This machine simulates climbing stairs. As there are a great variety of compact models, it has become popular among beginners and people who workout at home.
The Stepper has a list of potential risks primarily for people who have musculoskeletal problems.
Knees or lumbar spine problems can prevent you from exercising on this machine as there is a high emphasis on these areas.
During the workout, do not try to forcefully push the platform with your feet, push the pedals slowly to protect your knee joints. For the same reason, avoid letting your feet hang over the pedals - your feet should be fully on the supports.
There are models which allow you to work out not only your legs but arms as well (with the help of handles or special elastic ropes-expanders).
The best way to estimate the necessary load is your heart rate (cardiac rate). To burn fat you should workout at a rate of 65-75% of maximum. You can calculate your maximum cardiac rate with the following formula: 220 minus your age.