21 male. heart rate was 120 while washing dishes and then sat down went to 84? big difference? had ecg, echo, stress ecg, 24h holter.

POTS?: If every test is negative consult your physician about pots ( postural orthostatic syndrome ). Most commonly young females but can happen in males. Heart rate goes up when standing over 30 beats from normal. Other symptoms can be associated. Secondary causes most be r/o like electrolyte unbalance, endocrine disorders, food allergies etc. Consult your physician.