I got the Litvi thing from Dan John. You might have heard of him, flies around Utah in a flying saucer.
Basic premise is you perform a lifting movement, say a kettlebell swing or a power clean with a sandbag, bang out a couple of reps and then dump and immediately sprint a given distance. It's complex training really. Keep the distance short.
A tool called a Powerbag has become very popular in rugby circles (where it was developed) and is ideal for this kind of thing:
but it is essentially a sandbag so you can easily improvise.
One of the main draws of stuff like this? It's fun. Just like playing with your kids.