Previous research has highlighted the role of internal states in the experience of flow in the sports performance context. This systematic review investigates the relationship between psychological correlates, personality dispositions, traits and internal states (motivation, goals, focus, and arousal) with the experience and occurrence of flow in professional athletes. There have been identified 17 studies published between 2012 and 2017 updating and extending Swann, Keegan, Piggott and Crust's (2012) systematic review. The results indicate that specific psychological correlates, personality traits and dispositions, and internal states are strongly correlated with the appearance of flow. The present study adds to the current research on the sports' flow experience highlighting the importance of constructs, such as confidence, anxiety, commitment, motives, goals, attention, optimal focus and arousal, and the "letting it go" state.The basic aspects of the flow state are, as outlined by Csikszentmihalyi (1996): 1) a merging of action and awareness, 2) a sense of control, 3) a transformation of time, and 4) an autotelic experience. Important key conditions to facilitate the flow experience are: a) clear goals and immediate feedback in a structured activity, b) balance of challenge versus skills, and c) an autotelic personality. Thus, in the flow experience, attentional resources are fully invested in the task at hand. Furthermore, the loss of self-consciousness and pursuit of clear goals result in the exclusion of thoughts and feelings that people experience as negative. The experience becomes enjoyable and rewarding as we gain a sense of control over what we are doing. Our attention is so fully invested in the task at hand that there is little, or none left over to devote toward the mental processes that contribute to the experience of duration. Finally, we want to repeat the activity for the sake of the experience itself, not expecting external rewards but experiencing an intrinsic motivation towards the activity. The concept of flow, therefore, is based both on the self-determination theory (SDT) and the self-determination continuum as presented by Deci and Ryan (2002), and the autotelic personality concept (Csikszentmihalyi, Rathunde, & Whalen, 1993).Rules and a clear outline facilitate flow experiences because they help to orientate the person while feedback gives information that they are on the right pace towards their desired goals. Also, in order to reach and maintain positioning within the flow channel, there must be a delicate balance between our skills and challenges level, otherwise we might experience boredom or apathy (Csikszentmihalyi, 2009; Hefferon & Bonniwell, 2011). Flow lays as a growth principle in the maintenance of the challenge-skill balance. Commitment and motives towards mastering the challenges and skills drive the person towards practice and gaining expertise in a task (e.g. a sport). That continuum fosters enjoyment and peak performance as a result. The feeling of enjoyment and intrinsic...