Simplify the following text for a Grade 11 native English-speaking person.
Original: Mechanical bulls have existed for decades as a training device for rodeo competitors , as they enable a rider of rough stock ( bucking horses and bull riding ) to enhance rodeo performance and refine skills without the risk and unpredictability of a live animal .
Simplified: Mechanical bulls have been around for decades as a training machine for rodeo riders , as they enable a rider to improve their rodeo performance and skills without the risk .