Fat-burning vs. cardio
 

My cardio workouts are typically done on a treadmill at the gym. Lately, I've been wondering about this little chart that is printed next to the treadmill screen, which has target heart rates for different ages--with one column of rates for "fat burning" exercise (60% of max HR, I think), and another column for "cardio" exercise (80% of max HR).

Now, as a rule, my pulse rate (per minute) when I'm running has always hovered around 162. It has been this way since I was in high school. However, according to the chart and my age (29), I'm at way over 80% of my max HR and am probably working "too hard."

So, 2 questions for the athletically-informed out there:

1) Should I be taking my cardio down a notch to avoid pushing my heart too hard, or is this chart just BS?

2) If I am working out at 80% plus of my max HR, does that mean that I am in the anaerobic threshold and am therefore not burning fat whatsoever? It's been a long time since I studied this stuff in school.

I guess I thought that as long as I was working myself hard, I'd be burning fat as well as improving cardio health/stamina. But if I do just want to lose weight, should I be down around that 60% of max HR range (which would mean a very light jog--really not my style!)?

Thanks for any tips. :thumbsup: The main goal is to stay in shape, of course--but I wouldn't mind shaving off a pound or two this winter, now that I've finished my 10k goal and am just looking to tone up in the next few months.

Bumped to see if anyone has ideas...

You should always work within the safe heart rate range for your age, to be safe.

"Fat burning" means burning fat during the session.

Depending on your workout and your diet, you can easily burn more fat during recovery if you work above the "fat burning" range.

Interval training is something to look into.

Right... but what is "safe?" Is 90% not safe? I always thought that 162 beats per minute was fine, but when I look at that chart (and now that I'm 29)... it appears that I am working too hard. But it feels good/natural for me... not sure what to do.
I get the fat-burning part... but if I am working above 60% ("fat burning" range), does that mean that I'm no longer burning fat during the workout, because I'm working too hard (anaerobic zone)? Or does it just mean that I am still burning plenty of fat during the workout, and will just continue burning more during recovery, too?

Ask your doctor for your target heart rate for aerobic fat burning. Those charts are like nutrition percentages on food; one size definitely does not fit all. The fact is that you're really, really healthy for a 29 year old, so the general rules may not apply to you. Doctors (specifically doctors specializing in physical therapy and sports training) would be able to tell you what Abaya can do, not just what Jill Schmo 29 year old can do.

Willravel answered this well.

It varies person to person, but for the sake of argument let's say above 60% is what you experience. If you go above the "fat burning" range, your body doesn't have enough time to break down fat to glucose for energy use, so gets it from other energy stores, typically found in your skeletal muscles. (A high level of energy expenditure such as this isn't nearly as sustainable as long-term lower-intensity exercise.)

Basically, this means your recovery requires far more calories to replace the expended energy from your body. If you eat right, this means your body will turn partially to your fat stores to do this.

Thank you, Will. This is very good advice. Sometimes I just depend too much on the internet, what can I say? :)
Hmm, interesting. It sounds like overall, if my aim is to burn fat, it would be better to stay in that 60% range (or whatever range is ideal for me)--especially since I'm not training for any races/competitions right now, just wanting to tone up and lose the fat. After my 10k (and bruising my already-black toenail again--from a nasty hike earlier this summer) a few weeks ago, I've dropped the treadmill from my workouts and focused entirely on the elliptical, and have seen my heartrate stay right around 135 instead of 162. At first it felt like I wasn't working hard enough, but I'm still sweating and breathing hard, and burning a lot of calories. I figure the 135 is probably more where I should be for burning fat only (especially because I am not sure whether or not I "eat well")--but will check with the doctor.

I can't tell you what is 'safe' for you.

However, I can explain the 'fat burn' range a little better.

When you workout, your body burns whatever fuel is most readily available. Usually this is Glycogen (which is released from your liver), but your body can also burn fat and muscle fiber.

If you are working hard enough, your body won't be able to run off glycogen alone, and will have to substitute one of it's backup fuels (fat or muscle). Fat provides more calories, but muscle fiber is more quickly accessed. If you work out too hard, your body won't be able to burn fat quickly enough to fuel it and will break down muscle fiber for energy (so you will end your workout with just as much fat and less muscle). If you go too slow, you will just use glycogen which will be replenished as soon as you eat something. In between, you will use mostly body fat for fuel, thus directly burning fat off your body.

Higher heartrates make for a stronger cardiovascular system, so the range above 'fat burn' is typically a good training range for improving your cardiovascular endurance and health.

Of course, this is a very simplistic answer, and you can burn fat by running hard also as it will boost your metabilism for a long period of time. Same with heavy weight training as your body will raise your metabolism to help heal itself.

Hope this helps,
Greg

NP. It's good to remember that eAdvice isn't always coming from professionals.

One good thing about the elliptical that I've found is it has a lower impact than the treadmill, so it's easier on your joints.

this makes more sense why my workouts seem to be less efficient lately.
i decreased the time and increased the intensity and it says i'm burning around the same amount of calories, but i'm still not burning any fat. which in turn pisses me off.
so, i can't keep my heart rate below 150 on the elliptical for any time frame past 10 minutes

so i'll just extend the time and decrease the crossramp, while keeping the resistance to "feel the burn".... is that right?

Thanks, Greg (and others). This was very helpful for me... it all sounds familiar, but the details are fuzzy, so now I have a much better understanding of what these heart rates are meant to illustrate.

I was aiming to have a stronger cardio system for most of the summer, since I was doing a lot of intense hiking and road races... I trained mostly for running, and didn't have as much time for weights. And when I was an athlete in the past, I was just used to running at that pace (in the 160's). However, now that winter is coming up, I don't want to stay at that level... I still feel very good, easy breathing, after 30 mins of cardio, and I do like that. But it would be great to lose some fat, and to get back on the weights more consistently, and I guess take my cardio intensity down a notch. So we'll see how this goes. :thumbsup:

The age charts are crap and are built for the lowest common denominator. Your fitness level is what really counts. It's all based on your maximum heart rate and also the level (anaerobic threshold AT) where you go from aerobic to anaerobic. That the point where you shift to burning sugar exclusively for fuel. The simple math is to decuct your age from 180 but if you are fit you can't deduct as much. My AT at 52 should be around 130 but my at actually runs around 150-160.

I'm attaching a link for a chart that will help you help yourself. The second page discusses the various ways to determine your AT. It's alos important to understand that your AT can change 15-20 bpm from day-to-day depending on how much rest you've had, etc.

http://www.lifetimefitness.com/modul...ning_chart.pdf

And a few good articles:

Finding Your Maximum Aerobic Heart Rate : trifuel.com

Mark Allen on Heart Rate Training