**1.1 Intellectual disability**

Approximately 200 million people, 1–3% of the global population, have an intellectual disability (ID) characterized by difficulties in learning and adapting to new environments. According to the American Association of Intellectual and Developmental Disabilities, ID is a condition characterized by IQ below 70–75 points, significant limitations in two or more adaptive areas such as communication or self-care, and manifests before the age of 18 [1].

Adults with ID are at increased risk of health decline associated with aging, low physical fitness, and related chronic diseases [2]. People with ID are not a homogeneous group as in many cases ID is not associated with a known biological etiology [3]. Some causes of ID happen before the delivery or soon after the birth due to genetic conditions, pregnancy complications, or toxic exposure, e.g., Down syndrome, fetal alcohol syndrome, fragile X syndrome, birth defects, and infections; other causes happen when the child is older, and these causes include severe head injuries, infections, or stroke [4].

In previous studies similar lifestyles were observed in persons with ID. Among the ID population, levels of smoking and regular alcohol intake are low compared to general population. Nevertheless, also the adherence to physical activity and healthy diet is poor [2, 5–8]. In sports, ID reduces the capacity to learn tactical concepts and to make correct decisions in constantly changing sport context. Besides, technical ability was found to be negatively

correlated with the level of ID as technical skills are dependent on cognitive processes such as information processing, visualization, and memory capacity [9]. Furthermore, the levels of physical activity among ID population are usually insufficient to achieve health benefits [3]. Previous studies on physical activity interventions show significant improvement in coronary heart disease risk factors after 12-week physical activity intervention [7], and the engagement in physical activity has been observed to improve also the social and general life competences needed for community inclusion [10, 11]. However, several barriers to engage physical activity such as lack of resources, limited options, or transportation constrain have been recognized [12].
