Lifting capacity in construction workers with musculoskeletal disorders

After the evaluation of the reproducibility in two previous studies, validity
of the Ergo-Kit (EK) tests is the next clinimetric property that has to be
evaluated. From the literature, two aspects of validity are particularly
relevant for functional assessments: construct (convergent and discriminative)
and criterion-related (concurrent and predictive) validity.
In the construction industry, many jobs are characterized by heavy physical
work demands, often leading to work-related musculoskeletal disorders. The
Academic Medical Center and the Erasmus Medical Center, in collaboration with
the construction industry, developed an instrument to identify workers at risk
of long-term disability for work, the IRA. The EK tests are used to report the
functional physical capacity of workers with or without musculoskeletal
disorders. Before it can be legitimately applied in the field for
discriminative or evaluative purposes, the clinimetric properties of the EK
must be defined. For functional assessments, reproducibility, validity and
responsiveness are the most relevant clinimetric properties.

The purpose of this study is the evaluation of the construct and
criterion-related validity of the Ergo-Kit lifting tests in construction
industry employees on sick leave due to musculoskeletal disorders. The EK
lifting tests are: two static lifting tests, the Back-torso lift test (Btlt)
and Shoulder lift test (Slt), as well as three dynamic lifting tests, Carrying
Lifting Strength Test (Clst), Lower Lifting Strength Test (Llst) and Upper
Lifting Strength Test (Ulst).

After their inclusion in the study, construction industry employees are
assessed on the EK lifting tests (at baseline, about 6 weeks after first day of
work disability) and asked to fill in a questionnaire to determine the IRA and
the musculoskeletal disorders related pain intensity and disability. The same
measurements are repeated about 6 and 12 months after the first day of sick
leave. Return to work (RTW) is also recorded by the occupational physician.

For each subject, the following effort is expected during the EK lifting tests:
- Back-torso lift test and Shoulder lift test: maximal isometric pull capacity
/ total effort ± 16 seconds (2 x 4 sec per test)
- Carrying Lifting Strength Test, Lower Lifting Strength Test and Upper Lifting
Strength Test: maximal safe weight for lifting / total effort ± 90 seconds (4-6
x 8 sec per test)