Report on the results of a study on workers' postural instability while lifting or hanging drywall sheets.
According to the
Bureau of Labor Statistics, falls accounted for 32% of traumatic injuries
among drywall installers (1992-1995). Falls are significant contributing
factors in causing fractures, musculoskeletal injuries, or even fatalities.
Drywall lifting and hanging tasks require workers to handle heavy and
bulky drywall sheets and maintain awkward postures to install materials
onto the wall or ceiling. Previous studies indicated that drywall lifting
and hanging tasks cause more fall-related injuries than any other tasks.
Activities associated with these two tasks often result in muscle fatigue
and propensity for loss of balance. In addition, drywall installers are
exposed to high risk of falls since they often work at elevations. The
objective of this study is to investigate workers' postural instability
while lifting or hanging drywall sheets. Forty-seven construction workers
(mean age = 34.7±9.1 years) with at least 6 months of drywall installation
experience (mean experience = 9.1±6.8 years) participated in this
study. Each subject performed four lifts of a 4 foot by 8 foot drywall
sheet using one of the four lifting methods: 1) vertical lift of the drywall;
2) horizontal lift of drywall with both hands positioned on the top of
the drywall; 3) horizontal lift of drywall with both hands positioned
on the bottom of the drywall; and 4) horizontal lift of drywall with one
hand positioned on the top and one positioned on the bottom. The subject
was also asked to perform 4 hanging trials using one of the four hanging
methods: 1) vertical hanging onto the wall; 2) horizontal hanging onto
the wall; 3) vertical hanging onto the ceiling; and 4) horizontal hanging
onto the ceiling. This study is a completely randomized design with lifting
and hanging methods randomly assigned to each subject. Workers' postural
instability was quantified using a piezoelectric type force platform.
Two postural sway variables (sway length and sway area) and two indices
(Index of Proximity to Stability Boundary (IPSB) and Stability Area Ratio
(SAR)) were used to describe workers' propensity for loss of balance associated
with drywall lifting and hanging. Analyses of variance showed that the
effects of different lifting and hanging methods were significant on the
two postural-sway variables (all p values < 0.001) and the two postural
instability indices (all p values < 0.002). Horizontal lift of a drywall
sheet with both hands positioned on the bottom of the drywall was found
to cause significantly greater postural sway and instability than vertical
lift or horizontal lift with both hands positioned on the top of the drywall
(all p values < 0.01). Postural sway and instability associated with
horizontal hanging onto the ceiling were greater than for vertical hanging
onto the wall or horizontal hanging onto the wall (all p values < 0.001).
All the simulated drywall lifting and hanging tests were performed at
the floor level. Workers' postural sway and instability may be more drastic,
leading to higher risk and severity of fall, if workers perform drywall
lifting and hanging at elevations, such as ladders, scaffolds, and stilts.
Results from this study indicate that, to minimize postural instability,
workers should avoid lifting drywall sheets in the horizontal position
with both hands on the bottom of the sheet. Workers should also avoid
horizontal hanging of drywall sheets onto the ceiling (method 4).