Lactate thresholds have long been used for endurance training, but does the average triathlete actually understand them and know how to use them to their advantage in training. In simple terms lactate is the by-product of burning fuel (glucose) in the muscles, the harder you work the higher the lactate production and the higher your heart rate. You may have heard people talk about aerobic threshold and anaerobic threshold or lactate turn point or even maximal steady state. You may have heard coaches talk about working at tempo or threshold but what exactly do they mean?
First, we need to look at what happens to lactate during different exercise intensities. Lactate is measured in millimoles per litre of blood (mmol/L), if your blood lactate was tested whilst reading this article it would probably be slightly under or over 1 mmol/L. The best way of describing how blood lactate increases at different intensities is to give an example of how physiologists test lactate thresholds in a lab. Firstly, you would start by running (can be done on a stationary bike too) at a slow pace. Then every 4 minutes (average amount of time for your heart rate needs to reach steady state) the pace would increase by say 1km/h. Your lactate is tested by taking a small sample of blood after every 4-minute stage. Your blood lactate would remain very similar until you reach a point where it increases significantly, we call this 1st threshold or LT1 (see figure 1). Your LT1 is usually around 2 mmol/L but this does vary. The test would then continue to a point where there is another significant increase in your blood lactate, we call this 2nd threshold or LT2 (figure 1). Your LT2 is usually around 4 mmol/L but again this also varies. After this point your lactate will increase exponentially until you can’t run anymore.
LT1 and LT2
So basically, we’ve discussed that exercise intensity is positively correlated with an increase in blood lactate, and there are 2 points (LT1 and LT2) where lactate starts to significantly increase. If you were to run at LT1 then you could probably sustain this (for well trained individuals) for 3-4 hours (usually longer for cycling and less for swimming). LT1 can roughly be defined as marathon pace or half ironman pace. Furthermore, if you were to run at LT2 then you could sustain this (again, usually longer for cycling and less for swimming) for around 30-45 minutes. LT2 can be roughly defined as your 10k pace or sprint distance triathlon pace. Therefore, you could estimate your LT1 and LT2 by recording your heart rate during these events and taking an average. Obviously, this will just be an estimation and getting a physiological test is the only accurate way of calculating your LT1 and LT2.
A point of note: when running, your LT1 and LT2 is around 5 beats per minute higher than when you are cycling.
As with my point above, when coaches refer to tempo and threshold training, they usually mean LT1 and LT2. Also, you may have heard coaches mention CSS (critical swim speed) or FTP (functional threshold power), these are basically different ways of describing LT2 in specific disciplines. They are slightly different and have their own merit, but in simple terms they are the same.
So what does all this actually mean and how can this relate to training?
Now that we have defined the 2 thresholds, we can look at how you can use them in training. This will be slightly different depending on your history of training and what race you are competing at. Therefore, having a coach to help you with this is critical to optimise your individual needs. Due to the endurance nature if triathlon it is critical, in order to get faster, that you increase your thresholds. If you are looking at shorter distance triathlons then your focus should be on improving your LT2 and longer distance triathlons should be more towards LT1 development. However, both are critical in any distance triathlon and shouldn’t be ignored.
There is a lot of discussion on how to use these thresholds to optimise performance. There are several methods but the 2 most popular are ‘threshold training’ and ‘polarised training’. Threshold training loosely refers to doing most of your training in zone 2 (see figure 1), and polarised training refers to doing 80% of your training in zone 1 and 20% in zone 3. A study in 2012 showed the effects of both types of training on 40k TT cycling performance (ave watts). After 6 weeks of training at both methods the results showed an average of 8% increase for polarised and only just over 1% increase using the threshold training method (see figure 2).
Note on table above: lactate threshold refers to LT2 and %change is the increase of average watts over a 40km TT.
The reason why you may not improve by doing a lot of your training in zone 2 is because it’s not intense enough to properly stimulate muscular improvement but is still intense enough to produce accumulated fatigue and delayed recovery, basically you are producing lactate without the rewards.
Now you can’t always take everything from studies as gospel, however you can’t ignore the results. Most coaches and elite athletes now will suggest using the polarised model of 80:20. What people can often get wrong is the thinking that all year round I should do 80% of my training really easy and 20% really hard (very polarised), this will give you improvements in the short term but will mean that you peak really quickly and then plateau. Most elite coaches and athletes will manipulate the thresholds so that most of their program is polarised but potentially isn’t as polarised as a lot of studies will suggest. Throughout periods of the year coaches will use other models to manipulate training, and as I said before this is different depending on your race distance and training history.
There are limited studies looking into LT1 development and even in shorter distance triathlons having a good LT1 is critical. This can be still done by adopting the polarised (80:20) method, however your so-called easy training is pushed more towards LT1. Finding a point where you aren’t producing lots of lactate but are still working in Zone 1 is argued as the most ‘bang for your buck’ method. This method is famously adopted by the Norwegian triathletes, and they’ve done pretty well in recent years. A typical run session, especially in the winter, would look at manipulating LT1 by doing under over sessions. For example, you might do an hours run where at points you are working slightly over LT1 and at points working slightly under LT1. They would do this once a week with minimal running above LT2 and majority of their running below LT1.
In short, knowing about/ knowing your LT1 and LT2 (heart rate and power at each threshold) will help you understand how you can get the most out of training and understand how you can individualise your sessions to suit your needs.
Rob Bridges is a full time Triathlon coach based out of Loughborough University. To find out more about Rob and read his bio click HERE.