The intent is to create oxygen debt that your body will work hard to recover from. (tctmed.com)
That intense burning sensation after a hard set — that's lactic acid building up in your muscles when your body enters into oxygen debt during intense exercise. (fitnessandpower.com)
Anaerobic activity incurs oxygen debt and a build - up of lactic acid; muscle imbalances and fatigue can result if continued. (sock-doc.com)