do russians, set cones up 25 yards apart, start at one side and have someone time you. you want to be able to do 6 up and backs in under a minute. so sprint to the end, turn sprint back, turn sprint back, turn sprint back. the point is to do it without stopping. you wanna be able to do it in under a minute. its what RL does, and i just did it last weekend. its tough but it is possible.