V-Up

Move · Resistance Training · Movement, Typed Supps

Most of the movement is the hips folding, not the spine bending — the abs' actual job is stopping your lower back arching off the floor.

Stage by stage

Set-up (Straight legs, long lever): Extended knees put the leg mass far from the hip, which is what makes the rep hard.
During the rep (Hip flexion dominates): Most of the fold comes from the hip flexors; the spine contributes a comparatively small arc.
As fatigue builds (Pelvic control fails first): The lower back lifting off the floor is the signal that abdominal control of pelvic tilt has been exceeded.
Weeks later (Range through control): Strength through the longer range makes partial ab work such as crunches feel easier by comparison.

Muscles trained

Primary: abs
Secondary: hip flexors, obliques

Intensity

3.8 METs (Calisthenics (e.g., push ups, sit ups, pull-ups, lunges), moderate effort).

Time to effect

Weeks: You can lift both legs and torso higher, and bring your hands closer to your toes, before your lower back arches off the floor to compensate.
Months: Real strength through this longer range of motion tends to make partial ab exercises, like crunches and sit-ups, feel noticeably easier by comparison.

Common myth

"If you cannot do a full V-up, your abs are weak." In reality: The V-up is simply a demanding lever: lifting straight legs and torso together requires substantial hip flexor and ab strength, plus enough hamstring flexibility to let the legs rise without the pelvis tucking under. Many people with genuinely strong abs struggle with it early on because the movement pattern and mobility demands are unfamiliar, not because their core is deficient.

In the glossary

Evidence grade