HYPOTHESIS: Periodization refers to the systematic changing of workout variables every few weeks (i.e., weight, reps, sets, rest, exercises) to prevent plateaus in strength and muscle gains. A “newer” style of periodization — undulating periodization, which involves changing variables every workout — has exercise scientists very excited. Most exercise scientists think this is an innovative way to train, but Joe Weider has been promoting this style of training for decades. It’s called the Weider Muscle Confusion Training Principle. By constantly changing the training variables, this method prevents stagnation and better promotes gains in muscle strength and muscle mass than changing training every few weeks.

RESEARCH: For 12 weeks, researchers from Brazil had trained subjects follow either an undulating periodization program, a standard (linear) periodization program or a consistent program of 8-10 reps per set that was not periodized. The training program consisted of a two-day split with three or four total training days per week.

FINDINGS: They reported that the group following the undulating (muscle confusion) program increased their bench-press strength by about 60 pounds, almost 200% more than the linear periodization and the nonperiodized programs, which both led to an increase in their bench press
by slightly more than 20 pounds. The undulating program also increased the subjects’ strength on the leg press by a staggering
275 pounds (400% more than the nonperiodized program) and leg-press strength by about 65 pounds (over 300% more than the linear program, which increased by 55 pounds).

CONCLUSION: This study shows that the Weider Muscle Confusion Training Principle is one of the best ways to increase muscle strength. None of the subjects gained significant muscle mass, likely because the training programs were not bodybuilding-style regimens, but rather sport-conditioning
programs. Therefore, they did not do enough exercises and total sets for each muscle group to experience decent gains in muscle
mass. However, if you used muscle confusion (undulating periodization) in a bodybuilding workout, you would probably make serious gains in both strength and size.

APPLICATION: Change the weight you use and the corresponding rep ranges the weight allows. For example, when training legs, use light weight and high reps (12-15) one workout, heavy weight and low reps (5-7) the next leg workout, very light weight and very high reps (20-30) the following workout, and then moderate weight and moderate reps (8-10) in the session after that. Keep cycling your weight and rep ranges in a similar fashion every workout.

— Jim Stoppani, PhD