Here are a few questions to consider as you plan your 2020 exercise routines: Are your muscles confused? Should they be? And just how do we confuse our muscles, anyway?

These concerns are at the heart of a timely new study of what happens when we add variety to our gym workouts and, in the process, “confuse” our muscles. The study finds that shifting, quicksilver workouts can yield some benefits that more rote regimens do not, but the benefits may not be the ones that most of us would expect.

Anyone who pays attention to fitness trends (or perhaps to politics) likely has heard the term “muscle confusion.” It was invented and popularized in the past decade by the creators of various weight-training regimens, particularly P90X, which was a favorite of the former congressman and vice-presidential candidate Paul Ryan.

The P90X and similar weight-training programs advise participants to alter their routines all the time, threading in different combinations of exercises and rarely, if ever, repeating any particular workout. The rationale for this inconstancy is that unfamiliar routines should perplex and discombobulate our bodies and muscles and prevent them from settling into a groove or reaching a training plateau. Instead, our muscles supposedly will respond to the unfamiliar demands of the workouts by continuing to adapt.