@article{southard_freeman_drum_mirka_2007, title={Ergonomic interventions for the reduction of back and shoulder biomechanical loading when weighing calves}, volume={37}, ISSN={["0169-8141"]}, DOI={10.1016/j.ergon.2006.10.016}, abstractNote={Workers in the agriculture industry have exposure to many of the recognized risk factors for work-related musculoskeletal disorders. The focus of the current project was to develop and evaluate devices designed to reduce exposure to risk factors during the process of weighing beef calves. Ergonomic task analysis of current techniques used to weigh these calves indicated significant stress in the cervicobrachial and lumbar regions. Two ergonomic interventions—the “Handle Attachment” and the “Lever Arm”—were developed to improve the body posture of the lifter and reduce joint loading. A laboratory study and field evaluations were conducted for each of these designs. In the laboratory, muscle activities were quantified for the major muscles of cervicobrachial region, the lumbar region and knee extensor muscle group during the performance of the lifting task while using the two new interventions and the standard method. In the field evaluations, farmworkers used these devices and biomechanical models of the whole body postures were developed to quantify changes in the joint loading when using the interventions. The results show that both intervention techniques reduce the required muscle activity (8–71.6% reduction for the muscles of the cervicobrachial region, 2–43% reduction for the muscles of the lumbar region) and the joint loading (33–100% reduction in shoulder abduction moment and 42–57% reduction in spine compression) as compared to the standard method. Overall, the farmworkers noted that the “Handle Attachment” design is less cumbersome to move and use than the “Lever Arm” design, but laboratory study and field study revealed that the “Lever Arm” design provides the highest reduction in muscle activity and joint loading. Using either intervention while performing this task should decrease the risk to the low back and shoulders. The ergonomic intervention research described in this report documents a reduction in exposure to risk factors for shoulder and low back injury in an at-risk population in the agriculture industry.}, number={2}, journal={INTERNATIONAL JOURNAL OF INDUSTRIAL ERGONOMICS}, author={Southard, Stephanie A. and Freeman, Jacklyn H. and Drum, Jonathan E. and Mirka, Gary A.}, year={2007}, month={Feb}, pages={103–110} }
 @article{jiang_shu_drum_reid_mirka_2006, title={Effects of age on muscle activity and upper body kinematics during a repetitive forearm supination task}, volume={36}, ISSN={["1872-8219"]}, DOI={10.1016/j.ergon.2006.07.008}, abstractNote={The principal objective of this study was to assess the effects of age on upper extremity muscle activation patterns and upper body kinematics during a forearm supination task. Age-related physiological and biomechanical changes in the musculoskeletal system have been documented in the literature. It was hypothesized that these changes may have an impact on muscle recruitment and work technique (postural/kinematic) employed during work tasks. A simple repetitive forearm supination task was used to evaluate these hypotheses. Twenty subjects (ten in each age group 19–29 and 55–65) performed a series of static and dynamic forearm supination tasks on a work simulator. These exertions were performed at eight different levels of supination torque: 5–40 lb-in in 5 lb-in increments. As the subjects performed the static exertions the activation levels of several key muscles of the upper extremity were captured using surface electromyography. As the subjects performed the dynamic exertions, the motions of the upper body and upper extremity were captured using a magnetic field-based motion analysis system. The results of the static exertions showed that older subjects generated 135% greater trapezius muscle activity (significant at p<0.05 level) but no other muscle group sampled showed a significant difference between the age groups. In the dynamic exertions, age had no effect on upper limb/torso kinematic responses. In both the static and dynamic exertions, supination torque level had a significant impact on muscle activity and kinematics. These results provide empirical evidence that age alone does not have a consistent impact on biomechanical responses during physically demanding work tasks.}, number={11}, journal={INTERNATIONAL JOURNAL OF INDUSTRIAL ERGONOMICS}, author={Jiang, Zongliang and Shu, Yu and Drum, Jonathan and Reid, Stephanie and Mirka, Gary A.}, year={2006}, month={Nov}, pages={951–957} }
 @article{shu_drum_southard_shin_mirka_2005, title={The effect of a repetitive, fatiguing lifting task on horizontal ground reaction forces}, volume={21}, ISSN={["1065-8483"]}, DOI={10.1123/jab.21.3.260}, abstractNote={There are many outdoor work environments that involve the combination of repetitive, fatiguing lifting tasks and less-than-optimal footing (muddy/slippery ground surfaces). The focus of the current research was to evaluate the effects of lifting-induced fatigue of the low back extensors on lifting kinematics and ground reaction forces. Ten participants performed a repetitive lifting task over a period of 8 minutes. As they performed this task, the ground reaction forces and whole body kinematics were captured using a force platform and magnetic motion tracking system, respectively. Fatigue was verified in this experiment by documenting a decrease in the median frequency of the bilateral erector spinae muscles (pretest-posttest). Results indicate significant (p < 0.05) increases in the magnitude of the peak anterior/posterior (increased by an average of 18.3%) and peak lateral shear forces (increased by an average of 24.3%) with increasing time into the lifting bout. These results have implications for work environments such as agriculture and construction, where poor footing conditions and requirements for considerable manual materials handling may interact to create an occupational scenario with an exceptionally high risk of a slip and fall.}, number={3}, journal={JOURNAL OF APPLIED BIOMECHANICS}, author={Shu, Y and Drum, J and Southard, S and Shin, G and Mirka, GA}, year={2005}, month={Aug}, pages={260–270} }