Your genetic variation is well connected to your VO2max and overall aerobic potential. There are several genes that influence and count for your training responses. For instance, HIF1A gene encodes a protein that is an important regulator of the body´s response to low oxygen environment. When oxygen is lacking, this protein starts the process of making new blood vessels and red blood cells which will increase oxygen delivery. It is also a regulator of glucose metabolism, a central source of fuel during anaerobic or power-based exercise.