Why should you not fatigue the core before performing a heavy leg workout with squats and lunges??

All motion relies on the integrity of our mid bodies, so if you are really going for a heavy leg workout you may want to warm up the core body but not fatigue it so that it can have enough energy to maintain a secure position while working the lower body

Another option would be to work the core on a day when you can work core and back and leave the legs out of it!