Again the Pacing Thing – Heart Rate Monitors

In the last two posts I wrote about one of my favorite topics – race pacing. In the first I once again described the issue I’ve written about so many times. In the second I briefly discussed the issue of pacing when fast starts are necessary to race strategy. In this post I want to comment on how heart rate monitors affect pacing. Bottom line: they teach you to pace the start of the race poorly and finish weakly.

Why is that? Well, it’s simply because heart rate responds relatively slowly to sudden changes in intensity. It can take several minutes for heart rate to catch up with your output intensity (power, pace, speed). And that’s good for cardiovascular health. We really wouldn’t want it any other way. But if you rely on heart rate to pace yourself in workouts and races then you have a dilemma: How do you pace during those few minutes when heart rate is “low” but catching up?

I’ll come back to this dilemma and its solution shortly. But let’s first establish what the problem looks like. In the accompanying graphic (click to enlarge) you see a bike interval workout done by a real athlete. What you see here is the interval portion of the workout that was 5 x3-minutes at power zone 5 with 3-minute recoveries – a hard workout intended to boost aerobic capacity (VO₂ max). The black line is power (it could just as easily be speed or pace for running). The red line is heart rate. The 5 work intervals are highlighted in green. The dashed lines indicate the general slope of heart rate and power within each interval.

Notice that the slope of power in each of the first four intervals is fairly flat. That means the athlete was holding a steady output. On the last interval, power output slopes up slightly after starting at about the same power as the previous four (I like to see this as it means the athlete was holding back early in the workout and so was able to finish strongly).

Also notice how heart rate slopes upward quite steeply for each interval not reaching a peak until near the very end. Heart rate at the end of each interval was zone 5b, the same as the power zone. But how they got to their zones was greatly different. While heart rate took more than half of each interval to reach the zone, power was there in about 5 pedal strokes.

Now if the athlete only had a heart rate monitor and not a power meter for this workout he would not have a clear indication of how intensely he was working until about the last minute. So how do athletes typically manage this conundrum? They push themselves at a higher level than is called for in each interval in order to force heart rate up sooner. If we were to cover up the power data on the athlete’s handlebar head unit so he could only see heart rate we probably find that his power was zone 6 or even 7 in the first half of each interval. This would create considerable fatigue so it’s unlikely he would have been able to finish the workout so strongly.

So relying on heart rate for pacing, in any type of workout, teaches the athlete to start too fast and then finish weakly. That’s exactly the opposite of what we want in most steady-state races. So it’s no wonder that races; such as 10km runs, 40km bike time trials, and even the bike portion of a triathlon; start overly fast. Not only is the athlete emotionally excited by starting line or transition enthusiasm, but he or she has also been trained to start too fast due to the heart rate monitor. Thus, trying to teach athletes to pace themselves early on in races is very challenging.

So if you don’t have output equipment (power meter or speed-distance device) and all you have is a heart rate monitor (shame on you!) you have to learn to ignore it in the early portions of higher-intensity workouts like intervals. Instead, learn to use a Rating of Perceived Exertion (RPE) to rate how hard you are going on a 1 (low) to 10 (high) scale. To do this in a race takes considerable practice. It won’t be mastered in a single workout. It could take you weeks of constant practice to become good enough to do it precisely at the start of a race when your emotions are telling you to go faster.

Well-paced races are signs of an emotionally strong athlete.

Comments

[Robin Judice]

Joe, thank you for an excellent analysis of the heart-monitor/pacing conundrum. Heart rate can also be a poor indicator when the athlete is dehydrated or hot in a race or workout. Just because HR is over the "limit" doesn't mean they should stop or slow down.

Even when I use HRM's with athletes, we do speed work and races without them... athletes need to learn the motor memory/pacing knowledge/recognition what's happening in their body without the use of the machine.

(And I was a HRM addict from way back, by the way)

I appreciate your time and will share your post.

Robin Judice

[Bruce]

Hi Joe, I don't think a HRM is as bad as you make it out to be. I use one to great effect simply by taking into account the HR-lag you describe. For short intervals such as the 3-minute ones in your example, I only pay attention to the HR at the end of the interval and strive to hit my goal HR there. For longer intervals and long endurance workouts, I pay attention to the HR average. For racing, I don't use a HRM and go by feel instead. I think HRMs work well, and I think there is no shame in not having other measuring devices!

[Philip Madonia]

A trained athlete starts a race with a power output or pace goal to maintain, but in the end, the heart decides whether the athlete can do so, or do perhaps even better on that day. The athlete gathers this info. either from one's RPE knowledge or from one's heart rate (average). If this info. tells one the going is easy, then the pace or power meter numbers are adjusted upward to where the heart leads.
It is useful to know what average heart rate can be maintained over the time frame of a race so that one can rise above pace or power output expectations .

[Mtbgilgames.wordpress.com]

Very instructive article. Thank you!

[Rob]

Hi Joe:

Thank you for the above - I now understand why investment in a power meter can optimize the investment in saddle time.

Sorry to hijack the post. Though, have you time/interest to share thoughts on the value of the likes of Compex muscle stimulator units?

[Madeleine]

If the athlete is pacing himself/herself well and finishing strong with five intervals per set, how do you decide whether it is appropriate to add on a sixth interval to the set? Is there something that you look for in the power curve of the fifth interval to know that it would be appropriate to add an interval onto the set? Or would you look at the area under each of the recovery phase HR curves (or their slopes) to evaluate the rapidity with which the athlete recovers ? While I depend on my powermeter for a great deal, I am always interested in what the heart rate can tell me too.

Thanks,
Madeleine

[Hans]

You could get a indication of the output using a garmin gps to get the intervall lap speed or distance, this you can use when you ride the same hill and compare the different intervalls, if finishing the last intervalls faster than the previous then you have reached what you want.

[Cris]

Great post Joe! Recently started using a PMeter and had already begun working on using it to pace my workouts in combination with my HR monitor. I hope to use it to help me avoid overtraining when doing my AT workouts as I figure out what my power zones are compared to my HR zones.

On a related topic, I'm wondering about recommended total interval/ ME effort time for a day's workout. Often the recommended effort times for interval workouts total 30min. I imagine this increases during the season as fitness increases, as well as successive seasons as base fitness increases. I know age groups will probably differ as well. Would there be some total effort time guidelines for novice/ Int./ Expert/ Elite? Pro level athletes?

I'm a Cat.2 road rider, 38yrs old. My longest race is 3-4hrs but usually only 2x year. Most of my races are just under an hour (crit.) although several circuit races go to about 1 1/2 hours. We'll finally have a TT champs this year but I don't imagine it will be much longer than 20km.

THX

[Cris]

PS: Does total combined effort time increase as workouts are combined or should the time be divided up for a recommended effort time (ex: 30min. total?)

i.e.: SE day (P1, P2, A2, A3, & S6)

[Joe Friel]

Cris--Thanks for your comment. But I'm afraid I have to start the answer with my old saw, "it depends." You suggested some things it depends on. I might also add the precise level of "AT" intensity. If it is truly at FTP then one would do less total time in the workout than if it was somewhat below that, say 92% of FTP. And 102% would tilt it the other way. One's capacity for work was mentioned by you. That's a huge one. Then there's one's capacity for recovery. That varies between individuals and throughout the season (base-build-peak). Recovery is impacted by nutrition, sleep, lifestyle stress and what one has done in training in the previous days. This could keep on going. When it comes to "it depends" what any given individual may do is simply too hard to closely define. In general (very "general"), the answer would be some place between 20 minutes and 90 minutes within a single workout. But I've known athletes to do more and not be able to do the minimum here. The only way to find out is through trial and error. Good luck.

[Joe Friel]

Madeleine--This is a hard question to answer with any degree of confidence (see my reply to Cris' question above for details). Actually, I do it the other way around. I always schedule an athlete to do fewer intervals than I think he/she is capable of based on our experience. Then I tell the athlete to do less if power declines 5% on a subsequent interval or if the motivation is simply not there. It's _always_ better to know you could have done one more quality interval than to find out you couldn't.

[charley]

Hi Joe,
Thanks for the article. I noticed that you mentioned that it usually takes several minutes for heart rate to catch up with power...(and you said thats good for cardiovascular health and that you wouldnt want it the other way)...well, unfortunately, the opposite applies to me. I find that my heart rate usually spikes right away...should I be concerned? Usually, if I start out embarrisingly slow, I can keep my heart rate where it needs to be for that particular workout...Thanks for any feedback!

[Cris]

Great reply Joe! Your "It depends" answer is much more informative and helpful than perhaps you think it is. THX

[Björn from Sweden]

Very interesting Joe. One comment though. Back in the day (early 90s) drafting in Olympic races was not allowed hence you needed to pace yourself optimally over the whole distance.

Today its a different story. If you're not out of the water with the rest you're left behind. Drafting changes the pacing-plan completely and it may be well worth doing a larger effort at the beginning of the bike and then (hopefully) be able to settle in at the later part to be fresh for the running. Still, it doesn't diminish your point of using a power output meter.

[Joe Friel]

Cris--Thanks. Happy to be of help by muddying the water whenever I can. :)

[Joe Friel]

Charley--I can't comment on whether or not you may have a medical condition. That's not my realm. What I typically see is that high aerobic fitness leads to a slow increase in HR. The opposite is also common.

[pieter]

I'm wondering about mtb races of six to 10 hours rom 2000hm up to 5500hm, would you try to pace the first hills (from 15minutes up to an hour) at the same power as the last hills ? Or would optimal pacing allow for some "natural decay" ?

[Joe Friel]

Pieter--You're trying to avoid race pace decay as much as possible. Start at a pace which allows this.