We’ve been practising our handstands in class over the past couple of weeks and a few different students have asked me a similar question: "why can’t I get my body in a straight line?".
Sometimes people that make a slightly curved shape in their lower back in handstand (like that you see me making here) are told it's because they need to engage their core more. It's true that if I switched on my abdominal muscles more here it'd move my legs towards the left hand side of this photo. But then I'd probably lose my balance, because my whole body from chest to feet would be tilting to the left. For me (and for many of my students) this body shape in handstand is caused by limited range of motion in the shoulders.
You can see that my chest doesn't go straight up above my arms here - it tilts a little to the left of the photo. That's because my shoulders don't have quite enough range of motion to let me reach my arms straight over my head without also curving a bit in my lower back. They reach almost all the way, run out of mobility in the shoulders and then the last little bit of reach has to come from movement in the rest of my spine. For a lot of people it's actually that curve in the lower back that creates a banana-shaped handstand 🍌 So of course your core muscles are important. They help to make your upper and lower body move as one congruent unit. But shoulder mobility plays a role for lots of people too 🙌🏼