Background: Physical inactivity is a significant public health problem with extensive evidence associating low levels of physical activity with increased mortality and morbidity and high healthcare costs (WHO, 2006). Encouraging the UK population (especially those who are most sedentary) to adopt a more active lifestyle has become a key aspect of Public Health Policy. Since working age adults spend up to 60% of their waking hours at work, the workplace provides a unique and appropriate opportunity to reach large numbers of individuals for physical activity promotion and is recognised as a site for primary prevention (WHO/WEF, 2008). Specifically, the NHS worksite has been identified as an important setting for health promotion with healthcare professionals targeted to ‘set the example´ for healthy behaviours as important role models to the general public (DH, 2009). This is particularly important given recent evidence that the health behaviours of NHS are not exemplary - many do not meet the health recommendations that they are expected to promote to their patients and are not active enough to benefit their health (DH, 2009). There is need for immediate action to encourage physical activity in NHS employees to ensure a healthy NHS workforce in the future and the infrastructure for supporting these initiatives is already in place in many NHS settings. However, these interventions must be innovative, efficacious and low cost. SMS and email are already known to be low cost, popular and convenient, and have considerable potential for health promotion both in clinical practice and in the workplace (Blake, 2008a; 2008b). E-mail and text messaging (SMS) interventions have already shown improvements independently in important health parameters in non-healthcare workplace settings (Block et al, 2008), and tailoring the communication for the individuals increases the relevance, credibility and receptivity of the message (Rimer & Kreuter, 2006). It is not yet known whether SMS has potential for the same, greater or less health behaviour change than email intervention although this is important as SMS would have greater resource implications for health communication in the long term. Aims: 1. To encourage participants to engage in ‘moderate physical activity for at least 30 minutes on most, preferably all, days of the week’. 2. To compare physical activity levels and self-reported quality of life in health professionals who receive a) access to generic information about physical activity, plus 2 weekly tailored emails for 12 weeks or b) access to generic information about physical activity, plus 2 weekly tailored SMS communications for 12 weeks. 3. To establish recruitment, attrition, follow-up rates, primary outcome and expected effect sizes to inform a large-scale definitive trial. The null hypothesis is that the proportion reporting an increase in exercise is identical in the two populations. Experimental protocol and methods: 12 week theory-based and guided intervention. Communication is tailored to individuals and designed to encourage meeting or exceeding daily physical activity recommendations. Two randomised groups: one receiving tailored text messages, and the other receiving tailored emails. Participants will complete an online questionnaire assessment at 4 points during the study: at baseline (pre-intervention), mid way (at 6 weeks), immediately following the intervention (at 12 weeks), and 1 month after the intervention (at 16 weeks).