This paper offers a brief synopsis of the five preceding papers which constitute the proceedings of the symposium “Mechanistic basis of the slow component of &OV0312;O2kinetics during heavy exercise.” The key features have been taken from each paper and a coherent position regarding the site and potential underlying mechanisms for the “excess” &OV0312;O2is presented. The hypothesis is developed that some aspect of fiber type recruitment patterns might be responsible for this phenomenon. Elucidation of the precise determinants of &OV0312;O2during heavy exercise is fundamental to our understanding of muscle energetics. Furthermore, certain patient populations, whose exercise tolerance is limited by impaired cardiovascular and/or respiratory capacity, may benefit from interventions designed to constrain the magnitude of the &OV0312;O2slow component.