Maximal heart rate?

beatyfamily1

I was looking through some of the MFP blogs and came across this one: http://blog.myfitnesspal.com/a-beginners-guide-to-your-metabolism/

It mentions that if your heart rate is above 70% maximal heart rate you will use fat as a source of energy compared to carbs when your heart rate is under 70% maximal heart rate.

First, how do I know what my maximal heart rate is?
Second, could this be a reason I have plateaued in weight loss since I can run comfortably now?

Wheelhouse15

beatyfamily1 wrote: »

I was looking through some of the MFP blogs and came across this one: http://blog.myfitnesspal.com/a-beginners-guide-to-your-metabolism/

It mentions that if your heart rate is above 70% maximal heart rate you will use fat as a source of energy compared to carbs when your heart rate is under 70% maximal heart rate.

First, how do I know what my maximal heart rate is?
Second, could this be a reason I have plateaued in weight loss since I can run comfortably now?

The only way to know your maximum heartrate for sure is to have a stress test. Their is a rough formula of 222-age but there is some variance to that, and sometimes a lot of variance as I can personally attest to. I wouldn't worry to much about heartrate training zones since they are rather doubious at best.

To the second question the answer is no, you are going to burn pretty much the same amount of calories as before, but slightly less due to weight loss and a small amount of efficiency gains but the efficiency gains won't make much difference. If you aren't losing weight then you need to reassess your eating and exercise calories such as eating a little less or running longer and/or faster, but also remember that there are a lot of reasons people stall including water retention.

juliegilburd

Plateaus are fairly common on a long journey. Your maximal (maximum) heart rate is considered to be, per the American Heart Association, 220 minus your age, so at 32 years old, mine is 188 (220-32 = 188). Fitness machines will often have a heart rate monitor that can tell you what your heart rate is while exercising.

I read the blog you linked to and I think you have it backwards. It states that when your heart rate is above 70% of your max, you use carbs as fuel, when lower than 70% you use stored fat as fuel (that portion pasted below for your reference.)

From the blog:
•Exercise above 70% maximal heart rate: At this intensity, it’s difficult to talk because your body focuses on breathing to deliver oxygen to your exercising muscles. Under lower oxygen conditions, your body turns to carbs for fuel. Why? Because carbs can be burned quickly and it can be used in oxygen-deprived conditions.
•Exercise below 70% maximal heart rate: At this intensity, you’re able to freely chat with your jogging partner and still get enough oxygen. In this scenario, the body prefers fat as fuel for these activities because this slow-burning fuel is perfect—especially when there’s plenty around.

As to the accuracy of that statement, I haven't researched it myself so I don't know.

azulvioleta6

Wheelhouse15 wrote: »

The only way to know your maximum heartrate for sure is to have a stress test. Their is a rough formula of 222-age but there is some variance to that, and sometimes a lot of variance as I can personally attest to. I wouldn't worry to much about heartrate training zones since they are rather doubious at best.

I can attest to the fact that if you have low blood pressure, this formula absolutely will NOT work for you.

beatyfamily1

@juliegilburd I think you're right. I had it backwards. This leaves me to think I should be keeping my heart rate lower?

Wheelhouse15

azulvioleta6 wrote: »

Wheelhouse15 wrote: »

The only way to know your maximum heartrate for sure is to have a stress test. Their is a rough formula of 222-age but there is some variance to that, and sometimes a lot of variance as I can personally attest to. I wouldn't worry to much about heartrate training zones since they are rather doubious at best.

I can attest to the fact that if you have low blood pressure, this formula absolutely will NOT work for you.

That's certainly one case, there are also two methods that the hear uses to increase blood supply under stress and that is to pump harder and to pump faster. Althought the heart uses both, some people's hearts preference harder and some faster. Mine likes to beat faster and I often note that my heart rate is somewhere north of dead by the given formula. My working heartrate for a typical 5K will get me into 170's and my final push will put me around 191. I'm just a ghost.