Static Biomechanical Model Research Articles

Study on Static Biomechanical Model of Whole Body Based on Virtual Human.

Material handling tasks often lead to skeletal injury of workers. The whole-body static biomechanical modeling method based on virtual humans is the theoretical basis for analyzing the human factor index in the lifting process. This paper focuses on the study of humans' body static biomechanical model for virtual human ergonomics analysis: First, the whole-body static biomechanical model is constructed, which calculates the biomechanical data such as force and moment, average strength, and maximum hand load at human joints. Secondly, the prototype model test system is developed, and the real experiment environment is set up with the inertial motion capture system. Finally, the model reliability verification experiment and application simulation experiment are designed. The comparison results with the industrial ergonomic software show that the model is consistent with the output of the industrial ergonomic software, which proves the reliability of the model. The simulation results show that under the same load, the maximum joint load and the maximum hand load are strongly related to the working posture, and the working posture should be adjusted to adapt to the load. Upright or bent legs have less influence on the maximum load capacity of the hand. Lower hand load capacity is due to forearm extension, and the upper arm extension greatly reduces the load capacity of the hand. Compared with a one-handed load, the two-handed load has a greater load capacity.

Biomechanical and physiological responses to allowable load handling limits in Iranian female workers

AbstractIn 2017, load limit values for manual material handling (MMH) tasks were confirmed to protect workers from low back disorders without prior validity investigation for Iranian workers. The present study investigated the applicability and feasibility of the Washington State Department of Labor and Industries (WISHA) lifting method as an occupational exposure limit (OEL) for the MMH tasks in a sample of young Iranian female workers using biomechanical and physiological criteria. A laboratory study was conducted with 10 female participants performing lifting tasks as described in the Iranian OEL for the MMH tasks based on the WISHA checklist. Each participant completed 21 lifting task combinations that varied in height and reach with the maximal allowable load. To test the applicability of the WISHA method, the maximum aerobic capacity and the equivalent heart rate (EHR) were estimated for 10 young Iranian female workers using an ergometer and Astrand protocol. Moreover, spinal loads for each lifting task were calculated using a static biomechanical model. From a physiological point of view, approximately 38% of the lifting tasks resulted in an increase in the physical workload. For 33% of the lifting trials, the estimated compression loads exceeded 3400 N. The findings revealed that the weight and lift height of the loads affected the lifting capacity of the participants. It seems that the allowable weight limits for manual lifting are not matched to the biomechanical and physiological capacities of the Iranian women. Therefore, the Iranian guideline for manual lifting is recommended to be revised based on the physiological and biomechanical capacities of the Iranian women.

Analysis of the coaptation role of the deltoid in reverse shoulder arthroplasty. A preliminary biomechanical study.

Lateralization of the glenoid implant improves functional outcomes in Reverse Shoulder Arthroplasty. Lateralization does not appear to impact the Deltoid's Moment Arm. Therefore, the stabilizing effect described in the literature would not be the result of an increase this moment arm. A static biomechanical model, derived from Magnetic Resonance Imaging, can be used to assess the coaptation effect of the Middle Deltoid. The objective of this study was to analyze the impact of increasing amounts of glenoid lateralization on the moment arm but also on its coaptation effect. Eight patients (72.6 ± 6.5 years) operated for Reverse Shoulder Arthroplasty were included in the study. Three-dimensional models of each shoulder were created based on imaging taken at 6 months postoperative. A least square sphere representing the prosthetic implant was added to each 3D models. A static biomechanical model was then applied to different planar portions of the Middle Deltoid (from 3D models), first without lateralization and then with simulated lateralization of 6, 9 and 12mm. This static model enables to compute a Coaptation/Elevation Ratio and to measure the Deltoid's Moment Arm. The inter- and intra-rater agreement of the 3D models was evaluated. One patient was excluded due to motion during imaging. The inter- and intra-rater agreement was over 0.99. The ratio increased starting at 6 mm of lateralization (p<0.05), compared to the initial position. The moment arm was not affected by lateralization (p<0.05), except in two slices starting at 9 mm (S1 p<0.05 and S2 p<0.05). Our hypothesis that the Middle Deltoid's coaptation role would be greater with glenosphere lateralization was confirmed. This trend was not found in the moment arm, which showed little sensitivity to lateralization. The stabilizing effect therefore appears to stem from the coaptation role of the Middle Deltoid.

Shoulder joint load and muscular activity during lifting

The aim of this study was to investigate load on shoulder joint and muscles in healthy adults during four different ways of lifting a moderate burden (12.8 kg) from floor to table level. The methods used were surface electrode EMG with linear envelope, and calculation of loading moments of force using a static biomechanical model. The shoulder load at the beginning of the lift was lowest for the straight knee lift. The peak load occurred in the late phase of all lifts. On completion of the lift, load and activation were considerably lower when the subject was allowed to step forward before putting the box down. The most activated shoulder muscles were the anterior and lateral parts of the deltoid, and the serratus anterior. Around 80% of the shoulder load moment was caused by the weight of the burden. Some 75% of maximum shoulder strength was required for lifting the burden.

Torso Segment Parameter Prediction in Working Adults

Body segment parameters (BSPs) such as segment mass, center of mass, and radius of gyration are used as inputs in static and dynamic ergonomic and biomechanical models used to predict joint and muscle forces, and related risks of musculoskeletal injury. Because these models are sensitive to BSP values, accurate and representative parameters are necessary for injury risk prediction. While previous studies have determined segment parameters in the general population, as well as the impact of age and obesity levels on these parameters, estimated errors in the prediction of BSPs can be as large as 40% (Durkin, 2003). Thus, more precise values are required for attempting to predict injury risk in individuals. This study aims to provide statistical models for predicting torso segment parameters in working adults using whole body dual energy x-ray absorptiometry (DXA) scan data along with a set of anthropometric measurements. The statistical models were developed on a training subset of the study population, and validated on a testing subset. When comparing the model predictions to the actual BSPs of the testing subset, the predictions were, on average, within 5% of the calculated parameters, while previously developed predictions (de Leva, 1996) had average errors of up to 30%, indicating that the new statistical models greatly increase the accuracy in predicting BSPs.

Hominin Hip Biomechanics: Changing Perspectives

The shape of the human pelvis reflects the unique demands placed on the hip abductor muscles (gluteus medius and gluteus minimus), which stabilize the body in the frontal plane during bipedal locomotion. This morphological shift occurred early in hominin evolution, yet important shape differences between hominin species have led to significant disagreement about abductor function and locomotor capability in these extinct taxa. A static biomechanical model that relies on a close association between skeletal measurements of the pelvis and femur has traditionally been used to reconstruct hip biomechanics in these species. However, experimental biomechanical approaches have highlighted the dynamic nature of mediolateral balance in walking and running, challenging the assumptions of the static hip model. This article reviews traditional approaches for understanding hip abductor function, shows how they have been applied to the fossil hominin record, and discusses new techniques that integrate the dynamic nature of mediolateral balance during human locomotion. Anat Rec, 300:932-945, 2017. © 2017 Wiley Periodicals, Inc.

Using a Bayesian Network to Predict L5/S1 Spinal Compression Force from Posture, Hand Load, Anthropometry, and Disc Injury Status.

Stochastic biomechanical modeling has become a useful tool most commonly implemented using Monte Carlo simulation, advanced mean value theorem, or Markov chain modeling. Bayesian networks are a novel method for probabilistic modeling in artificial intelligence, risk modeling, and machine learning. The purpose of this study was to evaluate the suitability of Bayesian networks for biomechanical modeling using a static biomechanical model of spinal forces during lifting. A 20-node Bayesian network model was used to implement a well-established static two-dimensional biomechanical model for predicting L5/S1 compression and shear forces. The model was also implemented as a Monte Carlo simulation in MATLAB. Mean L5/S1 spinal compression force estimates differed by 0.8%, and shear force estimates were the same. The model was extended to incorporate evidence about disc injury, which can modify the prior probability estimates to provide posterior probability estimates of spinal compression force. An example showed that changing disc injury status from false to true increased the estimate of mean L5/S1 compression force by 14.7%. This work shows that Bayesian networks can be used to implement a whole-body biomechanical model used in occupational biomechanics and incorporate disc injury.

A wider pelvis does not increase locomotor cost in humans, with implications for the evolution of childbirth.

The shape of the human female pelvis is thought to reflect an evolutionary trade-off between two competing demands: a pelvis wide enough to permit the birth of large-brained infants, and narrow enough for efficient bipedal locomotion. This trade-off, known as the obstetrical dilemma, is invoked to explain the relative difficulty of human childbirth and differences in locomotor performance between men and women. The basis for the obstetrical dilemma is a standard static biomechanical model that predicts wider pelves in females increase the metabolic cost of locomotion by decreasing the effective mechanical advantage of the hip abductor muscles for pelvic stabilization during the single-leg support phase of walking and running, requiring these muscles to produce more force. Here we experimentally test this model against a more accurate dynamic model of hip abductor mechanics in men and women. The results show that pelvic width does not predict hip abductor mechanics or locomotor cost in either women or men, and that women and men are equally efficient at both walking and running. Since a wider birth canal does not increase a woman’s locomotor cost, and because selection for successful birthing must be strong, other factors affecting maternal pelvic and fetal size should be investigated in order to help explain the prevalence of birth complications caused by a neonate too large to fit through the birth canal.

The impact of ergonomics intervention on trunk posture and cumulative compression load among carpet weavers

Work-related musculoskeletal disorders of back among weavers are prevalent. Epidemiological studies have shown an association between poor working postures and back disorders among carpet weavers. Therefore, the present study aimed to evaluate the impact of the traditional (A) and ergonomically designed (B) workstations on trunk posture and cumulative compression load in carpet weavers. In this study, subtasks were identified in terms of stressful postures and carpet weaving process. Postural data were collected during knotting and compacting subtasks using inclinometer during four hours for each workstation. Postural data, weight and height of the weavers were entered into the University of Michigan three-dimensional static biomechanical model for estimation of the compression load and cumulative load were estimated from the resultant load and exposure time. Thirteen healthy carpet weavers (four males and nine females) participated in the study. Median trunk flexion angle was reduced with workstation B during knotting subtask (18° versus 8.5°, p< 0.01 in males; 18.5° versus 7°, p< 0.001 in females). Average cumulative compression load was reduced with workstation B (22.17MN-s versus 16.68MN-s, p < 0.01 in males; 13.05 MN-s versus 10.14, p < 0.001 in females). Using workstation B led to significant decrease in cumulative compressive loading during an entire shift (8 hours), which indicates reduced level of stress on the back. It is suggested to conduct biomechanical studies on the shoulder and wrist regions in carpet weavers in order to achieve further development and improvement in the ergonomically designed workstation.

A model dilemma: how assumptions about locomotion and birth have shaped the obstetrical dilemma (335.1)

The obstetrical dilemma posits that the human female pelvis is under antagonistic selection pressures: narrow enough for efficient locomotion, but large enough to pass a large‐brained infant through the birth canal. This adaptive trade‐off is thought to explain the apparent difficulty of human childbirth, the helplessness of human neonates, and sex differences in human locomotor performance. However, core assumptions of the obstetrical dilemma model have gone untested. One assumption, that wider pelves in women increase locomotor cost, is based on a static biomechanical model of hip abductor function. Wider biacetabular width is thought to increase the external torque about the hip by moving the body center of mass farther from the hip joint, thereby increasing hip abductor muscle force and energetic cost to stabilize the pelvis. However, skeletal dimensions are actually poor proxies for the mechanical determinants of hip abductor function measured during locomotion and do not correlate significantly with locomotor cost. While this first assumption of the obstetrical dilemma can be empirically rejected, it is harder to directly assess the bases for and evolutionary history of cephalopelvic disproportion (CPD) that uniquely imperils human birth. A novel hypothesis to be tested suggests that recent environmental conditions have made CPD more common today than through most of human evolutionary history.Grant Funding Source: National Science Foundation BCS#0850841, The Leakey Foundation, The Wenner‐Gren Foundation

A regression model predicting isometric shoulder muscle activities from arm postures and shoulder joint moments

Tissue overloading is a major contributor to shoulder musculoskeletal injuries. Previous studies attempted to use regression-based methods to predict muscle activities from shoulder kinematics and shoulder kinetics. While a regression-based method can address co-contraction of the antagonist muscles as opposed to the optimization method, most of these regression models were based on limited shoulder postures. The purpose of this study was to develop a set of regression equations to predict the 10th percentile, the median, and the 90th percentile of normalized electromyography (nEMG) activities from shoulder postures and net shoulder moments. Forty participants generated various 3-D shoulder moments at 96 static postures. The nEMG of 16 shoulder muscles was measured and the 3-D net shoulder moment was calculated using a static biomechanical model. A stepwise regression was used to derive the regression equations. The results indicated the measured range of the 3-D shoulder moment in this study was similar to those observed during work requiring light physical capacity. The r2 of all the regression equations ranged between 0.228 and 0.818. For the median of the nEMG, the average r2 among all 16 muscles was 0.645, and the five muscles with the greatest r2 were the three deltoids, supraspinatus, and infraspinatus. The results can be used by practitioners to estimate the range of the shoulder muscle activities given a specific arm posture and net shoulder moment.

A quantitative approach to assess upper limb fatigue in the work field

Background: Fatigue is a timely topic that has been studied in a laboratory setting, yet still remains difficult to apply in an industrial setting. Objective: The aim of the present study was to define possible indicators of fatigue accumulation for an over shoulder level repetitive lifting work while performing lifting in two different ranges (LR1, LR2) in a supermarket. Methods: Video-based kinematics parameters were estimated and surface electromyography (EMG) of the anterior deltoid muscle was analyzed for nine healthy female subjects. A static biomechanical model to assess the effect of LRs on fatigue and a new fatigue index to allow for the estimation of substantial fatigue onset time (TSFO) were developed. Results: The data showed that fatigue accumulation strongly depends on the LRs. According to TSFO (time to substantial fatigue onset), shoulder muscle fatigue was unexpectedly lower when performing LR1 than LR2. Conclusions: The study shows a holistic analysis approach, suitable for the design of work/rest ratios in the occupational ergonomics field.

A KINETIC AND ELECTROMYOGRAPHIC COMPARISON OF THE STANDING CABLE PRESS AND BENCH PRESS

This study compared the standing cable press (SCP) and the traditional bench press (BP) to better understand the biomechanical limitations of pushing from a standing position together with the activation amplitudes of trunk and shoulder muscles. A static biomechanical model (4D Watbak) was used to assess the forces that can be pushed with 2 arms in a standing position. Then, 14 recreationally trained men performed 1 repetition maximum (1RM) BP and 1RM single-arm SP exercises while superficial electromyography (EMG) of various shoulder and torso muscles was measured. The 1RM BP performance resulted in an average load (74.2 ± 17.6 kg) significantly higher than 1RM single-arm SP (26.0 = 4.4 kg). In addition, the model predicted that pushing forces from a standing position under ideal mechanical conditions are limited to 40.8% of the subject's body weight. For the 1RM BP, anterior deltoid and pectoralis major were more activated than most of the trunk muscles. In contrast, for the 1RM single-arm SP, the left internal oblique and left latissimus dorsi activities were similar to those of the anterior deltoid and pectoralis major. The EMG amplitudes of pectoralis major and the erector muscles were larger for 1RM BP. Conversely, the activation levels of left abdominal muscles and left latissimus dorsi were higher for 1RM right-arm SP. The BP emphasizes the activation of the shoulder and chest muscles and challenges the capability to develop great shoulder torques. The SCP performance also relies on the strength of shoulder and chest musculature; however, it is whole-body stability and equilibrium together with joint stability that present the major limitation in force generation. Our EMG findings show that SCP performance is limited by the activation and neuromuscular coordination of torso muscles, not maximal muscle activation of the chest and shoulder muscles. This has implications for the utility of these exercise approaches to achieve different training goals.

Evaluation of Spinal Internal Loads and Lumbar Curvature under Holding Static Load at Different Trunk and Knee Positions

A study was performed to investigate how different trunk and knee positions while holding static loads affect the lumbar curvature and internal loads on the lumbar spine at L4-L5. Ten healthy male subjects participated in this study. Two inclinometers were used to evaluate the curvature of lumbar spine, lordosis, while a 3D static biomechanical model was used to predict the spinal compression and shear forces at L4-L5. Eighteen static tasks while holding three level of load (0, 10 and 20 kg), two levels of knee position (45 and 180 degrees of flexion) and three levels of trunk position (neutral, 15 and 30 degree of flexion) were simulated for 10 healthy male subjects. The results of this study revealed that the lordosis of lumbar spine changed to kyphosis with increasing weight of load from 0 to 20 kg in trunk flexion position (p<0.05), but in squatting position (45 degrees knee full flexion) the higher load did not affect the curvature. The results of this study suggested, at a more flexed trunk and standing position with higher loads both external moment and internal loads increased significantly at L4-L5 level but with 45 knee flexion external moment and compression force increased and shear force decreased significantly (p < 0.05). Subjects made more effort to maintain stability of the body in squat position. The highest external moment and compression force were computed at flexed knee and trunk position with highest loads. Hence holding weight in this position must be avoided by implementing ergonomic change to the workplace.

A Kinetic and Electromyographic Comparison of the Standing Cable Press and Bench Press

This study compared the standing cable press (SCP) and the traditional bench press (BP) to better understand the biomechanical limitations of pushing from a standing position together with the activation amplitudes of trunk and shoulder muscles. A static biomechanical model (4D Watbak) was used to assess the forces that can be pushed with 2 arms in a standing position. Then, 14 recreationally trained men performed 1 repetition maximum (1RM) BP and 1RM single-arm SP exercises while superficial electromyography (EMG) of various shoulder and torso muscles was measured. The 1RM BP performance resulted in an average load (74.2 +/- 17.6 kg) significantly higher than 1RM single-arm SP (26.0 +/- 4.4 kg). In addition, the model predicted that pushing forces from a standing position under ideal mechanical conditions are limited to 40.8% of the subject's body weight. For the 1RM BP, anterior deltoid and pectoralis major were more activated than most of the trunk muscles. In contrast, for the 1RM single-arm SP, the left internal oblique and left latissimus dorsi activities were similar to those of the anterior deltoid and pectoralis major. The EMG amplitudes of pectoralis major and the erector muscles were larger for 1RM BP. Conversely, the activation levels of left abdominal muscles and left latissimus dorsi were higher for 1RM right-arm SP. The BP emphasizes the activation of the shoulder and chest muscles and challenges the capability to develop great shoulder torques. The SCP performance also relies on the strength of shoulder and chest musculature; however, it is whole-body stability and equilibrium together with joint stability that present the major limitation in force generation. Our EMG findings show that SCP performance is limited by the activation and neuromuscular coordination of torso muscles, not maximal muscle activation of the chest and shoulder muscles. This has implications for the utility of these exercise approaches to achieve different training goals.

Estimation of finger muscle tendon tensions and pulley forces during specific sport-climbing grip techniques

The present work displayed the first quantitative data of forces acting on tendons and pulleys during specific sport-climbing grip techniques. A three-dimensional static biomechanical model was used to estimate finger muscle tendon and pulley forces during the “slope” and the “crimp” grip. In the slope grip the finger joints are flexed, and in the crimp grip the distal interphalangeal (DIP) joint is hyperextended while the other joints are flexed. The tendons of the flexor digitorum profundus and superficialis (FDP and FDS), the extensor digitorum communis (EDC), the ulnar and radial interosseus (UI and RI), the lumbrical muscle (LU) and two annular pulleys (A2 and A4) were considered in the model. For the crimp grip in equilibrium conditions, a passive moment for the DIP joint was taken into account in the biomechanical model. This moment was quantified by relating the FDP intramuscular electromyogram (EMG) to the DIP joint external moment. Its intensity was estimated at a quarter of the external moment. The involvement of this parameter in the moment equilibrium equation for the DIP joint is thus essential. The FDP-to-FDS tendon-force ratio was 1.75:1 in the crimp grip and 0.88:1 in the slope grip. This result showed that the FDP was the prime finger flexor in the crimp grip, whereas the tendon tensions were equally distributed between the FDP and FDS tendons in the slope grip. The forces acting on the pulleys were 36 times lower for A2 in the slope grip than in the crimp grip, while the forces acting on A4 were 4 times lower. This current work provides both an experimental procedure and a biomechanical model that allows estimation of tendon tensions and pulley forces crucial for the knowledge about finger injuries in sport climbing.

Cumulative spinal load among X-ray technologist: A field study of techniques, frame rate and prediction

A handful studies performed in laboratories, have been published on cumulative load and its measurement. There is no consensus on a methodology for estimation. So far little attempt has been made to demonstrate the predictability of this variable in field. Nine X-ray technologists were weighed, measured, and videotaped while they performed eight common occupational tasks. The postural data, object weight, height and weight of the technologists were fed to the University of Michigan three-dimensional static biomechanical model for estimation of the lumbosacral compression and shear at frame rates of 0.25, 0.5 and 1, 2, 4, 5 and 10 fps. From the output the cumulative compression and shear were estimated using five techniques (the product of peak load X time, average load X time, half of the initial+final load X time, half peak load X time, area under the curve). Regression equations were developed using data from four tasks and they were validated on the other four. The results obtained from five different techniques were significantly different ( p < 0.01 ). Area under the curve was most accurate. The frame rates produced significant difference ( p < 0.01 ). Area under the force curve determined at 5 fps was the optimal sampling method. The regression equations were significant ( p < 0.01 ) and predicted cumulative loads with errors generally under 1% but not exceeding 3.9%. The area under the curve method of estimation of cumulative load at 5 Hz is suggested as the technique of choice. At this stage this methodology may be occupation specific.

Modeling of object movement capability in the spinal cord injured population

Static biomechanical modeling has revealed that human reaching and object movement capabilities are dependent on both torso and upper extremity muscle strengths, and the ability to maintain balance throughout the movement. This paper describes data and biomechanical models that can be used to understand the dynamic motions of people with and without thoracic level spinal cord injuries (SCIs) while moving objects around in their environments. This paper also discusses how data gathered in the Human Motion Simulation (HUMOSIM) Laboratory from volunteer subjects performing various seated tasks are used in multi-joint inverse biomechanical models to predict both shoulder moments and body center of pressure locations. The results demonstrate that when symptomatic control subjects moved a box from a small table in front of them to a shoulder-high shelf, it was performed in a smooth fashion that could be well modeled and understood with the use of sequential static biomechanical models. The motions of those subjects with thoracic and high lumbar level SCIs, however, contained an additional dynamic component. The dynamic component revealed that healthy, active SCI subjects were quite capable of extending the distance over which they can move objects to rigid shelves by using a ballistic motion technique. This dynamic motion allows them to move objects to shelves located over twice the distance predicted by static models of such motions, but also raises questions of safety due to falling forward if the object being moved does not land securely on the shelf. These types of motions also are shown to cause much higher (by about 30%) shoulder moments, thus raising the risk of injury to shoulder tissues in people with SCIs. Relevance to industry This paper shows that biomechanical models for predicting the capabilities of people to move objects when they have thoracic level spinal cord injuries (SCIs) will require dynamic elements to be carefully considered. It is believed that the results of the data and biomechanical modeling included in this study provide a scientific basis for improving design guides, so that in the future such workplaces will better accommodate people with SCIs.

Determining the minimum sampling rate needed to accurately quantify cumulative spine loading from digitized video

Cumulative low back loads have been linked to the reporting of low back pain. Traditional video-based methods used to estimate these loads are time intensive for data collection and analysis. Sampling less frequently would help to reduce the associated time and cost of this type of approach. The purpose of this study was to determine how the error in estimated cumulative low back loads is affected by reducing video sampling rate. Ten healthy male university students performed three laboratory, sagittal plane lifts of varying mass (2.3, 8.8, and 15.9 kg), speed (0.2, 0.4, 0.8 m/s), and postural demand (lift from floor to table; lower from shelf to table; lift from floor over barrier and lower to floor) while being videotaped (60 frames/s). Digitized body coordinates and anthropometrics were input into a static biomechanical model, resulting in estimates of low back compression and shear forces, and moment. Load-time histories for each condition underwent rectangular integration at 60 (gold standard), 30, 20, 15, 12, 10, 6, 5, 4, 3, 2 and 1 frames/s, resulting in estimates of low back cumulative loads. Mean relative errors with respect to 60 frames/s for all cumulative loads and all conditions were found to be below 8% at 1 frame/s, and less than 3% at 2 frames/s. In addition, analyses at sampling rates above 3 frames/s were not significantly different than the cumulative loads determined at 60 frames/s, for all conditions. The accuracy of cumulative loads exhibited even at low sampling rates can be attributed, in part, to the fact that overestimations and underestimations of the integrated loads tend to cancel out over the length of the tasks considered.

Measurement of physical work capacity during arm and shoulder lifting at various shoulder flexion and ad/abduction angles

AbstractThe purpose of this study was to provide information on physical work capacity during arm and shoulder lifting at various shoulder flexion and ad/abduction angles. We measured the maximum voluntary contractions (MVCs) in 20 male participants during controlled one‐arm lifting. The lifting involved upward motion of the scapula at various shoulder angles. Simultaneously, the electromyographic (EMG) activity of 3 shoulder muscles and psychophysical workload were also recorded. The various measurements were compared to provide a multidimensional assessment of the physical work capacity of the shoulder at various working angles. In particular, 90 and 120 degrees of flexion, 30 degrees of adduction, and 90 degrees of abduction were found to be the most vulnerable angles based on the measured MVCs. The average root mean square value of the EMG increased most significantly at 90 to 150 degrees of flexion and at 30 and 60 degrees of abduction. Slightly different measurements were compared to validate the results. In addition, a 3‐D static biomechanical model was used to show whether the estimated shoulder workload matched the measured physical capacity of the shoulder. In conclusion, these results may help ergonomists to identify shoulder angles associated with a relatively high risk of injury, and to match the workload with the physical capacity of the shoulder. Task‐specific information on shoulder work capacity is needed in the manufacturing and shipbuilding industries to protect workers from acute injuries and cumulative trauma disorders of the shoulder. Experimental results provide various data on shoulder work capacity during realistic multijoint arm and shoulder lifting, and should help lead to improvements in workplace ergonomic design. © 2003 Wiley Periodicals, Inc. Hum Factors Man 13: 153–163, 2003.