How to Do Jack Knife Crunches


When you are in a hurry at the gym, but do not want to neglect either your cardiovascular workout or your strength conditioning, jack knife crunches can provide a quick and comprehensive compromise. This variation on the standard crunch will get your heart rate up, strengthen your core and leg muscles and give your abdominal muscles a serious workout. While jack knives alone will not be sufficient in a daily exercise routine, they are the perfect solution when you simply do not have time to fit your regular workout in.

Things You'll Need

  • Exercise bench

How to Do Jack Knife Crunches

  • Lie on your back on the exercise bench. Your legs should extend off the end of the bench from your upper thighs down. Your hands should be clasped behind your head so that your elbows extend outward in opposite directions, and your back should be pressed flat against the bench.

  • Raise your upper body by pulling it into a sitting position using only your abdominal muscles. You should not sit straight up, but rather reach a half-sitting position. You can either leave your legs extended or draw them in toward your chest.

  • Tense your abs. You can hold this position for as few as 5 seconds or as many as 30. The important thing is to pause and tense your abs to hold yourself upright. If you have drawn your legs up as well, this will require good balance as well as intense abdominal focus.

  • Return to your starting position. Use your abdominal muscle to gently lower your body back to the bench. Allowing yourself to fall backward not only negates the benefits of this part of the exercise, but also can result in serious back and neck injuries.

  • Repeat this exercise as many times as you wish. If you are using jack knife crunches as a quick workout, then you should do a high number of repetitions before stopping for a rest. However, if you are just starting you may want to start out with three sets of 20 repetitions each, then raise the number of repetitions as your stamina increases. Remember, it is better to do fewer repetitions correctly than a large number incorrectly.

Tips & Warnings

  • Inhale as you raise your body and exhale when you return to the supine position. This will help you maintain a regular breathing pattern so that you do not tire as quickly and do not get out of breath.
  • If you start to feel pain in your neck, back or hips, stop exercising and contact your physician. You may need to work with a trainer to develop a personalized version of this exercise that is appropriate for your physique.

Related Searches

  • Photo Credit,
Promoted By Zergnet


You May Also Like

Related Searches

Check It Out

10 Delicious Game Day Eats That Rival the Game

Is DIY in your DNA? Become part of our maker community.
Submit Your Work!