.5mm st segment depression

I recently had a treadmill stress test. I am a 37yr old male. The reasons for the test were shortness of breath, poor aerobic capacity (at least in my non-professional opinion), weakness/lightheadedness with lifting heavy objects and daily palpitations (at times 3 or 4 consecutively). The Cardiologist reported my exercise tolerance to be good however an ST depression of less than .5mm was displayed. He indicated this is not conclusive of ischemia however I would like to know if any ST segment depression should be considered normal. ie: would an average 20yr old with no health issues have any ST segment depression? (not that I'm 20, just referencing)