Amazing results just by sitting! Equivalent to about 20 sit-ups in 1 minute. ※ This is a used item. There are no major scratches, but there are stains and minor scratches. Fujiiryoki's "Core Trainer FF-100" is an electric core slow training machine. Just by sitting, your body is automatically and slowly swayed from side to side, and the action of trying to maintain and correct your posture, which is about to collapse, stimulates the abdominal muscles around your stomach, leading to core training.