Lie flat on the floor (or exercise mat) on your back with your arms extended straight back behind your head and your legs extended also. This will be your starting position.
As you exhale, bend at the waist while simultaneously raising your legs and arms to meet in a jackknife position. Tip: The legs should be extended and lifted at approximately a 35-45 degree angle from the floor and the arms should be extended and parallel to your legs. The upper torso should be off the floor.
While inhaling, lower your arms and legs back to the starting position.
Repeat for the recommended amount of repetitions.
Variation: If you are really advanced you could use a medicine ball for added resistance.
Aug 26, 2011 7:30 PM:
great workout really tough on the abs. btw does work upper abs as well or its more towards just lower?
great workout really tough on the abs. btw does work upper abs as well or its more towards just lower?-See Less
Mar 24, 2011 7:56 AM:
i love to hate this. So freaking hard...so much so that i cant freaking do it. :(
i love to hate this. So freaking hard...so much so that i cant freaking do it. :(-See Less
Mar 4, 2010 3:33 AM:
during the exercise try to reach your leg with you hand and straighten your knees
during the exercise try to reach your leg with you hand and straighten your knees -See Less
Mar 3, 2010 8:33 PM:
Sit on a bench, rather than on the floor, with your body perpendicular to the bench. This will allow for a greater range of motion (downwards) and will also force you to balance thus engaging your core.
Sit on a bench, rather than on the floor, with your body perpendicular to the bench. This will allow for a greater range of motion (downwards) and will also force you to balance thus engaging your core.-See Less
Aug 26, 2011 7:30 PM:
great workout really tough on the abs. btw does work upper abs as well or its more towards just lower?
great workout really tough on the abs. btw does work upper abs as well or its more towards just lower?-See Less
Mar 24, 2011 7:56 AM:
i love to hate this. So freaking hard...so much so that i cant freaking do it. :(
i love to hate this. So freaking hard...so much so that i cant freaking do it. :(-See Less
Mar 4, 2010 3:33 AM:
during the exercise try to reach your leg with you hand and straighten your knees
during the exercise try to reach your leg with you hand and straighten your knees -See Less
Mar 3, 2010 8:33 PM:
Sit on a bench, rather than on the floor, with your body perpendicular to the bench. This will allow for a greater range of motion (downwards) and will also force you to balance thus engaging your core.
Sit on a bench, rather than on the floor, with your body perpendicular to the bench. This will allow for a greater range of motion (downwards) and will also force you to balance thus engaging your core.-See Less
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of people found this review helpful
Review: Jackknife Sit-Up
Dec 14, 2011 8:40 PM: one of the most brutal ab exercises ever
of people found this review helpful
Review: Jackknife Sit-Up
Dec 5, 2011 8:17 AM: This one burns like hell but I still love it
of people found this review helpful
Review: Jackknife Sit-Up
Oct 28, 2011 5:35 PM: love it
of people found this review helpful
Review: Jackknife Sit-Up
Aug 26, 2011 7:30 PM: great workout really tough on the abs. btw does work upper abs as well or its more towards just lower?
of people found this review helpful
Review: Jackknife Sit-Up
Mar 24, 2011 7:56 AM: i love to hate this. So freaking hard...so much so that i cant freaking do it. :(
of people found this tip helpful
Tip: Jackknife Sit-Up
Jan 22, 2011 9:48 AM: VEry good
of people found this tip helpful
Tip: Jackknife Sit-Up
Mar 4, 2010 3:33 AM: during the exercise try to reach your leg with you hand and straighten your knees
of people found this tip helpful
Tip: Jackknife Sit-Up
Mar 3, 2010 8:33 PM: Sit on a bench, rather than on the floor, with your body perpendicular to the bench. This will allow for a greater range of motion (downwards) and will also force you to balance thus engaging your core.
of people found this review helpful
Review: Jackknife Sit-Up
Mar 1, 2010 2:38 PM: perfect and feeling great progress