Why do I need a medical check-up before and during my training?

As a young trainee, i.e. under the age of 18, you must be examined by a doctor before beginning your training and again after one year. The doctor will establish your health and development and check if your health could be affected by certain work. You must attend an initial examination at the start of your training, and further examinations during the course of your training.

 What about training materials?