An investigation of the construct validity of free-living physical activity as a marker of functional ability in people with chronic low back pain

Cormac Ryan, Heather Gray, Mary Newton, Malcolm Granat

Research output: Contribution to conferencePoster

Abstract

INTRODUCTION: The aim of the study was to investigate the construct validity of free-living physical activity (PA) monitoring
as an objective outcome measure of functional ability in people with chronic low back pain (CLBP). Levels of known difference validity, convergent validity and responsiveness to change were assessed.
METHODS: A sample of 38 individuals (25F, 45±11 years) with CLBP was recruited. These individuals were assessed in terms of free-living PA level, self-reported functional ability and physical performance testing (PPT). Known
difference validity was investigated by comparing healthy participants (n = 15, 12F, 39±11) to those with with CLBP, to identify if free-living PA level differed between the groups. Known difference validity was further investigated by examining the change in free-living PA for the participants with CLBP following therapeutic intervention. Convergent validity was investigated by exploring the correlations between free-living PA and self reported functional ability and physical performance testing (PPT) at a single point in time. Convergent validity
was further assessed by looking at the correlation between the changes in all three outcome measures following a therapeutic intervention. The responsiveness of free-living PA to change was assessed using effect-size
statistics.
RESULTS:The individuals with CLBP were less active than the group of matched controls and the free-living PA levels
of the individuals with CLBP increased following the therapeutic intervention. These findings provide evidence of known difference validity. At a single point in time, relatively weak but statistically significant relationships
between free-living PA and both self-reported functional ability and PPT were identified. There was a similar relationship between change in free-living PA and change in self-report and PPT over time. These findings demonstrated evidence of convergent validity. Free-living PA responsiveness to change was small to moderate.
DISCUSSION : This study found evidence of construct validity of free-living PA level as a marker of functional ability in individuals with CLBP. The weak relationships between free-living PA level and both self-reported functional
ability and PPT, suggest that they all measure related but distinct components of the functional ability construct. Using all three measures may produce a more comprehensive assessment of functional ability in this
patient group. The responsiveness to change of free-living PA was lower than for self-reported functional ability and PPT. A limitation of this study was the small sample size and the collection of different forms of validity
evidence from the same individuals.
CONCLUSIONS: Measurement of free-living PA level may be a useful adjunct to current methods of functional ability assessment in people with CLBP and this may facilitate a more comprehensive assessment of the functional
ability construct.
Original languageEnglish
Pages119-119
Number of pages1
Publication statusPublished - 2008
EventInternational Conference on Ambulatory Monitoring of Physical Activity and Movement - World Trade Center, Rotterdam, Netherlands
Duration: 21 May 200824 May 2008
https://ismpb.org/wp-content/uploads/2016/11/2008Program.pdf

Conference

ConferenceInternational Conference on Ambulatory Monitoring of Physical Activity and Movement
CountryNetherlands
CityRotterdam
Period21/05/0824/05/08
Internet address

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Keywords

  • back pain
  • RCT
  • activity monitoring

Cite this

Ryan, C., Gray, H., Newton, M., & Granat, M. (2008). An investigation of the construct validity of free-living physical activity as a marker of functional ability in people with chronic low back pain. 119-119. Poster session presented at International Conference on Ambulatory Monitoring of Physical Activity and Movement, Rotterdam, Netherlands.