(Taken from myhomepersonaltrainer.com)
Fitness Tip: The last rep of any set should be difficult – Remember that the point of resistance training is to OVERLOAD the muscles. Muscles will only get stronger if they need to due to progressive training. But make sure you are advanced in your training program and are well prepared for overloading by being engaged in an on going exercise program. Participants at a Beginner and Intermediate level or those who had longer breaks in their program are advised to first consult a fitness specialist before engaging in intense overloading of the muscle.