What happens to blood pressure during steady state exercise?

After 30 minutes aerobic on a Bowflex Treadclimber my systolic pressure dropped by 50 - from 144 to 94 and the diastolic by 20 - from 85 to 65. The effort was fairly intense - sweating after 13 minutes for more than 17 minutes. Others' experiences would be interesting. Please email to kk@rpf.com thanks