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fitness & McArdle's disease (myophosphorylase deficiency/glycogen storage disease Type V)

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Anna1976 Fri 15-Mar-13 01:36:16

Does anyone on here have, or know someone with McArdle's disease?

I've recently discovered that I have struggled all my life with fitness, particularly anaerobic exercise, because I can only pull glycogen out of my liver, not my muscles, because I lack myophosphorylase, the enzye that permits use of muscle glycogen.

This means that while i can run, and can improve a bit with training, I have to work extremely hard, my heart rate goes through the roof (typically >180 on a gentle run), I find very fast or very strenuous exercise impossible to sustain, and I "hit the wall" very frequently (often coming back from an easy run hypoglycaemic and hypothermic; sometimes ending up with severe cramps and black urine after pushing myself to the limit).

But provided I take things slowly and gently, warm up at my own pace, and don't try to compete with anyone, I can run up and down hills for about an hour without any problem, cycle slowly up hills, swim laps etc. - I am one of the very lucky ones, even though I would quite like to be able to run or cycle with others but am too slow. Typically McArdle's leads to quite severe exercise intolerance and cramping, myoglobinuria and kidney problems after hard exercise, and often thus leads to a very sedentary lifestyle.

However some proportion of cases have a relatively mild presentation like mine, and I am wondering if any of you know what this feels like? I'm just interested in how variable the presentation is. The medical literature is a bit uninformative about the range of how the disease presents, because the severe end of the spectrum gets diagnosed, whereas the mild end probably just gets labelled "unsporty" and never discovers that exercise is possible.

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