chair diminished and a personal commitment to workstation
behaviors had yet to be made. Continuing in this logic, somewhere
between 6 and 12 months the behavior changes were adopted and
a signiﬁcant reduction in visual symptoms was seen.
Replication studies make crucial contributions in evaluating the
generalizability of an intervention. Each worksite offered its own
unique challenges with respect to pre-existing workstations, ofﬁce
layout, and expectations from management as to how the study
would be conducted. External validity represents the extent to
which a causal relationship holds over variations in persons,
setting, interventions, and outcomes (Shadish et al., 2002).
Observing the reduction in visual symptoms occur for the chair
with training group and training only group at ofﬁce worksites that
are completely different from each other serves only to raise the
external validity of the causal relationship between the interven-
tions and the visual symptoms. Successful interventions such as
these are easier and more practical to implement in other ofﬁce
environments because of the demonstrated generalizability.
This research was funded by grants from Steelcase, Inc. to the
University of Texas, The Upjohn Research Institute, York University
and Health and Work Outcomes and through the support of the
Liberty Mutual Research Institute for Safety. At the time of the study
Cammie Chaumont Menéndez was a doctoral student at the
University of Texas supported by NIOSH Occupational Injury
Prevention Training Grant T42 0H008421.
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Hours spent sitting in ofﬁce chair in typical week
Hours spent working at ofﬁce computer in typical week
Total computer use
Number of breaks taken in the past week
Repetitive hand and wrist activity
How much force used with hand and wrists in ofﬁce
Using skills at work
Authority at work
Decision latitude at work
Psychological demands at work
Level of glare produced by lighting
Level of distraction by noise at work
Satisfaction level of workplace privacy
Body mass index
General (Poor) Health
Taken any medicine at all for pain
Frequency of prescription pain medications taken in past month
Exercise to relieve pain
Type of eyeglasses lenses worn
Number of persons living in household
Did job demands prevent rest breaks from computer
C.C. Menéndez et al. / Applied Ergonomics xxx (2011) 1e66
Please cite this article in press as: Menéndez, C.C., et al., A replicated ﬁeld intervention study evaluating the impact of a highly adjustable chair
and ofﬁce ergonomics training on visual symptoms, Applied Ergonomics (2011), doi:10.1016/j.apergo.2011.09.010