Reliability of moderate-intensity and vigorous physical activity stage of change measures for young adults

The purpose of this study was to examine the reliability of stage of change (SOC) measures for moderate-intensity and vigorous physical activity in two separate samples of young adults. Staging measures have focused on vigorous exercise, but current public health guidelines emphasize moderate-intensity activity.

For college students in the USA (n=105) and in Australia (n=123), SOC was assessed separately on two occasions for moderate-intensity activity and for vigorous activity. Test-retest repeatability was determined, using Cohen's kappa coefficient.

In both samples, the reliability scores for the moderate-intensity physical activity staging measure were lower than the scores for the vigorous exercise staging measure. Weighted kappa values for the moderate-intensity staging measure were in the "fair to good" range for both studies (0.50 and 0.45); for the vigorous staging measure kappa values were "excellent" and "fair to good" (0.76 and 0.72).

There is a need to standardize and improve methods for staging moderate-intensity activity, given that such measures are used in public health interventions targeting HEPA (health-enhancing physical activity).