If you have been looking for a new challenge in the gym, I compel you to try the 100 rep squat challenge.
The 100 Rep Squat Challenge requires that you first take 60% of your max weight and put it on the squat bar. You then need to squat 60% of your one rep max for 100 reps.
You can break these 100 reps up into sets or you can do all 100 at once. I recommend splitting it up. Most who attempt this challenge will do 10 sets of 10 reps with minimal rest times taken between each set.
If your legs haven't been sore in a while, I guarantee you will be feeling it in the morning after this workout. Not only is this a great muscle and endurance builder, it is awesome for cardio as well.
If you've never done high rep squats before, you will be shocked at just how gassed out you get after finishing the challenge.
Give it a shot, and let me know how you do.