HRM calorie burn accuracy

Succorso

Couldn't find anything when googling this group, but I'm sure this must
have been asked here before.

I had a very enjoyable 100+km ride today in the "spring" sunshine (what
happened to winter? I must have blinked and missed it) wearing my HRM as
usual.

It claimed I used 4600 calories. This seems excessive to me. I was
riding for about 4 hours all told, at about 75% of my Max HR (avr 140).
I would describe my cycling as "moderate" - not a tough workout by any
means. Most websites I've been to about calorie consumption would put a
rate of about 500 calories an hour for "moderate" cycling.

Ergo, I would have expected to use about 2000 calories. Are HRM's just
that approximate?

--
Chris

NC

Succorso wrote:
> Couldn't find anything when googling this group, but I'm sure this
> must have been asked here before.
>
> I had a very enjoyable 100+km ride today in the "spring" sunshine
> (what happened to winter? I must have blinked and missed it) wearing
> my HRM as usual.
>
> It claimed I used 4600 calories. This seems excessive to me. I was
> riding for about 4 hours all told, at about 75% of my Max HR (avr
> 140). I would describe my cycling as "moderate" - not a tough workout
> by any means. Most websites I've been to about calorie consumption
> would put a rate of about 500 calories an hour for "moderate" cycling.
>
> Ergo, I would have expected to use about 2000 calories. Are HRM's just
> that approximate?

Well.. two things here.

a) The HRM. Unless you can get a trace from it, or at a minimum some
estimates of max and average HR for the time period its pretty hard to tell
if the HRM was measuring heart-rate accurately.
Most are pretty accurate if the chest strap has a good electrical contact
with the skin and the watch is in range of the strap.
However, even ignoring rogue signals from a badly fitting chest strap, there
are things which can interfere with some models, including another HRM in
the vacinity, a wireless bike computer, a mobile phone, car electronics
(usually inside the car, not outside), etc. More modern designs are less
susceptible to interference, particularly from adjacent HRMs.

b) The Calorie conversion. This is approximate regardless of the HRM
heart-rate accuracy. It needs some calibration based on a person's weight
and resting heart rates, but even then, its no more than a rough guide.



- Nigel

--
NC - Webmaster for http://www.2mm.org.uk/
Replies to newsgroup postings to the newsgroup please.

Brian Wakem

Succorso wrote:

> Couldn't find anything when googling this group, but I'm sure this must
> have been asked here before.
>
> I had a very enjoyable 100+km ride today in the "spring" sunshine (what
> happened to winter? I must have blinked and missed it) wearing my HRM as
> usual.
>
> It claimed I used 4600 calories. This seems excessive to me. I was
> riding for about 4 hours all told, at about 75% of my Max HR (avr 140).
> I would describe my cycling as "moderate" - not a tough workout by any
> means. Most websites I've been to about calorie consumption would put a
> rate of about 500 calories an hour for "moderate" cycling.
>
> Ergo, I would have expected to use about 2000 calories. Are HRM's just
> that approximate?


My Polar S410 says I burn around 40-45kcal/mile on-road, 60-70kcal/mile
off-road (hilly). For comparison when I was running twice a day I would
burn 80-90kcal/mile, though it would be considerably higher for most.



--
Brian Wakem