Muscle confusion is a bro science staple. It even fostered an industry of mix-it-up programs. P90X, once an infomercial mainstay, sold over 5 million copies (at $120 each) in the years after its introduction in 2004. The concept behind muscle confusion is exercise variety forces muscles to grow stronger and bigger by adapting to different stimuli from workout to workout. So, variety is, in effect, a form of progressive resistance. You’re making it harder on your muscles by changing exercises in the same way it’s harder for a baseball batter to hit an unknown variety of pitches instead of only fastballs, or it’s harder for a guitarist to play 100 randomly chosen songs than 10 always in the same order.
Muscle confusion seems to make sense. But does it work?
MUSCLE CONFUSION STUDY
A study set out to determine if there are any benefits to muscle confusion. Nineteen trained young men were divided into two, randomized groups for an eight-week study. One group performed workouts consisting of the same six exercises for upper body and the same six for lower body, always in the same order, four workouts per week (two for upper, two for lower), three sets per exercise. The other group followed the exact same parameters (number of exercises, sets, reps), except the upper and lower body exercises were selected randomly from a database of 80 exercises with an app programmed for the study. So, one group made no exercise changes while the other group was always changing its exercises and order in a way that even participants couldn’t predict.
The researchers concluded that there was no significant difference in strength gains between the two groups. Likewise, as determined from ultrasound imaging, there was no significant difference in muscle growth. However, from a questionnaire, it was concluded that the muscle confusion group displayed a “significant, moderate” improvement in the motivation to train, while the control group displayed insignificant decreases in that variable.
One of the researchers, Brad Schoenfeld, PhD, explained, “Muscles don’t get ‘confused.’ Simply switching around exercises doesn’t improve muscular adaptations. However, it should be noted that the study blindly rotated variation, without attention to muscular anatomy and individual needs. There, logically, is a benefit to selectively varying movements to target the different aspects of the musculature, as well as targeting individual weak points. Moreover, variety alone seems to be beneficial for motivation, and thus may positively impact adherence.”
EXERCISE VARIETY RULES
✅ If you feel better motivated mixing things up, change exercises regularly. Combatting boredom is a valid reason for maximum workout variety.
✅ And if you thrive on doing the same exercises in the same order most of the time, this too is a perfectly sound method. After all, both groups in the study grew stronger and bigger by statistically equal amounts.
✅ When it comes to exercise variety, don’t swap out what works best for you merely for “confusion” sake. Instead, select exercises that target different aspects of the bodypart (such as upper chest or inner back), especially if those aspects are lagging.
✅ Generally, bodyparts that are commonly worked with multi-joint exercises (back, chest, thighs, shoulders) require more variety to work their multiple muscles or muscle areas than single-joint bodyparts (biceps, triceps, calves).
✅ Brad Schoenfeld says: “A good rule of thumb is to keep more complex free weight exercises (squats, presses, rows, etc.) in a regular rotation and vary the less complex exercises (machines and single joint movements) more frequently.”
✅ Finally, the term “muscle confusion” has outlived its usefulness.
For more on selecting the best exercises for you, check out: What is the Best Workout?