If you work out, you’ve probably heard the advice to switch things up. Depending on who you ask, trying new activities can help you beat a workout rut, motivate you to hit the gym (instead of the snooze button), and even “confuse” your muscles and help you reach new fitness goals. It’s hard to ignore the boredom-busting benefit of getting off the treadmill and hitting up a Zumba class, but can mixing things up really help get you in better shape, too? We asked fitness pros who make it their business to be fit for the lowdown:

Your body adapts easily — and that’s not a good thing
Variety is the spice of life — and the cornerstone of a more effective workout routine. The body has an impressive ability to adjust to stress and change, explains Nadia Murdock, founder of Nadia Murdock Fit. The result of that adjustment? Plateaus. “The muscles are no longer responsive to your workouts and diet,” says Murdock. “On top of that, we naturally lose muscle mass and bone density as we age,” adds Robert Herbst, a personal trainer, coach, and world champion powerlifter. “Thus, you need to stress the body through exercise to make it adapt and build more muscle and bone and improve cardio health.”

Once your body adapts, it’s time to change it up. “If you always run a mile, [your body] will adapt to that, get good at it, and stop making progress. It will also slow your metabolism so you burn fewer calories and lose less fat. The same thing happens if you just do the same exercise or lift the same amount of weight,” says Herbst. “You need to periodically change things up, run sprints or hills, increase the pace, lift heavier or more reps, use dumbbells instead of barbells, [and so on].”

Variety helps prevent injury, too
“By varying your movements, you give your muscles and joints a much-needed break, when they can repair and get ready for the next workout,” says Sonia Satra, creator of mindset-meets-fitness company Moticise. “That’s why people have ‘leg day’ at the gym, and never do it twice in a row — you can overtax your muscles, and cause real injury. Change up your workouts to allow for each muscle group to rest.” That advice goes for cardio, too. “Changing movements helps avoid [overuse injuries],” says Galina Denzel, co-author of Eat Well, Move Well, Live Well: 52 Ways to Feel Better in a Week. “You can easily see that with people who rely on cardio machines for their aerobic workouts — tens of thousands of repetitions of the same movement daily can lead to aches and pains that will keep them away from the gym.”

You don’t have to make a huge change to see results
Don’t exchange your spin shoes for a tennis racket just yet. Small changes to reps and movements can reap big benefits. “[The] change could be something as simple as increasing the weight/reps or progressing to a more difficult version of the exercise (moving from press ups off knees to full press ups for example),” says Richard Wilcock, a personal trainer and strength and conditioning coach. “It could also be something a bit more complicated such as moving onto a different exercise that works the same muscle groups (leg press to squats for example).”

So how often should you change things up?
Rebecca Weible, founder of Yo Yoga!, cautions against switching things up too soon. “Muscle memory and strengthening comes from repetition. You need to ‘master’ your workout in order for it to be effective so I recommend waiting at least 6-8 weeks for switching it up,” she says. “For example, you need to learn to row correctly for it to be effective, which may take some time, and then you need to spend time regularly doing it correctly to build strength and muscle memory.” Once you’ve mastered your routine, pay attention to how you feel during it. If you find yourself paying more attention to the TV at your gym than the workout itself, that’s a good sign some variety is in order.

A boring workout can be a less effective workout — and changing it up could give you a bigger calorie burn, says Satra. “When you learn something new, you tend to work a bit harder, so you tend to sweat more.”

Diana Vilibert is a freelance writer and copywriter living in Brooklyn, NY. She loves flea markets, martinis, to-do lists, traveling, and wearing leggings as pants. You can see more of her writing at www.dianavilibert.com and follow her on Twitter at @dianavilibert.