By Matt Darnell
Aerobic literally means "with oxygen" and refers to how muscles use oxygen to make energy. Aerobic work includes any heart-rate-increasing exercise performed at a moderate intensity level for more than three minutes.
Anaerobic work is high-intensity activity that lasts less than three minutes. For this type of exercise, your body relies on energy stored in your muscles.
VO2 Max is the highest rate at which your body can take in and use oxygen during exercise.
Anaerobic Threshold is the point during activity when your body starts working anaerobically, because it is no longer getting the oxygen it needs. Lactic acid starts accumulating in your bloodstream faster than it can be used. It's when you feel like you're hitting the wall.
Interval Training sessions involve repeated bouts of activity separated by periods of rest or lighter activity. Depending on the length of exercise and rest periods, interval training can be either aerobic or anaerobic.
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