By request, we work on some handstands today. I threw a little pincha in too while we were at it. To that end, it was important to warm up our core with planks. After all, handstands are just planks with your arms overhead and turned on your side. Your core should be providing the same stability in both. So, the more we can stabilize your core, the more successful your handstands (and pincha, and headstands, and most arm balances) will be.