Bryan Buchholz

PATH: a work sampling-based approach to ergonomic job analysis for construction and other non-repetitive work.

A high prevalence and incidence of work-related musculoskeletal disorders have been reported in construction work. Unlike industrial production-line activity, construction work, as well as work in many other occupations (e.g. agriculture, mining), is non-repetitive in nature; job tasks are non-cyclic, or consist of long or irregular cycles. PATH (Posture, Activity, Tools and Handling), a work sampling-based approach, was developed to characterize the ergonomic hazards of construction and other non-repetitive work. The posture codes in the PATH method are based on the Ovako Work Posture Analysing System (OWAS), with other codes included for describing worker activity, tool use, loads handled and grasp type. For heavy highway construction, observations are stratified by construction stage and operation, using a taxonomy developed specifically for this purpose. Observers can code the physical characteristics of the job reliably after about 30 h of training. A pilot study of six construction laborers during four road construction operations suggests that laborers spend large proportions of time in nonneutral trunk postures and spend approximately 20% of their time performing manual material handling tasks. These results demonstrate how the PATH method can be used to identify specific construction operations and tasks that are ergonomically hazardous.

Anthropometric data for describing the kinematics of the human hand

The major goal of this investigation was to collect statistically-based anthropometry describing the kinematics of the human hand and to model this anthropometry as a function of external hand measurements, so that it may be predicted noninvasively. Joint centres were anatomically estimated as the centre of curvature of the head of the bone proximal to the given joint. Joint centres determined using Reuleauxs method for PIP and DIP were within 1.4 mm of this anatomical estimate. Models using bone length as the independent variable explain more than 97% of the variability in the anatomically estimated joint centre position along the mid-line of the bone. Models for estimating the lengths of the kinematic segments using external hand length as the independent variable account for between 49 and 99% of the variability in segment length. Models for estimating the axial location of the finger MCP and thumb CMC joints with respect to the distal wrist crease using external hand length as the independent variable account for between 82 and 96% of the variability in these locations. Models for estimating the radio-ulnar location of the finger MCP and thumb CMC joints with respect to the long axis of the third metacarpal using external hand breadth as the independent variable account for between 30 and 74% of the variability in these locations.

An investigation of human palmar skin friction and the effects of materials, pinch force and moisture.

A study was conducted to determine the friction characteristics for various materials against human palmar skin. Seven materials were tested using two pinch-force levels under both moist and dry conditions. Using a two-fingered pinch grip, subjects held a specially designed dynamometer covered with one of the test materials. They maintained a constant pinch force as load force was increased at a constant rate until the dynamometer slipped from their fingers. The load force at the slip point was then used to determine the coefficient of friction from Amontons Law. The effects of subject, material, moisture, pinch force and the material-moisture and pinch force-moisture interactions were all significant. The coefficient of friction decreased with increased levels of pinch force for every material-moisture combination. The coefficient of friction for porous materials showed a significant increase when moisture was present. This information may be applicable in tool handle and work station surface design.

Practical Operation of a Biaxial Goniometer at the Wrist Joint

The objectives of this study were (a) to determine errors in wrist angle measurements from a commercially available biaxial electrogoniometer and (b) to develop a calibration routine in order to correct for these errors. Goniometric measurements were collected simultaneously with true angular data using a fixture that allowed wrist movement in one plane while restricting motion in the orthogonal plane. These data were collected in two sets of trials: flexion/extension with radial/ulnar deviation restricted, and radial/ulnar deviation with flexion/extension restricted. During these trials, we studied discrete 30° increments of forearm rotation. The results showed the expected cross talk and zero drift errors during forearm rotation. The application of mathematical equations that describe the effect of goniometer twist resulted in significant error reduction for most forearm rotations. The calibration technique employs both a slope and a displacement transformation to improve the accuracy of angular data. The calibration technique may be used on data collected in the field if forearm rotation is measured simultaneously with the goniometer data.

Reliable exposure assessment strategies for physical ergonomics stressors in construction and other non-routinized work

The objective of this research was to provide guidelines for the reliable assessment of ergonomics exposures in non-routinized work. Using a discrete-interval observational sampling approach, two or three observers collected a total of 5852 observations on tasks performed by three construction trades (iron workers, carpenters and labourers) for periods of several weeks. For each observation, nine exposure variables associated with awkward body postures, tool use and load handling were recorded. The frequency of exposure to each variable was calculated for each worker during each of the tasks on each of the days. ANOVA was used to assess the importance of task in explaining between-worker and within-worker variability in exposures across days. A statistical re-sampling method (bootstrap) was used to evaluate the reliability of exposure estimates for groups of workers performing the same task for different sampling periods. Most exposures were found to vary significantly across construction tasks within trade, and between-worker exposure variability was generally smaller than within-worker exposure variability within task. Bootstrapping showed that the reliability of the group estimates exposure for the most variable exposures within task tended to improve as the assessment periods approached 5 – 6 d, with marginal improvements for longer assessment periods. Reliable group estimates of exposure for the least variable exposures within task were obtained with 1 or 2 d of observation. The results of this study demonstrate that an initial estimate of the important environmental or task sources of exposure variability can be used to develop an efficient sampling strategy that provides reliable estimates of ergonomics exposures during non-routinized work.

Quantification of Ergonomic Hazards for Ironworkers Performing Concrete Reinforcement Tasks During Heavy Highway Construction

A study was conducted to assess the ergonomic hazards of ironwork job tasks associated with concrete reinforcement work at a large highway construction site. PATH (posture, activity, tools, and handling) analysis, a work-sampling method, was used to provide task-based estimates of the percentage of time ironworkers spent in specified postures of the trunk, arms, and legs; performed activities; used tools; and handled loads. A total of 2128 PATH observations were made of 17 ironworkers performing 5 job tasks: (1) ground-level reinforcement bar (rebar) construction, (2) wall rebar construction, (3) ventilation rebar construction, (4) preparation work, and (5) supervising. Nonneutral trunk postures were observed frequently (exceeding 30%) and manual material handling (MMH) was the most commonly observed activity (exceeding 20%) for all job tasks except supervising. The percentage of time workers spent in specific postures, activities performed, tool use, and MMH activities differed significantly between the five main job tasks, even when supervising was excluded from the analysis. It was concluded that ironworkers are exposed to significant ergonomic hazards when performing concrete reinforcing tasks, and that opportunities exist for the implementation of ergonomic interventions. Further, the results of this study can be used to target specific hazardous tasks for ergonomic interventions and confirms the need to use a task-based exposure assessment strategy to properly assess ergonomic risk profiles for nonstructured jobs such as construction.

An ellipsoidal representation of human hand anthropometry

The goal of this study was to collect anthropometric data that describe the geometry of the surface of the hand and to model this anthropometry as a function of gross external hand measurements. The depth and breadth of each segment of the hand were measured at points that were spaced at approximately equal distances between the joints of the hand. Linear models using hand breadth as the independent variable explained from 12% to 47% of the variation in segment breadths and from 6% to 74% in segment depths. Ellipsoids are used in biomechanical models as an efficient mathematical description of the shape of kinematic segments for use in the determination of contact with other objects. Therefore the primary objectives of this study were to approximate the semiaxis dimensions for these hand segment contact bodies using a linear model of the gross anthropometry and to evaluate the accuracy with which ellipsoids describe the geometry of the hand segments. Graphical comparisons showed that differences between the ellipsoidal approximations and the breadth and depth measurements were largest near the joints. Data collected in this study could be used to create a set of overlapping ellipsoids that would provide a more accurate representation of hand geometry, and this representation could be adapted to biomechanical models that use ellipsoids to define segment geometry.

Paclitaxel/sirolimus combination coated drug-eluting stent: in vitro and in vivo drug release studies.

Paclitaxel and sirolimus are the two major drugs for the treatment of coronary arterial disease in current drug-eluting stents. The two drugs can effectively inhibit the in-stent restenosis through their independent pathways and show synergistic effect in preventing tumor tissue growth. We hypothesize that the combination of the two drugs in a drug-eluting stent (DES) can also effectively suppress the neointima growth in the stented artery. The present work was focused on the investigation of paclitaxel/sirolimus combination release profiles from a novel biodegradable polymer (poly (D, L-lactide-co-glycolide)/amorphous calcium phosphate, PLGA/ACP) coated stent both in vitro and in vivo. For the in vitro, the drug releasing profiles were characterized by measuring the drug concentration in a drug release medium (Dulbeccos phosphate buffered saline, DPBS, pH 7.4) at predetermined time points. For the in vivo, a rat aorta stenting model was employed. The results showed that both paclitaxel and sirolimus had a two-phase release profile both in vitro and in vivo, which is similar to the drug release profile of their individual coated DESs, and there is no evident of interference between two drugs. The data suggest that paclitaxel and sirolimus can be combined pharmacokinetically in a DES for the treatment of coronary arterial diseases.

Emerging participatory approaches to ergonomic interventions in the construction industry

The Central Artery/Third Harbor Tunnel (CA/T) construction project in Boston is the largest and most costly highway construction project ever undertaken in the United States. The Construction Occupational Health Project (COHP) of the Work Environment Department at the University of Massachusetts-Lowell was established to conduct exposure assessment and to develop, introduce, and evaluate interventions in the areas of ergonomics and industrial hygiene on the CA/T project. For both political and practical reasons, COHP is using a participatory approach to intervention in the construction industry. The research process is employing participation at all the levels of the construction hierarchy in the form of various advisory groups. These advisory groups have been formed from existing joint labor-management advisory committees and are presently engaged in two participatory intervention activities: (1) evaluations of intervention ideas, and (2) comparisons of safety systems.

Upper extremity kinematic and kinetic adaptations during a fatiguing repetitive task

Repetitive low-force contractions are common in the workplace and yet can lead to muscle fatigue and work-related musculoskeletal disorders. The current study aimed to investigate potential motion adaptations during a simulated repetitive light assembly work task designed to fatigue the shoulder region, focusing on changes over time and age-related group differences. Ten younger and ten older participants performed four 20-min task sessions separated by short breaks. Mean and variability of joint angles and scapular elevation, joint net moments for the shoulder, elbow, and wrist were calculated from upper extremity kinematics recorded by a motion tracking system. Results showed that joint angle and joint torque decreased across sessions and across multiple joints and segments. Increased kinematic variability over time was observed in the shoulder joint; however, decreased kinematic variability over time was seen in the more distal part of the upper limb. The changes of motion adaptations were sensitive to the task-break schedule. The results suggested that kinematic and kinetic adaptations occurred to reduce the biomechanical loading on the fatigued shoulder region. In addition, the kinematic and kinetic responses at the elbow and wrist joints also changed, possibly to compensate for the increased variability caused by the shoulder joint while still maintaining task requirements. These motion strategies in responses to muscle fatigue were similar between two age groups although the older group showed more effort in adaptation than the younger in terms of magnitude and affected body parts.