## 1 Introduction  
Cardiovascular diseases (CVDs) constitute one of the major health problems in Europe, accounting for about 45% of all causes of death, and with a continuously increasing prevalence [1]. This high incidence and prevalence of CVD leads to a high personal health burden and places a huge burden on society, with EUR 210 billion/year spent on the management of CVD [2]. Considerable differences in prevalence are observed between European countries, mainly associated with the prevalence of several risk factors, such as smoking, obesity, diabetes, and physical inactivity. Physical activity has been recognized to have a beneficial effect on the prevention of CVD. Therefore, exercise training is a central part of secondary prevention programs, referred to as \"cardiac rehabilitation\" (CR) [3]. Based on the clinical guidelines [3], moderate exercise for at least 150 min per week and behavioral changes towards a less sedentary lifestyle can reduce cardiovascular risk factors. The WHO [4] defines adherence as the extent to which a person's behavior (e.g., lifestyle changes) corresponds with current recommendations. Adherence to physical activity can be quantified in several ways [5]. In general, adherence to lifestyle changes has been recognized as a crucial component towards better management of patients with chronic disease, but this goal is rarely achieved [6; 7]. However, despite the beneficial effects of CR, participation rates remain low, with less than 40% of eligible patients attending CR programs [8; 9]. Low socioeconomic status, age, gender, the proximity to a CR center, and behavioral aspects such as lack of motivation and reduced self-efficacy have been identified [9] as the main barriers to CR participation. In order to overcome the aforementioned barriers and increase both uptake and adherence to CR, home-based telerehabilitation services have been developed, considering the advances in technology and the Internet of things (IoT) [10]. Indeed, telerehabilitation programs have proven to be a safe and effective approach to managing heart failure (HF) patients [11]. In a meta-analysis by [PERSON] [12], it was found that center-based and home-based CR had equal effects on exercise capacity, while others found equal effects on quality of life (QoL) and cost-effectiveness [13]. One major advantage of modern telerehabilitation services is the personalized guidance that they offer, which is facilitated by the availability of low-cost and unobtrusive devices that integrate various sensors that are useful for the quantification of exercise response [11]. For example, accelerometry data can be used to evaluate the volume of exercise, heart rate sensors are able to capture exercise intensity, and geolocation services allow for the estimation of walking distance. However, the plethora of available devices also leads to a large heterogeneity in intervention design, ranging from motivational messages [14] to telephone counseling [15] or personalized real-time adaptation of exercise sessions [16]. However, the problem of non-adherence is also apparent in home-based or self-management interventions [17], where significant variations in the levels of adherence have been reported compared to center-based CR programs. Several RCTs [18] and meta-analyses [19; 20] have reported that patient-centered approaches show an improvement in patient adherence to CR programs. However, most of these studies were observational and used subjective information and self-reports to quantify adherence [21]. Both patient-related factors and intervention design could be addressed to increase adherence [22]. In a systematic review, it was found that both the program characteristics and personal factors, including health and cognition status, influence adherence to exercise programs [23]. [PERSON] et al.