ab builder crunching against a machine on a fixed path
the pads hold your hips and shoulders, so the spine is the only thing that can
move and the hip flexors cannot take a share
nothing to balance and a stack to set, so the set can be pushed to failure and
loaded in small steps
Execution
Sit in the crunch machine with your back against the pad and your shoulders or
chest under the pads. Set the seat so the pivot sits level with your waist.
crunch your ribs down towards your hips, rounding your spine
keep your hips against the seat throughout
continue until your spine is fully rounded
let the pads take you back up under control
reach full extension at the top before the next rep
Set the seat height once and keep it. If you change it, pick Changed technique
or equipment in the exercise menu, so the jump doesn't count as a strength
change.