https://www.mayoclinic.org/diseases-conditions/tachycardia/symptoms-causes/syc-20355127#:~:text=In%20tachycardia%2C%20an%20irregular%20electrical%20signal%2C%20called%20an,a%20heart%20rate%20over%20100%20beats%20a%20minute.
Arial tachycardia is NOT the same as a fast heart rate where the entire heart speeds up in order to allow the person to meet a requirement. Atrial tachycardia is where only the atria are beating quickly, while the ventricles continue to respond to the normal signals descending down the Bundle of His and thence to the impulse moving along the two bundle branches. What you are describing, atria beating quickly to exercise, would normally be accompanied by a commensurate rise in ventricular speed. Clearly our OP is not experiencing this, and that is why the formal diagnosis is 'atrial tachycardia', and not just tachycardia.

IOW, this is an arrhythmia. People running to meet a bus don't normally fall into an arrhythmic rate. If they do, it's a pathology, not normal.

My highest heart rate recorded was 163 bpm, any time my heart rate increased or I would get light headed or black out for a couple seconds was all just from me standing up from a sitting position.