FitCi
Side Jackknife is an isolation exercise for the core: one joint works, so it comes after the compound lifts to finish the target muscle. Equipment: bodyweight. Difficulty: beginner, suitable for beginners. It takes 5 steps; the most common mistake is covered in the tip below.
Step-by-step
- Lie on your side with the bottom arm in front and top hand at your temple
- Stack your legs on top of each other
- Raise your top leg and torso at the same time
- Squeeze your oblique for one second
- Lower under control; finish the reps, then switch sides
Coaching tip
Torso and leg rise together; think of the two ends of your oblique closing toward each other.
Caution
Skip this move or ask a professional first if you have pain or an injury in: lower back, neck. FitCi filters it out of your program automatically based on the injuries in your profile.
How to program it
Sets × reps and rest by goal; tempo and controlled reps matter most on isolation work. Start at the bottom of the range in week one; add 2.5–5% when you hit the top with clean form.
| Goal | Sets × Reps | Rest |
|---|---|---|
| Strength | 3 × 6-8 | 120 s |
| Muscle gain | 3 × 10-15 | 75 s |
| Fat loss / conditioning | 3 × 12-15 | 60 s |
FitCi applies this table to your age and goal automatically and writes weekly progression.
Alternatives
- At home, no equipment: Plank, Hanging Leg Raise
- Same muscle, different equipment: Cable Crunch, Ab Wheel Rollout, Pallof Press
More core exercises
Add this exercise to your program
Build your own program in FitCi, pick an expert template, or photograph the plan your coach gave you; the app tracks sets, reps and weight.