How To: Kettlebell Swing

You can also do this movement a dumbbell if you don't have access to kettlebells.

At 0:26, he says the knees are not bent. I know what he means, but he was not describing "soft knees" well in my opinion. Soft knees means the knees bend not due to an active bending of the knees but incidental to the motion of pushing the hips back. Basically, the knees are just along for the ride and have to bend for you to reach the "table top" position.