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What is the Burning Sensation?

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HNNstyle

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I was wondering if anyone can explain the burning sensation when you are doing heavy cardio? I can feel it in and around my body but generally from within my shoulders.

The type of Cardio I do is 4 sessions of HIIT. Each session is 12 minutes and then I break for 5 minutes between sessions. I jog at speed 4 on the treadmill for 1 min and sprint at speed 8 for 45 seconds for a total of 6 intervals/sprints in the 12 minute cycle. I do this 4 times and on the fourth cycle, I can feel a burning sensation radiating in my body with hints of wanting to puke.
 
Pretty sure it's lactic acid. SC will jump in shortly with the science of it I'm sure, but it would fit the bill.

As our bodies perform strenuous exercise, we begin to breathe faster as we attempt to shuttle more oxygen to our working muscles. The body prefers to generate most of its energy using aerobic methods, meaning with oxygen. Some circumstances, however, --such as evading the historical saber tooth tiger or lifting heavy weights--require energy production faster than our bodies can adequately deliver oxygen. In those cases, the working muscles generate energy anaerobically. This energy comes from glucose through a process called glycolysis, in which glucose is broken down or metabolized into a substance called pyruvate through a series of steps. When the body has plenty of oxygen, pyruvate is shuttled to an aerobic pathway to be further broken down for more energy. But when oxygen is limited, the body temporarily converts pyruvate into a substance called lactate, which allows glucose breakdown--and thus energy production--to continue. The working muscle cells can continue this type of anaerobic energy production at high rates for one to three minutes, during which time lactate can accumulate to high levels.

A side effect of high lactate levels is an increase in the acidity of the muscle cells, along with disruptions of other metabolites. The same metabolic pathways that permit the breakdown of glucose to energy perform poorly in this acidic environment. On the surface, it seems counterproductive that a working muscle would produce something that would slow its capacity for more work. In reality, this is a natural defense mechanism for the body; it prevents permanent damage during extreme exertion by slowing the key systems needed to maintain muscle contraction. Once the body slows down, oxygen becomes available and lactate reverts back to pyruvate, allowing continued aerobic metabolism and energy for the body�s recovery from the strenuous event.
 
Hmm I read about that before but I never figured out if it's safe to maintain such a high level of lactate acid and I never figured out if I'm burning more fat that way. Would you happen to know?

Edit: I remember reading one article that said your body uses lactate acid for energy and that it might actually prefer using it. It was some test that was done using frogs.


I just found this and I'm about to read it.
http://www.sciencedaily.com/releases/2006/04/060420235214.htm
 
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SC has the science behind the answer. But I thought I would throw in the Cardio burns both Muscle and Fat, not just fat. But if over all skinny is what your looking for its better then over all fluffy.

I do two 30 min resistance cardio sets 6 days a week on my eliptical machine going through the preset training sessions. I dont have the burning feel your talking about but many times on the 2d session I can start to smell the ammonia-smell from the NO2 in my sweat.
 
HNNstyle said:
Hmm I read about that before but I never figured out if it's safe to maintain such a high level of lactate acid and I never figured out if I'm burning more fat that way. Would you happen to know?

Edit: I remember reading one article that said your body uses lactate acid for energy and that it might actually prefer using it. It was some test that was done using frogs.


I just found this and I'm about to read it.
http://www.sciencedaily.com/releases/2006/04/060420235214.htm
Click to expand...

The lactic acid theory is an old one that, for some reason or another, won't just die. Anaerobic glycolysis is used heavily at higher workloads when oxygen is unable to be utilized due to the cells working at a maximum. When the oxygen can't be used, pyruvate become lactate (also known as lactic acid), which can give off hydrogen ions that are acidic. However, that doesn't contribute that much to pH changes (measure of acidity). In actuality, the CO2 created by increased metabolism results in increased carbonic acid within the blood. In addition to this, potassium levels get skewed from baseline, which contributes to to that sensation of burning. In actuality, the burning sensation and true fatigue during cardio have more to do with the central nervous system. The mechanisms aren't entirely understood, but the central nervous system responds to the high demand and actually sends out inhibitory input to function. This results in excessive fatigue. Technically, what you think your max is during exercise and what your max actually is in a life-or-death situation is very different, based on stimulation of your nervous system. It changes.

But yeah, it's definitely not lactic acid. As others have said, lactate can actually be utilized by other sources as energy (the liver, cardiac muscle, etc), but it's not really contributing much to the energy cycle. Since it wouldn't be forming unless the oxidative cycles were maxed out, even if it goes to places like the heart to be utilized, it likely won't.
 
Exodist said:
SC has the science behind the answer. But I thought I would throw in the Cardio burns both Muscle and Fat, not just fat. But if over all skinny is what your looking for its better then over all fluffy.

I do two 30 min resistance cardio sets 6 days a week on my eliptical machine going through the preset training sessions. I dont have the burning feel your talking about but many times on the 2d session I can start to smell the ammonia-smell from the NO2 in my sweat.
Click to expand...

If your nutrition is fine, it won't really affect either. During cardiovascular exercise, you directly burn fat and carbohydrate. The higher the workload, the more carbohydrate you metabolize. The lower the workload, the more fat you metabolize. However, don't misconstrue this and think low intensity cardio is better for directly burning fat stores. The overall affect must be mediated by caloric intake, if fat loss is desired. No matter if you do high intensity or low intensity and burn the same amount of calories - if you're not in a caloric deficit, you won't lose fat. Also, muscle is really only broken down during longer, higher effort exercise. That's due to low glycogen stores as exercise goes on. Muscles get broken down into amino acids, amino acids get converted into pyruvate or glucose for energy.
 
Exodist said:
SC has the science behind the answer. But I thought I would throw in the Cardio burns both Muscle and Fat, not just fat. But if over all skinny is what your looking for its better then over all fluffy.

I do two 30 min resistance cardio sets 6 days a week on my eliptical machine going through the preset training sessions. I dont have the burning feel your talking about but many times on the 2d session I can start to smell the ammonia-smell from the NO2 in my sweat.
Click to expand...


I'm overweight by about 35 pounds right now. I'm thinking it's about time to get back into shape. Want a before and after picture? heh..


SociallyChallenged said:
The lactic acid theory is an old one that, for some reason or another, won't just die. Anaerobic glycolysis is used heavily at higher workloads when oxygen is unable to be utilized due to the cells working at a maximum. When the oxygen can't be used, pyruvate become lactate (also known as lactic acid), which can give off hydrogen ions that are acidic. However, that doesn't contribute that much to pH changes (measure of acidity). In actuality, the CO2 created by increased metabolism results in increased carbonic acid within the blood. In addition to this, potassium levels get skewed from baseline, which contributes to to that sensation of burning. In actuality, the burning sensation and true fatigue during cardio have more to do with the central nervous system. The mechanisms aren't entirely understood, but the central nervous system responds to the high demand and actually sends out inhibitory input to function. This results in excessive fatigue. Technically, what you think your max is during exercise and what your max actually is in a life-or-death situation is very different, based on stimulation of your nervous system. It changes.

But yeah, it's definitely not lactic acid. As others have said, lactate can actually be utilized by other sources as energy (the liver, cardiac muscle, etc), but it's not really contributing much to the energy cycle. Since it wouldn't be forming unless the oxidative cycles were maxed out, even if it goes to places like the heart to be utilized, it likely won't.
Click to expand...

Thanks for the info SC.
 
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