How to Do Side Jackknife
Start and end of one clean rep of Side Jackknife.
Quick facts
| Primary muscle | Core |
|---|---|
| Secondary muscles | — |
| Equipment | Bodyweight |
| Category | Strength |
How to perform Side Jackknife
- Lie on your side with your legs extended and stacked, resting your lower hand across your torso.
- Place your top hand behind your head with the elbow pointing up. This is your starting position.
- Exhale and simultaneously raise your top leg and your torso toward each other, crunching your obliques.
- Squeeze at the top, then inhale and lower under control back to the starting position.
- Complete the recommended repetitions, then switch to the other side.
Muscles worked
- Core (primary): braces the trunk and resists twisting to protect the spine.
Sets & reps by goal
| Goal | Sets × reps | Load | Rest |
|---|---|---|---|
| Strength | 3–5 × 3–5 | Heavy (~85%+) | 2–3 min |
| Hypertrophy | 3–4 × 8–12 | Moderate (~65–75%) | 60–90 s |
| Endurance | 2–3 × 15–20 | Lighter (~50–60%) | 30–45 s |
Bodyweight movement: once you own the top of a rep range, progress by slowing the tempo, pausing at the hardest point, or moving to a harder variation instead of adding load.
Form tips
- Brace as if about to take a light punch and breathe shallowly — don't hold your breath for the whole set.
- Own the largest range you can control with clean form before you chase extra reps.
- Treat every rep the same — a repeatable setup and bar path is what lets you add weight safely over time.
- Warm up the pattern with a couple of lighter, submaximal sets before your working sets.
Common mistakes
- Cranking with the hip flexors or neck instead of moving from the trunk.
- Cutting the range short to squeeze out extra reps instead of owning each full one.
- Chasing weight jumps before the current load feels solid on every rep.
Frequently asked questions
What muscles does Side Jackknife work?
Side Jackknife is a focused movement that primarily works the core.
What equipment do I need for Side Jackknife?
None — Side Jackknife is a bodyweight movement, so you only need your bodyweight and a little space.
How many sets and reps should I do for Side Jackknife?
It depends on your goal: about 3–5 sets of 3–5 heavy reps for strength, 3–4 sets of 8–12 for muscle growth, or 2–3 sets of 15–20 for endurance. Bodyweight movement: once you own the top of a rep range, progress by slowing the tempo, pausing at the hardest point, or moving to a harder variation instead of adding load.
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