Call it smart, efficient, or lazy, but every time you perform a biceps curl, go for a three-mile run, or swim a few laps in the pool, your body learns how to make that particular exercise easier, says women's strength expert Holly Perkins, CSCS. Down to the cellular level, your muscles, neurological system, and heart all improve their ability to perform your workout of choice. "So if you're doing cardio, your muscular endurance will rise up to a point that it supports your sport (say, running) and doesn't go anywhere above that," she says. "If you're strength training, your muscles will get as strong as they need to be to lift the weights you're choosing, and then they'll plateau."
But when you switch up your workout—whether that's by mixing up your sets and reps or completing an entirely new exercise—you "shock" your body and make it start adapting to something else entirely, says Perkins. "You won't run faster until you run faster. You won't lift heavier until you lift heavier. The body needs to be stressed past its point of comfort before it adapts."
But how you switch up your workout depends on what you want to achieve. If you're a runner, consider completing a long run one day, a speed-focused workout another day, and a hill workout another day, says Janet Hamilton, CSCS, a clinical exercise physiologist with Running Strong in Atlanta. If you're performing a lot of strength work—and want to progress at those exact lifts—you can switch up your number of sets, reps, and how much weight you lift. "I've strength trained every week of every year for years and years. The only thing I've changed up was my sets, reps, weights, and rest periods," Perkins says. "As long as you're making some changes, you can make progress." That's true whether you want to put on muscle, burn fat, or just shore up muscle imbalances.
As a general rule, it takes about four to six weeks for your body to get comfy with a workout, but the exact amount varies both from person to person and workout to workout, Perkins says. After all, if you're running five miles five times a week, your body is going to get bored with five-mile runs a lot more quickly than it would than if you were running five miles just once a week.
No matter your workout, we have a few workout-plateau signs to keep in mind:
You're not seeing improvements.
If you don't see yourself improving from week to week—your runs aren't getting faster or longer and you're not getting any stronger in the gym—you probably need to change up what you're doing. "While people still need to be following a program to gauge their progress, I basically tell them to mix it up as much as possible," says Perkins. Perform strength workouts some days, cardio other days, and throw a class or two in there from time to time.
You're not sore after your workouts.
That's another sign that your workout isn't forcing your body to adapt any more than it already has, says Perkins.
You're always sore.
It's possible that your routine is so repetitive that your body doesn't have the opportunity to properly rebuild itself after each workout. Again, you need to switch up your workouts.
Perhaps the biggest sign that your body is bored with your workout is, well, boredom. "If you're doing a workout for several weeks, you're loving it, and suddenly you're not in the mood to do it any more, it's your body saying, 'we are sick of this,'" Perkins says. And what's the point of doing a workout you're just not into? "Let's keep it fun. If you aren't having fun, you need to give yourself the freedom to do something different," Hamilton says.