It’s a new year, but are you stuck in the same old routine? 

One of the most commonly asked questions in the fitness world is: How often should I change my workout routine? The current wisdom is that you should make changes to your exercise patterns once a month, but should you try something new even more often than that? Or less?

Most personal trainers support the once-a-month switch ups, claiming that changing the way you work out will prevent injury and keep you from hitting a “plateau”: a place where your workouts help you less and less. The idea is to keep your muscles “confused” by preventing them from getting too comfortable with the status quo. Taking that to its logical extreme, some suggest that you change your routine every day to avoid plateaus and to maximize the amount of benefit you get from each workout.

Richard Weil is an exercise physiologist and a consultant for MedicineNet. He believes the idea of muscle confusion isn’t backed up by science. “There is no evidence to support either claim,” he said in an article on the topic. He argues that plateaus happen because the body makes rapid improvements in the beginning of a workout regimen. In other words, it’s not that you’re getting in shape more slowly, it’s that you were way out of shape to begin with.

Weil does admit that changing up a strength training routine might have some unforeseen benefits, but for most of us, he suggests we do what feels right, whether that’s keeping our normal routine or changing “when your strength or performance decreases, when your physique stops changing in the way that you’d like it to, or when you’re bored.”

So, go ahead and change up your routine if you want to, but don’t feel like it’s an absolute necessity. Ace Fitness gives you a simple formula for workout changes: just change one factor in your workout. For example, if you’re running, perhaps do more hill work, or go to the elliptical machine. Increase your pace, or maybe your duration, but not by too much. Most of all, do what feels good to you—that’s what will keep you in the gym and help you stay young.