We don't think of protein as a way to improve cardiovascular performance in the same light as we do with strength gains. If protein improves strength, does it also do the same with cardio? More specifically, does soy protein improve cardiovascular performance?
High intensity exercise is characterized by, "brief, intermittent bouts of vigorous exercise interspersed by periods of rest or low intensity activity." If the limiting factor of this activity is slow ATP synthesis, supplementing may show some improvement.