Jennifer A. Hess

The effect of overhead drilling position on shoulder moment and electromyography

The effect of overhead drilling tasks on electromyographic (EMG) activity and shoulder joint moment was examined in this study. Twenty subjects simulated an overhead drilling task using a close, middle and far reach position while standing on either a lower or a higher step of a stepladder. Root mean square amplitude (AMP) of EMG activity from the dominant side anterior deltoid, biceps brachii and triceps brachii muscles was used to determine muscular load. Digital video was used to determine shoulder joint moment using 2-dimensional static link segment modelling in the sagittal plane. The results demonstrated that, compared to the far reach position, using the close reach position significantly decreased anterior deltoid AMP and biceps brachii AMP and moment, but increased triceps brachii AMP. Compared to the lower step, using the higher step significantly decreased anterior deltoid AMP and triceps AMP and moment, while increasing biceps AMP in the close position. There was no significant change noted in EMG median frequency indicating that fatigue was minimized. Moment increased monotonically with AMP. The findings indicated that workers performing overhead tasks should work close to their body in order to minimize shoulder forces. The implications of this recommendation are discussed.

Ergonomic evaluation of masons laying concrete masonry units and autoclaved aerated concrete

Masons working with concrete masonry unit block have high rates of work-related musculoskeletal disorders to the low back and shoulders associated with repetitively lifting and buttering heavy block. A new material, autoclaved aerated concrete, may reduce the risk of shoulder and back injury but, ergonomic evaluation is needed. This study evaluated shoulder exposure parameters, low back stress, and worker perceptions in two groups of journey level masons, one using CMU and the other using AAC block. Results indicate that for the left arm AAC masons spent significantly more time than CMU masons in static (38.2% versus 31.1%, respectively), and less time in slow motions (48.2% versus 52.2%, respectively) and faster motions (13.6% versus 16.7%, respectively) (p<0.05). CMU masons had significantly greater shoulder and low back pain (p=0.009) and they held block significantly longer than AAC masons (p<0.001). Low back compressive forces were high for both materials. Masons handling AAC demonstrated less left upper extremity stress but both materials were estimated to be hazardous to the low back.

Ankle force and rate of force production increase following high intensity strength training in frail older adults.

Background and aims: The most common cause of accidental injury and death in people over age 65 results from impacts associated with falling. Balance impaired older adults have poorer balance control than healthy young adults or healthy older adults. Lack of sufficient lower extremity strength and inability to rapidly produce muscle force may contribute to diminished balance control in the elderly. This study evaluated the effect of a 10-week high intensity strength- training program targeting key lower extremity muscles for the purpose of improving postural control in frail older adults. Methods: Thirteen experimental and fourteen control subjects, all balance impaired older adults were evaluated in response to unexpected platform perturbations that simulated slips. Results: Following strength training the experimental group was significantly stronger than the control group. Mean ankle moments improved in the experimental group following strength training during forward sway (Right: p=0.067, Left: p=0.009) and backward sway (Right: p=0.031, Left: p=0.058). For the backward sway condition the ankle rate of torque production increased significantly in the experimental group (Right: p=0.016, Left: p=0.031). Conclusions: Enhancement of lower extremity strength contributed to improvements in balance stability demonstrated by greater ankle force production, in response to balance threats.

Ergonomic best practices in masonry: regional differences, benefits, barriers, and recommendations for dissemination.

Within construction the masonry trade has particularly high rates of musculoskeletal disorders (MSDs). A NIOSH-sponsored meeting of masonry stakeholders explored current and potential “Best Practices” for reducing MSDs in masonry and identified potential regional differences in use of practices. To verify and better understand the regional effects and other factors associated with differences in practice use, a national telephone survey of masonry contractors was conducted. The United States was divided into four regions for evaluation: Northeast, Southeast, Midwest, and West Coast. Nine practices with the potential to reduce MSDs in masonry workers were evaluated. Masonry contractors, owners, and foremen completed 183 surveys. The results verify regional differences in use of best practices in masonry. Half-weight cement bags and autoclave aerated concrete were rarely used anywhere, while lightweight block and mortar silos appear to be diffusing across the country. The Northeast uses significantly fewer best practices than other regions. This article examines reasons for regional differences in masonry best practice, and findings provide insight into use and barriers to adoption that can be used by safety managers, researchers, and other safety advocates to more effectively disseminate ergonomic solutions across the masonry industry.

Comparison of three single-person manual patient techniques for bed-to-wheelchair transfers.

The uniqueness of the home environment still requires home health clinicians to lift and transfer patients manually, tasks that are known to cause back injuries. Three manual patient transfers were evaluated to establish the technique with the least risk to the low back. Patient and worker perceptions as well as preferences, exposure duration, and a biomechanical low back evaluation are presented, together with transfer technique recommendations.

The impact of drywall handling tools on the low back.

Carpenters and other construction workers who install drywall have high rates of strains and sprains to the low back and shoulder. Drywall is heavy and awkward to handle resulting in increased risk of injury. The purpose of this study was to evaluate several low-cost coupling tools that have the potential to reduce awkward postures in drywall installers. Five coupling tools were evaluated using the Lumbar Motion Monitor that measures trunk kinematics and predicts probability of low back disorder group membership risk (LBD risk). Workers answered surveys about their comfort while using each tool. The results indicate that use of the 2-person manual lift and the J-handle provide the best reduction in awkward postures, motions, low back sagittal moment, and LBD risk. The two-person manual lift appears to be the safest method of lifting and moving drywall, though using the two-person J-handle also significantly reduces injury risk. Given that carpenters are skeptical about using equipment that can get in the way or get lost, a practical recommendation is promotion of two-person manual lifting. For single-person lifts, the Old Man tool is a viable option to decrease risk of MSDs.

Alternatives to lifting concrete masonry blocks onto rebar: biomechanical and perceptual evaluations

This study examined the use of and barriers to H-block and high lift grouting, two alternatives to lifting concrete masonry blocks onto vertical rebar. Peak and cumulative shoulder motions were evaluated, as well as adoption barriers: H-block cost and stakeholder perceptions. Results indicated that using the alternatives significantly decreased peak shoulder flexion (p < 0.001). A case study indicated that building cost was higher with H-block, but the difference was less than 2% of the total cost. Contractors and specifiers reported important differences in perceptions, work norms, and material use and practices. For example, 48% of specifiers reported that use of high lift grouting was the contractors choice, while 28% of contractors thought it must be specified. Use of H-block or high-lift grouting should be considered as methods to reduce awkward upper extremity postures. Cost and stakeholders’ other perceptions present barriers that are important considerations when developing diffusion strategies for these alternatives. Practitioner Summary: This study provides information from several perspectives about ergonomic controls for a high risk bricklaying task, which will benefit occupational safety experts, health professionals and ergonomists. It adds to the understanding of shoulder stresses, material cost and stakeholder perceptions that will contribute to developing effective diffusion strategies.

The effect of lift teams on kinematics and muscle activity of the upper extremity and trunk in bricklayers.

STUDY DESIGN Workplace-simulation study using a crossover design. OBJECTIVES To evaluate the effect of lift teams on trunk and upper extremity kinematics and muscle activity among bricklayers. BACKGROUND Healthcare practitioners often instruct individuals with work-related musculoskeletal disorders in proper lifting techniques. Bricklayers are especially affected by lifting-related musculoskeletal disorders. Lift teams are a possible intervention for reducing exposure to heavy lifting. METHODS Eighteen apprentice bricklayers constructed walls with concrete blocks alone (1 person) and in 2-person lift teams. Peak shoulder and trunk kinematics and normalized mean surface electromyography of the upper trapezius, lumbar paraspinals, and flexor forearm muscles were collected bilaterally. Differences between construction methods and rows 1, 3, and 6 of the wall were calculated with repeated-measures analyses of variance. RESULTS Working in lift teams required less trunk flexion (P = .008) at row 1 but more sidebending at row 6 (P<.001) than working alone. Dominant-side lumbar paraspinal activity was lower at row 3 (P = .008) among lift-team workers. Lift-team peak shoulder flexion was lower at row 3 (P = .002), whereas abduction was higher at rows 1 (P = .007) and 6 (P<.001). Concomitantly, nondominant upper trapezius activity and flexor forearm activity were significantly higher for lift teams at row 6 (P<.001 and P = .007). Block moment arm was significantly greater for lift teams at all rows (P≤.002). CONCLUSION Working in lift teams may be a beneficial intervention for reducing trunk flexion and lumbar paraspinal activity when bricklayers work at heights between the knees and waist, but lift teams are not recommended at higher working heights.

Protecting workers in the home care industry: workers’ experienced job demands, resource gaps, and benefits following a socially supportive intervention

ABSTRACT The Community of Practice and Safety Support (COMPASS) program is a peer-led group intervention for home care workers. In a randomized controlled trial, COMPASS significantly improved workers’ professional support networks and safety and health behaviors. However, quantitative findings failed to capture workers’ complex emotional, physical, and social experiences with job demands, resource limitations, and the intervention itself. Therefore, we conducted qualitative follow-up interviews with a sample of participants (n = 28) in the program. Results provided examples of unique physical and psychological demands, revealed stressful resource limitations (e.g., safety equipment access), and elucidated COMPASS’s role as a valuable resource.

Effect of Step Height on Overhead Drilling in Construction

The purpose of this study was to determine the effect of moving closer to the work while performing overhead drilling. This task was simulated by twenty subjects while standing on either a lower or a higher step of a stepladder. Shoulder load was estimated by root-mean-square amplitude of electromyographic (EMG) activity and cinematographic analysis to determine shoulder joint moment using static link segment modeling. The results indicated that moving closer to the work surface by moving up a step reduces shoulder joint moment and anterior deltoid EMG. However, biceps brachii EMG increased by moving up a step. There was no significant change noted in EMG median frequencies suggesting that fatigue was not a significant factor. We conclude that while moving up a step reduces the muscular load on some muscles and the shoulder joint, other muscles may work harder. There are also safety considerations regarding moving up a step and alternative methods to move closer to the work surface are suggested.