Walking upside down

I started with a quick anaerobic sprint that felt better than anticipated.  Afterward, I rested a little and then tried walking 200m on my hands.  I almost quit during this one.  Once my shoulders and core fatigued I had no balance. 200m doesn't sound far but try it walking on your hands, a lot further than you would think.  I didn't realize that my core played such a crucial part in balancing until I realized my legs were flopping over and making me unstable.  The last 40m or so I focused on sucking in my core and balance got a little more manageable.  I finally finished after some long rests to allow my shoulders to recover, but this one was tough, although good practice in case I see it in a WOD.