Variety
	A major challenge for all fitness training programs is maintaining enthusiasm and interest. A poorly designed strength-training program can be very boring. Using different equipment, changing the exercises, and altering the volume and intensity are good ways to add variety, and they may also produce better results.
	You should periodically substitute different exercises for a given muscle group(s). For example, you can do squats with a barbell instead of leg presses on a weight machine.