What is That Burn? The Scientific Finding!

By: FitSource17 - August 18, 2007
So, what is that burning, hurting, breathless, “pain” we get climbing that last mountain, pushing that last shoulder press above our heads? FINALLY, science has found the answer…and you may be surprised at their findings.

Eighty years ago scientists discovered how our muscles contract, which is a finding that garnered the Nobel Prize. It is also a long story as to the process of a muscle contraction. However, to understand the “burn” we must know that calcium (which is stored in the sarcoplasmic reticulum) is involved, as is ATP (adenosine triphosphate), S1 units, myosin and actin fibers, water, acetylcholine, and other minerals and vitamins of the body.
Eighty years ago scientists discovered how our muscles contract...

Because these scientists won the Nobel Prize, the general world believed them when they said that lactate (lactic acid) was the direct reason and byproduct that makes us feel the burn. This is not the case so—take a deep breath. During a workout, glycolysis (breakdown of sugar) uses ATP, which when used, the ATP splits off a hydrogen ion. There is so much glycolysis occuring during a set of squats, the byproduct of glycolysis (pyruvate) is actually trying to bond with the hydrogen ion. This bond between pyruvate and hydrogen ions is what gives us lactic acid. Therefore, the lactic acid (lactate) is actually buffering the hydrogen ion! Lactic acid is trying to help you keep doing an extra rep, or climb that hill a little longer, by storing the hydrogen ion. So the hydrogen ion is what causes the burn. Hoorah for the hero lactic acid!!!! (This is also why staying hydrated is so important). Within 45 minutes, the body converts lactate back to glycogen to store it, or uses it! This is the reason when you slow down your intensity to recover a bit, you can do more reps, or run a little longer with renewed stores of energy! There is more…

Physiologically…why do we stop at number 8, 12, 15 of a set? What caused total fatigue? It is NOT lactic acid. Those of you who studied under Dr. Hackney at UNC will remember the enzyme acetylcholine (ACh). ACh is our body’s catalyst that takes the message from the nerve to make calcium help contract the muscle fiber. If we didn’t have ACh we would all be sloth-like creatures! The hydrogen ions interfere with the calcium’s binding with this fiber—again why lactate is the hero! But there is so much hydrogen, lactate can only store so much, and acidosis begins. Eventually, hydrogen ions begin to slow down the ACh activity which, to reiterate, takes the message from the nerve that says “muscles move.” This is why at rep 8, we begin to see a slowing of the rep, until by number 12 we just can’t do another squat!

WOW! That’s a lot of info to absorb…so much that books will be written about it soon. Be looking for research from Dr. Len Kravitz (yes he’s heard the jokes, and he can’t carry a tune) and from his and other colleagues in Exercise Sciences. Some brave new things are happening that directly relate to the athlete and general public as well. Remember: with new research comes companies looking to make a quick buck. So watch out for supplements in the future claiming to help this buffering system! Claims can be squashed at supplementwatch.com which is a great site to research latest findings. Now…go forth and prosper.

About the Submitter


I am a Personal Trainer with over 10 yrs experience with all types of athletes, sedentary folks, and weekend warriors. Active Concept Training...that's me...Mobility, Motivation, and Mindful Contitioning. I also own a company that provides continuing education credits for fitness professionals called FitSource.

I love to bike! Go down a road I've never been, and see where it goes!!

Public Comments

Login to post a comment.

FitLink is a Venture Technology company. Copyright © 2006-2012 Fitlink, LLC