要达到健身目标，运动量要多大才合适？

Better mobility, stronger muscles and bones, improved mental health, and the energy to do the things you want: exercise has a host of potential benefits for everyone, regardless of age or fitness level. But making an exercise plan—much less sticking with one—is a tall order for many people. Here, three experts share what you need to know to create a routine you can keep up for the long haul, even when you’re really busy.

How much exercise you need

Exercise takes time: there’s no silver bullet, pill, or diet that will get you where you want to go. But it probably doesn’t take as much time as you think. The Centers for Disease Control and Prevention recommend 150 minutes of moderate to vigorous physical activity per week to maintain your current fitness levels. That’s about 20 minutes every day, or 30 minutes five days per week. However, you’ll need twice that much if you’re trying to lose weight or increase your fitness level, says Deborah Salvo, PhD., a physical activity researcher and professor of public health at Washington University in St. Louis.

If you’re really busy, these may seem like intractable numbers. But the good news is that not all of that time needs to be spent in gym clothes. The exercise you get doing day-to-day activities is an important part of those minutes, Salvo says. “It may also be something you can build into your life that can serve many purposes,” she says.

The other piece of good news is that it doesn’t matter whether the activity is vigorous, which the CDC defines as activity during which you can say only a few words before getting out of breath. “As long as you cross the threshold of moderate intensity, the activity’s good for you,” Salvo says. That means a brisk walk from the car to work, general gardening, a comfortably-paced bike ride, or an easy weekend hike all count.

Do activities you like—and start slow

When people start exercising, they often gravitate towards workouts that seem like they’ll have the quickest results, like lifting heavy weights or long runs. Enjoyment isn’t usually top of mind, says Dr. Kevin Vincent, medical director of the University of Florida’s Sports Performance Center. But you’re never going to be successful if you don’t like what you’re doing. For basic fitness, he says, it doesn’t really matter which form of exercise you choose to pursue: “Just be consistent.” It can take two to three months for your body to become acclimated to new activities and start showing real results.

While the CDC’s general rule is that each minute of vigorous activity is the equivalent of two minutes of moderate activity, pushing yourself hard right away could cost you time in the long run. Vincent suggests starting at a pace that is slower than you think you should. While you’ll start to see improvement even in the early days, he says, don’t take it as a cue to push yourself harder. Working slowly minimizes your chance of injury, and maximizes the chance you’ll stick with it.

The CDC also suggests doing two muscle-strengthening workouts each week in addition to aerobic exercises. Strength training can be as simple as a bodyweight workout, but even that carries a risk of injury if you aren’t careful about your form and mindful of any existing injuries. To get started, Vincent suggests taking live classes or trying out some YouTube videos.

Good exercise videos have three elements, Vincent says: they’re made by an exercise professional credentialed by the American College of Sports Medicine, the American Council on Exercise, or another major organization; they contain options to help you modify the exercise if you have an injury or limitation; and they’re part of a series that progresses. “It should look pretty easy and feel pretty easy, and it should get harder as time goes on,” he says.

Get into the right mindset

It’s important to figure out how your workouts are going to fit into your life as it is now—not your ideal. When it comes to fitness, many people have a long history of trying and giving up on different regimens, says Michelle Segar, PhD., a University of Michigan sustainable behavior change researcher and the author of The Joy Choice: How to Finally Achieve Lasting Changes in Eating and Exercise.

“So many people plan and begin a behavior change in what I call a motivation bubble,” says Segar, when they are only focused on the end goal. But what to do when their motivation runs up against an obstacle? Maybe you just couldn’t get out for your scheduled run one day or maybe an injury stopped you in your tracks.

The key, Salvo says, is in developing the resilience to reshape your plans when things go awry. Can’t go for your lunch run? Find 15 minutes later in the day to jog up and down a flight of stairs a few times. Won’t have time for that yoga class? You can do a yoga video at home. “Sustainable change is the result of making decisions that consistently favor your exercise goal,” she says.

Keep up the momentum

Salvo suggests scheduling exercise a week out, because it’s easier to keep momentum going when you have a whole week to look at. And when one day goes haywire, you can still see the bigger picture, she says.

She also suggests thinking about what motivates you. Research has found that most people get exercise motivation from at least one of three things: affect, or the way that exercise makes them feel; quantitative cues, like the information they get from a smartwatch or other trackers; and social cues, like competition and teamwork.

Many people have a combination of motivations. To figure out your own personal motivators, Salvo suggests thinking about what motivates you in other areas of your life—or even trying out the different approaches to see what sticks.

Choosing to incorporate exercise into your life and dealing with challenges by adapting, rather than stopping “is a sign and a symptom that we are achieving lasting change,” Segar says. “We’re reaffirming our identity as someone who knows how to navigate these challenges.”