Need help with my new HRM!!

keiraev

I think you are supposed to subtract your "sedentary burn" from whatever your HRM tells you burned to get an accurate reading.

For example my BMR is 1236 so my hourly sedentary burn is 1236/24 which is 51.5 cals an hour (sitting in a chair/sleeping)

I thought about getting one but it just seems like a pain in the neck to have to keep doing all this maths. I just go with what MFP tells me- they may be too high or low in some cases but I am sure it all balances out and I lost the weight using their figures.

Gt3ch

My HRM requires:

Age
Weight
VO2Max
Max HR (it sets this on its own since I add in my age)

I have had a hard time finding my correct VO2Max. Since I have little kids, I can not just go the the track and run a mile. I did one step test and it came up with a VO2Max of 51. I am in good shape, but that did seem high.

So, I found another step test, it required double steps (44 instead of 22) and then that calculated 40. I think this is more accurate.

Does your HRM require you to enter a VO2Max?

This is good to mention. My HRM use VO2 Max also. Not all HRMs are equal and cheaper ones make more assumptions about the user and are often less accurate.

The only way to know VO2 Max is to get tested in a lab. Otherwise you are just guessing.

TinkrBelz

Ya, I figure that I am guessing, so I am making it as educated of a guess as I can! haha! I figure that is is a ballpark figure.

SteveHunt113

I would try this. Use the HRM only when doing high aerobics. Like karate, elliptical, running (not walking, ill explain why), boxing etc.

Not while using weights.

You should never use a HRM to calculate calories when doing weights ...except if you are doing circuits, super sets, or anything where you spend a lot of time lifting and very little time resting.

Gt3ch

Ya, I figure that I am guessing, so I am making it as educated of a guess as I can! haha! I figure that is is a ballpark figure.

Yeah you're exactly right. It's an educated guess & ballpark figure that you're getting from your test. Even though it isn't precise it's probably much better than leaving the HRM to guess your fitness level based on age or something.

Just want to be clear. HRMs are absolutely useful. I just worry when people are overconfident about precision because they see a digital display. It's absolutely helpful to get a ballpark figure for your work. We all just have to be honest with ourselves when we log it if we want to follow MFP's advice and eat all the exercise calories. Also IMHO the OP shouldn't be surprised he's getting different numbers from different equipment or on different days.

MrsR0SE

I want to re-read all of this again when my HRM arrives in the post later this week!

najla56

hei guys,

thanks a lot for the replies.

There are a few things that i got wrong first time. my avg HR was 137 and not 120. and i was in my target zone about 60% of the time. but i guess its still over estimating. I have tried all the websites you guys mentioned, and all of them came up with lesser results than my hrm. so I am gonna enter about 30% less values, but as you guys said, its just great for checking your HR and pushing your body forward safely.

PS: i did substract about 200 cal for 2 hr sedentary burning from my calorie burned value.

Gt3ch

A few things. You're very young so avg HR of 137 is't super demanding. You're also very petite so you're BMR is significantly less than 2400cal (probably more like 1400). So you'd have to subtract significantly less than 200 cal. What variables does your HRM ask for? VO2 Max or fitness level? Weight? age? height? Max & resting heart rate?

I would think you should get the most accurate numbers if it uses a recent, reliable VO2 Max figure and the strap is nice and tight and you are always well rested, never dehydrated, and don't use stimulants of any kind. Your unit might be calibrated more for a taller male advanced athlete. If you think it's about 30% off, and you definitely can't change it, maybe just take 30% off when you log it. The important thing is it will tell you when it's safe to push harder, when you have to back off, and whether today's workout is more intense than last month's.

najla56

@Gt3ch:

my hrm does not ask for the VO2, but i have calibrated weight, age, height, and the max and resting HR and gender. strap was nice and tight, but i would try a little tighter in today's workout.

one more thing, the machines at the gym- i dint try and calibrate my age/ht/wt/gender into them last time:p I would try doing them also today and would get back.

and i substracted the 200 cal, just to be on the safe side:)

Gt3ch

Everything you've done is good but the HRM still doesn't really know the efficiency of your cardiovascular system. It's trying to guess that to get in the general ballpark based on those variables you've given them. Things would be a lot better calibrated if you had a VO2Max performed recently at a good lab and had a more pricy unit that could use that value. I'm not sure that's really practical or ultimately all that important though.

I'm interested to hear how it compares to the machines in your gym. But because they're s all approximations I don't think it's surprising to see a 100-200 cal or greater difference in a 90 minute workout. I have and can't imagine we're the only ones.

I think the idea of subtracting a large number as a safety margin is basically correct (although it's no longer a real BMR figure). In the end you're going to want to view the calorie number from your HRM or machines at the gym more as an intensity score than real food calories. You're also going to have to come up with a safe range of calories you can eat when you exercise.

As an aside I think this is where MFP falls short. I understand the rationale of counting everything, trying to be precise, and sticking to a specific calorie deficit. The reality, though, is that any precision is an illusion. Some people find it easier to stay on track if they just try to eat a specific number of calories (plus or minus a narrow range) and just stick to a workout schedule without counting their exercise calories for their daily food budget. You have to experiment and see what works for you.