1. 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

2. 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.

3. 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

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

5. 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

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

7. 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)

8. 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”

9. 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 (±3.2) yrs
Weight (±4.6) kg
Height (±3.7) cm

10. 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

11. 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

12. Methods - Data Collection
Muscles Studied
Upper Trapezius
Erector Spinae

13. 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

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

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

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

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

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

19. 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

20. Thank You! Questions?