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Luc H.V. van der Woude, Dirk-Jan E.J. Veeger and Rients H. Rozendal

A review of wheelchair research within the scope of the wheelchair as a means of daily ambulation is presented. The relevance of a combined biomechanical and physiological research approach is advocated for enhancing the body of knowledge of wheelchair ergonomics, that is, the wheelchair/user interaction in relation to aspects of vehicle mechanics and the user’s physical condition. Results of experiments regarding variations in the wheelchair/user interface stress the possibilities of optimization in terms of wheelchair dimensions and user characteristics. Analysis of propulsion technique is aimed at the within-cycle characteristics and the time-dependent organization of technique.

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Melissa M.B. Morrow, Bethany Lowndes, Emma Fortune, Kenton R. Kaufman and M. Susan Hallbeck

Upper body kinematic measures are widely used in ergonomics, 1 , 2 orthopedics, 3 , 4 and rehabilitation 5 – 7 to describe normal and pathological motion of the trunk, head, and arms. Traditional methods of motion capture utilize marker-based and electromagnetic laboratory-based systems to

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Dwight E. Waddell, Craig Wyvill and Robert J. Gregor

A field study was performed using a new data collection system looking at upper extremity kinetics during two different cutting tasks, wing vs. tender cuts, in three poultry plants. The Ergonomic Work Assessment System (EWAS) was designed to simultaneously record knife forces (Fx, Fy, and Fz), electromyographic (EMG) activity (forearm flexors/extensors), and goniometric data (wrist flexion/extension), all of which may represent risk factors associated with cumulative trauma disorders, specifically carpal tunnel syndrome (CTS). The objective of this study was to monitor workers in an unencumbered fashion as they performed two different poultry cutting tasks. It was assumed that the variables measured by EWAS would be able to discriminate between the two cuts and quantify possible differences between the two. The results confirmed that EWAS successfully showed significant differences in knife forces between the wing and tender cuts. Knife force differences were also observed between plants for the same cut. Differences in the two cuts were also identified in the EMG and wrist angles. EWAS successfully quantified variables that may represent risk factors associated with CTS in three poultry plants. Knowledge of a better quantitatively described external work environment may enable plants to better design rotation schedules for their deboners.

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Steven L. Fischer, Bryan R. Picco, Richard P. Wells and Clark R. Dickerson

Exerting manual forces is critical during occupational performance. Therefore, being able to estimate maximum force capacity is particularly useful for determining how these manual exertion demands relate to available capacity. To facilitate this type of prediction requires a complete understanding of how maximum force capacity is governed biomechanically. This research focused on identifying how factors including joint moment strength, balance and shoe-floor friction affected hand force capacity during pulling, pressing downward and pushing medially. To elucidate potential limiting factors, joint moments were calculated and contrasted with reporte joint strength capacities, the balancing point within the shoe-floor interface was calculated and expresess relative to the area defined by the shoe-floor interface, and the net applied horizontal forces were compare with the available friction. Each of these variables were calculated as participants exerted forces in a series o conditions designed to systematically control or restrict certain factors from limiting hand force capacity. The results demonstrated that hand force capacity, in all tested directions, was affected by the experimental conditions (up to 300%). Concurrently, biomechanical measures reached or surpassed reported criterion threshold inferring specific biomechanical limitations. Downward exertions were limited by elbow strength, wherea pulling exertions were often limited by balance along the anterior-posterior axis. No specific limitations wer identified for medial exertions.

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Marie-Louise Bird, Cecilia Shing, Casey Mainsbridge, Dean Cooley and Scott Pedersen

Background:

Sedentary behavior is related to metabolic syndrome and might have implications for the long-term health of workers in a low activity environment. The primary aim of this pilot study was to determine activity levels of adults working at a University during work hours. A secondary aim was to determine the relationship between actual and perceived activity levels.

Methods:

Activity levels of university staff (n = 15, male = 7, age = 53 ± 7 years, BMI = 26.5 ± 2.5kg·m2) were monitored over 5 consecutive workdays using SenseWear accelerometers, then participants completed a questionnaire of their perception of workplace sedentary time.

Results:

Each participant spent 71.5 ± 13.1% (358 ± 78 min) of their workday being sedentary (< 1.5 METs), 15.6 ± 9.0% involved in light activity (1.5–3 METs), 11.7 ± 10.0% in moderate activity (3–5 METs), and 1.1 ± 1.3% in vigorous activity (> 5 METs) (P < .0001). The mean difference between actual (SenseWear < 1.5 METs) and perceived sitting time was –2 ± 32%; however, perceived sedentary time was reported with a range of under-to-over estimation of –75% to 51%.

Conclusion:

This pilot study identifies long periods of low metabolic activity during the workday and poor perception of individual sedentary time. Interventions to reduce sedentary time in the workplace may be necessary to ensure that the work environment does not adversely affect long-term health.

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Chip Wade and Mark S. Redfern

Locomotion over ballast surfaces provides a unique situation for investigating the biomechanics of gait. Although much research has focused on level and sloped walking on a smooth, firm surface in order to understand the common kinematic and kinetic variables associated with human locomotion, the literature currently provides few if any discussions regarding the dynamics of locomotion on surfaces that are either rocky or uneven. The purpose of this study was to investigate a method for using force plates to measure the ground reaction forces (GRFs) during gait on ballast. Ballast is a construction aggregate of unsymmetrical rock used in industry for the purpose of forming track bed on which railway ties are laid or in yards where railroad cars are stored. It is used to facilitate the drainage of water and to create even running surfaces. To construct the experimental ballast surfaces, 31.75-mm (1¼-in.) marble ballast at depths of approximately 63.5 mm (2.5 in.) or 101.6 mm (4 in.) were spread over a carpeted vinyl tile walkway specially designed for gait studies. GRF magnitudes and time histories from a force plate were collected under normal smooth surface and under both ballast surface conditions for five subjects. GRF magnitudes and time histories during smooth surface walking were similar to GRF magnitudes and time histories from the two ballast surface conditions. The data presented here demonstrate the feasibility of using a force plate system to expand the scope of biomechanical analyses of locomotion on ballast surfaces.

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Alan C. Cudlip, Steven L. Fischer, Richard Wells and Clark R. Dickerson

This study examined the influence of frequency and direction of force application on psychophysically acceptable forces for simulated work tasks. Fifteen male participants exerted psychophysically acceptable forces on a force transducer at 1, 3, or 5 repetitions per minute by performing both a downward press and a pull toward the body. These exertions were shown previously to be strength and balance limited, respectively. Workers chose acceptable forces at a lower percentage of their maximum voluntary force capacity during downward (strength-limited) exertions than during pulling (balance-limited) exertions at all frequencies (4% to 11%, P = .035). Frequency modulated acceptable hand force only during downward exertions, where forces at five repetitions per minute were 13% less (P = .005) than those at one exertion per minute. This study provides insight into the relationship between biomechanically limiting factors and the selection of acceptable forces for unilateral manual tasks.

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Jason C. Gillette, Catherine A. Stevermer, Stacey A. Meardon, Timothy R. Derrick and Charles V. Schwab

Farm youth commonly perform animal care tasks such as feeding and watering. The purpose of this study was to determine the effects of age, bucket size, loading symmetry, and amount of load on upper body moments during carrying tasks. Fifty-four male and female participants in four age groups (8–10 years, 12–14 years, 15–17 years, and adults, 20–26 years) participated in the study. Conditions included combinations of large or small bucket sizes, unilateral or bilateral loading, and load levels of 10% or 20% of body weight (BW). During bucket carrying, elbow flexion, shoulder flexion, shoulder abduction, shoulder external rotation, L5/S1 extension, L5/S1 lateral bending, and L5/S1 axial rotation moments were estimated using video data. The 8–10 year-old group did not display higher proportional joint moments as compared with adults. Decreasing the load from 20% BW to 10% BW significantly decreased maximum normalized elbow flexion, shoulder flexion, shoulder abduction, shoulder external rotation, L5/S1 lateral bending, and L5/S1 axial rotation moments. Carrying the load bilaterally instead of unilaterally also significantly reduced these six maximum normalized joint moments. In addition, modifying the carrying task by using smaller one-gallon buckets produced significant reductions in maximum L5/S1 lateral bending moments.