH tasks.

Adult↗

PubMed1999

A low-cost, portable system for the assessment of the postural response of wheelchair users to perturbations.

Maintaining seated postural stability presents a serious challenge to wheelchair users in vehicles, even during normal driving conditions. The purpose of this research was to develop a system for the study of seated postural control in response to perturbations similar to those that might be experienced during vehicle turning and braking. A servo-controlled tilt platform was constructed to provide a low-cost, small, and easily transportable device for generating precise and repeatable perturbations. Tilt platform operation was examined for accuracy and reproducibility of a desired perturbation. Repeatability was high with a mean signal-to-noise ratio (SNR) of 45.4 for a given perturbation measured across 11 subjects. An initial comparison of stability results obtained on the tilt platform and in a vehicle showed a correspondence, although differences were apparent. The tilt platform has been used successfully to assess balance in spinal cord-injured subjects and to test wheelchair securement systems.

Acceleration↗

PubMed1999

Significance of nonsagittal power terms in analysis of a dynamic elastic response prosthetic foot.

Dynamic elastic response prosthetic feet generally utilize a solid ankle, limiting dominant motion to the sagittal plane. However, researchers often use total rotational ankle joint power in the analysis of these feet. This investigation measured joint power terms in each plane for the Carbon Copy High Performance prosthetic foot. The significance of the frontal and transverse plane terms was assessed. Addition of these terms to the dominant sagittal power term revealed only slight differences, indicating that the sagittal power term is likely sufficient.

Adult↗

PubMed1999

Regression models for predicting peak and continuous three-dimensional spinal loads during symmetric and asymmetric lifting tasks.

Most biomechanical assessments of spinal loading during industrial work have focused on estimating peak spinal compressive forces under static and sagittally symmetric conditions. The main objective of this study was to explore the potential of feasibly predicting three-dimensional (3D) spinal loading in industry from various combinations of trunk kinematics, kinetics, and subject-load characteristics. The study used spinal loading, predicted by a validated electromyography-assisted model, from 11 male participants who performed a series of symmetric and asymmetric lifts. Three classes of models were developed: (a) models using workplace, subject, and trunk motion parameters as independent variables (kinematic models); (b) models using workplace, subject, and measured moments variables (kinetic models); and (c) models incorporating workplace, subject, trunk motion, and measured moments variables (combined models). The results showed that peak 3D spinal loading during symmetric and asymmetric lifting were predicted equally well using all three types of regression models. Continuous 3D loading was predicted best using the combined models. When the use of such models is infeasible, the kinematic models can provide adequate predictions. Finally, lateral shear forces (peak and continuous) were consistently underestimated using all three types of models. The study demonstrated the feasibility of predicting 3D loads on the spine under specific symmetric and asymmetric lifting tasks without the need for collecting EMG information. However, further validation and development of the models should be conducted to assess and extend their applicability to lifting conditions other than those presented in this study. Actual or potential applications of this research include exposure assessment in epidemiological studies, ergonomic intervention, and laboratory task assessment.

Adult↗