This exercise is called "Wo Hu Gong" ( resting tiger workout ).
"WO" means to rest, "HU" means tiger and "GONG" stands for work ( same gong as in the word gongfu aka kung fu )

Wohugong is a traditional wushu exercise used to harden and strengthn the grip and the forearms. It's often used by practicioners of external and traditional styeles such as: Jinna, External Qigong, Eagle Claw etc.

At the beginning just do pushups on your fingers.
Not extending the fingers totally makes the exercise even harder.
Do pushup and snake movements. ( see video )
Later you can try pushups on your back hands, but don't jump from your palms onto your back hands yet. Be careful with this exercise, becasue you caninjure your wrists badly.

Animated Instructions:

Qigong Main

Hardening the Shins

Meridians

Perforemd by Feng Jia Bin From the Song Jiang Wushu School.
Tel: 138-6976-8195