What causes DOMS is not believed to be the enzyme, CPK (creatine phosphokinase). The indication of DOMS is the presence of extra CPK in the bloodstream after resistance training. This extra CPK can be in the blood up to 48 hours after your resistance training, but it is not the cause of DOMS.
This is fresh research I just obtained from the convention I attended- DOMS seems to be caused by the actual lengthening phase (eccentric exercise phase) of the resistance training. This lengthening of the muscle pulls the muscle fibers apart, creating a tearing, which leads to DOMS. At the cellular level, when the muscle fibers are torn, the muscle cell releases CPK from it's cytoplasm (or sarcolemma, if you want to be more technical) into the bloodstream (along with other substances, such as calcium), and that's why you see a an increase of CPK into the bloodstream. It seems as though the increase of calcium in the bloodstream may activate the immune response by attracting all those white blood cells typically seen in an inflammitory response, which also adds to that feeling of soreness experienced in DOMS.
With all that said, would massage help to alleviate DOMS? No. All massage does is "aggrevate" the torn muscle fibers, which may result in a further release of these electrolytes and the CPK (aggrevate is the only word I can think of to describe this phenomenon) into the tissues and blood. The lecturer showed us a picture of a healthy (pre-exercise) slide of muscle cross section, then showed another cross section of a muscle after undergoing repeated exercise- it looked yucky- like a Monet painting or something along those lines. It was a big 'ole mess compared to the healthy (as in pre-exercise) muscle cross section. Does massage feel good? He!! yes, it does! But does it really do any good for DOMS? He!! no. For this reason, if you're experiencing DOMS, don't expect massage to do the trick.
What will help alleviate the symptoms of DOMS is ibuprofin- ibuprofin typically works by reducing the inflammatory effects caused by the release of free radicals and calcium into the tissues.
Here's where I begin to theorize based on what I've read- can you still work out while undergoing DOMS? I think so. If you can minimize the eccentric part of the exercise, you could continue to exercise. However, this would be extremely difficult to do, but if you severely lighten your training load, you could get away with it. Often, when I am experiencing DOMS, such as when running hard and the next day, feeling muscle "irritation", I begin walking with short, jerky movements, which feels soooooooo much better than walking with longer strides. I am (subconsciously) avoiding the eccentric phase of the walking by shortening my steps and walking a bit slower than normal. Of course, everything thinks I'm just trying out a new shuffle or something, but that's not it at all! I just can't get my muscles to lengthen enough to take full steps. I'm too sore. The best thing you can do is lay off the training until the DOMS symptoms disappear, then you can resume your training again.
Now, as far as lactic acid buildup, you may feel that "burning" sensation during or just after a high intensity training session, but that is from the buildup of lactate in the blood while exercising. Remembering that fat is only burned in the presence of oxygen, when the body's demand for oxygen exceeds what is being taken in, anaerobic threshold is reached, and the body begins using other energy sources in the body to meet the demands of the body.
There is an enzyme in the fat burning process that drives the Krebs (or citric acid cycle) Cycle- the Krebs cycle is the mechanism in the body's cells that facilitates fat breakdown to ATP+ carbon dioxide +water. This enzyme is called pyruvate. It is an enzyme that is used early in the Krebs cycle, and when oxygen is present, the oxygen will react with ions outside of the mitochondria (mitochondria are structures, or organelles located in the muscle cells)- this ion, which reacts with the oxygen will then allow the pyruvate begin the Krebs cycle when the pyruvate enters the mitochondria, resulting in the production of ATP- the molecules of energy needed to contract the muscle to do further work.
When oxygen is lacking, the Krebs cycle is largely arrested (there will always be a small amount of pyruvate that will enter the Krebs cycle because the only time we don't have oxygen present is when we die! which is what they call rigor mortis...), and the pyruvate is converted to lactic acid through glycoloysis, which is inefficient, because the glycolysis breakdown produces less ATP. This process (or the steps involved, rather) is short- and when the body is in anaerobic mode, it needs ATP right NOW, so it takes glucose from wherever it can get glucose quickly. Fats take a long time to break down, BUT we all know that glucose is located in its free form in different parts of the body- like in the muscles, in the liver, etc. The body will grab these free glucose molecules and use it instead to undergo glycolysis, resulting in the end product of lactic acid and only a few paltry ATP. This system is largely inefficient, as a lot more ATP is required for high intensity demands, so eventually, you will either slow down to the point where you will bring in more oxygen, which will lead to more fat metabolism, or you will cease completely from exercise.... whichever comes first. BUT... this buildup of lactate in the muscles creates an acidic environment, which causes the pain you feel in the legs (burning sensation) when the lactic acid builds in the legs. As soon as you get enough oxygen in the legs, the oxygen will then cause the krebs cycle to resume again, and the lactic acid will be used in the krebs cycle to begin burning fats again. As the lactic acid slowly is converted to pyruvate and enters the krebs cycle, you'll notice the burning sensation leaving the legs. That is why lactic acid buildup could not occur because of lactic acid buildup.
Here's the catch in the difference between lactic acid reuse for krebs and DOMS.... the CPK enzyme, which is used to convert ADP to ATP is USED in the conversion of lactic acid back to pyruvate to produce the ATP.... the basic reaction happening during Krebs is:
ADP +P (with CPK present)-> ATP
Soooooo..... there is not an excess of CPK in the blood when the lactic acid is reused. DOMS is different (re-read the explanation of why CPK is in the blood and do the side by side comparison).
Overtraining has something to do with DOMS, but it ranges beyond that- overtraining is simply not allowing the body enough time to recover from strenuous activity. Overtraining messes with your hormonal levels, releases free radicals into the bloodstream, increases the stress hormones into the body by overstimulating the adrenal cortex, and can cause symptoms of depression, and even sickness in some cases. You'll often feel a run down feeling, accompanied by some other feelings of sickness. When I'm at my most overtrained, I'm feeling like I want to vomit, I feel like I need to sleep all the time, and I am sore and achy. The symptoms vary with different people, but you will experience some of these symptoms. Overtraining can be experienced for a short time if you catch it early, but if you're pushing yourself constantly, the symptoms will intensify until your body makes you slow down, and that's no fun. We all know better- don't overtrain!