Jackknife Sit-Up
How to do the Jackknife Sit-Up
- 1
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.
- 2
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.
- 3
While inhaling, lower your arms and legs back to the starting position.
- 4
Repeat for the recommended amount of repetitions.
How to program the Jackknife Sit-Up
Sets and reps
As a compound movement, the Jackknife Sit-Up responds well to heavier loading. For strength, work in the 3–5 sets of 4–8 reps range with 2–3 minutes of rest between sets. For muscle growth, 3–4 sets of 8–12 reps with 90 seconds of rest is the classic hypertrophy zone. Place it early in your session, when you're freshest, and leave 1–3 reps in reserve on most sets.
Progression
The Jackknife Sit-Up is beginner-friendly. Start with a load (or rep count) you can complete with clean form on every set, then add a small amount of weight or 1–2 reps each week. When you hit the top of your rep range on all sets, increase the load and drop back to the bottom of the range — simple double progression.
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Frequently asked questions
What muscles does the Jackknife Sit-Up work?
The Jackknife Sit-Up primarily targets the Abdominals.
What equipment do I need for the Jackknife Sit-Up?
You need Body Only. Difficulty level: Beginner.
How many sets and reps of the Jackknife Sit-Up should I do?
For strength, do 3–5 sets of 4–8 reps with 2–3 minutes rest. For muscle growth, do 3–4 sets of 8–12 reps with about 90 seconds rest.
