Exercise guide · Beginner · Compound

Knee Touch Crunch: How to Do It & Muscles Worked

The knee touch crunch is a bodyweight abdominal exercise that targets the abs and also engages the hip flexors. It involves alternating reaching across the body to touch the opposite knee while performing a crunch motion.

Primary muscles
Abs
Secondary muscles
Quads
Equipment
Body Weight
Level · type
Beginner · Compound
Demonstration of the knee touch crunch
Front view: muscles worked by the knee touch crunch. Primary: abs. Secondary: quads.
Back view: muscles worked by the knee touch crunch. Primary: abs. Secondary: quads.
Primary Secondary

How to do the knee touch crunch

  1. Step 1: Lie flat on your back with your knees bent and feet flat on the ground.
  2. Step 2: Place your hands behind your head with your elbows pointing outwards.
  3. Step 3: Engaging your abs, lift your shoulder blades off the ground and reach your right hand towards your left knee.
  4. Step 4: Return to the starting position and repeat, this time reaching your left hand towards your right knee.
  5. Step 5: Continue alternating sides for the desired number of repetitions.

Sets, reps and programming

Suggested sets, reps and rest for the knee touch crunch by training goal
Goal Sets Reps Rest Effort
Strength 3–5 3–6 3–5 min 1–3 reps in reserve
Muscle growth 3–4 6–12 2–3 min 1–2 reps in reserve
Muscular endurance 2–3 12–20 1–2 min 1–3 reps in reserve

Ranges follow the ACSM position stand on progression in resistance training. Muscle grows across a wide range of loads when sets end close to failure (Schoenfeld et al., 2017), longer rests between heavy sets support strength and size (Schoenfeld et al., 2016), and stopping a rep or two short of failure works about as well as training to failure (Grgic et al., 2022). Estimate your working weights with the strength calculators.

Knee Touch Crunch alternatives

More exercises that train the abs as their main target:

More abs exercises

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Sources

  1. American College of Sports Medicine. Progression models in resistance training for healthy adults. Med Sci Sports Exerc. 2009;41(3):687-708.
  2. Schoenfeld BJ, Grgic J, Ogborn D, Krieger JW. Strength and hypertrophy adaptations between low- vs. high-load resistance training. J Strength Cond Res. 2017;31(12):3508-3523.
  3. Schoenfeld BJ, Pope ZK, Benik FM, et al. Longer interset rest periods enhance muscle strength and hypertrophy in resistance-trained men. J Strength Cond Res. 2016;30(7):1805-1812.
  4. Grgic J, Schoenfeld BJ, Orazem J, Sabol F. Effects of resistance training performed to repetition failure or non-failure on muscular strength and hypertrophy: a systematic review and meta-analysis. J Sport Health Sci. 2022;11(2):202-211.

Step-by-step instructions and demonstration media are from the ExerciseDB exercise dataset.

This guide is general fitness information, not medical advice. Stop if an exercise causes pain and speak to a doctor or physiotherapist about injuries or health conditions before starting a new programme.