Skip to main content

Reverse Crunch

The lower ab specialist — targets the lower rectus abdominis with posterior pelvic tilt and spinal flexion

⚡ Quick Reference​

AspectDetails
PatternReverse Spinal Flexion
Primary MusclesLower Rectus Abdominis
Secondary MusclesObliques
EquipmentBodyweight, Mat (optional), Bench (optional)
Difficulty⭐⭐ Beginner-Intermediate
Priority🟡 Accessory

Movement Summary​

🎯 Setup​

Starting Position​

  1. Body position: Lie flat on back on mat or bench
  2. Leg position: Lift legs so knees are bent at 90°, thighs perpendicular to floor
    • Shins parallel to ground
    • Feet together or hip-width apart
  3. Hand placement:
    • Option 1: Palms down at sides for stability (easier)
    • Option 2: Hands under hips/lower back for support (if needed)
    • Option 3: Holding onto bench/anchor above head (on bench)
  4. Lower back: Starts neutral, will flatten during movement
  5. Head and neck: Relaxed on floor throughout

Equipment Setup​

EquipmentSettingNotes
MatOptionalCushioning for spine and tailbone
Flat benchOptionalCan grip edge above head for stability
Decline benchAdvancedIncreases difficulty
Setup Cue

"Lie back, knees up at 90 degrees — imagine pulling your hips up toward your ribs, not just lifting your legs"

🔄 Execution​

The Movement​

What's happening: Establishing starting position with legs raised

  1. Lie flat on back, arms at sides
  2. Lift legs so knees are bent at 90 degrees
  3. Thighs perpendicular to floor, shins parallel to ground
  4. Engage core, prepare to move pelvis
  5. Inhale to prepare

Tempo: Set up calmly, establish position

Feel: Core engaged, stable starting position

Key Cues​

Primary Cues
  • "Hips to ribs" — curl pelvis toward chest, not just legs
  • "Lift your hips off the ground" — essential for lower ab activation
  • "Exhale and curl" — breathe out as you curl up
  • "Tailbone to ceiling" — cue for posterior pelvic tilt

Tempo Guide​

GoalTempoExample
Strength2-0-3-02s up, no pause, 3s down, no rest
Hypertrophy2-1-2-02s up, 1s squeeze, 2s down, no rest
Endurance1-0-1-01s up, no pause, 1s down, continuous

💪 Muscles Worked​

Activation Overview​

Primary Movers​

MuscleActionActivation
Lower Rectus AbdominisPosterior pelvic tilt and spinal flexion from below█████████░ 90%

Secondary Muscles​

MuscleActionActivation
Upper Rectus AbdominisAssists with spinal flexion██████░░░░ 60%
ObliquesStabilize and assist with flexion█████░░░░░ 50%

Stabilizers​

MuscleRole
Hip FlexorsControl leg position, less active than in regular crunches
Muscle Emphasis

Reverse crunch vs. regular crunch: Reverse crunch emphasizes lower abs by moving pelvis toward ribcage. Regular crunch moves ribcage toward pelvis, emphasizing upper abs. Both work entire rectus abdominis, but emphasis differs.

⚠️ Common Mistakes​

MistakeWhat HappensWhy It's BadFix
Not lifting hipsJust rocking legs, hips stay on groundNo lower ab activation, wasted effortFocus on curling pelvis upward — hips must lift
Using momentumSwinging legs back and forthNo time under tension, poor resultsSlow, controlled movement with pause at top
Straightening legsExtending knees during movementHip flexors take over, less ab workKeep knees bent at 90° throughout
Excessive rangePulling knees too far toward headLoses tension at end range, uses momentumStop when hips lift 2-6 inches, maintain control
Lower back archingAnterior pelvic tilt, back off groundLower back strain, not engaging absPosterior tilt — press lower back into floor
Most Common Error

Not lifting the hips — many people just rock their legs back and forth without actually curling the pelvis. The hips MUST lift off the ground for this to work the lower abs effectively.

Self-Check Checklist​

  • Hips physically lift off the ground (2-6 inches)
  • Movement is pelvic curl, not just leg swing
  • Knees stay bent at 90° throughout
  • Lower back presses into floor at top of movement
  • Controlled tempo both up and down

🔀 Variations​

By Equipment and Position​

AspectDetails
PositionFloor, arms at sides
LegsKnees bent 90°, thighs perpendicular
Best ForBeginners, standard progression
EmphasisLower rectus abdominis

By Training Purpose​

VariationChangeWhy
Weighted Reverse CrunchAdd 2.5-10 lb ankle weightsProgressive overload
Slow Tempo3s up, 2s pause, 3s downIncreased time under tension
Decline Reverse CrunchUse decline benchIncreased resistance

Leg Position Variations​

Leg PositionDifficultyWhen to UseProsCons
Knees bent 90°StandardDefault positionLeast hip flexor involvementStandard difficulty
Knees to chestEasierTrue beginnersShorter ROM, easier to learnLess range of motion
Legs straightHardestAdvanced onlyMaximum challengeHeavy hip flexor involvement

📊 Programming​

Rep Ranges by Goal​

GoalSetsRepsRestLoadRIR
Strength3-48-1260-90sWeighted if needed1-2
Hypertrophy3-412-2045-60sBodyweight or light weight2-3
Endurance2-320-30+30-45sBodyweight3-4

Workout Placement​

Program TypePlacementRationale
Core-focused workoutMiddleAfter planks, before isolation
Full-body workoutEnd of sessionCore work at finish
Lower body dayEnd of sessionAdd core volume
Ab circuitMiddlePair with upper ab work (crunches)
Core Fatigue

Don't do heavy core work before big compound lifts. A fatigued core compromises stability in squats, deadlifts, and overhead pressing.

Frequency​

Training LevelFrequencyVolume Per Session
Beginner2-3x/week2-3 sets of 10-12 reps
Intermediate3-4x/week3-4 sets of 12-20 reps
Advanced4-5x/week4 sets of 20+ reps or weighted

Progression Scheme​

Progressive Overload

Progress by: 1) Adding reps (up to 25-30), 2) Adding ankle weights (2.5-10 lbs), 3) Slowing tempo, 4) Using decline bench

Sample Progression​

WeekVariationSets x RepsNotes
1-2Floor Reverse Crunch3x10Master pelvic curl
3-4Floor Reverse Crunch3x15Add reps
5-6Bench Reverse Crunch3x12Better stability
7-8Bench Reverse Crunch3x20Continue progression
9+Weighted or Decline3x12Increase difficulty

🔄 Alternatives & Progressions​

Exercise Progression Path​

Regressions (Easier)​

ExerciseWhen to UseLink
Pelvic TiltLearning pelvic control
Dead BugBuilding core stability first
Knees-to-chest holdVery weak lower abs

Progressions (Harder)​

ExerciseWhen ReadyLink
Weighted Reverse CrunchCan do 3x20 with perfect form
Decline Reverse CrunchMastered weighted version
Hanging Knee RaiseReady for vertical core work
Hanging Leg RaiseAdvanced core strength

Alternatives (Same Goal, Different Movement)​

AlternativeDifferenceGood For
Hanging Knee RaiseVertical positionAdvanced, more challenging
Leg RaiseLegs straight throughoutMore hip flexor involvement
Mountain ClimbersDynamic, cardio componentConditioning + lower abs

🛡️ Safety & Contraindications​

Who Should Be Careful​

ConditionRiskModification
Lower back painStrain if not controlling movementReduce ROM, focus on pelvic tilt first
Hip flexor strainAggravation if using too much hip flexionKeep knees bent, focus on pelvic movement
Pregnancy (2nd/3rd trimester)Supine position affects blood flowUse standing cable crunches or planks
Tailbone painDirect pressure on coccyxUse thicker mat or switch to other core work
Stop Immediately If
  • Sharp pain in lower back
  • Tailbone pain from impact
  • Hip flexor sharp pain
  • Dizziness from supine position (pregnancy)

Injury Prevention​

StrategyImplementation
Master pelvic tiltPractice posterior pelvic tilt before adding movement
Controlled movementNo swinging or momentum
Keep knees bent90° knee angle reduces hip flexor dominance
Proper breathingExhale on exertion (curling up)
Padded surfaceUse mat to protect tailbone

Lower Back Protection​

Critical points to protect your back:

  • Posterior pelvic tilt — lower back should press into floor at top
  • No momentum — controlled movement prevents jarring
  • Start with small ROM — don't need to curl knees to chest initially
  • Stop if pain occurs — muscle burn is OK, sharp pain is not
Most Common Issue

Using momentum instead of muscle — swinging legs creates no time under tension and can strain the back. Focus on slow, controlled pelvic curl.

🦴 Joints Involved​

JointActionROM RequiredStress Level
SpineFlexion (lumbar region)20-30° of lumbar flexion🟢 Low
HipFlexion (static hold)90° flexion maintained🟡 Moderate

Mobility Requirements​

JointMinimum ROMTestIf Limited
Hip90° flexionCan bring knees to chest comfortablyHip flexor stretches, mobility work
Lumbar Spine30° flexionCan perform posterior pelvic tiltCore activation drills, pelvic tilts
Joint Health Note

Reverse crunches involve lumbar flexion through pelvic movement, which is a natural, safe motion when done with control. The movement trains the abs functionally while minimizing compression compared to loaded spinal flexion.

❓ Common Questions​

Why aren't I feeling this in my lower abs?

Most common reason: You're not actually lifting your hips off the ground. You're just rocking your legs. The pelvis must curl upward — your tailbone should lift 2-6 inches. Focus on "hips to ribs" cue and really squeeze at the top.

Is there really a "lower ab" exercise?

The rectus abdominis is one continuous muscle, but EMG studies show greater activation in the lower region during reverse crunches vs. standard crunches. It's about emphasis, not isolation. Reverse crunches emphasize lower portion through posterior pelvic tilt.

Should my knees be bent or straight?

Keep knees bent at 90 degrees. Straight legs dramatically increases hip flexor involvement and difficulty. Bent knees keep tension on abs and reduce lower back strain. Use straight legs only if you're advanced.

How is this different from leg raises?

Reverse crunch: Knees bent, focus on curling pelvis toward ribs (posterior pelvic tilt) Leg raise: Legs straight, lifting from hips with more hip flexor involvement

Reverse crunches better isolate lower abs with less hip flexor dominance.

Can I do reverse crunches and regular crunches together?

Yes, they complement each other well. Reverse crunches emphasize lower abs (pelvis to ribs), regular crunches emphasize upper abs (ribs to pelvis). Doing both covers the entire rectus abdominis. Typical order: reverse crunches first, then regular crunches.

How high should my hips lift?

2-6 inches is plenty. The goal is to curl the pelvis, not to do a full rollover. If you're lifting more than 6 inches, you're likely using momentum. Focus on the squeeze and contraction, not height.

📚 Sources​

Biomechanics & Muscle Activation:

  • McGill, S. (2007). Low Back Disorders: Evidence-Based Prevention and Rehabilitation — Tier A
  • Escamilla, R.F. et al. (2006). Core Muscle Activation During Swiss Ball and Traditional Abdominal Exercises — Tier A
  • American Council on Exercise (ACE) — Best Ab Exercises Study — Tier B

Programming:

  • NSCA Essentials of Strength Training and Conditioning — Tier A
  • Schoenfeld, B. (2010). The Mechanisms of Muscle Hypertrophy — Tier A

Technique:

  • Contreras, B. Core Training Articles — Tier B
  • Stronger by Science — Core Training Research Review — Tier B

Safety:

  • McGill, S. (2015). Back Mechanic — Tier A
  • NSCA Position Statement on Core Training — Tier A
For Mo

When to recommend this exercise:

  • User wants to target lower abs specifically
  • User has mastered basic crunches and wants variety
  • User wants to reduce hip flexor involvement compared to leg raises
  • User needs bodyweight core work with minimal equipment

Who should NOT do this exercise:

Key coaching cues to emphasize:

  1. "Hips to ribs — curl your pelvis upward, not just your legs"
  2. "Your hips must physically lift off the ground"
  3. "Exhale and curl, squeeze at the top"
  4. "Keep knees bent at 90 degrees throughout"

Common issues to watch for in user feedback:

  • "I don't feel it in my abs" → Not lifting hips, just rocking legs — emphasize pelvic curl
  • "I feel it in my hip flexors" → May be straightening legs or using momentum
  • "My lower back hurts" → Not controlling descent or allowing back to arch
  • "These are too easy" → Progress to bench, decline, or weighted versions

Programming guidance:

  • Pair with: Regular crunches (upper abs), planks (stability), leg work
  • Avoid same day as: Nothing — low fatigue exercise
  • Typical frequency: 3-4x per week, 3-4 sets of 12-20 reps
  • Place at end of workout or in ab circuit

Progression signals:

  • Ready to progress when: 3x20 with perfect form, clear hip lift, strong contraction, 1-2 RIR
  • Regress if: Cannot lift hips, using momentum, back pain
  • Consider variation if: Plateau at high reps — move to bench, decline, or weighted version

Red flags:

  • Hips never leaving ground → not doing the exercise correctly
  • Excessive swinging/momentum → slow down, reduce ROM
  • Lower back arching → need posterior pelvic tilt, reduce ROM

Last updated: December 2024