An employee was in a skid steer with a bucket attachment, and was shoveling up cardboard. The operator picked up a load and began backing up; he noticed that a piece of plastic was attached to the bucket. The employee decided to detach the plastic from the bucket. In the process of doing this, the employee stood up without disengaging the controls, placed his right hand on the right front post of the skid steer, then reached with his left hand for the plastic. When he reached with his left hand, his chest came in contact with the controls, lowering the bucket. As the bucket lowered, the right arm of the skid steer came in contact with the employee's right index finger and crushed it.