Exercise guide
Side To Front Knee-Up
- Intermediate
- Compound
- Rep-based
- Lower legs
- Upper legs
- Waist
This dynamic core exercise combines lateral and frontal hip flexion to target the obliques and rectus abdominis while improving hip mobility and balance. It effectively engages the lower abs and quadriceps through a multi-planar movement pattern.
Reviewed by the Crucible Fit team · Updated June 2026
Muscles worked
Setup
- Stand tall with your feet hip-width apart and your core engaged.
- Place your hands lightly behind your head with elbows wide, or on your hips for better balance.
- Shift your weight slightly onto your standing leg while maintaining a soft bend in the knee.
How to do it
- Lift your active knee out to the side toward your elbow, performing a lateral crunch to engage the obliques.
- Lower the foot controlled, then immediately drive the same knee straight up toward your chest to engage the front of the core.
- Exhale forcefully on each knee drive (the exertion) and inhale as you return your foot toward the floor.
- Complete the side-to-front sequence on one leg before alternating to the other side.
Form checklist
- Keep your chest lifted and avoid rounding your upper back during the crunch.
- Focus on bringing the knee up to the torso rather than dropping the elbow down to the knee.
- Maintain a stable, upright posture on the standing leg without leaning excessively.
- Move with control to ensure the core is doing the work rather than momentum.
Pro tips
- To maximize oblique recruitment, focus on shortening the distance between your lower ribs and your hip bone during the side lift.
- Keep your toes pointed up (dorsiflexion) during the movement to maintain tension throughout the lower chain.
Make it harder
- Perform the movement without letting the active foot touch the ground between the side and front reps to increase time under tension.
- Add a small hop on the standing leg during each knee drive to turn the exercise into a high-intensity cardio move.
Frequently asked
- What muscles does the side to front knee-up work?
- The side to front knee-up primarily targets the abs and obliques, and also works the glutes and hamstrings as secondary muscles.
- What equipment do you need for the side to front knee-up?
- The side to front knee-up requires no equipment — just your body weight.
- Is the side to front knee-up good for beginners?
- The side to front knee-up is rated intermediate. Build a base with simpler variations first, then progress to it with light load and strict form.