**3.4 Behavioural mechanism: the role of self-esteem and self-efficacy**

Several aspects of the physical activity experience should be considered, such as enjoyment, mastery of skills/goals, autonomous motivation, social interaction, selfefficacy, self-esteem, and sense of belonging.

Exercise can promote several behavioural changes and may lead to a sense of mastery [27]. The activity-based perception of physical strength and flexibility is associated with increased physical self-esteem and, consequently, global selfesteem [28].

Self-efficacy is another important construct to better understand the relationship between exercise and mental health. Self-efficacy is an "individual's confidence in their ability to achieve specific, personally significant goals" [29]. Greater engagement in an exercise program has been shown to increase exercise self-efficacy [30] and improve self-image [31]. Self-esteem and self-efficacy mechanisms may explain the association between physical activity and depressive symptomatology [28].

Another important factor is the social interaction that the exercise can provide when performed as a group or just outdoors and is an important mediator of the association between exercise and depression, especially among older adults [32].
