Undulating periodization is a type of almost unplanned training. The training uses different exercise choices each day that vary weight, reps, sets, intensity and exercises. Undulating Periodization can be determined judging how your body feels from day to day, or can be programmed. With the choice of exercise, a number of different lifts can be chosen from day to day which may include exercises that stress the core large muscle groups or the prime movers, while others may utilize the smaller muscles that assist the lift. The choice of the exercise will set the stage for what muscles will be worked on that day.
To insure maximal effort is used, larger muscles or compound exercises should be used in the beginning of the exercise session. This is not always the situation, where some heavier lifts or power exercises can be used later on during the session but will not be able to produce as much power. The order in which you use exercises each day can determine the resistance used. The constant variation of choice, order, sets, rest and resistance, forces the body to constantly adapt to change. During undulating periodization you may find the same muscle group being worked two or more days in a row. This is possible by varying the reps and rest used during each lift. The differing reps and sets will stimulate different fibers, so while you are working the same muscle group two days in a row, the reality is you are really not. Different muscle fibers are being worked while allowing previously worked muscle fibers to take in needed nutrients from the blood.