It’s a bro science staple: Exercise variety is great because the muscles are forced to adapt to different stimuli from workout to workout. 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 is called muscle confusion (or, more scientifically, undulating periodization), as if your triceps become perplexed when instead of starting with pushdowns like you did last time you begin with skull crushers this time. 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.
Okay, but does it work?
A study set out to determine if there are any benefits to muscle confusion. Nineteen trained young men were divided into two, randomized groups. One group performed workouts consisting of the same 6 exercises for upper body and the same 6 for lower body, always in the same order, four workouts per week (two for upper, two for lower), three sets per exercise, with the reps reduced over the eight weeks from 12 to 6. The other group followed the same parameters, except the exercises were selected randomly from a database of 80 with an app programmed for the study.
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.”
Don’t get confused: When it comes to variety, emphasize what works. If you thrive on constant variety, change exercises regularly. However, don’t swap out what works best merely for variety’s sake. 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). And if you thrive on doing the same exercises in the same order, this too is a perfectly sound method. After all, both groups in the study grew stronger and bigger by statistically equal amounts. Maybe the biggest takeaway: The marketing term muscle confusion has outlived its usefulness.