Why do blood pressure recommendations say rest 5 minutes before checking? if your constantly active through out the day, wouldnt this be a false read?

Blood Pressure: Excellent question. Blood pressure is typically measured while sitting and resting arm at heart level . But why? Blood pressure increases in response to stressors such as exercise & work. The average level is thought to matter most but the American Heart Association believes diurnal variation & short term variability contribute to pathology.Read: http://circ.ahajournals.org/content/111/5/697.full