Aerobic means requiring oxygen; anaerobic means proceeding without it. In exercise, aerobic activity is sustained and oxygen-fuelled, while anaerobic work is short and intense, outpacing oxygen supply. The same prefix pair applies to bacteria and to industrial processes like composting and brewing.
The core difference
One prefix pair applied across biology, fitness and chemistry.
- aerobic — with oxygen: running, cycling, swimming at a sustainable pace.
- anaerobic — without: sprinting, heavy lifting, and the fermentation that produces beer and yoghurt.
In exercise
The distinction is about whether your oxygen supply keeps up with demand. Aerobic work can continue for a long time; anaerobic work produces energy faster than oxygen can be delivered, accumulates metabolic byproducts, and therefore cannot be sustained.
In microbiology
Anaerobic bacteria live without oxygen and some are killed by it. That is why deep puncture wounds carry particular risk, and why anaerobic digestion is used to break down waste in sealed tanks.
Frequently asked questions
Is weightlifting aerobic or anaerobic?
Anaerobic. It is short and intense, demanding energy faster than oxygen can be supplied.
What does the prefix an- mean?
Without, from Greek. Aerobic means with air or oxygen; anaerobic means without it.
Are anaerobic bacteria harmed by oxygen?
Some are — obligate anaerobes cannot survive in it, which is why they thrive in sealed or deep environments.