Date of Award

May 2013

Degree Type


Degree Name

Doctor of Philosophy


Health Sciences

First Advisor

Barbara B. Meyer

Committee Members

Scott J. Strath, Lisa K. Berger, Michael J. Brondino, Carol Hartlein Sells


Adult, Intervention, Motivational Interviewing, Pedometer, Physical Activity, Web-Based


Interventions to enhance physical activity (PA) participation are needed given the high prevalence of under-activity and inactivity (CDC, 2001) and related occurrence of negative health consequences among the general adult population (Kung, Hoyert, Xu, & Murphy, 2008). Preliminary support for a therapeutic technique called Motivational Interviewing (MI) suggests promise for application to enhance PA participation (Burke, Arkowitz, & Menchola, 2003). Given the need for interventions to enhance PA and the preliminary support for MI as an intervention to increase PA, the aims of the current study were to: (a) determine if web-based MI is effective in enhancing PA participation, and (b) assess the mechanisms by which web-based MI enhances PA through changes in targeted cognitive variables. Participants (n= 23, under-active or inactive adults) engaged in four web-based MI sessions. Steps per day, PA, and cognitive variables were assessed across time. Efficacy of MI in enhancing PA participation was demonstrated through: (a) increases in steps per day (t[22]= 2.085, p = 0.049); (b) increases in total PA energy expenditure per week( χ2= 8.430, p = 0.015); and (c) increases in moderate intensity PA energy expenditure per week ( χ2= 13.853, p = 0.001). Although mediation of change in PA by cognitive variables was inconclusive due to sample size, changes were observed in the expected direction for cognitive variables including: (a) percentage of participants classified as action or maintenance stages of change (pre = 25.00%, post1= 70.81%, post2 = 68.18%); (b) decisional balance pros (F[2,42] = 16.192, p < 0.001) and cons (F[2,42] = 12.755, p < 0.001); (c) behavioral processes of change (F[2,20] = 7.010, p = 0.005); (d) self-efficacy (F[2,42] = 3.297, p =0.047); (e) intrinsic regulation for PA (F2,38] = 14.274, p < 0.001); and (f) PA enjoyment (F[2,2] =3.851, p = 0.038). Implications of the current findings are that web-based MI could be used as a tool to promote PA participation. Additional research is needed to corroborate the current findings, and to refine MI program content by further considering cognitive mediators in a larger sample.