The efficacy of Motivational Interviewing toward enhancing self-regulated physical activity.

Objectives: The objective was to investigate the efficacy that motivational interviewing (MI) had upon increasing self-regulated physical activity (PA) and adherence to PA. Specifically, it was expected participants receiving MI would significantly increase PA compared to a control group. Design: An independent group design randomised participants into a treatment group receiving MI and a control group during eight weeks of self-regulated walking. Method: Six control (age 28.00 SD+ 9.70 years) and five treatment (age 24.20 SD+ 7.76 years) female participants volunteered to take part in an eleven week intervention consisting of: a) one week baseline PA recording, b) eight weeks PA monitoring, c) two week washout period, d) one week PA follow-up assessment. The treatment group received MI eight times during the eight week monitoring period. The efficacy of MI was evaluated via: a) increases in pedometer (Yamax SW200 Digi-Walker) steps, b) estimated minutes of PA (Scottish Physical Activity Questionnaire), c) stages of change (SoC) questionnaire, and d) self-determination (Behavioural Regulation in Exercise Questionnaire 2). Results: Repeated measures of variance showed non-significant (P = < 0.05) changes in pedometer steps, minutes of PA, self-determination and SoC throughout the intervention. Furthermore, discrepancies among subjective and objective measures of PA were observed. Conclusions: The disparities among the objective and subjective measures of PA are linked to the habitual nature of PA, whereby efficacy beliefs are impacted by faulty self-knowledge. Discrepancies between SoC and self-determination also indicated inconsistent efficacy and outcome expectations towards PA. Thus, future research might investigate the impact that MI has upon self-knowledge and efficacy expectations with regard to PA participation.