Question: Does strenuous exercise effect cortisol levels? If so, should I avoid exercise during a 24 hr urine test and/or for how long before starting the test?

Answer: Strenuous exercise may be stressful enough to increase cortisol levels transiently. If one wishes to obtain a perfect baseline cortisol level it would be best to avoid exercising during the 24 hour period of urine collection. Avoiding strenous exercise at least overnight before the beginning of the collection should be sufficient.

By Dr. David E. Schteingart M.D. (Spring, 2005)