I'm participating in my first race by doing the 90km bike part of a half-iron man relay - I'm hoping to complete within 3 hours.

I would like to know how I should pace myself with a heart rate monitor. I have been training with Carmichael's Time Crunched method so would appreciate if the heart rate's were given as a percentage of the CTS field test HR (max sustainable HR in 8 mins). Any other pacing strategies are of course welcomed as well.

  • Are you able to pre-ride the course as part of your training? Learn where you can go hard and where pacing is good. Many people go hard on the first climb and run out of herbs on the latter ones. The winner tends to be the one who can go hard on all of it. Also, set yourself some strava times for each segment and compare.
    – Criggie
    Mar 5, 2016 at 3:01
  • @criggie unfortunately I can't do a pre-ride. It's in a different country but luckily it only has one small hill. It's on the coast so wind could be an issue
    – mchangun
    Mar 5, 2016 at 4:09
  • OK try and trace out a route that is convenient to you, which has about the same amount of flat, to a roughly equal grade in terms of height and slope, and then back home. This will be a round trip to get you home, whereas the other will probably finish in a different location, but within 10% would be fine, and within 20% good enough for training and practice purposes. Also try and practice at the time of day your event will be happening.
    – Criggie
    Mar 5, 2016 at 9:49
  • Did you ever paced with a HR monitor in a race? If not, starting now would be an experiment and probably make you go slower as HR is elevated because of adrenaline. I think you are better of with RPE pacing. I also took part in such a rely Half Iron Man competition, never looked at HR, just pushed constantly from start to finish, enough to feel that I am working but without burning or gasping, I had the second bike time( on a regular road bike ) and we won with 15 minutes advantage. Mar 17, 2016 at 8:36
  • I would strongly recommend getting a Lactate Threshold test done to determine your heart rate zones, as any system based on percentages is inherently inaccurate.
    – Ealhmund
    Apr 26, 2016 at 13:55

1 Answer 1


For those unfamiliar with the CTS system, there is a guide here

The answer is a hard one without knowing the individual athlete, as a better trained athlete will be able to tolerate much more work in the tempo and sweet spot ranges.

On race day HR is often a few beats higher and you can squeeze out that bit more due to a combination of adrenaline and motivation. I would be looking to target 86-90% for the first half and push on to 88-92% in the 2nd half if you feel you have more in the tank.

Putting the HR monitor to one side, it is also useful to pay close attention to your RPE (Rate of Perceived Exertion) during the first half. You should feel like you are pushing firmly on the pedals, but if your legs are burning, you are probably going too hard and will pay for it later.

In general push towards the top of the HR band on the inclines, and ease off a little to the bottom of the band on the declines. Using this minor variation in effort is more efficient as at higher speeds, wind resistance is higher, and you are gaining less speed for every Watt of power you are producing.

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    I am curious how you come up with the HR percent values. Mar 17, 2016 at 8:36
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    The CTS zones described in the linked document map fairly well to the more commonly used zones from Coggan or Friel. The steady state range reflects a 60-90 minute continuous effort. The Tempo range 90-180 minutes. Note that this is for 'continuous' efforts small breaks when descending etc will stretch this - it is common for cyclists to do 5-6hr sportives with average heart rates in the tempo range. The OP's target is a sub 3hr ride, so I recommended tempo to begin with, and pushing on in the second half if he had more to give.
    – Andy P
    Mar 17, 2016 at 9:40
  • Ok, so its 86-90% out of CTS HR, that makes sense now, I had the impression that it is 90% out of Max HR, which is a different story. I would advise against pacing with a HR, what you have in training as HR its different than racing, as many people have noticed. Mar 17, 2016 at 17:53
  • I have been trying out your HR zones (in shorter distances, but at the end of a hard workout) and they are bang on! The lower zone feels very sustainable and the higher zone is where I start "feeling it". I'm wondering if it makes sense to take "breaks" during these long time trial efforts by utilizing a lower HR? I might be able to recharge quite a bit by slowing to 82% for 3-5 mins and so I can push harder in the latter portion (e.g. final third, final quarter).
    – mchangun
    Mar 31, 2016 at 0:54
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    Glad to hear they are working for you. For a time trial you will get the best results putting out the most consistent effort rather than taking "breaks". If you are going to ease up a bit, don't do it for a fixed duration of 3-5 mins, but rather do it on downhill sections where power you are applying is giving the least benefit.
    – Andy P
    Mar 31, 2016 at 7:58

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