Standing and sitting have different body positions, so the heart rate will be affected, but the difference will not be too big.
Heart rate is the number of times the heart beats in a minute in a quiet state, the heart can regulate the heart rate to affect the output of blood, so when the body position is changed, the amount of blood back to the heart is affected, the heart rate will also change.
In a standing position, the blood is affected by gravity, which affects the blood of the lower limbs to rise and return to the heart, so the heart rate needs a higher frequency of pumping blood to meet the needs of the organism.
When sitting, the lower extremity blood is affected by gravity lower, back to the heart blood rises, so the heart rate will be slower, but only relatively slower, the difference between the two will not be too much.