The Upper Cut
The upper cut is used in close fighting. The blow is an upward scooping motion with the palm facing you and can be administered with either the lead or rear hand.
To deliver an effective short uppercut keep your knees bent before striking and straighten them as you throw the punch. At impact you should be on your toes and leaning slightly backward. The weight should be on your left foot if the blow is a right and vice versa if the blow is a left.
(Lee & Uyehara 1991 vol 4 )