[Scott Johnston]

Ryan:

The lactate shuttle does become the limiter to your endurance at the lactate threshold.  By definition, the lactate threshold or anaerobic threshold occurs when the lactate removal rate just equals the lactate production rate.  Since this metabolic threshold represents your endurance limit and since the removal rate is dependent on the shuttle the shuttle becomes the limiter to your endurance.

I hope this helps.  You might want to read this article https://evokeendurance.com/126579-2/

Scott