Defining Training Zones and Aerobic Threshold

Alan Couzens, M.Sc. (Sports Science)

June 13th, 2018

I recently had a really great question from a fellow coach on the subject of 'just how many zones do we need?' so figured I would post some follow up thoughts here...

"I know you're super busy, but I was wondering if you could shed some light on these two topics for me or point me in the direction of some good reading that sums it up well. My two questions are: 1. what HR zone model do you prescribe to and why? 2. How do you best find aerobic threshold (outside of a lab)? Thanks so much for your time."

1. What HR zone model do you prescribe and why?

With the number of zone models available these days it can get downright confusing! 20 years ago, Joe Friel’s model was fairly ubiquitous and lined up well with the federation models from a number of endurance sports. Nowadays, options have expanded in both directions, with Coggan’s 6 zone model that attempts to line HR up with his power zones and on the other end of the spectrum, Seiler and co’s 3 zone model (which has the advantage of being used in a lot of real world studies on elite endurance athletes) that looks to simplify the process by dividing intensity according to 2 reasonably well defined physiological markers - VT1 and VT2.

My take is that...

The number of training zones need to be sufficiently precise to cover the major training objectives of the event.

These might differ depending on the nature of the event. E.g. when I was swim coaching at the elite level, we used a 7 zone model and had further distinctions of the ‘top end’ zones into Lactate Production (important for specialist sprint swimmers) v Lactate Tolerance (important for middle distance swimmers) and VO2max (important for distance swimmers). And these groups were divided (& prescribed to) accordingly.

In Ironman/70.3 & even Olympic Distance triathlon, this level of 'top end' distinction probably isn’t necessary. However, I'm not sure a 3 zone model adequately covers all bases either, as VT1 (if we define it as the first change in the VO2/VCO2 relationship) can still represent a fairly metabolically costly level of intensity, especially for larger/high performance athletes. If I was dealing with beginners or low volume athletes, where the difference in output between 'recovery' and 'base' wasn't all that substantial, a 3 zone model might suffice, but for the population I work with, I think that distinction is significant enough to be important.

So, for high performance triathletes, my major session objectives can be broken down as..…

1. Recovery (Sub AeT) - Minimal (or ideally negative!) glycogen cost
2. Aerobic base (AeT – Max Fat Ox/VT1) Maximal volume/number of contractions via maximal fat contribution
3. Specific endurance – Specific conditioning to event.
4. Threshold (sub OBLA/VT2) – Maximal aerobic conditioning of IIa fibers.
5. VO2/Speed (VT2+) – Type IIb aerobic development/maintenance.

With the above in mind, I use a 5 zone model with the triathletes I work with, focused around these key objectives. I'd advocate a similar approach: Identify the session distinctions that you think are most important for your athletes/sport and plan your training zones around these.

2. How do you best find aerobic threshold (outside of a lab)?

I guess it depends a bit on your definition of ‘outside of a lab’. Portable lactate analyzers are under-utilized in my opinion. They’re cheap, easy to use in the field & they enable us to answer that question very specifically for a given athlete. Glycogen metabolism produces pyruvate which leads to changes in lactate. When we have a ‘window’ into these changes, we have a window into the metabolic state of an individual athlete for a given training intensity.

Specific to aerobic threshold, the first rise in lactate (above the baseline plateau) shows the first rise in glycolytic contribution. This is a really handy thing to know when dosing a given amount of energy over a training week or block. Knowing where this point lies and just how quickly it 'ramps up' for a particular athlete represents such worthwhile information that it makes the acquisition of a portable lactate analyzer a ‘no brainer’ in my book.

Thanks for the great Q. Hope this is helpful.

AC

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