The Dark Art of “Threshold”
Threshold is one of the most talked-about intensities in endurance sport. Today I want to share how I see it and how I use it in coaching. Not by diving deep into lab science, but by keeping it practical for athletes.
Definition :
Anaerobic threshold, often referred to as MLSS (Maximal Lactate Steady State) is the point where lactate production and clearance are balanced. In theory, it’s the hardest intensity you can sustain for around an hour before fatigue markers accumulate. At this effort, you’re leaning heavily on carbohydrate metabolism while still operating primarily within the aerobic system.
Threshold as a Training Tool
Perhaps the most well known of all the training intensity tools we use these days is FTP. Functional Threshold Power. A term created by Hunter and Allen in their seminal work “Training and Racing With a Power Meter”.
The concept being establishing the power that an athlete could sustain for about one hour and base everything off that.
This concept of using FTP as the basis for establishing training zones and intensities has now become industry standard and has overflowed into establishing TSS scores for load management. (1 hour at FTP being 100 TSS points)
What about Swim and Run?
Of course Swimming and Running were ahead of this curve as power meters on the bikes were only a recently accessible and affordable training tool.
In Swimming we have the CSS (Critical Swim Speed) test which uses a two point test to predict a third point. In running we generally use a one off point of a time trial.
Challenges
One could be expected to assume that the best way to predict lactate steady state would be to do a one hour time trial in each discipline. This has its challenges but. Namely it relies heavily on the mental strength of the athlete to execute a test to their physiological capacity for that long.
You could also assume that lactate testing might be a smart move but of course that brings many challenges as well. Cost, inaccuracies in test execution, dehydration, etc etc.
We Got Smart
We needed tests that could easily be executed in the field or at home.
We had to :
Have shorter tests that minimised the mental strength competent
Would be simple to execute in the context of a demanding training program
Be accurate
Be repeatable
Enter the Algorithm
If we could use all the data of those before us we could get maths on our side and be able to do shorter tests and apply an equation that would predict what our paces and powers would be anaerobic threshold.
Swim :
In the pool we now have the Critical Swim Speed test where we use 200m and 400m time trials to predict what our 1500m pace would be by subtracting the 200m pace from the 400m pace and dividing by 2.
Bike :
On the bike we have:
The 20min test - taking 95% of the average power to establish our FTP
The 2 x 8min test - taking 90% of the average of power results to get FTP
The Ramp Test - taking 75% of the Mean Maximal 1 minute Power to come up with an FTP
Run :
On the run we have a lot more simplicity :
2.4km Time Trial and apply pace decay models such as VDot (Daniels formulas)
5km Time Trial
10km Time Trial
My Testing Preferences :
I like using shorter maximal tests that allow us to go to the full extent of our capacities. This way we aren’t testing sub-maximally and relying on pacing strategies.
Swim : 200m and 400m tests allow us to see what our true levels are in the water and we can use that to get a threshold pace.
Bike : On the bike I love the Ramp Test. It’s a ramp until exhaustion test that gives me a true maximal aerobic power (our real target) and use algorithms to give us a Vo2max number and an FTP for use in training.
Run : For the run it’s similar to the ramp test. 2.4km is a good distance to go at your best aerobic power and we can apply calculations to get a Vo2max number and a threshold 5km or even 10km pace using VDot tables
How do we use these numbers ?
For training we can set our thresholds to establish training zones. Of course we can and do at times set those numbers slightly higher to help get us stronger. A 10w increase in FTP on Training Peaks is similar to adding another weight onto the bar in the gym. We can also temporarily set them lower if we have been off training due to a holiday or sickness.
For racing we can use these paces and powers to help establish a pacing model. Using a model of threshold + and based on previous races we can go into a race knowing that over a 70.3 distance we might target a pace of say threshold + 45sec.
Conclusion :
Threshold is a construct. It’s the combination of different physiological factors and as such can be misleading at times. It shouldn’t be use as a gospel but as a tool for training and racing knowing where your current levels currently sit and if your current training prescription is having the desired effect.
What matters is how we use it: to set zones, track training adaptations, and build race strategies.
The balance point where lactate oxidisation equals lactate production is the anaerobic threshold