New research study reporting that high doses of oral supplemental vitamins C and E blunt the positive effects of 20 min of aerobic and 45 min of circuit training (for 4 weeks) on insulin sensitivity. Free article online. (Proc Natl Acad Sci U S A. 2009 May 11. [Epub ahead of print]
Note that warm up and cool down do not qualify as exercise. The article reports 20 min of warm up and cool down together.