Inactivity is the most widespread health risk factor in modern societies today, causing not only

individual health problems but also immense costs for the healthcare systems. This emphasizes the

need for improving population-wide impact of activity interventions, with particular attention to costeffectiveness, scalability, and delivery channels. In this paper, we present the theory-motivated design

(drawing on the transtheoretical model) and empirical test of an IT-based physical activity

programme (Personal Health Manager, PHM). In order to be as cost-effective as possible, the PHM

was designed to have only few face-to-face contacts and to deliver supervision through the internet.

Our design and implementation proved to be successful in a pilot test with 88 employees of an

automotive company. The PHM increased participants’ activity, motivational readiness for change,

functional capacity and transported the feeling of being well taken care of. Enhanced supervision did

not increase performance. The results are first evidence that internet-mediated supervision can be

successful in promoting physical activity and provide a starting point for investigating the role of faceto-face-contact and service levels in physical activity programs. The PHM and similar designs are

also relevant to practice as the semi-automation makes them eligible for large-scale corporate or

public health programs.