HR versus Cadence (was Powercranks)

[DaveH]

Phil Holman wrote:

>A method I have used is to ride at a constant power output, say 200watts, starting off at 60 rpm
>and increasing cadence every 3 minutes until exhaustion and note HR at each cadence. I googled my
>results which I've previously posted.
>
> Cadence Heartrate Power External
>
> 60 96 200W 75 100 200W 90 105 200W 105 112 200W 120 132 200W

This is in fact the complete opposite of what I found when I did the same test. I used an exercise
bike in the gym. It was a while ago now but I remember being suprised at the result.

First I warmed up. Then I selected a power that I could sustain for a reasonable period. It was 250W
in this case. I pedalled at a normal cadence (90) for 2 minutes and my heart rate was 154. I did the
same for a number of different cadences from about 60 to over 100. In EVERY case my heart rate was
EXACTLY 154. Not even 1 beat difference!!! I should repeat the test, but then I am sure that some of
you will repeat this and post a reply.

I am interested in seeing the relationship of power to heart rate and cadence. If any of you have
the polar 710 or 720 with power sensor could you please send me some of your records to see if I can
find any correlation in the real world. I will post the results.

Does anyone have any comment?

Dave

PS Please send emails to: david dot dn dot harton at pdo dot co dot om

 

[Richard]

My experience is based on riding the taxc at constant speed (sensor on rear wheel yes) my
heartrate definitely goes up for the higher cadence while at constant speed so in line with the
numbers of Phil.

Richard [email protected] (DaveH) wrote in message
news:<[email protected]>...
> Phil Holman wrote:
>
> >A method I have used is to ride at a constant power output, say 200watts, starting off at 60 rpm
> >and increasing cadence every 3 minutes until exhaustion and note HR at each cadence. I googled my
> >results which I've previously posted.
> >
> > Cadence Heartrate Power External
> >
> > 60 96 200W 75 100 200W 90 105 200W 105 112 200W 120 132 200W
>
> This is in fact the complete opposite of what I found when I did the same test. I used an exercise
> bike in the gym. It was a while ago now but I remember being suprised at the result.
>
> First I warmed up. Then I selected a power that I could sustain for a reasonable period. It was
> 250W in this case. I pedalled at a normal cadence (90) for 2 minutes and my heart rate was 154. I
> did the same for a number of different cadences from about 60 to over 100. In EVERY case my heart
> rate was EXACTLY 154. Not even 1 beat difference!!! I should repeat the test, but then I am sure
> that some of you will repeat this and post a reply.
>
> I am interested in seeing the relationship of power to heart rate and cadence. If any of you have
> the polar 710 or 720 with power sensor could you please send me some of your records to see if I
> can find any correlation in the real world. I will post the results.
>
> Does anyone have any comment?
>
> Dave
>
> PS Please send emails to: david dot dn dot harton at pdo dot co dot om

 

[Jens Kurt Heyck]

"DaveH" <[email protected]> wrote in message
news:[email protected]...
> Phil Holman wrote:
>
> >A method I have used is to ride at a constant power output, say 200watts, starting off at 60 rpm
> >and increasing cadence every 3 minutes until exhaustion and note HR at each cadence. I googled my
> >results which I've previously posted.
> >
> > Cadence Heartrate Power External
> >
> > 60 96 200W 75 100 200W 90 105 200W 105 112 200W 120 132 200W
>
> This is in fact the complete opposite of what I found when I did the same test. I used an exercise
> bike in the gym. It was a while ago now but I remember being suprised at the result.
>
> First I warmed up. Then I selected a power that I could sustain for a reasonable period. It was
> 250W in this case. I pedalled at a normal cadence (90) for 2 minutes and my heart rate was 154. I
> did the same for a number of different cadences from about 60 to over 100. In EVERY case my heart
> rate was EXACTLY 154. Not even 1 beat difference!!! I should repeat the test, but then I am sure
> that some of you will repeat this and post a reply.
>
> I am interested in seeing the relationship of power to heart rate and cadence. If any of you have
> the polar 710 or 720 with power sensor could you please send me some of your records to see if I
> can find any correlation in the real world. I will post the results.
>
> Does anyone have any comment?

I have a few. On a trainer, the 710 is exactly the wrong way to test this. The 710 gives erratic
readings on trainers. Even on the road, it can give different readings for different cogs, as the
distance from the chain and the sensor varies. Use a Computrainer, a Powertap, or an SRM.

I don't think 2-3 minutes at a cadence is sufficient. Figure that the HR change from increased
stress will take 30-90 seconds to manifest itself. There's also the issue of HR drift -- at a given
wattage your HR is going to go up a bit no matter what cadence you choose. So you should at least
test both ways -- e.g. start at high cadence and go to low and vice versa.

From my own experience with a Powertap and a Computrainer, I have little doubt that my HR at a given
power output climbs as the cadence goes above 70. I'm not sure I have specific files to substantiate
this, but the correlation seems easy to eyeball.

Lastly, Phil, I'm impressed that you can maintain 200 watts at 90-100bpm. Either you weigh 200lbs or
you're a damn strong rider.

regards,

Jens

 

[Michel Sabourin]

I made a test keeping my rear whell free (not touching the roller) I checked my heart rate at
various cadence.

It gave:
Cadence HR
rpm /min
40 72
60 75
71 78
80 83
100 93

It looks like a quadratic function. I believe that rotating legs faster takes more energy to
fight against body inertia (mainly legs up and down) and friction. My opinion is this is true at
any power.

Michel

 

[Robert Chung]

DaveH wrote:
>
> First I warmed up. Then I selected a power that I could sustain for a reasonable period. It was
> 250W in this case. I pedalled at a normal cadence (90) for 2 minutes and my heart rate was 154. I
> did the same for a number of different cadences from about 60 to over 100. In EVERY case my heart
> rate was EXACTLY 154. Not even 1 beat difference!!!

Yes, I too have had a defective HRM. Fortunately, it was still under warranty and I was able to get
a replacement.

 

[Andrew Bradley]

[email protected] (Michel Sabourin) wrote in message news:<[email protected]>...
> I made a test keeping my rear whell free (not touching the roller) I checked my heart rate at
> various cadence.

Thanks for the data, but why not do the same thing using a realistic resistance and constant speed?
Muscles may well have to fire differently in unloaded pedalling.

>
> It gave: Cadence HR rpm /min 40 72 60 75 71 78 80 83 100 93
>
> It looks like a quadratic function. I believe that rotating legs faster takes more energy to
> fight against body inertia (mainly legs up and down) and friction. My opinion is this is true at
> any power.

As long as "inertia fighting" energy doesn't mean the work done to accelerate leg masses per se.

Andrew Bradley

 

[Trg]

Robert Chung wrote:
> DaveH wrote:
>>
>> First I warmed up. Then I selected a power that I could sustain for a reasonable period. It was
>> 250W in this case. I pedalled at a normal cadence (90) for 2 minutes and my heart rate was 154. I
>> did the same for a number of different cadences from about 60 to over 100. In EVERY case my heart
>> rate was EXACTLY 154. Not even 1 beat difference!!!
>
> Yes, I too have had a defective HRM. Fortunately, it was still under warranty and I was able to
> get a replacement.

Aren't you jumping to conclusions here? Maybe the HRM is fine and it's his heart that's defective
Or he just has to adjust his limiter screw...

 

[Per Elmsäter]

trg wrote:
> Robert Chung wrote:
>> DaveH wrote:
>>>
>>> First I warmed up. Then I selected a power that I could sustain for a reasonable period. It was
>>> 250W in this case. I pedalled at a normal cadence (90) for 2 minutes and my heart rate was 154.
>>> I did the same for a number of different cadences from about 60 to over
>>> 100. In EVERY case my heart rate was EXACTLY 154. Not even 1 beat difference!!!
>>
>> Yes, I too have had a defective HRM. Fortunately, it was still under warranty and I was able to
>> get a replacement.
>
> Aren't you jumping to conclusions here? Maybe the HRM is fine and it's his heart that's defective
> Or he just has to adjust his limiter screw...

I just recently learned that a Beta blocker has this effect on the heart

--
Perre

You have to be smarter than a robot to reply.

 

[Trg]

Per Elmsäter wrote:
> trg wrote:
>> Robert Chung wrote:
>>> DaveH wrote:
>>>>
>>>> First I warmed up. Then I selected a power that I could sustain for a reasonable period. It was
>>>> 250W in this case. I pedalled at a normal cadence (90) for 2 minutes and my heart rate was 154.
>>>> I did the same for a number of different cadences from about 60 to over
>>>> 100. In EVERY case my heart rate was EXACTLY 154. Not even 1 beat difference!!!
>>>
>>> Yes, I too have had a defective HRM. Fortunately, it was still under warranty and I was able to
>>> get a replacement.
>>
>> Aren't you jumping to conclusions here? Maybe the HRM is fine and it's his heart that's defective
>> Or he just has to adjust his limiter screw...
>
> I just recently learned that a Beta blocker has this effect on the heart
I found that out as well about 15 years ago. Not a welcome side effect when playing in a squash
tournement