Lactic Acid / Lactate Threshold

nutrients in >> chemical reactions >> movement / muscle contraction & waste byproducts .. lactic acid is a waste byproduct.

In day to day conversational usage: lactate threshold is commonly referred to as lactic acid burn.

We recommend Circuit Training.    4 weight training videos (streamed from Google) on this page .. play & enjoy

Exercise bio-chemistry: Exercise 'burns calories or utilizes glucose'  via chemical reactions in the muscle cell, converting glucose ( sugar ) into contraction / movement via chemical reactions = a multitude of 'waste byproducts' from the chemical reactions.

Lactic acid is ONE of the 'waste byproducts' resulting from the chemical reactions that result in muscle contraction.

exercise >> more nutrients converted to more energy>> more waste byproducts

& more exercise >> more waste byproducts>> increased concentration of waste products in the worked muscle

The increased metabolic activity ..  the increased work load of exercise .. Produces increased waste byproducts

The 'muscle burn' is due to the neural ( nerve ) irritation associated with an altered pH  ( pH = measurement of acidity, more below ) within the worked / exercised muscle

The pH (potential of Hydrogen) scale is from 1 to 14, with 7 being neutral. Anything that lowers pH makes the solution more acidic.

... the altered pH ( acidity ) is due to a multitude of increased metabolic waste products accumulating in the exercised muscle.



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An elevation in blood lactic acid levels is a major trigger of growth hormone (HGH) release.

High-repetition, short-rest interval exercise produces a significant amount of lactic acid accumulation within working muscles.


The chemical reactions of the Krebs Cycle result in muscle contraction and metabolic byproducts.

The build up of these waste products lowers the pH ( makes more acidic ) of the extra cellular tissue & neural (nerve) irritation results.  Nerve irritation = burning sensation = lactic acid burn.

  • With increased intensity of exercise the amount of metabolic byproducts produced exceeds the body's ability to utilize or remove them from the muscle

  • The inability of the excretory system to keep up with removing the waste byproducts of the Krebs cycle results in increased concentrations of the byproducts.

    • The increased concentrations of these byproducts initially induces a burning sensation ( neural irritation ).

    • Eventually these byproducts will interfere with the Krebs cycle and muscle contraction will cease.

      • An example of this is experienced in drop sets or forced reps .. when a light dumb bell can barely be moved.. :-)

Amino Acids are the building blocks of protein and perform many specialized functions.

Our recommended Lactate Threshold Program takes intervals & circuits to the next level.

If you have ever been there, you will always want to return.

The doer alone learneth. ~ Friedrich Nietzsche (1844-1900)

  • Q. An honest politician and a merciful 'Ultimate Program' instructor both fall out of an airplane. Which one hits the ground first?

  • A. Invalid question - neither of them exist.


  • Green Dash =Insulin
  • Yellow Line = Blood glucose
  • Red Line = HGH
  • Orange Line = Average Glucose

There are positive hormonal responses  with both aerobic and anaerobic exercise.

  • The body has separate and unique positive responses to the different exercise modalities.

Lactate threshold is a second major factor of endurance.

In addition to localized muscular benefits of exercise there are systemic effects of exercise, occurring through the reaction of the endocrine / hormonal system to the increased serum concentrations of the metabolic byproducts.

  • The heat byproduct of the cellular chemical reactions is dissipated by sweating.

  • The CO2 ( & other blood gases ) byproduct is corrected by increased respirations.

  • & increased metabolic byproducts are dealt with by a multitude of physiological changes including vascular dilation & hormonal changes.

"From a muscle perspective, when you do long, slow endurance training, you are only recruiting part of your muscle fibers to do the work," Gibala said. "In high intensity exercise, you call upon all of your muscle fibers. They respond and adapt."

Advanced Principles   Interval Training   A Lactate Threshold Program   Exercise Home   Lab analysis of amino acids

Our hormonal system is constantly the 'analyzing our blood' .. looking for changes in O2, CO2, glucose, waste byproducts.

The American Society of Exercise Physiologists, reported at it's 2001 annual conference in Memphis, Tennessee  that six sets of 10 rep-maximum squats raised peak HGH significantly in the control group from 0.1 to 1.0 ug/L.   A 10X increase in that wonderful hormone, HGH!

Interval Training     Advanced concepts, routines & principles.


Intensity of exercise appears to be the key factor in increasing HGH secretion.

  • Intense training is the most effective stimulus for HGH secretion.  

    • An increase in the lactic acid burn in the exercised muscle is a good indicator that you are "pushing it" enough to optimize hormonal secretions.   

  • These cellular chemical byproducts of exercise are transported systemically by the blood, to cause systemic hormonal changes.

  • Consider an exercise program designed to be a 'Lactate Threshold Aerobic Exercise Program', with waste product production / elimination being given near equal status with nutrient / oxygen delivery.

  • In addition to the commonly referred to "cardio vascular / aerobic endurance", other factors are involved in endurance and usually exist under the 'other aerobic exercise  benefits' groupings.

  • Our body makes internal adjustments to respiration rate, heart rate, vaso dilation & hormonal release in order to adapt to the needs of the exercised muscles .. systemic changes based on the needs of the exercised body part.

Interval Training     Advanced Concepts, Routines & Principles    Circuit Training

pH levels are pretty involved chemistry, however all we need to be concerned with is the fact muscle and blood pH are strictly controlled within narrow ranges. Homeostasis (normal) pH is 7.4.  When we subject the muscle to hard exercise  large amounts of glucose are utilized to generate ATP (the energy molecule of the Krebs Cycle) very quickly. To obtain this large amount of energy the glucose molecules are spit in half to produce two molecules of lactic acid. The research on working muscle shows that the accumulation of lactic acid  in the muscle causes pH levels to drop. A lower pH means an increase in Hydrogen ions in the blood and/or muscle (that’s what the ‘H’ stands for). This is shown to interfere with the contractile force of muscle fibers, gradually preventing further contraction until movement ceases.

Higher rep / endurance / aerobic exercise / work includes primarily enzymatic / hormonal adaptation to lactate and ion accumulation first in the worked muscle then systemically.

Lactate threshold is mainly determined by the ability of the circulatory / vascular / excretory systems  to remove the increased metabolic byproducts ( including lactate ) being produced by a 'worked muscle' at the cellular level.

In addition to supplying oxygen & nutrients to the muscle, the circulatory / vascular / excretory systems must efficiently remove the metabolic waste byproducts created in the exercise / calorie burning / aerobic / anaerobic session.

Our endocrine system reacts to the exercise induced changes in blood chemistry, increased systemic metabolic byproducts, by releasing a variety of hormones. 

Exercising even one muscle to the 'lactate threshold' has systemic hormonal impact!

Let 'lactate threshold' window be an exercise goal in addition to the aerobic 'pulse rate' window.

  If you’re working at a low-enough intensity, your body will be capable of removing the lactic acid and other metabolic waste byproducts "on the fly" and you will be able to continue indefinitely, :-o.

When you start doing more than six reps, you start fatiguing the muscles. The muscles will start retaining lactic acid because the body  & the circulatory system cannot dispose of this increased level of the waste byproducts of exercise.

Lactic Acid burn is in the true physiological sense is a misnomer.  The burn has to do with a change in pH ( acid / base ) in the muscle due to the increase in lactic acid.  The burn is actually the result of the pH change.  But common usage refers to Lactic Acid Burn & we use that terminology here. 

Interesting stuff fatigue. It keeps many university faculties employed through the world and the answer is still not definitive!  Probably the clearest explanation can be seen from work by Dr. Hogan and colleagues at the university of California-San Diego and Auburn University. Their research investigated lactic acid accumulation (that burning in muscles when you reach failure) and pH levels. 

This research indicates that the body reacts to lactic acid build up by increasing  vascular capacity ( improved circulation ) & increased hormonal secretions.  It's a well-known fact that endurance training increases capillary density, increased diameter of existing blood vessels in addition to actually creating more blood vessels.

In regard to blood flow, the body has a network of extremely small blood vessels called capillaries. Their primary function deals with the exchange of oxygen, hormones, amino acids, glucose and lipids among other things. The exchange of certain nutrients at the capillary level is sometimes referred to as nutrient transfer. This blood flow through the capillaries remains relatively constant under resting conditions, but as soon as a muscle starts contracting, the blood flow is increased. It's with these extremely small capillaries that the muscles are supplied with all the nutrients they need for recovery.

Increased demand on the nutrient delivery / waste removal system causes the body to adapt by improving this delivery / removal vascular system.  This improvement in muscular circulation will increase ones lactate threshold, the second bodily system involved in endurance.  

Taking a week off from training every 8 to 10 weeks is very important for overall recuperation

Recuperation is everything.