Sit-Up with Knee Tuck — how to, muscles worked, alternatives

How to do the Sit-Up with Knee Tuck

Lie on your back, knees bent, hands behind your head.
Curl up while your feet lift slightly off the floor.
Rise until your torso is near upright.
Lower your torso and feet back down under control.

Full technique — 7 steps

Lie on your back with knees bent and feet flat on the floor.
Place your hands lightly behind your head with elbows pointing out to the sides.
Press your lower back into the floor and keep your ribs pulled down.
Exhale and curl your torso up, letting your feet lift slightly off the floor with your knees staying bent.
Continue rising until your torso is near upright and close to your knees.
Lower your torso and feet under control until your upper back and feet return to the floor.
Reset the bottom position before starting the next repetition.

Common mistakes

Pulling the head with hands
Swinging knees for momentum
Stopping at a crunch
Dropping back without control
Letting lower back arch

Form cues

Hands stay by head
Curl, don't yank up
Keep the knee bend fixed
Exhale on the way up
Lead with your ribs

Substitutes by equipment

Same muscles, same movement — pick the version you have the gear for.

Where to start and where to go next

Same muscles, same movement. Too hard for now — step down; once it gets easy — step up.

Easier Reverse Crunch 25% of bodyweight
Easier Ab Wheel Pass Crunch 30% of bodyweight
This exercise Sit-Up with Knee Tuck 35% of bodyweight
Harder Ab Wheel Half Rollout 40% of bodyweight
Harder Ab Wheel Knee Tuck 60% of bodyweight

Too hard for now? Start with the Ab Wheel Pass Crunch.

Quick answers

What muscles does the Sit-Up with Knee Tuck work?

Primary: Abs 9/10. Also works: Obliques 5/10.

When should I do the Sit-Up with Knee Tuck in a workout?

Finisher. Goes last, once the heavy work is done. ≈ 5 min with rest.

How many sets and reps of the Sit-Up with Knee Tuck?

Strength: 3 sets of 8–12 reps, rest 1 min 15 s, 3 reps in reserve. Muscle growth: 3–4 sets of 12–20 reps, rest 1 min, 2–3 reps in reserve. Endurance: 2–3 sets of 20–30 reps, rest 45 s, 3–4 reps in reserve.

What can I do instead of the Sit-Up with Knee Tuck?

Dumbbells: Dumbbell Decline Sit-Up, Dumbbell Straight Arm Crunch. Resistance bands: Lying Resistance Band Crunch, Lying Resistance Band Knee Tuck. Medicine ball: Medicine Ball Toe Touch Crunch, Medicine Ball Straight Arm Crunch. Suspension trainer: Suspension Trainer Hanging Knee Raise, Suspension Trainer Hanging Leg Raise.