# Question about "cardiac drift"



## DalyCityDad (Oct 11, 2009)

Yesterday I started the TCTP. I don't have a power meter, only heart rate monitor. I was doing steady state intervals on my trainer yesterday which for me means 166-169 bpm. During the first 6 minute interval (of 4) I managed to find the gear and cadence needed to keep my heart rate in this range. During the second interval with the same gear and cadence my hr was more like 168-171. By the 4th time it was up around 173-175. 

My question: is that much "drift" normal or was I doing something wrong. I was drinking plenty of water (40 oz. during the hour on the trainer). The only thing I can think of was that I was overheated. I didn't have a fan set up.

Thanks


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## dwgranda (Sep 8, 2009)

How long are your steady state intervals? I looked back on a mostly steady state (power) ride I did on the trainer awhile back. It looks like I kept the same power and cadence for ~10 minutes and any drift looks like it would be minor, almost in the noise in this period. I think they have to be longer to notice a real drift and 10 bpm for the same power and cadence seems like a lot for not being a hydration issue. 40oz seems like a lot for an hour. That's just my experience without knowing or being able to explain to you any of the science behind it. Duration was 1:15


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## DalyCityDad (Oct 11, 2009)

The intervals were 6 min. long.


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## dwgranda (Sep 8, 2009)

DalyCityDad said:


> The intervals were 6 min. long.


I did some googling after replying to your post. One of the summaries of a research paper said that the effect was noticed 40 minutes in. That would matchup with my suspicions. I think I just googled cardiac drift.


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## tom_h (May 6, 2008)

I've occasionally done trainer intervals & hill climbs with both a powermeter and HR strap. 

When I'm near my FTP (functional threshhold power), I'll see an HR drift from mid 160s to mid 170s over about a 5-7 minutes period.

40 minutes for HR to drift up and stabilize sounds like a lot, but I suspect the particulars depend on your % FTP during the effort, environmental factors, age , your level of fitness, state of recovery from prior workout, etc.

The shorter the interval, the more problematic using HR. You may want to do the earlier intervals using a combination of "perceived exertion" and HR, and going a little "easier" on the first ones.

From what I understand, the best training response to intervals will be if you can maintain the same work output on all of the intervals -- or increase slightly at the end -- and not "fading" on the last ones.


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## Alex_Simmons/RST (Jan 12, 2008)

tom_h said:


> From what I understand, the best training response to intervals will be if you can maintain the same work output on all of the intervals -- or increase slightly at the end -- and not "fading" on the last ones.


I'm not sure we can actually really say that, but nonetheless, with power you know for sure you are hitting the right levels when doing shorter duration stuff, and also know when there's no point in continuing with another effort. HR is pretty useless as a guide to short duration efforts, as my earlier chart shows (see the HR trace for the 4-min on/off API interval set).

As for cardiac drift, it happens at sub-threshold levels too. How much depends on what % of threshold power you are riding at, and also your level of fitness. Here's another example of cardiac drift from a 1 hour ride at ~ 90% of threshold power.


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## MontyCrisco (Sep 21, 2008)

It may not be cardiac drift, just trainer weirdness. As the trainer warms up, the effort needed to hold a certain cadence/speed will also vary. It's entirely possible your power is actually higher in that second interval due to the fluid warming up or whatever.

I really do sympathize - I did the Carmichael plan last spring using HR and wheel speed on the trainer, and it really was hard to know if I was nailing the efforts just right. Just don't be a slave to your HR readings. That said, it's possible to get the effort levels 'close enough' to see the kinds of improvements you are aiming for.


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## NCLRACER (Dec 3, 2009)

Perhaps you just weren't completely warmed up for the first interval. Without (and even with) a good warmup I seem to need the first interval to "get the juices flowing". Each one after that gets easier to raise my HR. Towards the end, I usually have to adjust my gearing so that I am working less to maintain the target HR. You said "you just started" so maybe you just need to find the proper amount of effort? Just my two cents....Also, a fan is a must!!


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## Alex_Simmons/RST (Jan 12, 2008)

NCLRACER said:


> Towards the end, I usually have to adjust my gearing so that I am working less to maintain the target HR.


Why do less work? Let the HR rise.


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## NCLRACER (Dec 3, 2009)

Because my goal is a steady state interval (say 6 minutes for example) at a HR of 166-169, isnt the point then to keep my HR within these guidelines, more or less? I don't have a power meter... so thats where my thinking comes from, am I wrong? I sure could be...


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## Alex_Simmons/RST (Jan 12, 2008)

NCLRACER said:


> Because my goal is a steady state interval (say 6 minutes for example) at a HR of 166-169, isnt the point then to keep my HR within these guidelines, more or less? I don't have a power meter... so thats where my thinking comes from, am I wrong? I sure could be...


Your goal should be to do the work that elicits the desired physiological adaptation. 

If you are doing relatively hard efforts (which I imagine intervals of 6-min would be, not much point in doing 6-min intervals at an endurance pace), and lowering you trainer speed in order to keep HR down, then you are lowering your power output and probably not really riding them to best advantage.

I can't say whether or not such efforts are best for the desired outcome (since I don't know what your goal is for doing them). How hard are those 6-min efforts? Are they meant to be as hard or harder than riding at threshold / time trial pace/effort?

If so, then the utility of HR as a guide to effort declines somewhat.

See this example of the HR response when riding 20-min threshold efforts and harder 4-min efforts. How one could possibly pace quality supra threshold efforts using HR is beyond me.


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## NCLRACER (Dec 3, 2009)

hmm...good point


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## nyvram (Apr 11, 2002)

i started out using HR only and i'm so happy i have a powermeter now. it really does make all the difference..you can get your power to where you need in anywhere from 15 to 45 seconds and can tell instantly if you're slacking off. i don't pay much attention to HR now (although I still wear the band) and i've found my HR is WAY low..especially on those first intervals.

watching power is pretty easy, i just focus on maintaining x RPMs as my cadence and the power output is generally pretty static as long as you can keep that cadence fairly steady.

i admit i'm still learning..but i'm starting to really like having the powermeter to provide an 'honest' assessment of my actual workout intensity. yes..it is the instrument of pain but much like eating your veggies..its good for you. :lol:


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## [email protected]@K I am yo father (Aug 9, 2011)

DalyCityDad said:


> Yesterday I started the TCTP. I don't have a power meter, only heart rate monitor. I was doing steady state intervals on my trainer yesterday which for me means 166-169 bpm. During the first 6 minute interval (of 4) I managed to find the gear and cadence needed to keep my heart rate in this range. During the second interval with the same gear and cadence my hr was more like 168-171. By the 4th time it was up around 173-175.
> 
> My question: is that much "drift" normal or was I doing something wrong. I was drinking plenty of water (40 oz. during the hour on the trainer). The only thing I can think of was that I was overheated. I didn't have a fan set up.
> 
> Thanks


A fan set up will give you a night and day difference! 40oz of water is not enough considering you are doing hard efforts. You should have lower heart rates than that if you are recover better. It also depends on what are you training for, speed, cadence or power?

Regardless your HR looks like 95%. If you are not urinating frequently with clear fluids, you need more water. If you wake up in the middle of the night twice or more, you are over-hydrated.


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## gluteus (Jun 27, 2007)

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