V-Up
The V-up is a floor core exercise in which you lie flat with your arms overhead and legs straight, then lift your upper body and straight legs at the same time so your hands meet your feet above your hips in a V shape. It works the stomach muscles through a long range, with the hip flexors lifting the legs, and it takes more coordination and balance than a crunch or sit-up.
Also called: Jackknife Sit-Up, V Sit-Up, Pike Sit-Up, Jackknife (used loosely) · Equipment: bodyweight · Pattern: isolation
Step by step
- Lie on your back with your legs straight and together and your arms stretched overhead, just off the floor.
- Brace your stomach so your back rests flat on the floor, ribs down.
- Breathe out and lift your arms, upper body and straight legs at the same time, curling your spine up off the floor.
- Reach your hands towards your feet so your body forms a V, balanced just behind your tailbone.
- Hold the top for a moment without rocking.
- Bring your upper body and legs back down together under control, keeping your back flat as they reach the floor.
- Touch down lightly and start the next rep from the stretched-out position, or rest after the last rep.
- Fold like a closing book
- Reach your hands to your feet over your hips
- Brace before each rep
- Curl your spine as you rise
- Both ends come down slowly together
- Back flat as you touch down
In VALDA, these cues are one tap away on the exercise while you train.
What it trains
| Muscle | Role | Evidence |
|---|---|---|
| Rectus abdominis | Prime mover | C |
| Hip flexors | Prime mover | C |
| Rectus abdominis: lower | Secondary | C |
| Obliques (internal/external) | Stabiliser | D |
| Hip adductors | Stabiliser | D |
Evidence grades: A = strong research base · B = good · C = limited · D = coaching consensus.
What goes wrong, and the fix
Back arching off the floor as the legs come down
Fix: Brace harder and bend your knees into a tuck if your back lifts.
Swinging the legs up
Fix: Lift slowly and together, with a brief hold at the top.
Lifting with a stiff, flat back
Fix: Curl your spine up one section at a time as your hands reach for your feet.
Crashing back to the floor
Fix: Take about two seconds to bring your upper body and legs back down.
Rocking at the top
Fix: Meet your hands and feet directly above your hips and pause.
Chasing reps as control fades
Fix: End the set when you can no longer lift and return with control.
What the research says
Muscle growthGeneral fitnessEndurance
- Muscle activity — EMG studies show sit-up-style exercises produce high stomach and hip-flexor activity. There is no EMG data for the V-up itself, and EMG measures activity, not growth.
- Load — Research finds muscle growth is similar across a wide range of loads when sets are hard, while lighter, higher-rep work favours muscular endurance. Holding a light ball or dumbbell is a common way to add load.
- Volume — Research links more weekly sets for a muscle to more growth, with diminishing returns. There is no research specific to the V-up.
- Reps — Many programmes use sets of about 8–15 controlled reps, or use the V-up as a station in a conditioning circuit. There is no research on the best rep range for this exercise.
- Progression — A common approach is to learn the bent-knee tuck-up first, then move to straight legs. There is no research comparing progressions.
Swap it mid-workout
With VALDA Pro, FLEX offers alternatives like these when you swap an exercise mid-workout.
Log the v-up in VALDA, with these cues one tap away while you train and your history for it in one place.
General information about exercise technique, not medical advice. If you have an injury or a health condition, your healthcare provider is the right person to ask.