exercise intolerance

[a.k.a]

I run about five and half miles twice a week. Clearly, I’m not over training, but my leg muscles feel as if I have. After a workout my muscles are stiff, weak, and ache. Its mostly my quadriceps that ache, they start aching during my run. Its difficult to walk around the next day because my legs feel so beaten up. It takes at least two/three days of rest to recover. My muscles always feel stiff and tight. I’ll start running at an easy pace. Its gets progressively harder as my legs muscles run out of fuel. This is followed by a strong second wind which happens after around 20  minutes. Now I’m running with ease and going faster. At this point I must be using fatty acids as fuel.  This is a general pattern that varies between workouts. Consuming a sugar drink before running seem to help. I’ll have more energy and won’t run out of gas. But it does not help me recover from the workout. I haven’t seen any indication that I’m causing damage to my muscles, even though they feel damaged, which  is a concern of mine. My cpk was normal at rest, but was not checked after a workout. I been running for the last six years. My symptoms have gotten worse over the last two, which is another concern of mine. Since I never did any running until six years ago, its possible I have always been this way. Even though its rare, could these symptoms be due to an inefficacy in one of my metabolic pathways.  I would appreciate any insight you can give me.  My  aldolase was normal, sed rate 0, crp {low .3 mg/l}, ana neg, rheumatoid factor and thyroid normal. I’m in my late fifties.

[CCF-Neuro-M.D.-SH]

First of all, keep in mind that I am unable to diagnose you because I am unable to examine you, this forum is for educational purposes.    
   The symptoms that you describe are non-specific, but sound the most like normal fatigue.  I suspect that your diet may not allow for adequate glycogen stores in your muscles, you are relatively dehydrated or you have gained some weight and have increased work of running.  Some metabolic diseases and myopathies have very mild symptoms, so I would recommend some testing to evaluate for these.  First I would recommend serum lactate and pyruvate levels along with ammonia to evaluate for mitochondrial disorders.  I would also suggest serum and urine amino acids along with urine organic acids.  I would also suggest an MRI of your lumbar spine to evalute for spinal stenosis. If the above si negative, then an EMG of the lower extremities may be warranted.
I hope this has been helpful.

[johnflox]

Have you taken statins (for cholesterolemia)? Have you gone abroad and taken antimalarials (lariam)? Have you taken cipro, levaquin, avelox or similar antibiotics during the last three years?
All those prescription drugs and many others cause ALL the symptoms that you mention when the reaction is rated as mild. In more severe cases, CPK's, aldolase, bilirrubin and other liver enzymes are also elevated.

Just to rule out potential causes, so that you can center your search.

[problemmatic]

I am not a doctor but the "second wind" phenomenon sounds like descriptions I have read of one of the metabolic myopthies of muscle/mitochondrial disorders.  You might want to look those up and see if anything rings true.