# Alternating Tuck-Up

A floor core exercise that sits you up from lying flat while one knee comes to your chest and the other leg stays straight. Switching legs each rep trains the abs and hip flexors.

- Intermediate · Isolation
- Equipment: 
- HD video: https://media.seto.fit/exercises/alternate-leg-pull/video/male.mp4
- HTML: https://seto.fit/exercises/alternating-tuck-up/

## Muscles worked

- Abs: 9/10
- Obliques: 5/10

## How to do the Alternating Tuck-Up

1. Lie on your back, legs straight, arms extended above you.
2. Sit up and pull one knee to your chest, reaching your arms forward.
3. Keep the other leg straight and off the floor.
4. Lower back down, straighten the leg, and switch knees each rep.

### Full technique — 7 steps

1. Lie flat on your back with legs straight and arms extended overhead.
2. Raise both straight legs a little off the floor and press your lower back toward the floor.
3. Sit up onto your buttocks as you pull one knee toward your chest.
4. Reach both arms forward along the shin of the bent leg.
5. Keep the other leg straight and off the floor throughout the rep.
6. Lower your torso back down as you straighten the bent leg and return your arms overhead.
7. 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

## How much to do

- **Strength**: 3–4 sets of 8–10 reps · rest 1 min 15 s · 2 reps in reserve · lower 2 s, lift 1 s
- **Muscle growth** (good fit): 3–4 sets of 10–15 reps · rest 1 min · 2–3 reps in reserve · lower 2 s, lift 1 s, pause 1 s
- **Endurance** (good fit): 2–3 sets of 20–30 reps · rest 45 s · 3–4 reps in reserve · lower 1 s, lift 1 s

Reps in reserve: how many more you could still do when you end the set.

## Substitutes by equipment

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

- **Dumbbells**: [Dumbbell Decline Sit-Up](https://seto.fit/exercises/dumbbell-decline-sit-up/), [Dumbbell Straight Arm Crunch](https://seto.fit/exercises/dumbbell-straight-arm-crunch/)
- **Resistance bands**: [Lying Resistance Band Crunch](https://seto.fit/exercises/lying-resistance-band-crunch/), [Lying Resistance Band Knee Tuck](https://seto.fit/exercises/lying-resistance-band-knee-tuck/)
- **Medicine ball**: [Medicine Ball Toe Touch Crunch](https://seto.fit/exercises/medicine-ball-toe-touch-crunch/), [Medicine Ball Straight Arm Crunch](https://seto.fit/exercises/medicine-ball-straight-arm-crunch/)
- **Suspension trainer**: [Suspension Trainer Hanging Knee Raise](https://seto.fit/exercises/suspension-trainer-hanging-knee-raise/), [Suspension Trainer Hanging Leg Raise](https://seto.fit/exercises/suspension-trainer-hanging-leg-raise/)

## 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](https://seto.fit/exercises/reverse-crunch/) — 25% of bodyweight
- Easier: [Ab Wheel Pass Crunch](https://seto.fit/exercises/ab-wheel-crunch/) — 30% of bodyweight
- **This exercise: Alternating Tuck-Up — 40% of bodyweight**
- Harder: [Captain's Chair Knee Raise](https://seto.fit/exercises/captains-chair-knee-raise/) — 45% of bodyweight
- Harder: [Ab Wheel Knee Tuck](https://seto.fit/exercises/ab-wheel-knee-tuck/) — 60% of bodyweight

## 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).

How we rate exercises: https://seto.fit/guides/methodology/

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