Scientific citation please? A common term or a scientific term?
Both really, this term is understood and used in sport science, certainly not common among the population that doesn't train for endurance sport. But you'll find legit sources in Human Kinetics if you do the research (I'm not doing that for you), and Pfitzinger has some very accessible descriptions in his marathon training book. Also described by Bompa et al. Again, not claiming Kara has some great knowledge of this, just that it's a common training term.