How to do the Alternating Tuck-Up
- Lie on your back, legs straight, arms extended above you.
- Sit up and pull one knee to your chest, reaching your arms forward.
- Keep the other leg straight and off the floor.
- Lower back down, straighten the leg, and switch knees each rep.
Full technique — 7 steps
- Lie flat on your back with legs straight and arms extended overhead.
- Raise both straight legs a little off the floor and press your lower back toward the floor.
- Sit up onto your buttocks as you pull one knee toward your chest.
- Reach both arms forward along the shin of the bent leg.
- Keep the other leg straight and off the floor throughout the rep.
- Lower your torso back down as you straighten the bent leg and return your arms overhead.
- Repeat with the other knee, alternating legs each rep.
Common mistakes
- Swinging arms for momentum
- Dropping heels between reps
- Bending both knees at once
- Arching hard through lower back
Form cues
- Lift with abs first
- Straight leg stays up
- Alternate every rep
- Keep ribs down
Substitutes by equipment
Same muscles, same movement — pick the version you have the gear for.
Dumbbells
- Dumbbell Decline Sit-Up Same level
- Dumbbell Straight Arm Crunch Easier
Resistance bands
- Lying Resistance Band Crunch Easier
- Lying Resistance Band Knee Tuck Easier
Medicine ball
Suspension trainer
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
- Easier Ab Wheel Pass Crunch
- This exercise Alternating Tuck-Up
- Harder Captain's Chair Knee Raise
- Harder Ab Wheel Knee Tuck
Too hard for now? Start with the Ab Wheel Pass Crunch.
Quick answers
What muscles does the Alternating Tuck-Up work?
Primary: Abs 9/10. Also works: Obliques 5/10.
When should I do the Alternating Tuck-Up in a workout?
Finisher. Goes last, once the heavy work is done. ≈ 5 min with rest.
How many sets and reps of the Alternating Tuck-Up?
Strength: 3–4 sets of 8–10 reps, rest 1 min 15 s, 2 reps in reserve. Muscle growth: 3–4 sets of 10–15 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 Alternating Tuck-Up?
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.
What is an easier version of the Alternating Tuck-Up?
Ab Wheel Pass Crunch (30% of bodyweight), Reverse Crunch (25% of bodyweight).
What is a harder version of the Alternating Tuck-Up?
Captain's Chair Knee Raise (45% of bodyweight), Ab Wheel Knee Tuck (60% of bodyweight).
