Effects of a worksite intervention on autonomous motivation, exercise and health: a randomised controlled trial

Abstract

Background: The worksite is regarded as an important arena for health promotion initiatives due to less attrition and the presence of natural social networks. However, in order to support long-term behavioural change the programs must avoid cohesion and controlling the participants' motivation. This study aimed to test the hypotheses that a team-based exercise intervention would increase the participants’ autonomous motivation and perceived competence for exercise, and that this would increase their level of regular exercise as well as their cardiorespiratory fitness and health. Methods: N=xx participants were randomly allocated at team level to an intervention and a control condition. The team-based worksite intervention was designed based on the tenets of Self-Determination Theory (SDT) combined with techniques from Motivational Interviewing and self-help groups. Exercise motivation, exercise levels, cardiorespiratory fitness, blood pressure, waist, weight, and cholesterol were assessed at baseline and after 5 months. Findings: A MANOVA, repeated measures, indicated significant predicted effects in favor of the intervention group for all measures, except for physical activity that was marginally significant, and the non-significant outcomes of waist circumference and systolic blood pressure. Effect sizes (Cohens' d) were moderate for autonomy support (d=.62), autonomous motivation (d=.40) and cardiorespiratory fitness (d=.54), but small for all other measures. SEM analysis demonstrated a good fit between the data and the SDT process model. Discussions: Considering the moderate effects on motivation and cardiorespiratory fitness, which predicted all other health measures, offering autonomy supportive interventions at the work place has important practical implications for the health of employees.