The tale of the heart rate monitor - JP Fitness Forums

VanceMac · 11-20-2006, 11:20 AM

I have used a heart rate monitor for my cardio for many months, and I find it VERY useful since I count both my calories in and my calories out through exercise as part of my weight loss. But I never used it when lifting because I never really thought I was burning much (and I probably wasn't burning that much the way I was doing it).

But, having started NROL, Fat Loss I, I decided to see how much of a burn I was getting during the workout itself, compared to my cardio. After my workout, I did HIIT on the elliptical for 20 minutes and burned 240 calories (of course the machine itself showed a lot more, but that is another annoyance subject). The first 20 minutes of my weight training (so that it is apples and apples), was almost the same, at 225. Of course, Alwyn builds his workouts to do just that, but I was still surprised. The total workout took about 30 minutes, so I ended burning a bit more from the workout than I did my cardio, not to mention the afterburn effect.

I am going to keep checking this, and if there is anything very interesting, I will let you know.

Kaiser · 11-20-2006, 11:42 AM

A HR calorie burn estimator is probably going to be way off for a non-continuous activity like lifting. Personal testing over a few years proved this to be correct for me, at least. For me, in general, a very intense Turbulence Training session lasting 40 mins (a long one - and TT has very little rest time) will burn at most 350-400 kcals (most lifting will get an average guy around 200-300/hour if the online estimators are to be believed). If I go with my HR monitor, it will show much more - between 50-100% more in the case of my Polar (which I think I have pretty much zoned in on actual kcal burn - as much as it can be at least). Compared to an intense spin class, where I can burn 600-900 kcals an hour, or an outdoor road ride time trial (>1,000 kcals per hour) you can see that (for me at least), the actual exercise burn is going to be less for lifting. And that is what is expected according to the experts. The benefit comes in the 'afterburn' you talk about - that your metabolic rate can remain raised for 12-37 hours after that lifting session.

Anyway, I think the booklet that came with your monitor will probably tell you the same thing - that it is unreliable for kcal burn for stop and go type activities. After reading mine and sending off an e-mail to Polar, that is the reply that I got.

VanceMac · 11-20-2006, 12:20 PM

Ah, that could be, but my understanding (which could be flawed) is that the problem arises when your heart rate gets below 100 since the HRM does not accurately handle calorie burn when the heart rate is that low. When the rests are short enough that the heart rate stays up (mine never dropped below 109 during this workout), do you think that the accuracy would be maintained?

Marykaa · 11-20-2006, 12:22 PM

I log what my Polar tells me, for warm-ups, cardio, hiking, lifting.. even for my yoga class when I forget to take it off if I've trained just before.

aveHR, maxHR, calories burnt, etc.. but only use it as a comparison from one WO to the other.. I really don't think it helps me in any other way.

Kaiser · 11-20-2006, 12:33 PM

Quote:

Originally Posted by VanceMac

Ah, that could be, but my understanding (which could be flawed) is that the problem arises when your heart rate gets below 100 since the HRM does not accurately handle calorie burn when the heart rate is that low. When the rests are short enough that the heart rate stays up (mine never dropped below 109 during this workout), do you think that the accuracy would be maintained?

I don't know. I didn't save the reply from Polar, but I don't think it mentioned anything about a lower limit HR# - I would have recalled that. I simply recall that they said it was inaccurate for activities where you stopped the activity for a rest a lot.

Marykaa · 11-20-2006, 01:24 PM

Just my opinion.. I think that the calories are calculated on the Average Heart Rate for the period.. so High Intensity activites for short periods in a long time frame hardly elevate the average HR enough to make a difference, specially if the HR comes back to almost normal between the Intervals..

VanceMac · 11-20-2006, 01:29 PM

The way it works for me with HIIT on the elliptical is that I control where my heart rate goes. During the intensity phases, I get it up to 145 to 150, then during the rest periods, I let it go down to 120 to 125. So, my heart rate is never going down to normal during the workout.

When lifting, I have found that it does not come below 105 during the entire workout, which is not anywhere near my normal of 55.

Q. · 11-20-2006, 01:49 PM

There's a guy at my gym who recently started wearing a HR monitor in the weight room. I noticed it because I teased him about his bra strap.

He told me that he was using it to determine how long his rest should be between sets. I've been dying to see him again to get him to explain that (because I got a "free" Nike monitor from Lipton) but, as of right now, I don't know how that is supposed to work. The watch is helpful, though!

Marykaa · 11-20-2006, 02:13 PM

Hi Q,

When I was starting weight lifting, I sometimes used my HR monitor to help me decide of the rest periods.. but no-one had ever told me how to do it.. so it's just my idea.

What I did was try to take 60 second rests (or whatever perscribed in my program) but if my HR was still way up.. I'd at least wait until it was down to 75% of my (unofficial) Maximum HR.

I think I would still do it now if I was doing a program like NROL FL. It just feels good.

But I AM curious to see how others do it.

JoshDunn · 11-20-2006, 09:52 PM

Never done it myself however a average person (normal health, no diseases) heart rate drops about 30BPM in about 60sec after exercise.
Very generalised.

My thoughts would be HIIT rest shouldn't bother with that however weights rest 1min between sets or until HR has dropped 30BPM compared to the working heart rate.

Again nothing too scientific just thoughts.

BFG · 11-21-2006, 03:20 PM

Vance I made similar observations early on in my fatloss logs. Thats one of the goals with minimal rest between sets ie sub 60 seconds and more often than not sub 30 seconds and can be used to negate the need for traditional "CV".

Kaiser · 11-21-2006, 03:26 PM

I guess I should have been more specific. Heart rate is not a direct correlation between workload and calories burned. Work done determines calories. HR can go up for a number of reasons, but as Craig Ballantyne regularly reminds his readers in his posts and e-mails, HR is not a good indicator of caloric expenditure. As he says, you can get your heart rate up laying on the couch and watching an exciting sports game.

As Polar has acknowledge, HR is a proxy for caloric expenditure, not a determinant of it. Why does that matter? Because when you are resting between sets, you are not doing any work, yet your HR is still elevated from the work you did earlier. If you continued to do that work, the HR would be a possible proxy for kcal burn, but once you stop, you aren't doing that work, yet your HR monitor still thinks you are.

I hope that better explains why a HR monitor to determine caloric expenditure in a non-continuous activity like lifting will tend to be off. For HIIT where you go between an 8 and a 3 in PRE, I think it would be a better estimator than for lifting. But, I can hear Craig saying, "Why do you care?" My answer, which may be VanceMac's too judging by his posts, is that I don't, simply that it is a fun toy to motivate me.

BFG · 11-21-2006, 03:31 PM

indeed I agree with you kaiser its the intensity of the exercise that matters

Kaiser · 11-21-2006, 03:34 PM

What Polar and other HR manufacturers do is try to correlate that intensity into a caloric expenditure number using an algorithm based on HR. It isn't great, but works better for 'steady state cardio' and longer sustained efforts than it does for shorter or more varied work.

BFG · 11-21-2006, 03:43 PM

I agree. At the end of the day the calculations I assume are averaged over the period of exertion?

Im carefuly wording this so that it doesnt sound like an anti cardio rant, But when you questioning alot of people why they run its because you need to in order to work the cardio vascular system to maintain good health and fat loss which simply is not true. Its not to say you shouldnt do it, far from it, but treat it for what it can deliver not what you perceive other methods dont.

VanceMac · 11-21-2006, 04:02 PM

That makes very good sense, and I will take that into effect when I am counting. You are right that it is a good motivator for me, but it is also important in that I use it to determine my net calories each day. Rather than set a fixed calorie goal (I am still on a deficit), I adjust each day based on the calories out.

Kaiser · 11-21-2006, 04:07 PM

I've found Fitday seems to better estimate my lifting expenditure than my HR monitor. fwiw....

VanceMac · 11-21-2006, 04:33 PM

Before I tried this last experiment, I just wasn't even bothering factoring in any calories burned from a workout since I didn't think they could be that much. I know that the afterburn is significant, but since that is so hard to calculate, I just figured that would be a bonus "deficit-creator" and didn't make any of it part of my daily calculation. I may go back to that.