Whether you’ve been training for years or are new to triathlon, whether you follow your own schedule or have a coach, the chances are you have come across the idea of ‘training zones’ and very probably the huge variety of opinions depending on which ‘expert’ you choose to read. To be honest it’s not an exact science but there are some generally accepted views in the sports science and coaching community so let’s take a look at those, how to determine zones in the absence of a lab, and why and how you would choose to use them within your training regime.
Firstly with so much terminology out there, what exactly do we mean? In my experience coaches talk about either the 1st turnpoint or the aerobic threshold, and throw in the amount of mmls of lactate (lactic acid) you’re accumulating just to add to the complexity. Then there’s the 2nd turnpoint or anaerobic threshold with even more mmls of lactate. So let’s keep this simple - most of us don’t have the ability to go for physiological testing at a lab but hopefully you can do some field testing with a heart rate monitor, or with watts on a turbo or in the pool with a stopwatch.
What and why
1st turnpoint or aerobic threshold usually sits around 78% of your hr max and is also known (yes I know another title…!) as ventilatory threshold. Up to this level is where you should be doing the vast majority of your training – if you have the ability to train around 10-15hrs + pw then probably about 80% of your training will sit here. If you’re a weekend warrior, or do most of your training in club sessions, you might find this drops to more like 60-70%. This is your long slow duration training.
In this zone you are creating minimal systemic stress to the body and central nervous system while building mitrochondrial density (energy factories supplying the muscles) and capillary density (oxygen delivery). It’s extremely repeatable which creates better signalling for cell adaptation than stressing your body every time you train. It’s also a time for building
strength into your soft tissue connections. At this intensity we are using slow twitch muscles fibres which use little glucose and a lot of fat as fuel – as a result of minimal glucose oxidation there is minimal lactate production and most of what you do create can be metabolized by the body to create more energy. This means you can just keep going....
2nd turnpoint or anaerobic threshold usually sits at around 90% of your hr max. Above this level you are very limited in the amount of time you can maintain at this intensity. There is quite a range within this zone and the target of the training differs, but for most triathletes, who are all endurance athletes, then there is a lot of benefit from working just below/at/just above this level. In general this point is viewed as the maximum effort you can maintain for 1hour and is usually considered to be your FTP on the bike and your CSS pace in the pool, and probably around 10k race pace. Though as with everything else ‘it depends on the individual’ eg. what about the athletes who can run 10k in 40mins? You are now using mostly fast twitch muscle fibres to sustain short intervals of high intensity work with substantial recovery periods. At this level of work your body’s fuel of choice will be glucose, which in turn produces a larger amount of lactate which will be too much for your body to buffer, hence the required rest periods between reps.
So why work at this intensity? Most athletes are centrally limited by how much blood the heart can pump to working muscles. If you work well above anaerobic threshold you will be holding very short, very intense reps eg. 10-30secs max. Although this does work on economy of movement and recruits fast twitch muscles there is very little time when the heart is pumping hard and thus stretching the ventricles – it is this stretching of the heart ventricles which ultimately leads to an increase in cardiac output, the overall amount of blood that your heart can pump out in 1minute. The higher your output for every heartbeat the more oxygen and fuel getting to your working muscles. This effect will come from spending more time at a high intensity such as reps just at or above threshold which could be from 2-8mins approx. in length.
There is a progression from easy to moderate to hard as a continuous range, rather than three distinct effort levels, so you also have a ‘middle ground’, known as tempo – pretty much where you would probably race at Sprint & Standard distance. There is a lot of debate as to the value of training in this area but if it is your ‘race pace’ then you do need to do some training in this area, particularly in the build to racing. But what about LD athletes? In triathlon, the winner of a LD event will be the athlete who has slowed down the least and adding some blocks of lower end tempo training into your LSD sessions will build your tolerance, strength and robustness and help you to maintain pace towards the end of your race. Ultimately the biggest issue with zone 3 is that many athletes actually perform their long slow training at this level of intensity because it feels challenging enough without being really tough – however it’s not encouraging the basic cell adaptations that are only going to happen in an ‘unstressed’ body. Equally, VO2max sessions ( those 2-8min reps around threshold) are really tough and so this time many athletes dial them down into the top end of tempo work – again not stimulating the desired adaptations.
Intensity discipline is important
if the session is easy, make sure it’s easy. Do you finish feeling like you haven’t worked out?
if it’s tempo then it’s challenging but doable with reps up to around 20-30mins in duration
if it’s high intensity then it’s really tough with reps of 2-8mins, depending on your conditioning, and recoveries of a couple of minutes. Repeatable efforts is the goal so adjust the recoveries if you need to
Maximal effort will be for around 10-30 secs with as much recovery as you need to maintain maximal effort on every rep. But be careful, this level of intensity has a much higher injury risk. You don’t need to worry on HR for this one – it’s simply your max....
How
The good news is that what you really care about is the associated pace, power, and/or heart-rate at your lactate threshold, because those are the metrics you use and monitor in training, and you do have the ability to measure those things yourself outside a lab.
You can do a pretty good job of determining your threshold pace (run), power (bike), and/or heart-rate (run and bike) by performing a 30-minute all-out effort, after a proper 20-minute warm-up. Your average pace/power for the 30 minutes and your average heart-rate for the final 20 minutes are your thresholds. (Some also use a 20-minute test, where your threshold pace/power/heart-rate is 95% of your 20-minute average.) This works well because 20 to 30 minutes is short enough that you can work really hard while tolerating the extreme lactate build-up that occurs above your threshold. It’s right at that tipping point—right at your threshold.
Why not try to establish your zones and then really focus on the goals of your training within those zones – easy means easy , tempo means challenging but doable and hard means hard. You can start by simply running at below 78% hr max and see how that feels… and walk if you need to in order to keep the hr at the desired level
Simple guide to zones
Zone 1 Recovery rpe 3 / 4 <65% hr max approx
Eg. power walking , xtrainer. Long slow and very, very easy
Zone 2 Active easy rpe 5 /6 < 79% hr max
LSD sessions
Zone 3 Tempo rpe 7 / 8 80-90% hr max
20-40min blocks
Zone 4 Vo2M reps rpe 9 90 – 97% hr max
2-8mins reps & 2+mins recoveries
Zone 5 Max effort rpe 10 >98% hr max
10-30s reps & recoveries as needed
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