Attempting to Tame Training Zones

I couldn’t leave well enough alone. Much as I acknowledge many short comings in systems of training zones, they are a necessary evil, not least when you’re a coach. Training sessions need to be clearly and correctly defined in a way athletes can interpret and understand, despite their flaws zones can do this. They may present artificial boundaries over a continuum of intensity, but they also prevent an athlete doing entirely inappropriate sessions. Much as I dislike hard divisions and tend not to use them on a personal level, on a professional level I need to master them.

I was quite willing to reduce the system down to four simple zones reflecting the major regions long distance triathletes train, but practically a five zone system like Friel’s (ignoring his division of the fifth zone) makes life easier – athletes are familiar with it and my main coaching tool, Training Peaks, readily supports it. In practice additional layers of detail are needed, defining workouts by heart rate, power, pace, RPE and descriptively to help guide an athlete through the session. Seemingly simple systems mingle and the result is additional complexity, intent lying somewhere in the overlap of differing zones. I write about the value of perceived exertion in guiding training, but it takes time to develop confidence in our interpretations; for each of us feel is distinct.

From an idealistic start with four zones, I’ve settle on many more. Laying ten levels of perceived exertion (RPE) and seven or eight descriptive names over the top of the five zone system; taking terms from power training that sat awkwardly between heart rate zones and ordering them from recovery to max effort. Rather than referring to sweet spot as the bottom of zone 4, or perhaps the top of zone 3, I give it its own space, clarifying heart rate, power, pace and RPE. The system is led by RPE and names, because to me they are more meaningful divisions, session plans are built targeting a particular region – a sweet spot session, a threshold session, an endurance session; then I build a workout and determine zones.

The world doesn’t need more zones, but I need guidelines to ensure consistency. I am happy for my athletes to work with zones, but I still want them to appreciate their training in more descriptive terms, to have an understanding how their zones feel and relate so they can intuitively work towards appropriate goal. I want there to be a clear distinction between training at an inappropriate intensity and being on the borderlines, not serious concern when they are a watt or two off target.

Training Zones - a comparison of systems for measuring training intensity

To clarify my own thoughts as much as advise my athletes I developed the above chart, a (very) rough guide to how different levels of intensity and differing means of measuring them align. I can’t claim originality, I’ve blended a number of sources and mixed with my personal experience of training. My personal bias may limit its value for others, individuals vary, sports vary, but for those I coach I hope defining my terms and relating them to several methods of measuring effort will help guide the way they train. Perhaps giving them the sense that if it felt like a threshold effort, and perhaps the heart rate or power were close to the right figures, then it probably was good enough.

Ironman Training Library

From nutrition to pacing - a collection of CoachCox blog posts focused specifically on Ironman training and racing.


  • Hi Russ,

    I drew up a similar chart for athletes in our club when I was giving a seminar on training load last fall. There are a couple more columns that I consider to be even more constructive. Them being the typical substrate usage breakdown at those intensities.

    I also found it important to distinguish “pro” from “competitive AG” from “middle of the pack” when correlating these intensity zones to race distances. I am currently racing HIM distance an entire 10bpm higher on the bike and run than I started racing at the Olympic distance when my endurance was weak and I was muscularly and fuel constrained at 3 hours before I was HR and breathing constrained. This is a distinction that seems obvious to fast people but I learned the hard way that beginners often thought it worked the opposite way around.

  • Good to know I’m not the only person trying to cross reference zones and clarify how they relate. Good idea with the substrate usage too, certainly could help with an appreciation of race intensity and one of the issues with poor pacing. Similarly I’ve always thought Coggan’s table of expected adaptations was good for showing how the different zones share a lot in common.

    Adding the races in was a general guide, you’re right in saying that at differing levels of experience the actual intensity you can race at changes, especially when comparing HR and power; my experience over a few years racing Ironman is in the early days my HR was slightly lower, but the power was significantly so, now HR is higher and power is a much more stable 75%+ of FTP. Not an issue with an athlete I coach as obviously I can be specific in terms of how they pace a race, but in the case of generalising for a chart, it does gloss over the details.

    That’s part of the reason I try to encourage people to develop a feel for there training – I find that power or HR may change with fitness, but generally the feel remains quite consistent.