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September 16, 2008 6:18 AM

How does heart rate correlate to calories burned, and can I lose weight by just being incredibly nervous?

I understand that heart rate and calorie burning during exercise are related, but I'm a bit fuzzy on how this works when you get into various kinds of exercise and specifics. Running with a Polar watch, I can get my HR up into the 160s at a good jog, 170s with moderate effort, and 180s when I'm going full-bore or running uphill. On a rowing machine, however -- and I've used the ergometer a LOT over the years, mostly in winter, so this isn't a "never done it before" effect -- I get to the 150s at moderate effort, 160s when I push it, and full-out-crazy puts me at the mid-170s.

So the rowing machine feels like more of a workout -- I get winded faster when I go hard, I can't go hard for as long and I'm a lot more physically exhausted after. But by the HR numbers, running is a "harder" workout.

Is the higher HR necessarily the better workout from a straight calories-burned perspective?

And if I hired a bunch of creepy clowns to follow me around and jump out at inopportune moments, would I lose weight passively thanks to having my heart constantly going like a triphammer?

posted by Shepherd to health & fitness (6 comments total)

From what I remember, your target heart rate is 180 minus your age. Keeping HR above this number for 30mins is the goal, which is not hard to do on an ergometer.

Much respect for using the ergometer, for it is God's Chosen Exercise. Are you an ex-rower? Remember to keep your back straight, because improper form will kill your efficiency, and your back. With resistance on '10', try to keep your 500/m split below 2:10 for 5, 10, etc minutes. I'm just now getting back into rowing and 10mins below 2:10 kicks my ass.
posted by limited slip at 6:37 AM on September 16, 2008

From what I remember, your target heart rate is 180 minus your age.

This varies widely, and it ends up not being terribly useful, IMO. When I run on the treadmill, my heart rate hovers around 185. Also, the target rate depends on what your goals are... are you trying to improve your cardio endurance, or simply burn calories? Typically aerobic trainers target a lower heart rate for calorie burning, because you can keep it up longer (but then there are the HIIT people who don't buy into that).
posted by knave at 7:01 AM on September 16, 2008

I think your logic is correct (higher heart rate = fat loss) but being nervous/stressed causes massive amounts of cortisol to be released which will make it nearly impossible to lose any weight at all.
posted by wolfkult at 7:35 AM on September 16, 2008 [1 favorite has favorites]

When you exercise your higher heart rate is due to the higher rate of energy use in your muscles. As your muscles work, they need more oxygen, so they need more blood flow, so your heart pumps faster. In this case, the muscles (not your heart) are using lots of extra energy, which burns calories.

When you're terrified, your higher heart rate is due to stress-related chemicals like cortisol coursing through your system. This primes your body to be able to exert a lot of energy if necessary (it's the "fight or flight" response), but if you're just standing there with your heart pounding, your muscles aren't actually burning much in the way of extra calories.

In theory you might burn a few more calories if creepy clowns are jumping out at you, because your heart is itself a muscle that needs to burn calories to work. On the other hand, the effect is probably minimized as stress hormones make your body hang onto fat (as wolfkult said). If you really want to lose weight, get some lions to chase you down the street every day. That'll get you running, for sure.
posted by vytae at 7:54 AM on September 16, 2008 [2 favorites has favorites]

Is the higher HR necessarily the better workout from a straight calories-burned perspective?

And if I hired a bunch of creepy clowns to follow me around and jump out at inopportune moments, would I lose weight passively thanks to having my heart constantly going like a triphammer?

Not necessarily, and no. A higher HR tends to be strongly correlated with higher exertion and more calories burned, but it is not the cause of more calories burned (excepting the extremely small number of extra calories burned by the heart muscle itself). Higher HR can be an effect of greater and/or more inefficient exertion; it is not a cause of that exertion. This is why walking moderately fast for an hour, or doing a series of extremely heavy lifts, can burn as many or more calories than jogging fast for 10 minutes, despite the fact that jogging elevates your heart rate to a much higher level.

Consider running for 10 minutes at 180 and rowing for 10 minutes at 170. Generally, we would expect that you would burn more calories running, because the higher HR indicates that you were exerting yourself more. But it is also possible that you were burning the same amount of calories while rowing, but doing so more efficiently, and thus producing a lower HR. [Its actually a lot more complicated than this, but this communicates the basics]. HR is a good guideline for indicating calories burned, but is not always a perfect indicator.

And as for those clowns: they would raise your heart rate, but since it was the result of a neuroendocrine response, not increased exertion, the impact on your calories burned would be minimal.
posted by googly at 7:54 AM on September 16, 2008

You can probably get a better handle on this by thinking of your body as a machine (not always a good idea, but useful in this particular instance).

Fat is essentially stored energy. In fact, it's got the highest caloric density of anything we can metabolize, so as a means of storing energy for later use, it's as efficient a substance as can be found. To burn fat, you have to use more energy than you're eating. This will make your body dip into fat reserves to make up the amount you're consuming.

Your body uses energy in a number of ways, but they can be reduced to two fundamental types: heat and motion. To burn fat, you have to raise the amount of energy you expend. The easiest way of doing this is exertion, i.e. moving things around, e.g. your body. Thinking about it this way, having your heart beat faster uses a lot less energy than even walking across the room. The amount of mass and the distance traveled is a lot smaller for your heart than for even minimal physical activity. Work is equal to the force exerted times the distance traveled (w=fd). So minimal physical exercise will wind up using a lot more energy, i.e. burning a lot more calories, than having your heart beat fast.

Keeping your body warm and moving things around inside you (blood, water, nutrients, etc.) to actually stay alive consumes most of the energy a normal person uses in a day. Play around with this calculator a bit and you'll see what I mean. For example, a 25 year old man who weighs 180 pounds and is 5'11" who engages in a normal amount of activity without any dedicated exercise will burn almost 3000 calories a day. A woman of the same age who is 120 pounds and 5'6" will burn about 2100 calories. 30 minutes of exercise, even really strenuous exercise, will only burn a few hundred calories (rowing will probably burn about 300-400).

Exercise is great, and an essential part of staying healthy. Use it or lose it. But if you're really looking to lose weight, you need to combine that with eating less. In this context, what you eat is less important than how much you eat. Even a balanced, macrobiotic, all-organic diet that's 500 Calories too high for you will result in weight gain.
posted by valkyryn at 8:34 AM on September 16, 2008 [1 favorite has favorites]