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!