Dear Indoor Cycling Instructors: Please STOP saying these phrases…

“… flushing the legs…”

“…clearing out the lactic acid…”


To All:  How many times have you heard variations of these two phrases during an indoor cycling class?

To Instructors:  How many times have you said variations of these two phrases during your class?

They sound like cool science tips right?  After a hard effort with heavy resistance where our legs are burning we hear or say, “let’s flush out the legs by reducing resistance so we can clear out the lactic acid to prevent muscle soreness tomorrow.”  What if this command is inaccurate and impossible? 


To Instructors:  Do you know the people taking your indoor cycling class?

Here is a true story.  Small university town.  Premiere group fitness studio.  Newly certified instructor teaching a packed evening class and after the final mountain climb makes the above statements about flushing legs and clearing lactic acid.  Little do they know, but one of the participants is a professor in kinesiology.  Oh.  And he was also the chair of the Gatorade Sports Science Institute and editor of the national guidelines for exercise prescription.  The following week, he provides a physiology text book (that he wrote) with a personal inscription and signature.  Ooppss!  Awkward…

So what is really going on? 

Lactate is a molecule produced when glucose is utilized at any time.  Therefore, lactate is present in the blood, as well as multiple tissue types, during rest and exercise.  It is not a waste product, in fact, it is a FUEL! 

Since lactate is the byproduct of glucose utilization, when we exercise, more lactate is produced.  During challenging indoor cycling efforts, such as power intervals or hill climbs, fast twitch muscle fibers are recruited, requiring a greater amount of glucose which results in the production of a greater amount of lactate.  This lactate can be directly utilized as a fuel by the heart or indirectly as it is recycled into glucose in the liver.

When we exercise at high intensities, working tissues produce acids (but not from lactate and not lactic acid) faster than we can clear them and this likely causes the burning sensation.  When we lower intensity, by reducing resistance or cadence, acidity decreases.

Cycling at a faster cadence, in order to flush out the legs, does not have an effect on how quickly we return to resting pH or lactate concentrations.  And neither one of these affects muscle soreness in subsequent days.  The painful, stiff feeling is likely due to small tears in the muscle.  Try to think of this positively as you are creating a training effect!

Bottom line!  Let’s make sure our information while instructing is both accurate and motivating… delete flushing the legs and clearing lactic acid from your informational cues!


12 Responses

  1. I thought they flush was just when you take it easy at the end of class. I sometimes say this at the end of trip. And the last track in Les Mills Sprint is actually called flush!

    • Hello Alison! You are totally right. Glen and the presenters use FLUSH as a generic term for RECOVERY… they do not attach it to lactate or lactic acid. It is not my favorite replacement for recovery because it is not physiologically accurate. Jinger

  2. When would it be appropriate to say “flush the legs” I’ve heard Glen say it many times on RPM videos. Is he not using it appropriately? (I realize it’s possible for Glen/LM to make a mistake. Thanks for giving good science to the LM community.

    • Hi Danica! Glen uses FLUSH as a generic term for RECOVERY… he does not attach it to lactate or lactic acid. It is not my favorite replacement for recovery because it is not physiologically accurate. Thank you for caring! Jinger

  3. That’s Amazing Information! Please provide more similar knowledge about any other tips or cues so that we understand them deeper and be able to even interpret them with our own words!
    Me personally , I am a licensed massage therapist, personal trainer Certified nasm and corrective exercise specialist but a lot of the deeper information gets forgotten over the years and this reduces my attention to phrases like these so I can easy repeat what a filming instructor says without thinking whether it is true or not!! Please,
    We love your information! Continue scanning and providing , we are reading thirsty to know!!!

    • Thank you Milena! This is my main goal… useful tips that you can apply to enhance your training, your coaching and the experience for your clients/members. Please let me know if you have any specific questions. Jinger

    • Hi Sheldon!!! Super honored to have you check out the blog! YES! I think active recovery is perfect.

      • Thanks for the info. I also use the term “flush” during recovery – although haven’t attached lactic acid. I do like the members to get a sense of the recovery, purpose of each position, push, pace etc. Active recovery is good. I’m trying to think of other things to say. Ride easy?

        • Hi Tammy! YES! I like ride easy too… if there was something we were flushing, the term would be fine!
          Thanks for caring and reading!

      • Active recovery makes sense. Due to that’s what we say in some of the other formats. So it makes sense in cycling class too. But I too have fallen victim to saying what they say on the videos. Glad to be reading all of this neat information .

        • Hi Maura! It is totally a learning process for all of us… just a great lesson in thinking about the meaning of our coaching. Thank you for reading! Jinger

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