Exercise guide
Side And Front In Out
- Intermediate
- Compound
- Rep-based
- Lower legs
- Upper legs
- Waist
This dynamic core exercise targets the rectus abdominis and obliques by combining traditional leg tucks with lateral extensions, using a dumbbell to increase resistance and stability demands.
Reviewed by the Crucible team · Updated June 2026
Muscles worked
Setup
- Sit on the floor with your knees bent and place a light-to-moderate dumbbell vertically between your feet, gripping it firmly with your arches.
- Place your hands on the floor slightly behind your hips for support, leaning your torso back at a 45-degree angle.
- Lift your feet off the floor, keeping a slight bend in your knees to engage your lower abdominals.
- Pull your shoulder blades back and down to maintain a proud chest and neutral spine.
How to do it
- Exhale and pull your knees toward your chest in a central 'In' movement, crunching your abs as the dumbbell moves toward your torso.
- Inhale and extend your legs straight out in front of you, hovering the dumbbell just above the floor without letting your lower back arch.
- Pull the knees back in, then exhale as you extend your legs diagonally to the right side to engage the obliques.
- Return to center and repeat the sequence, alternating between center, right, and left extensions in a controlled tempo.
Form checklist
- Keep your lower back from arching excessively during the extension phase.
- Maintain a firm grip on the dumbbell with your feet throughout the entire set.
- Ensure the movement comes from the hips and core, not by swinging the upper body.
- Keep your neck neutral by looking slightly forward rather than at your toes.
- Move slowly and deliberately to maintain tension on the target muscles.
Pro tips
- Focus on 'hollowing' your stomach by pulling your navel toward your spine as you extend your legs.
- To maximize oblique recruitment, slightly rotate your knees toward the ceiling when extending to the sides.
- Maintain a constant 'V' shape with your torso and thighs to keep the abs under tension even at the bottom of the movement.
Make it harder
- Remove your hands from the floor and hold them across your chest or behind your head to eliminate the stability support.
- Slow down the extension phase to a 3-second count to increase time under tension.
Frequently asked
- What muscles does the side and front in out work?
- The side and front in out primarily targets the abs and obliques, and also works the erector spinae, glutes, and quadriceps as secondary muscles.
- What equipment do you need for the side and front in out?
- The side and front in out uses dumbbell.
- Is the side and front in out good for beginners?
- The side and front in out is rated intermediate. Build a base with simpler variations first, then progress to it with light load and strict form.