Daily undulating periodization has been shown to produce superior strength gains compared with periodization in which the weight loads progress linearly from light to medium to heavy over the course of several weeks or months.


Most periodization models have a fixed schedule of progression that lifters are not allowed to deviate from regardless of their “readiness” on the workout day. Flexible periodization allows the load to be selected on the day of each workout based on the lifter’s readiness.


  1. A recent study from St. Francis College in New York compared two methods of periodization, daily undulating and flexible, in a 12-week college weight-training class.
  2. Both groups performed the same total training volume. Those in the flexible periodization group significantly increased their leg press strength by an average of 136 pounds; lifters in the daily undulating group increased their strength by an average of only 35 pounds. Bench press strength did not differ significantly between groups.
  3. Daily undulating periodization is a method of applying the principle of progressive overload by incorporating heavy, medium, and light training days all within a single week. Workouts were established by using the subject’s 10-, 15-, or 20-rep max during a given workout.
  4. Flexible periodization is a form of undulating periodization. The total number of heavy, medium, and light workouts is established at the beginning, and then lifters can chose which weight load they want to use each day until they have performed all the predetermined workouts for each load.


Flexible periodization resulted in significantly greater gains in leg strength compared with daily undulating periodization.


Flexible periodization appears to be the most effective method of incorporating heavy, medium, and light workouts. That said, being flexible does not mean that you can skip heavy leg workouts whenever you feel like it. Stick to your predetermined number of heavy, medium, and light days. – FLEX