Heart Rate Question

mgogl27

Hi there! I'm new to the message boards, not so new to myfitnesspal (although I've been somewhat sporadic in my use of it since I joined). I am trying to recommit myself to eating well and exercising, and I was wondering if someone could shed some light on this for me:

The elliptical I use at my gym tells me that my target heartrate for fat burn is 126- (I am 5'2", 162 lbs)- However, on my last few visits, my heartrate skyrockets as soon as I start moving (I assume because I am out of shape?)- it typically hangs around 150 throughout my workouts, which usually are only 20 min or so.

Today, I decided to push myself, and stayed on for 45 minutes, and noticed that after I hit the 30 min mark, my heartrate started dropping steadily- until it was actually difficult to get it over 125. Is this a good thing? Does it mean that my body is getting used to moving?

I also recall reading once that you really don't start burning fat from cardio until after about 20 minutes- and I found it interesting that after 30 minutes, my heart rate was automatically in what I'm told is the "fat burning zone"-

And lastly, I'm confused as to what the difference is between fat burn and cardio heart rates- am I not going to lose weight/fat if I'm exercising and my heartrate is high? It tells me I've burned calories even when my heartrate is high (not in the fat burning zone), and I thought having a calorie deficit was what leads to weight loss?

If anyone can provide some clarification on these things, I'd really appreciate it. Thanks!!

silverbullet07

Well I'm not a cetified fitness trainer but I may help shead some light in simple understanding terms.

The fat zone or Low Intensity burns approx 50 % fat . The high Intensity or cardio zone burns approx 39.8% fat.

The body does burn a higher percentage of calories from fat in the fat burning zone or at lower intensities. However, at higher intensities (70-90% of your maximum heart rate), you burn a greater number of overall calories, which is what matters when it comes to losing weight.


The chart below details the fat calories expended by a 130-pound woman during cardio exercise:


Low Intensity - 60-65% MHR High Intensity - 80-85% MHR
Total Calories expended per min. 4.86 6.86
Fat Calories expended per min. 2.43 2.7
Total Calories expended in 30 min. 146 206
Total Fat calories expended in 30 min 73 82
Percentage of fat calories burned 50% 39.85%



As far as you moving into the fat zone after 30 min might be because after 20 min or so you tend to get a second wind and you maybe slowing down the pace or the intencidy of the resistance is getting harder to slow the pace down.

Here is a great article on Fat Burning zone. http://exercise.about.com/od/weightloss/a/The-Truth-About-The-Fat-Burning-Zone.htm

mgogl27

Thanks, I'll take a look at the article!

I use the random-intensity mode on the elliptical, and even at the higher intensities, my heart rate didn't go up after I was on for 30 min- and my pace was the same or faster than it was earlier in my workout-

Glad to know that I'm still burning fat when my heartrate is high, though. I have been losing pretty steadily and just trying to make sense of exactly what I'm doing and why it's working so that I can keep it up.

Thanks for your help!

BrianSharpe

Thanks, I'll take a look at the article!

I use the random-intensity mode on the elliptical, and even at the higher intensities, my heart rate didn't go up after I was on for 30 min- and my pace was the same or faster than it was earlier in my workout-

Glad to know that I'm still burning fat when my heartrate is high, though. I have been losing pretty steadily and just trying to make sense of exactly what I'm doing and why it's working so that I can keep it up.

Thanks for your help!

Are you using a heart rate monitor or the one built into some cardio machines? The one in machines tend to give fairly erratic readings.

The whole "fat burning zone" is best forgotten as staying in it will slow weight loss (and cardiovascular improvements) as in the previous post.