anaerobic/aerobic thoughts and input please

curvykent

I was just told to cut back on my exercise, that I shouldn't do any aerobic exercise for more than an hour but try to keep it at 30-45 min tops so that I don't cause my body to switch from aerobic to anaerobic because then my body is burning muscle instead of fat.

Is this accurate? So are marathon runners burning muscle instead of fat? I don't know why anyone in their right mind would do a marathon if that was the end result.

I'm confused and don't know whether to take what this person said seriously or just keep doing what I am doing.

grimendale

In short? No. I did the Insanity program (month 2 is an hour long each day) and I burned fat like nobody's business. Whether you burn fat or muscle is dependent on genetics, the size of your calorie deficit in relation to your body fat, getting your needed protein and whether you are using resistance training to continue to work the muscles. As long as your deficit is reasonably small and you are using your muscles, most of your calories burned will be fat. Some muscle loss is inevitable, but aerobic or anaerobic won't have much impact. Resistance training tends to be anaerobic and cardio tends to be aerobic, and resistance training is useful for minimizing muscle loss, so a garbled version of this may be what prompted that nonsense.

BrianSharpe

I was just told to cut back on my exercise, that I shouldn't do any aerobic exercise for more than an hour but try to keep it at 30-45 min tops so that I don't cause my body to switch from aerobic to anaerobic because then my body is burning muscle instead of fat.

Is this accurate? So are marathon runners burning muscle instead of fat? I don't know why anyone in their right mind would do a marathon if that was the end result.

I'm confused and don't know whether to take what this person said seriously or just keep doing what I am doing.

Whoever told you that doesn't know the first thing about how your body uses fuel or the difference between anaerobic and aerobic exercise.

In general your body uses a combination of glycogen (stored carbohydrates) and fat as fuel (in varying proportions depending on the intensity). Your body will use muscle for fuel but under some fairly specific circumstances (extreme caloric deficit, very low BF%, low dietary protein etc)

The difference between aerobic and anaerobic exercise relates to intensity and your body's ability to deliver enough oxygen to make use of fuel. And the threshold between aerobic and anaerobic varies widely from person to person (and will even vary for you as your fitness improves). Anaerobic exercise is normally something people can only do for very short durations.

Think of the two this way.......a sprinter running 100m in 10 seconds or so is relying almost exclusively on anaerobic metabolism (even the best sprinter would not be able to maintain this pace over a mile), on the other hand a longer distance runner relies on aerobic metabolism running at a pace that can be sustained for a long period of time.