I’ve written a lot about my health over the past few years, and my efforts to try and do something about it. Each little clue gave me new hope, into which I threw my full energy. I took every inch and reveled in it, moving as far as I could before inevitably declining once again (increased effort met with increased resistance). These were genuine steps forward though, rather than false starts: I lost weight, gained focus, and started sleeping better, so each time I was really complaining from a new place.
The biggest gains came from discovering sleep apnea, candidiasis, and suspicions of mitochondrial myopathy. None of these are naturally indicative of McArdle’s Disease (the eventual diagnosis) though, nor are they typically concomitant. They didn’t fall into their place in the puzzle until the picture was already becoming clear, when it all suddenly came together.
I should start by explaining a little about the condition. Glucose is the primary source of energy for nearly everything in the human body, the whole process referred to as “glycolysis.” Most cells, especially muscle cells, have an internal reserve of it in a compact polymer-like form called glycogen. When demand for energy increases, molecules are trimmed off the end of the chain and made available to the mitochondria to do their business of converting it into active energy (adenosine triphosphate, for those taking notes).
This store of energy is pretty high – enough for 12-20 hours worth of activity before needing to be replenished. That replenishment happens on a regular, ongoing basis, to keep stores topped off whenever spare glucose is available, and any surplus is either excreted or converted into starches and stashed elsewhere. Normally this is enough to keep the body readily burning glucose between meals without running low – an exception would be fasting (more than a day), starvation, or extremely high demand: marathon runners, for example, can completely deplete glycogen stores after about 20 miles of continuous running, a phenomenon they refer to as “hitting the wall.” At that point continued activity requires use of the stored fats as an alternative fuel, and risks damage to those tissues unable to do so.
McArdle’s refers to a defect in or absence of myophosphorylase, which is a fancy name for “the enzyme that breaks glucose off the glycogen chain.” This deficiency means that the primary source of stored energy is either completely off limits or so impaired as to be unable to meet the body’s demand. This results in dramatic exercise intolerance, and in some cases cramping or seizing of muscle fibers (which require energy both to contract and relax) in a disparate and uncoordinated state so severe that they can actually rupture (rhabdomyolysis – this will be on the test), spilling their proteins into the blood and straining renal functions. Alternatively, the secondary fuel source based on fatty acids can be engaged (lipolysis).
An interesting side note here is that this is the primary intent of low-carb diets: by lowering the intake of glucose (and things easily synthesized into it by the metabolism), glycogen stores are exhausted and the body has no choice but to turn to lipids in order to remain functional. It’s a hack, but a potentially effective one – your mileage may vary though, and not every system can handle the kind of stress this creates.
To point, too heavy a reliance on lipolysis floods the body with its waste products and increases the acidity of the blood (ketoacidosis). Healthy folks don’t normally get to this point – diabetics can be affected in pretty nasty ways though. Those with McArdle’s suffer a similar fate since the reliance on it is more absolute, and constant: this happens on regular diets without regard for carbohydrate intake. I had hit on a form of metabolic acidosis in my investigation earlier but had come to it from the wrong side, thinking that it was an inhibition of the mitochondria in making use of available oxygen, when in fact the mitochondria work wonderfully and are simply making-do with limited materials on hand. The effect is the same though: fatigue, memory disruption, stupor, and eventual unconsciousness.
