Aerobic vs. Anaerobic

Aerobic and anaerobic exercise – the yin and yang of fitness, if you will. Cardio vs. strength, spinning vs. gym, cutting vs. bulking, each its own. But what exactly makes an exercise aerobic or anaerobic?

Aerobic exercise means involving or improving oxygen consumption by the body and sends to cardiovascular exercise, i.e. keeping your heart rate up through exercises such as walking, running, jogging, cycling, and swimming. Most aerobic exercises are lower in intensity and muscular contraction than anaerobic exercises. Anaerobic exercise is a high-intensityphysical exercise that last for a few seconds to up to 2 minutes (and gets those muscles burning).

Let’s say you’re doing some HIIT, for example. At some point when you exceed ~90% of max. heart capacity, you would’ve just went from an aerobic exercise to an anaerobic one. For what concerns strength training, it usually involves at least a minimum amount of purely aerobic exercises for warm-up or endurance purposes, like those 10 minutes on the treadmill for example. But what does really differentiate an aerobic exercise from an anaerobic one?

Why, how, what?

Anaerobic and aerobic exercises differ in the sense that the anaerobic ones are intense enough for lactate to form, while the latter are not.

When you’re performing a challenging exercise, the glycogen in your muscle cells breaks down to produce glucose, which undergoes glycolysis – a metabolic pathway (a fancy way of saying linked series of chemical reactions within the cell) that converts glucose into pyruvate/ pyruvic acid. When oxygen is present (aerobic), pyruvic acid supplies energy to the cells. When oxygen is lacking (anaerobic), pyruvic acid ferments to produce lactate.

  • When oxygen is present in the muscle cells ⇒ cellular respiration (aerobic)
  • When muscle cells are starved of oxygen ⇒ a metabolic process called lactic acid fermentation (so an anaerobic fermentation reaction) through which different hexoses (sugars) are converted into cellular energy and lactate.

So, when you’re training hard and depriving muscle cells of oxygen and causing this anaerobic fermentation reaction which produces lactate, you’ll begin to feel the effects of the lactate build-up. We might not know about lactate, but we all know the burn and the subsequent nausea. At this point you’re going to have (and want) to stop and allow the lactate to clear from the bloodstream.

So be careful, don’t exhaust yourself, train and eat smartly, set specific goals, find a balance and enjoy!

Thank you for visiting FHW!


  1. Aerobic exercise
  2. Anaerobic exercise
  3. Glycolysis
  4. Fermentation
  5. Lactic acid fermentation
  6. Lactic acid

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