High levels of physical activity, low sedentary behaviour and a sleep duration of 7-8 hours are associated with beneficial health outcomes. When aiming to promote these behaviours, they should be studied and promoted together, since a change in the duration of one behaviour affects the duration of another. These behaviours have until now, however, mostly been studied and intervened upon in isolation. This project proposes to study 24-hour combined patterns of sleep, physical activity and sedentary behaviour. Behaviours will be studied for a longer period, to take variations in time into account. Smart wearables will be used as monitoring devices. To successfully promote these behaviours, it has been suggested that an intervention where individuals can set their own goals, create plans and anticipate barriers is most effective. Moreover, the more specific the intervention is to the person's needs, the more likely it will be effective. This project will thus study behavioural patterns and profiles, and time-and place specific behavioural determinants (e.g. via GPS and self-report logs on a mobile app), to provide specific tailored support in behaviour change. A randomized controlled trial will test the intervention's effectiveness. This type of tailoring is novel and expected to create higher effectiveness on behavioural and health outcomes. Intervening on several behaviours jointly is expected to have a multiplicative effect on health.