I recently bought an EDGE Lactate meter, and I would say it is the single best purchase I have ever made for a healthcare device. It is driving my understanding of my disease, and it is informing my doctors about places we should dig further.
What I think people are failing to appreciate is that the lactate meter is a direct window into how much anaerobic glycolysis your body is doing at a given point in time. The key to understanding when post-exertional malaise may strike is understanding when you have crossed a workload threshold and started to exert anaerobically. Different people will have different causes for CFS, but ultimately we all get to a combination of factors where a low level of exertion makes us produce significant components of our energy production anaerobically. I guarantee you that in a condition like CFS you probably cannot detect this threshold without the aid of a meter.
In my case, I got the shock of my life when I tested my peripheral limbs and had really elevated lactate levels, even at rest. In my fingers, I was getting numbers as high as 9 mmol/L at rest. In my toes, I was getting far larger numbers, as high as 17 mmol/L. I realized after significant testing that these were not reflective of systemic lactate. I was, in fact, measuring localized tissue hypoxia, and the amount of hypoxia was different in different parts of my body.
I have been able to totally clear these high lactate levels just by going to a gym and engaging in hot/cold therapy to dilate my vascular system. So, for example, I will alternate between a cold pool, steam room, sauna, jacuzzi, etc. After 50 minutes of that, my vascular system relaxes, and if I re-test lactate it normalizes below 2 mmol/L. It's too early in my experimentation cycle, but at this point, I am 80% certain that my version of CFS is being driven by narrowing of capillaries in my vascular system, or alternately by the presence of some immune or inflammatory reactions in the peripheral tissues.
The bottom line is that I believe my peripheral tissues are not receiving oxygen and the reasons for that likely deal with issues that exist outside the cell. Aerobic metabolism is impaired simply because oxygen cannot get into the mitochondria. The high lactate levels are only an artifact of a cell struggling to create energy by the more primitive anaerobic glycolytic system. The fact that I am able to totally reverse the lactate levels by a therapy that dilates small capillaries is highly suggestive to me that I will be able to take actions that reverse many of the symptoms.
I need a few months to follow through on this research, and I will try to come back and update on conclusions. But I would say that *if* you are a person with a careful mind and an ability to formulate valid experiments, run do not walk and buy a lactate meter and begin testing widely, in many different peripheral tissues, at many times of day, under many types of workload. Within three weeks of initiating testing, you will have a fairly precise understanding of when your body is going into anaerobic glycolysis and the steps you can take to stop that and reverse it before PEM sets in. Having said that, most people don't form valid experiments. If you don't know how to create experiments with single independent variables, and with well-defined dependent variables, you will have a harder time making progress with the meter.