Reverse Crunch

Move · Resistance Training · Movement, Typed Supps

The abdominal part of this is only the first few inches — lifting the pelvis. Everything above that is hip flexors.

Stage by stage

Set-up (Lower back flat): Settling the lumbar spine down removes the arch the hip flexors would otherwise pull against.
During the set (Pelvis curls toward ribs): The abdominal range is short — the posterior pelvic tilt at the start of the lift.
When it goes wrong (Hip flexors take over): Once the knees travel to the chest the iliopsoas dominates, and an uncontrolled pelvis loads the lumbar spine.
Weeks later (Control transfers upward): Better pelvic curling under load shows up in hanging leg raises and other lower-ab-emphasis work.

Muscles trained

Primary: abs
Secondary: hip flexors

Intensity

2.8 METs (Calisthenics (e.g., situps, abdominal crunches), light effort).

Time to effect

Weeks: You can curl the pelvis higher off the floor with control, rather than using momentum to swing the legs up.
Months: Better control of pelvic curling under load tends to translate into stronger hanging leg raises and other lower-ab-emphasis movements that use the same motion.

Common myth

"Reverse crunches target your lower abs as a separate muscle from your upper abs." In reality: The rectus abdominis is one continuous sheet of muscle running from the ribs to the pelvis; there is no separate upper and lower ab muscle. What changes between a crunch and a reverse crunch is which end of the spine moves and which end stays fixed, which shifts where you feel the greatest effort, but both exercises work the same muscle along its length.