Bodyweight
3/4 Sit Up
Abs · Core
Intermediate6
Demonstration
IntermediateIsolationBodyweight
Jackknife Sit Up
Abs · Core
3
sets
10–12
reps
1m
Rest time
~6
Calories / set
Instructions
- 1
Lie flat on your back with your legs extended and your arms overhead.
- 2
Engage your core and lift your legs and upper body simultaneously, reaching your hands towards your toes.
- 3
Pause for a moment at the top, then slowly lower your legs and upper body back down to the starting position.
- 4
Repeat for the desired number of repetitions.
Muscles worked
Primary
Abs
hip flexors
Secondary
hip flexors
Pro tips
- Move through the full range of motion under control.
- Keep tension on the target muscle — avoid using momentum.
- Breathe out on the effort, in on the return.
- Pick a weight that lets you keep clean form for every rep.
Common mistakes
- Using too much weight and sacrificing technique.
- Rushing reps instead of controlling the tempo.
- Cutting the range of motion short.
- Holding your breath throughout the set.
Safety notes
- Warm up thoroughly before working heavy.
- Stop immediately if you feel sharp or joint pain.
- Use a spotter or safeties for heavy barbell work.
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