Lactic Acid / Lactate Threshold

[BSHC]

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.

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.

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   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.
 
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 cause muscle fiber shortening = muscle contraction.

The chemical reactions ( glycolysis / Krebs Cycle amongst others ) convert the nutrients into waste byproducts to be dealt with by the excretory systems.

nutrients in >> movement & waste byproducts out.

The waste products are normally easily removed from the muscle.

As exercise (more muscle contraction = more chemical reactions ) increases the amount of byproducts produced also increases .. eventually the amount of byproducts produced  exceeds the bodies ability to remove them from the muscle group.

Common examples:

O2 to CO2

The chemical reactions are exothermic .. release heat = sweat!

The Krebs Cycle deals with converting ATP >> ADP >> ..

There are 1000s of 'chemical reactions' happening simultaneously in the body, each producing byproducts

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.. :-)

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.
 

ALBANY, N.Y. (AP) - A new study suggests that doing intense interval training for 20 minutes three times a week is just as effective at boosting strength and endurance as five to six hours of jogging or moderate cycling.

"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."

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

Huge HGH release associated with increased serum levels of lactic acid.

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!

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.

Both aerobic & anaerobic exercise increase the amount of these cellular metabolic byproducts. 

The most commonly noted byproducts of the increased muscle / cellular activity are heat buildup & sweating.

Increasing the amount of muscle activity ( exercise ) results in increased cellular metabolic reactions which results in increased metabolic byproducts ( in addition to the mentioned heat released by the chemical reactions! )

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.

As the body removes metabolic byproducts from the worked muscles ( venous return blood ), the byproducts flow systemically in the blood until they are excreted from the body.

Simultaneously with localized muscle buildup of metabolic byproducts, the systemic 'metabolic byproduct' levels are increasing.

The altered chemical makeup of the exercised muscle effects systemic blood chemistry.

The body is constantly monitoring the chemical composition of the blood. 

Increased waste products such as lactate and other byproducts of the energy producing Krebs cycle.

Blood gas concentration such as CO2 relative to O2.

The body reacts to the altered chemical composition of the blood with increased hormonal secretions, vascular dilation in some areas & vascular constriction in other areas.

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.

The burning sensation we are speaking of is a result of the  influx of lactic acid into the muscle fibers causing a change in pH  while training. This is caused through high repetitions both depleting glycogen in the muscle fibers and exhausting the oxygen supply in your muscles.

Endurance athletes try bi-carbonate loading. It tends to ‘buffer’ (reduce) the increase in hydrogen ions and keep blood pH levels within the narrow ranges thus delaying fatigue.

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.  

There are increases in HGH associated with relatively hard aerobics and relatively heavy anaerobic exercise ( weight lifting ).   

Participants in the  Ultimate Aerobic & Anaerobic Synergistic Exercise  Program will experience increased serum levels of HGH. 

High-repetition, short-rest interval anaerobic exercise results in a significant amount of lactic acid accumulation within the working muscles.

The Anaerobic portion of this program addresses Aerobic / lactate threshold fitness through the use of circuit training principles.

Short periods of increased intensity during periods of aerobic exercise also result in a significant increase of lactic acid present in the muscles.

The Aerobic portion of this program achieves some Anaerobic / lactate threshold benefits through the use of interval training principals.

Both the anaerobic & the aerobic portions of the complete program are designed to increase HGH releasing lactic acid.

For hormonal stimulation and weight loss do the aerobics first.   This will deplete blood glucose and stimulate fat metabolism for energy.  

You will tend to "bonk" or run out of energy during the anaerobic portion of the program.

The lower your blood glucose is when you exercise the more of a HGH spike you'll get, because HGH is part of the fat metabolism equation. 

With low blood sugar the body will need to metabolize / burn fat for energy.

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

Many people have a psychological barrier to taking time off from training. They feel like they are going to shrink. Not so. In fact after your week off for complete recovery  you will usually come back stronger and energized.   I am always surprised how many reps I can pump out after several days off!

As you perform your exercise routine many physiological reactions are taking place to make all this happen. Muscle contraction takes cellular energy, oxygen, chemical reactions within the cells, and a host of other molecular activities. As each rep is performed you deplete your muscles' capacity to contract with the same force as with the first rep. By the time you get to the last rep you have tapped out your muscle intra-cellular energy capacity.

It is rather critical to let your muscles recover.  We do not recommend hard aerobics on back to back days or lifting weights on consecutive days.  If a muscle is not allowed to recover between workouts muscle growth will be impeded, over-training will occur, and muscle breakdown will be inevitable.  The chance of injury increases greatly if you work the same muscle group / joint hard day after day.

Recuperation is everything.

http://www.csmngt.com/lactic_acid.htm

역치 [閾値, threshold value] 
 
 
생물이 외부환경의 변화, 즉 자극에 대해 어떤 반응을 일으키는 데 필요한 최소한의 자극의 세기이다.
 
감각세포에 흥분을 일으킬 수 있는 최소의 자극의 크기를 말하며, 문턱값이라고도 한다.
역치는 세포의 종류에 따라 다르고 같은 세포일지라도 그 세포가 자극을 받는 상태에 따라서도 달라진다.
이와 같은 역치의 변화는 그 세포가 흥분하기 쉬운가 어려운가를 뜻하므로, 흥분성은 일반적으로 역치값의 역수로 표시한다. 즉 약한 자극에도 흥분하면 역치가 낮고, 강한 자극을 주어야만 흥분하면 역치가 높은 것이다.

역치는 그 감각기의 수용기에 적합자극(adequate stimulus)을 주었을때 가장 낮게 나타난다. 예를 들면, 사람의 눈에 맞는 적합자극은 400~700nm의 가시광선이고 귀는 20~20,000Hz의 음파로 이때 가장 쉽게 흥분하게 된다. 그러나 귀에 음파 이외의 다른 자극을 주면 흥분하기 어렵고 이를 부적합자극이라고 한다.

역치의 법칙은 운동에도 적용된다.
덤벨을 들 때도 역치 이상의 무게를 들어줘야 근력이 늘어난다.
가벼운 덤벨을 10회 드는 것이 무거운 덤벨 1회 드는 것보다 못하다는 뜻이다.
횟수나 시간도 마찬가지인데 이때 역치가 운동의 규칙 중 하나인 '한번에 30분 이상, 일주일에 3차례 이상'이다.
평일 내내 가만 있다가 주말에 등산이나 골프를 한차례 했다고 온종일 운동했다고 자랑해선 곤란하다. 이 경우 오히려 부상 등 역효과를 불러올 수 있다. 운동 효과를 얻으려면 띄엄띄엄 해선 안되며 평일에도 꾸준히, 규칙적으로 해줘야한다.

같은 크기의 자극을 지속적으로 받으면 역치가 올라가 더 큰 자극을 주기전에는 자극을 느끼지 못하는 경우가 생기는데 이를 감각의 순응이라고 한다. 예를 들면 우리가 일상생활을 할때 속옷을 다른것으로 갈아입으면 그 즉시는 촉각을 느끼지만 어느 정도의 시간이 지나면 옷이 피부에 닿고 있다는 느낌이 없어지는 경험과 같은것이다.

http://blog.daum.net/hanngil/12406631

 http://blog.daum.net/hanngil/12405957

http://cafe.daum.net/bshealthclub/LwKy/44

http://blog.daum.net/hanngil/12406659