The above video brings you the two different demonstrations of a robotic limb throwing a ball:

• Optimal variable stiffness control
• Optimal fixed stiffness control

The researchers at University of Edinburg have developed this method to provide the easiest way of storing and releasing high energy for throwing, punching, jumping, and kicking. So, they programmed the elastic actuators for providing the explosive release energy to the robot arm.

The beauty of this invention is that it can create a large amount of energy without any usage of powerful motors. Overall, I feel that this method must be incorporated in the robots instead of teaching them to do.

Source: Autonomous Robots