Core Training Sites and Videos/ Tough Mudder/ Spartan Race style

[yoop33]

I am trying to get back into being more all around fit and not so much worrying about heavier weights or bulking. I wanna get back into sports like basketball and beach volleyball so flexibility and core is important to me. I would also like to start training for events like Tough Mudder and Spartan Races. Are there any good sites with videos and articles specifically for core exercises like these?
This is the kind of training I would like to do...http://www.youtube.com/watch?v=YErZ5GjOyas&feature=youtube_gdata_player

Thanks guys

 

[overgreen]

Here in a couple of months some friends of mine are doing the warrior dash but after that we wanted to move up to the spartan one the like 10k, the 8 mile one. Looks like it would be fun.