Table 1.

Contents of e-mail messages using the Health Action Process Approach (HAPA) model as the framework[27-29]

	Timing	Elements of HAPA	Content of the e-mail message
ORIENTATION
Preliminary meeting		Risk perception	· Information on the intervention, benefits of physical activity (PA), PA recommendations and walking
			· Instructions on monitoring PA with a pedometer and a logbook and assessing the average number of daily steps at baseline
			· Presentation of the ultimate goal of adding 4000 moderate-intensity steps to the baseline on 5 days of the week
MOTIVATIONAL PHASE (INTENTION BUILDING)
1st e-mail “Regaining strength by physical activity”	Within 2 weeks from the preliminary meeting	Positive outcome expectations, pre-action self-efficacy, action planning	· Benefits of integrating short bouts of PA into daily routine
			· The 1st goal of adding 2000 steps to the baseline on 2 days of the week
			· Simple tips for accumulating 2000 steps
VOLITIONAL PHASE (INTENTION): PLANNING, PREPARING AND INITIATING PHYSICAL ACTIVITY
2nd e-mail “Finding time through experience”	4 weeks after the 1st e-mail	Positive outcome expectations, risk perception, action planning, coping planning, self-monitoring	· Positive outcomes after even a short bout of PA
			· Examples of finding time and places to be more active
			· The 2nd goal of adding 2000 steps to the baseline on 5 days of the week
3rd e-mail “Making physical activity one’s own thing”	4 weeks after the 2nd e-mail	Positive outcome expectancies, risk perception, coping planning, maintenance self-efficacy, action planning	· Positive outcomes from being physically active
			· Examples of accumulating 4000 steps
			· The 3rd goal of adding 4000 steps on 2 days and 2000 steps on 3 days of the week to the baseline
VOLITIONAL PHASE (MAINTENANCE)
4th e-mail “Preparing oneself against barriers”	4 weeks after the 3rd e-mail	Action planning, coping planning, maintenance planning, maintenance self-efficacy	· The importance of regularity in PA
			· The most critical barriers for PA and the ways to overcome them
			· Example of a 30-minute walking session with 4000 steps
			· The 4th goal of adding 4000 steps on 4 days and 2000 steps on 1 day of the week to the baseline
5th e-mail “Getting oneself going”	4 weeks after the 4th e-mail	Action planning, coping planning, maintenance self-efficacy, recovery self-efficacy	· Tips for making it easier to “get oneself going”
			· The 5th goal of adding 4000 steps to the baseline on 5 days of the week
6th e-mail “Establishing a physically active lifestyle”	4 weeks after the 5th e-mail	Action self-efficacy, maintenance self-efficacy, recovery self-efficacy, action planning	· Learning sustainable ways to be physically active
			· The importance of regularity and the possibility of rewarding oneself
			· Maintenance of current PA level and supplementation with muscle strengthening exercises on 2 days of the week
			· A printable form for a weekly action plan and monitoring