Uzunova, Galina, Emilia Pavlova, Petar Somlev, Liuba Andreeva, and Lubomir Petrov. 2014. “Heart Rate and Blood Lactate Recovery After Queen’s College Step Test for Predicting VO2Max”. Jurnal Sains Sukan & Pendidikan Jasmani 3 (1):58-67. https://ojs.upsi.edu.my/index.php/JSSPJ/article/view/653.