Evaluation of a Construction Block Lift-Assist Device Presented by: Christopher Moore Suman Chowdhury, Ph.D., Christopher Moore, M.S., Ashish D. Nimbarte, Ph.D. Industrial and Management Systems Engineering, West Virginia University

Background Work-related musculoskeletal disorders (MSD) among construction workers account for over 37% of all injuries that result in days away from work (Schneider, 2001). Incidence rate of MSD to the neck, back and upper extremities is 6.2 per 100 full time employees (Rempel et al. 2006). Highest of all the U.S. industries. MSD among the construction workers associated with manual materials handling (NIOSH, 2007) 32% of Workers’ Compensation claims among the construction workers Average cost per claim: $9,240 25% of the cost of all claims across all the industries.

Background Among construction workers, masons have the highest rates of injuries resulting from overexertion due to manual materials handling activities (Anton et al., 2004) Workers compensation claims in Washington State (Silverstein et al., 2002) Industries at the highest risk of work-related MSD of neck, back and upper extremity: Trucking and courier services Nursing Masonry Air transportation Residential construction

Background Masonry work involves lifting of concrete blocks/concrete masonry units (CMUs) Construction of retaining walls Residential construction Average weight = 35 - 40 pounds Average weight = 80 pounds

Background Possible intervention: Light-weight construction blocks (NIOSH, 2004) Weigh 30-40% less than regular block Adjustable height scaffolding Keep working height between 60 and 90 cm Anton et al. (2005) Lower wall course  Lower muscle activation reported Higher wall course  No difference

Background Problems: Possible Intervention Odd shape and poor coupling Difficult to grip Heavy Average weight: 80 pounds Possible Intervention

Electrical activity of shoulder/back muscles Background This tool is claimed to make the lifting and maneuvering of CMUs easier and safer No quantitative data is available evaluating its effectiveness. Objective: To evaluate the effect of block handling tool on the musculoskeletal loading during simulated lifting and lowering tasks Musculoskeletal loading Electrical activity of shoulder/back muscles (Electromyography) Lifting technique (3D Kinematics)

Experimental Design Three-factor Factorial Design: Factor 1: Lifting Height – Two Fixed Levels 17”  Simulate placement on 3rd row 29”  Simulate placement on 5th row Lifting Ht. 2 (29”)   Lifting Ht. 1 (17”) Ground Level (0”) Block #4 Block #3 Block #2 Block #1 Pallet 6” 5”

Experimental Design Three-factor Factorial Design: Factor 1: Lifting Height – Two Fixed Levels 17”  Simulate placement on 3rd row 29”  Simulate placement on 5th row Factor 2: Type of Task – Two Fixed Levels: Lifting Lowering Factor 3: Use of Lift-Assist Tool – Two Fixed Level With tool Without tool Participants: Seven male participants Age - 23.5(±3.2) yrs Weight - 66.2 (±4.6) kg Height - 172 (±3.7) cm

Methods - Equipment Lifting Kinematics Eight Camera Optical Motion Capture System (Vicon Motion Labs) Set of 53 retro-reflective markers (12mm diameter) CMotion Visual3D Biomechanical Analysis Software Uses motion capture data to drive model motion

Disposable, Self-adhesive Ag/AgCl Snap Electrodes Methods - Equipment Muscle Activity Surface Electromyography System (Noraxon, Inc.) Disposable, Self-adhesive Ag/AgCl Snap Electrodes Telemyo 2400 EMG system

Methods - Data Collection Muscles Studied Upper Trapezius Erector Spinae

Methods - Data Collection/Processing Electromyography sampled at 1000Hz Motion Capture sampled at 100Hz 3D Kinematics Data Processing Motion Capture data labeled, gap-filled, and exported CMotion Visual3D  Model motion capture data Output: 3D Joint Kinematics of Shoulder and Trunk. Electromyography Processing Demeaned and Full-Wave Rectified Low-pass Filtered with 4th-order dual-pass Butterworth digital filter Averaged to determine Mean Absolute Values (MAV) (Acierno et al. 1995) MAV normalized using individual muscles’ peak activation to obtain N-MAV

Results - Trunk Kinematics Degrees (°) Degrees (°) Lifting Lowering Lifting Lowering Trunk Flexion reduced by 20 degrees Trunk Bending reduced by 6 degrees

Results - Shoulder Kinematics Degrees (°) Lifting Lowering Shoulder Flexion increased by 25 degrees Shoulder Abduction/Adduction – No conclusive trends

Results – Low Back Muscle Activation N-MAV Erector Spinae activity significantly affected by use of tool during lifting task

Results – Shoulder Muscle Activation N-MAV Upper Trapezius activity not significantly affected by use of tool

Results – Duration of Task Seconds Duration of Task reduced from 6.83 seconds to 5.44 seconds (~ 20% Reduction)

Conclusions Lift-Assist Device + Reduced Trunk Flexion and Bending + Reduced Erector Spinae activity during lifting + Reduced Task Duration Increased Shoulder Flexion Better for Low Back and Trunk, potentially worse for Shoulder Limitations Inexperienced subjects – convenience sample of college students Symmetric lifting tasks only

Thank You! Questions?