Physical activity plays a fundamental role in contrasting physiological deconditioning during ageing. Considering the complexity of the modifications that can occur in the physical activity domain, international guidelines recommend that older adults engage in a combination of aerobic, strength, flexibility, and balance training to promote active ageing and maintain adequate health status. For this reason, virtual coaches must be designed to prescribe appropriate physical activity plans in each of the specific target sub-domain. Technological solutions based on wearable devices and digital games are promising can be the key to a successful system. This chapter describes the physiological bases and the technological approaches implemented by the NESTORE system to evaluate users’ functional abilities and to propose a comprehensive and individualised coaching plan in the physical activity domain according to the internationally recognised guidelines. The main technological NESTORE components, co-designed together with users to monitor their status and behaviour and coach them to perform effective physical activity, are (i) the NESTORE wristband that will assess the users’ performances and monitor the main physiological parameters during aerobic activity and (ii) the NESTORE Pocket Odyssey mobile game that will engage the users during physical activities in the strength, flexibility and balance domains.

Virtual Coaches, also known as e-coaches, are a disruptive technology in healthcare. Indeed, among other usages, they might provide cost-effective solutions for increasing human wellbeing in different domains, such as physical, nutritional, cognitive, social, and emotional. This paper presents a systematic review of virtual coaches specifically aimed at improving or maintaining older adults' health in the aforementioned domains. Such digital systems assume various forms, from classic apps, to more advanced conversational agents or robots. Fifty-six articles describing a virtual coach for older adults and aimed at improving their wellbeing were identified and further analyzed. In particular, we presented how previous studies defined their virtual coaches, which behavioral change models and techniques they adopted and the overall system architecture, in terms of monitoring solutions, processing methods and modalities for intervention delivery. Our results show that few thorough evaluations of e-coaching systems have been conducted, especially regarding multi-domain coaching approaches. Through our analysis, we identified the wellbeing domains that should be addressed in future studies as well as the most promising behavior change models and techniques and coaching interfaces. Previous work illustrates that older adults often appreciate conversational agents and robots. However, the lack of a multidomain intervention approach in the current literature motivates us to seek to define future solutions.