I'm sure there are lots of us who aren't so clear on the distinction "aerobic" and "anaerobic": exercise, running, conditions, and so on. So: what is the difference between the two?

3 Answers 3


The body uses two different energy systems to fuel the body’s activity or exercise.

  1. Anaerobic - First the body uses the anaerobic system which has energy ready to go as soon as you start to use your muscles. Anaerobic means without oxygen.
  2. Aerobic - The second energy system, the aerobic system, kicks in when your short term, initial energy from the anaerobic system is used up. Aerobic exercise requires oxygen to produce energy.

    An exercise is determined to be aerobic vs anaerobic depending on which system is used to generate the energy needed for a particular exercise.

    Using running as an example, sprints are anaerobic and longer runs are aerobic exercise. When you sprint, you need explosive, quick energy to get going, so you use the anaerobic system. Readily available stores of ATP, glucose and glycogen provide energy quickly, but also deplete quickly. As these stores of ATP, glucose and glycogen deplete, you need a different system to produce ongoing energy.

    As you run longer distances, you generally lower the intensity so that you can keep going. You need endurance and a system that produces energy as long as you need it. The aerobic system uses oxygen and produces ongoing energy needed for endurance activities, exercises and sports.

    To exercise aerobically, you generally workout within a target exercise heart rate of between 60 to 85% of your maximum heart rate. Aerobic exercise trains your heart and lungs to become more efficient. Aerobic exercise is sometimes referred to as cardio. Examples of aerobic exercises are walking, running, cycling, hiking, swimming, water aerobics, aerobic dance, singles tennis etc.

    To exercise anaerobically, you generally work at a higher intensity for a shorter durations or intervals. Examples of anaerobic exercise are sprinting, strength training, and doubles tennis.

For more detailed information on how energy is produced, you may want to check into the Glycolysis, Krebs cycle, oxidative phosphorylation and Cori cycle.

  • Personally I'd say 60% is a bit low for aerobic exercise. When I'm zone training I'll be looking around 70%-80% for aerobic and 80%-90% for anaerobic
    – Jimsan
    Commented Mar 3, 2014 at 9:11
  • @Jimsan 55, Granted that Wikipedia is not the most accurate source, but it is the value they quote for aerobic exercise. This range would include the "fat burning" and "target heart rate" zones. Commented Mar 3, 2014 at 10:06
  • 2
    @Jimsan - Actually, exercising at ANY capacity is either aerobic, anaerobic or some mixture of the two. All that aerobic and anaerobic refer to is the primary energy source/pathway during exercise. "Zones" are arbitrary terms designed to present a complex concept in an easy to understand fashion. I grit my teeth occasionally when I hear HIIT trainees claim "Yeah, I spent a whole hour anaerobic!" So your 80-90%, if you keep that up for more than 2 minutes, you are exercising aerobically. Anaerobic doesn't last more than 30 sec - 2 mins, maximum.
    – JohnP
    Commented Mar 3, 2014 at 16:54
  • @JohnP, well said. Commented Mar 3, 2014 at 21:55

Aerobic means you're burning fatty acids as your primary fuel source, along side oxygen and small amounts of ATP in the muscle's. Anaerobic means you're burning ATP, and Oxygen as your primary fuel source. The latter being limited but more explosive in muscle contractions than the former.


At its simplest:

  • Anaerobic - Without Oxygen (Air)
  • Aerobic - With Oxygen (Air)

It's a bit more involved than that, as in this context we're talking about the conversion of chemical energy (Fat, Sugars, ATP, PCr) into kinetic (movement in your muscles), but essentially Anaerobic phase involves the conversion of ATP and PCr in your tissues into energy (your tissues only have around 8 sec worth of ATP reserves and 40 of PCr), while to process the Glucose / Fat in your body efficiently the process requires Oxygen. The following free chapter Nutrition for Health, Fitness, & Sport, cover the subject well.

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