Abdominal.

Sit-ups have an upper limit. This does not.

The abdominal muscles respond to load like every other muscle, but most people train them with reps until they get bored. The chest pad spreads the force evenly over the upper body so you curl against the stack without pulling on the neck, and the resistance increases in 5 kg steps all the way up to 100 kg. The LED counter counts the reps. Dimensions 1350 × 1000 × 1710 mm, dead weight 300 kg. The same progression on the core as on the rest of the programme, and considerably fewer reps.