I am sure this topic has been widely covered before, but I couldn’t find what I was looking for in the search.
Why do people consider HR unreliable to use for IM race pacing? and does a powermeter provide better info?
or is it the combination of the two that is best?
Thanks.
HR has many factors that can influence it and can lag behind effort. I feel that it is only an indicator of intensity. Used with pace and PE it works well.
Power can provide immediate feedback and isn’t influenced by anything other than the pressure you put on the pedals. Better is a matter of opinion and only if you know what to do with the information.
jaretj
Let’s say that two gorgeous women (or whatever turns your on) tell you they will do whatever you want…
If you check your HR it will be probably in Zone 5 (mine will for sure 
), even though you are sitting and barely moving…
Bottom line is HR is not just an indication of your effort but also of how you feel (i.e. running out of energy, dehydrated, tired, etc…)… so if you only rely on your HR to set your pace you could end up going too slow or too fast.
As already pointed out, Powemeter will give the best pacing feed back…
But ultimately it is also how you feel that will help determine your pacing and therefore how to use all the information as already mentioned…
Cheers,
Fred.
Here is a real world example of what Fred_h described, and it was REALLY funny (maybe you had to be there though).
Ironman California, 2001, in the water waiting for the swim start. Two guys, clearly friends, are close by me and talking as we all tread water (wearing wet suits, just floating really). One of them is wearing a heart monitor, and the HR alarm is going off. The guy looks at his HR monitor and exclaims “Oh my, I’m ABOVE my HR limit for the swim!”. I have to admit that I also had serious butterflys, and was amp’ed at that start, but it is a good example of HR not indicating anything.
If however, you are using a power meter on the bike, you are likely to know somthing along the lines of “I can hold X watts, and still run well, X + 25 watts and I’m going to blow”. Then even if your HR is high due to anxiety, you can have a good estimate for pacing.
Paul
The key is to understand what the two different devices are measuring and use the information appropriately. Power is a measure of exactly how hard you are riding your bike. It is immediate and assuming your power meter is working properly and calibrated accurate, you know how hard you’re riding. Watts are watts, whether uphill, downhill, hot weather, cold rain, whatever. Heart rates are indirect measures of exercise intensity as they are overall measures of the stress under which your body is under. The overall stress level you are experiencing, from deydration, excitement, exercise, etc., is still useful information in many cases, particularly early in an IM bike leg. Heart rate and power are not mutually exclusive as pacing tools, you just need to understand what the numbers mean and make appropriate decisions with that information. In my mind, making good decisions is the key to race execution, no matter the means to use to make those choices.
In my IM I rode above my 40K TT heart rate for the 1st 2 hours of the 112 mile ride.
Needless to say I ignored the data.
what information were you hoping for the hr monitor to provide. You must have thought it was worth something if you wore it.
When I trained and dialed in my Iron pace, I knew I was in the right zone if I started my ride at ~128 bpm and climbed to ~ 138 bpm by the end of the ride. Unfortunately, even after my 15 minute transition, my HR was above 160 bpm for the 1st 2 hours of the ride…despite the fact that my RPE and speed told me that I was WELL below that kind of effort.
The HR was a great tool for training, but it just didn’t pan out in this race.
what sort of hr did you have in the last 3 -4 hours of the bike? Did the effect ever wear off?
The advantage of the HRM is of course that works on all 3 legs. I don’t know of a tool for measuring power on the swim or run (not that I’ve ever looked at my HRM during the swim either for that matter) - you can use pace but of course that varies depending on the conditions, gradient, etc.
I would take the view that both HR and power are useful feedback but wouldn’t rely on either. A higher than expected HR may be an indicator that you’re overdoing it and are going to blow later in the race, but it may also be an indicator of a bunch of other things.
Question for the power users - is power that reliable? Surely the amount of power you can sustain for any given distance and still run effectively will also vary in a somewhat unpredictable way depending on how well you’ve peaked for a race? Is there a danger that by using power to pace yourself in an A race, based on training data or B- or C- race data, that you will actually limit yourself and not achieve your full potential on that day?
I relied entirely on HR for my IM training and the race and found it to be an excellent predictor of my performance and my pace. At my first IM I predicted my time and my avg HR prior to the race and was spot on, with nothing left to give.
When you paced yourself with HR during the race, did the first 2 hours on the bike feel REALLY easy on RPE with HR in the correct zone?
When I first paced myself on HR in an IM then yes - the RPE at the start of the bike did feel real easy.
Next IM I tried pushing a little more in those first few hours, went probably ~5 bpm higher than planned and paid for it in the last 20 miles of the bike. Didn’t have a major blow-up but had to ease off a little to keep in good shape for the run, whereas the previous race I had much more consistent bike splits.
Generally I find my HR is a very good guide of effort in race situations and most of the time in training. Can occasionally be a bit off in training if I am not fully recovered from the previous session, had a few drinks the night before, am tired, etc.
Yes, it finally settled back down into th eexpected range, but at that point I figured I couldn’t rely on it. I only knew it was in the right range because it gave me a number that I expected to see given the effort I was putting out. So what?..I was still relying on effort, not data.
Question for the power users - is power that reliable?
Under standardized conditions, human performance (e.g., maximal power that can be maintained for a fixed duration, or time required to complete a given amount of work) is reproducible to w/in +/- ~2%. Under the same conditions, heart rate is only reproducible to w/in +/- ~5%.
HR and Power can both be used to affirm that RPE is correct.
The big advantage of racing with power is to keep you from doing something stupid, such as climbing at 150% (or more) of your FTP. HR and RPE will screw you in that regard, unless you’ve developed a feel by training on hills with power. When you ride with a PM, your eyes are opened to how other riders absolutely hammer up hills (or even gradual grades), especially at the beginning of the hill, only to go down to about 100W by the top.
Question for the power users - is power that reliable?
Under standardized conditions, human performance (e.g., maximal power that can be maintained for a fixed duration, or time required to complete a given amount of work) is reproducible to w/in +/- ~2%. Under the same conditions, heart rate is only reproducible to w/in +/- ~5%.
Isn’t his question about the effect of “non-standardised” conditions though…?
… ie to what extent is the maximal power that can be maintained for a fixed duration a constant for differing levels of pre-existing fatigue, versus the HR being a constant, but the maximal power for the same differing levels of fatigue being a variable.
Question for the power users - is power that reliable?
Under standardized conditions, human performance (e.g., maximal power that can be maintained for a fixed duration, or time required to complete a given amount of work) is reproducible to w/in +/- ~2%. Under the same conditions, heart rate is only reproducible to w/in +/- ~5%.
Isn’t his question about the effect of “non-standardised” conditions though…?
It is, but that just makes heart rate look worse, not better. That is, there are numerous factors that can have a significant impact upon heart rate that won’t affect performance, but few (if any) factors that won’t impact heart rate but will affect performance.
That is, there are numerous factors that can have a significant impact upon heart rate that won’t affect performance, but few (if any) factors that won’t impact heart rate but will affect performance.
I’m intrigued by this. To take some extreme examples: if I were to do nothing but eat pies for six weeks, or decide to pedal with just one leg, or have a leg amputated, max performance level would clearly drop (presumably by somewhere not a million miles away from 50% in the later two cases). However, would one really expect a large change in HR at the maximal performance level?
That is, there are numerous factors that can have a significant impact upon heart rate that won’t affect performance, but few (if any) factors that won’t impact heart rate but will affect performance.
I’m intrigued by this. To take some extreme examples: if I were to do nothing but eat pies for six weeks, or decide to pedal with just one leg, or have a leg amputated, max performance level would clearly drop (presumably by somewhere not a million miles away from 50% in the later two cases). However, would one really expect a large change in HR at the maximal performance level?
Your example is really too contrived to have much relevance to this discussion, but to answer it anyway:
I would expect a larger change in heart rate at a given absolute intensity than at a given relative intensity, but even the latter would likely change.