Thread on Blood Lactate During Exercise

[Mij]

I found this thread on X interesting



We are probably familiar with the BLa curve during an incremental exercise test As intensity increases BLa accumulates at a faster rate, approximating an exponential increase

We can estimate a 'threshold' in this curve, but what is this threshold telling us?

 

[Mij]

We don’t actually care about the deflection point in a lactate curve on its own True exponential curves don't have deflections. it's like finding the corner of a circle There are lots of corners depending on our operational definitions

 

[Mij]

We care about what our lactate curve predicts about our *constant workload* performance at every intensity What happens to BLa if we clamped workload during a lactate test and continued exercising at that constant workload? At lower intensities, something like this

 

[Mij]

If we continued our incremental lactate test and clamped workload above the lactate threshold, would it continue to increase exponentially?

Nope! BLa accumulation *decelerates* over time, even at high intensity Because

 

[Mij]

BLa observed during a lactate test is the product of whole-body balance of: La⁻ production & release from working muscles into blood La⁻ oxidation/disposal by other tissues: muscle, heart, etc

 

[Mij]

BLa⁻ production & release is greatest at the start of exercise V̇O₂ (OXPHOS) is still ramping up, and substrate (“anaerobic”) glycolysis must buffer the immediate energetic demand

 

[Mij]

So why do we care about lactate testing? Two reasons: to monitor change over time The major thing that matters for monitoring is consistency of the test LTs are reliable within around 5-10% (10-15 W) 12/

 

[Mij]

to predict real world performance LTs can be useful to extrapolate / predict transitions between intensity domains, or race performances This 2018 study found that differences in LTs could explain 30-60% of the variance in TT performance

 

[Mij]

We need to keep in mind what information the test is trying to give us Try to picture *logarithmic*
BLa responses during your exercise sessions, instead of exponential This might improve how we apply information from our tests to our training!

 

[Mij]

Turns out hearing that "BLa increases exponentially at high intensity" is a bit of a pet peeve of mine
Hopefully this thread can help how we think about this If you chose 'exponential' were you thinking about a lactate test? Or were you thinking about it some other way?