Whether it’s splits or backbending, you want to avoid dumping into your low back. This means not placing all of your bend into a couple of vertebrae.
If you want to improve your front split, focus on back hip extension while minimizing lumbar extension. Control your pelvis so that it doesn’t tip forward into too much anterior tilt and control your ribs so they don’t lift and flare out too much.
A great place to practice this principle is in the lunged deadlift.
1️⃣ Prop the back leg on an object at about knee height when standing. (If this is too much of a stretch, lower the leg height.) Come into a lunge with your knee over your ankle and your body at the same level as your back leg. Your front foot can be slightly turned out for stability.
2️⃣ Bring your arms behind you, resting your stomach on your front thigh. Slightly close your ribs.
3️⃣ Press into your front foot as you lengthen through your back leg. Try to keep the back leg internally rotated.
4️⃣ Push your back hip forward and back thigh into the bench to leverage your upper body to an upright position. If you feel any pressure in your low back, connect more through the front body by curling the pubic bone up to the bottom of the sternum.
Don’t jump straight into this drill. It’s a doozy. Be sure the psoas, outer hip stabilizers, and inner thighs are activated and available to work.
Let me know how it goes!