Knee Lift Crunch
The knee lift crunch is a standing bodyweight exercise that targets the abs and obliques. Alternating knee lifts combined with rotational crunches create a dynamic core movement that also engages the hip flexors.
How to do it
- Stand upright with your feet hip-width apart and your hands behind your head.
- Lift your right knee toward your chest while simultaneously crunching your left elbow toward the rising knee.
- Lower your leg and return to the upright position.
- Repeat on the opposite side, lifting your left knee and crunching your right elbow toward it.
- Continue alternating sides for the desired number of repetitions.
Form cues
- Stand tall with feet hip-width apart.
- Place your hands lightly behind your head without pulling your neck.
- Lift your right knee toward your chest while bringing your left elbow across to meet it.
- Engage your abs and exhale as you twist.
- Return to the starting position with control before switching sides.
Breathing: Exhale as you lift your knee and crunch toward your elbow, then inhale as you return to the starting position.
Common mistakes
- Pulling on the neck with your hands, which can cause neck strain instead of working the core.
- Rushing through the movement using momentum, which reduces core engagement.
- Rounding your lower back forward, which shifts the focus away from your waist.
Muscles worked
Primary: abs. Secondary: hip flexors, obliques.
Suggested sets & reps
Get fitter
3 sets × 12–15 reps per side, rest 60 s
Lose weight
3–4 sets × 15–20 reps per side, rest 45–60 s
Build muscle
3 sets × 10–12 controlled reps per side, rest 60 s
Easier, harder & alternatives
Make it easier
Make it harder
Alternatives
Take care if…
- If you have lower back sensitivity, ease off and keep your torso upright.
General educational guidance, not medical advice. Stop on sharp pain and check with a qualified professional if unsure.
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Start free →Frequently asked questions
What muscles does the knee lift crunch work?
It primarily targets your abs and obliques, while also engaging your hip flexors for stability and lift.
Should I touch my elbow to my knee every time?
Aim for a close approach, but focus on the twisting crunch motion rather than forcing physical contact if it strains your back.
Can I do this exercise if I have lower back discomfort?
If you feel any sharp or pinching pain in your lower back, ease off and reduce your range of motion or try a gentler seated option.