This chapter presents a validated multifaceted assessment and intervention protocol that has been used on hundreds of athletes over the last 15 years. It provides data and findings on athletes who have experienced the Carlstedt Protocol (CP), and recommends for the integration of procedures and methodologies that are vital to evidence-based applied sport psychology, and the credibility of the field of sport psychology/biofeedback and its practitioners. In addition to guiding biofeedback, the established athlete’s profile is a strong predictor of intervention amenability and compliance tendencies, pain thresholds, attentional control during competitive stress, coachability, and the placebo-nocebo effects. During critical moments, athletes possessing the most negative or disruptive constellation of primary higher-order (PHO) factors exhibit heart rate acceleration (HRA) prior to action, while those having the most facilitative or protective constellation continue to demonstrate heart rate deceleration (HRD).