My bp is normally 96/70, after walking on treadmill for 60 min (heart rate at 105bpm) my bp was 87/74. why the drop after exercise? hydrated & ate

Low BP: Your low blood pressure is concerning. Please have a doctor recheck your pulse and pressure manually, since electronic monitors can give inaccurate results. Go to the ER if you are dizzy, short of breath or have chest pain. Also, it can take hours for the blood pressure lowering from dehydration to resolve with oral rehydration, and this may be the effect you are noticing.