The target number is based on age and can vary depending on your fitness level or whether you're resting or active. While ...

How can low oxygen levels lead to developmental abnormality and disease? It seems that proteins called hypoxia-inducible factors (HIFs) can affect gene expression in low-oxygen conditions.

The human body’s response to low oxygen could hold the key to understanding a number of persistent diseases ... At the molecular level, the presence of oxygen is so vital to so many functions ...

has brought the high-altitude, low-oxygen conditions of Mount Fuji ... functions faster than training at sea level. The oxygen concentration in the air at sea level is about 20.9 percent.