As we all know, cardio and strength training have completely different effects on your muscles, and your body's response to them. Strength training trains the body to make those big anaerobic muscle fibres, giving you the body-builder look, but cardio builds endurance muscles without hypertrophy. (Why does cardio/aerobic exercise lead to muscle loss? has a fuller explanation for anyone new to the site.)

When I swim, my breathing is restricted because of the water (let's say my technique is poor), so an intensity of exercise that's normally aerobic for me becomes anaerobic instead. I feel out of breath (the sign of an oxygen deficit) after a sprint that doesn't tire out my muscles: if I were on the bike instead, I'd be able to keep up that level of activity for hours.

So my question is this: how does an anaerobic exercise (my swim sprint) compare to an aerobic exercise of the same intensity (my bike ride)? I'm looking in particular for the effect it has on the muscle profile: the fat-burning effects are already covered by do low oxygen levels effect fat burn and/or muscle strengthening? and Does the amount of breathing (holding breath/breathing fast) affect the calories burned during a workout (not heavylifting)?

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    If the bike sprint is the same intensity, it is anaerobic as well. Or, (and much more likely) your swim is actually aerobic, not anaerobic. Oxygen deficit does not mean anaerobic.
    – JohnP
    Jul 31, 2014 at 15:08
  • I would question your assessment of the swim described as being an anaerobic exercise per se. While most anaerobic exercises are burst and short similar to sprinting, and you can certainly use swimming for anaerobic pursuits, it often doesn't qualify when a swimmer runs out of breath because of inadequate breathing. What inadequate breathing is, is simply "breathing without breathing." Basically you try to grasp air, but it doesn't make it to your lungs before your next attempt. O2 deficit, yes, but not on a muscular anaerobic level, simply out of breath & mild shock level. Jan 15, 2017 at 15:31

1 Answer 1


First and foremost: personally, anaerobic and aerobic exercises can't have the same intensity. Swimming is aerobic. Anaerobic exercises are pretty much the hardest exercises since they push your heart to its limits most of the times.

Anaerobic exercise is defined as short duration, high intensity exercise lasting anywhere from merely seconds up to around two minutes.

Judging from the definition, the intensity between those two exercises won't probably be the same. Training anaerobically is exerting our hearts to 80% (or plus) it's rate. Due to this, we end up burning calories both during exercise and after the exercise (up to 38 hours). This is known as the Excess post-exercise oxygen consumption. This type of training cause rapid loss of belly fat and increased growth hormone.

More on why anaerobic exercises are good.

More on the heart rate, since anaerobic exercises are brief, they raise the heart rate for a few seconds and then it gets back to normal but if you want to keep the improve your heart rate, consistent aerobic exercises will do a better job than anaerobic exercises.

More on both aerobic and anaerobic exercises here

  • Wouldn't a restriction in oxygen mean that the blood oxygen levels are lower than normal and would make your heart rate increase to adapt? Maybe this is the same as being in high altitude where its harder to take in enough oxygen.
    – Jason
    Jul 22, 2015 at 23:38
  • @Jason effectively but anaerobic exercises are short and brief. The heart rate is raised for a few seconds then it gets back to its normal rate. but research show that a constant and consistent aerobic training will improve your heart rate better than what anaerobic training will ever do. Jul 23, 2015 at 12:19
  • Yes, sprint swimming can be anaerobic when done right by any proficient swimmer. So, no, swimming is not only aerobic albeit most often people swim aerobically. Jan 15, 2017 at 15:37

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