Last week, the CrossFit Journal posted a video clip of CrossFit Endurance coach Brian MacKenzie lecturing on the burning sensation felt by athletes during workouts that tends to slow them down.  Many of us equate this pain to the build up of lactic acid (or lactate), but recent research has shown that lactate actually slows the acidosis process (the build up of acid in our cells) and is actually part of a previously undiscovered metabolic pathway that helps fuel our anaerobic activity.  According to Coach MacKenzie, the tingling or burning sensation we feel during exercise is actually caused by the accumulation of potassium in the tissue and that lactate actually helps alleviate that soreness.  Sodium ions are pumped out of cells while potassium is pumped in via the sodium-potassium pump.  The diagram below provides a summary of the process:

Courtesy of Professor Serianni of University of Notre Dame

What’s interesting is that the sodium-potassium pump becomes more and more efficient as more force is applied…just another benefit of including strength training into our programming.  This also helps explain why many CrossFit Endurance athletes are seeing tremendous results by using CrossFit and shorter, more intense running/swimming/biking/rowing sessions vice traditional training programs. 

You may be wondering then what causes soreness over the few days that follow intense workout sessions.  It’s not potassium which only causes that sensation during a workout, but rather the inflammation resulting from the break down of our tissue (just another reason to focus on strength training and minimizing inflammation via the Paleo diet and fish oil supplementation…I’m just saying).

We’ve had several Intrepid athletes experience better results by tapering down their endurance training and focusing more on the lifting and met-con workouts.  The most recent being Pooja who ran her fastest half marathon just a few weeks ago. 

Scott’s triathlon is next weekend and Alia is running a half marathon this coming Sunday so wish them both luck!

WOD 09.03.10

Back Squat 3×5
10 Deadlift (50% of 1RM)
10 1-Arm KB Push Press
100m Run

6 Responses to “Hurt So Good”

September 3, 2010 at 8:04 AM

Rock it hard Scott & Alia! I know both of you will do well in your respective events! Can’t wait to hear your success stories!

September 3, 2010 at 8:27 AM

Good luck this Sunday Alia!!!

Big ups to Drew for attacking Drewcifer by himself yesterday. Take that fish oil!

September 3, 2010 at 9:58 AM

Hey Sean:

If the burning sensation in our cells is a limiting factor in performance and the sensation is caused by a buildup of potassium in our cells, then is consumption of potassium detrimental (i.e. eating a banana)?

Also, if the pump cycle introduces potassium into the cells (and causes that burning sensation), would a more efficient pump introduce more potassium than a less efficient pump (thus causing more burning)?

Sorry for all the questions…just a little confused!

The way I understand it is the potassium builds up in those muscle tissues being utilized to help faciliate the proper function of our body’s anaerobic metabolic pathways (those that use ATP as fuel). The potassium buildup (burning) is the result of our celluar sodium-potassium pumps inability to pump the potassium into our cells at the rate at which it’s accumulating outside the cells. The potassium build-up outside the cellular walls stimulates our nerve endings which causes the tingling/burning sensation. The pumps’ efficiency improves the more they are forced to work under intense conditions (i.e. workouts that primarily test us anaerobically like strength training and met-cons under 20 mins) and over time are better able to move the potassium into the cells where it’s needed therefore lessening the potassium build up (burning) during our workouts. This phenomenon is part of what helps us increase our intensity over time and better utilize our anaerobic energy systems before relying on our aerobic metabolic pathway. Potassium is an essential element to our body’s functioning and eating foods rich in potassium, like bananas, should not increase the burning we feel during workouts.

Great questions! I hope my answers addressed the issues you brought up, but if something’s still not clear please let me know and I’ll do some more research.


September 3, 2010 at 10:23 AM

What doesn’t hurt so good is my quads!! Thanks for the shout out Ruth. Good Luck to both Alia and Scott. I have seen HUGE gains from both of you in my time with Intrepid. Keep it up.

September 3, 2010 at 10:48 AM

Def missing the pain

September 3, 2010 at 3:38 PM

Thanks Sean!

One more question, since the sodium-potassium pumps exchange sodium for potassium, is it necessary to have sodium in our cells to begin with? Should we try to maintain a level of sodium in our diets (or electrolytes)? If so, what level is recommended?