Physical performance tasks: what are the underlying constructs?

OBJECTIVES

To investigate the structural validity of a battery of physical performance tasks and to investigate the construct validity of the resulting factors.

DESIGN

A measurement study.

SETTING

A large, private orthopedic clinic and a physical therapy clinic in an urban area.

PARTICIPANTS

One hundred three consecutive adult patients with low back pain who were referred for physical therapy assessment.

INTERVENTIONS

Not applicable.

MAIN OUTCOME MEASURES

The physical performance battery was composed of the 50-foot speed walk, 5-minute walk, repeated trunk flexion, sit to stand, loaded reach, rollover tasks, and Sorensen upper-body lift. Participants also completed 5 self-report measures.

RESULTS

Two correlated (.74) factors, speed and coordination and endurance and strength, were derived from the physical performance tasks. The Sorenson upper-body lift task was the only indicator that was not useful in defining the factors. Both factors had statistically significant correlations with measures of physical disability, lack of self-efficacy, and negative affect. Both factors had a trivial correlation with a numeric rating of pain intensity.

CONCLUSIONS

There is support for 2 meaningful empiric groupings (ie, the derived factors) of the performance tasks. Pain intensity had a trivial overlap with speed-coordination and endurance-strength factors.