Are you a Serious marathoner who decides training outdoors in the winter is a good way to get a leg up on the competition.  What problems may result from continuing this type of activity in these conditions? She also believes in thorough checkups because of kidney dysfunction when she runs a marathon.  

Test results show renal failure with a reduction in GFR, increases in serum potassium and decreases in serum sodium.  Why would her body respond this way to a run?  Finally at the age of 64 years she sometimes has to deal with occasional constipation.  Why would she have to deal with that problem with proper diet and exercise?