Metabolic Equivalents of the Activity Card Sort: A Coding Study

PURPOSE: Interrater reliability and content validity of two coding systems for establishing the metabolic equivalent (MET) of items from the Activity Card Sort (ACS; Baum & Edwards, 2001) are described. We aimed to determine (1) interrater reliability of two MET coding systems, (2) content validity of the systems to discriminate categories of physical effort, and (3) MET values for activity domains of the ACS for each system.

BACKGROUND: The ACS measures older adults’ participation scores for retention, loss, or addition of activities. The Compendium of Physical Activities (CoPA; Ainsworth et al., 2011) and the American Time Use Survey (ATUS; Tudor-Locke, Washington, Ainsworth, & Troiano, 2009) coding systems were compared and interrater reliability was calculated to determine if one system is better suited to code MET values of ACS items.

METHOD: A descriptive design was used to address the study aims. The unit of analysis was the 89 ACS items. There are four activity domains: instrumental (20 items), low-demand leisure (35), high-demand leisure (17), and social (17). Each activity card has a descriptive photograph and label. We used the CoPA (21 activity categories) and ATUS (17 categories) to assign MET values. Both systems are documented as being valid for assessing physical activity participation and categorization based on energy use. Both also include similar activities, but some coding schemes differ. For example, the ATUS uses one category for all sports and recreation, while the CoPA separates these into categories like bicycling and dancing. Additionally, exact MET values attributed to activities sometimes differ between the systems.

Two ACS-trained occupational therapy graduate students independently coded activities using the two MET systems. To assign MET values, each coder chose the activity that most closely resembled the photograph on the ACS card. Coders used the photograph because the coding systems gave different MET values for the same activities (e.g., the CoPA has 25 different MET values for “running,” including running a marathon [13.3] and jogging in place [8.0]). Consistency reliability was calculated between coders with Pearson correlations, and intraclass correlations (ICCs) were calculated to determine the effective interrater reliability of averaged MET values for the two coders for each coding system. Reliability coefficients that reached a magnitude of .80 were deemed satisfactory. We measured content validity between systems as percentage of agreement with three categories of physical effort: light, <3 METs; moderate, 3–6 METs; and vigorous, >6 METs. Coders’ ratings were averaged to assign a MET value for each activity for each system.

RESULTS: Interrater reliability for the CoPA (r = .88; ICC = .93) and the ATUS (r = .94; ICC =.97) were both satisfactory. There was 92% (82 of 89) agreement across the three physical effort categories, suggesting adequate content validity. Across domains of the ACS, high-demand leisure had the highest MET values (CoPA = 4.62 METs; ATUS = 4.54 METs). The lowest average MET value domain of the CoPA was low-demand leisure (1.8 METs) and for the ATUS, social (1.82 METs).

CONCLUSION: These findings show satisfactory interrater reliability between coders for ACS items. MET values for the ACS were coded most reliably with the ATUS, yet CoPA values were also reliable. The assigned MET values produced from the current study may assist occupational therapists working with older adults to offer more targeted strategies and compensation assistance so older adults can continue participating in valued activities. Future studies will use these MET values to determine if ACS scores relate to patterns of activity change in older adults, specifically in people living with Parkinson’s disease and their caregivers.

References

Ainsworth, B. E., Haskell, W. L., Herrmann, S. D., Meckes, N., Bassett, D. R., Jr., Tudor-Locke, C., . . . Leon, A. S. (2011). 2011 Compendium of Physical Activities: A second update of codes and MET values. Medicine and Science in Sports and Exercise, 43, 1575–1581. https://doi.org/10.1249/MSS.0b013e31821ece12

Baum, C. M., & Edwards, D. (2001). Activity Card Sort. St. Louis, MO: Washington University at St. Louis.

Husband, M., Harris, C., Kapustka, D., Fitzmaurice, C., Schoen, E., Rengering, E., . . . Velozo, C. (2016, April). Metabolic equivalent as an underlying component of ADL measures. Poster session presented at the AOTA Annual Conference & Expo, Chicago.

Tudor-Locke, C., Washington, T. L., Ainsworth, B. E., & Troiano, R. P. (2009). Linking the American Time Use Survey (ATUS) and the Compendium of Physical Activities: Methods and rationale. Journal of Physical Activity and Health, 6, 347–353. https://doi.org/10.1123/jpah.6.3.347