The ability to maintain strength with high volume, or while fatigued is an essential part of crossfit success and can be incorperated into strength work to focus specifically on strength endurance. Todays exercise is focused on leg strength endurance with the goal of pushing the limit of what your legs can push for a high volume set.
Exercise: Back squat 3x20 reps ( Challenge yourself with the weight and dont be afraid to add weight on the 2nd and 3rd sets this should hurt.)
Here is a great video showing that squating heavy is a good thing for the ladies too.