A man squatting on the ground gets straight up and stands. The force of reaction of the ground on the man during the process is:

In the process of getting straight up and standing from the squatting position, the man exerts a variable force (F) on the ground to set his body in motion. This force is in addition to the force required to support his weight (mg). Once the man is in a standing position, the normal reaction becomes mg.

Therefore, N−mg>0⇒N>mg   (initially)

and later when he stands up and becomes static, then, N=mg