Thanks for your query.Based on the facts that you have posted it appears that you have been catheterised to relieve acute retention of urine and have noticed blood in urine after having exercise.You have not mentioned your age in your query.
This is due to friction of the catheter during treadmill exercise.However you can not be on catheter drainage
for a long period
Please consult qualified Urologist
for clinical examination to find out cause for acute retention of urine He may advise you to get following tests done to come to diagnose the cause of retention.
1) Routine urine test and urine culture,
scanning of abdomen to rule out any prostate
Further treatment will depend upon the nature of pathology.