This core exercise is known as the Turkish Get Up and it’s pretty great.

It was, I think, originally done with a Russian Kettleball, and though Kettleballs are now well-known enough that Tesco are selling them, I figured more people are likely to have dumbbells.

The guy in the vid is using a 25 pound weight (12 kg) which he says is a good starting weight, which seems crazy to me.  Try half (or even 4kg)  to start which is all I’m doing.