There is no mystery about exercise: You get what you put in. But you don’t have to exercise for hours every day. You just need to work smart.

Not all exercises are the same. Some are more efficient than others, whether they target multiple muscle groups, are suitable for various fitness levels, or help you burn calories more effectively.

So what are the best exercises? We posed this question to four fitness experts and compiled a list of their favorites.

Any exercise program should include cardiovascular exercise, which strengthens the heart and burns calories. And walking is something most people can do anywhere, anytime, with no equipment other than a good pair of shoes.

It’s not just for beginners, either: even people who are physically fit can get a good workout from walking.

“Going for a brisk walk can burn up to 500 calories per hour,” says Robert Gotlin, DO, director of orthopedic and sports rehabilitation at Beth Israel Medical Center in New York. Since it takes 3,500 calories to lose one pound, you could expect to lose one pound for every seven hours you walk, if you did nothing else.

But don’t go from the couch to walking for an hour a day. Beginners should start by walking five to 10 minutes at a time and gradually increase to at least 30 minutes per session, says Richard Cotton, spokesman for the American Council on Exercise.

“Don’t add more than 5 minutes at a time,” he says. Another tip: As you get fitter, it’s best to add more time to your walk before increasing the speed or increasing the incline of the treadmill.

Whether you’re a beginner or have been exercising for years, adding interval training to your cardio training will improve your fitness level and can help you lose weight.

“Varying the pace throughout the exercise session encourages adaptation of the aerobic system,” says Cotton. “The more power your aerobic system has, the more capacity you have to burn calories.”

The way to do this is to increase the intensity or pace for a minute or two and then reduce it for between 2 and 10 minutes (depending on the total duration of the workout and the time you need to recover). Continue doing this throughout the workout. Ask a trainer what the appropriate interval is for you.

strength training It is also essential. “The more muscular fitness you have,” says Cotton, “the greater your ability to burn calories.”

Experts interviewed for this article tended to favor strength training exercises that target multiple muscle groups. Squats, which work the quadriceps, hamstrings, and glutes, are an excellent example. “They give you the most bang for your buck because they use the most muscle groups at once,” says trainer David Petersen of Oldsmar, FL.

Good form is key. “What makes an exercise functional is how it is performed,” says Petersen. “If you have bad technique, it’s no longer useful.”

For squats, keep your feet shoulder-width apart and your back straight. Bend your knees and lower your butt. “The knee should remain above the ankle as much as possible,” says Cotton. “Think about how you sit in a chair, only the chair isn’t there,” Gotlin says.

Practicing with a real chair can help, says physical therapist Adam Rufa of Cicero, New York. “Start by working on getting in and out of a real chair correctly,” he says. Once you’ve mastered this, he tries to simply hit the chair with his butt and then climb back up. Then do the same movement without the chair.

Gotlin sees many patients with knee pain and says the cause most of the time is quadriceps weakness. If you experience pain walking down stairs, she says, strengthening your quads with squats can be a big help.

Like squats, lunges work all the major muscles in your lower body: glutes, quads, and hamstrings.

A lunge is a great exercise because it mimics walking, just in an exaggerated way, Petersen says.

Lunges are a little more advanced than squats, which also helps improve balance, Cotton notes.

Here’s how to do it right: Take a big step forward, keeping your spine in a neutral position. Bend your front knee approximately 90 degrees, focusing on keeping your weight on your back toes and dropping the knee of your back leg toward the floor.

Petersen suggests imagining yourself sitting on your back foot. “The back leg is the one to sit on,” he says.

To make a lunge even more functional, Rufa recommends trying to step not only forward, but also backwards and to each side.

“Life is not linear, it is multiplanar,” says Rufa. And the better they prepare you for the different positions you will adopt throughout the day, the more useful the exercises will be.

If done correctly, the push-up can strengthen your chest, shoulders, triceps, and even your core trunk muscles all at the same time.

“I really like plank exercises, almost yoga“type movements,” says Petersen. “Every time you have your pelvis and core [abdominals and back] In a suspended position, you have to rely on your own adhesive force to stabilize yourself.”

Push-ups can be done at any fitness level. “For someone who is at a more entry-level level, start by pushing from kitchen counter height,” says Cotton. “Then progress to a desk, a chair, the floor with your knees bent, and finally the floor on your tiptoes.”

Here’s how to do a push-up: From a prone position, place your hands a little wider than shoulder-width apart. Place your toes or knees on the floor, and try to create a perfect diagonal with your body, from your shoulders to your knees or feet. Hold your glutes [rear-end muscles] and compromised abdominals. Then lower and raise your body by bending and straightening your elbows, keeping your torso stable at all times.

There are ways to make it more difficult. Once your form is perfect, try what Rufa calls the “T-stabilization” push-up: Get into a push-up position, then do the push-ups with one arm raised to the side, balancing on your remaining three limbs without twisting . Your hips.

When done correctly, the familiar crunch (along with its variations) is a good option for working your abdominal muscles.

For a standard crunch, Cotton says, start lying on your back with your feet flat on the floor and your fingertips supporting your head. Press your lower back down and begin the exercise by contracting your abs and lifting your head first (tucking your chin in slightly), then your neck, shoulders, and upper back off the floor.

Be careful not to pull your neck forward by sticking out your chin; Don’t hold your breath and keep your elbows out of your line of vision to keep your chest and shoulders open.

Petersen teaches his clients to do sit-ups with their feet off the ground and knees bent. He says that with their feet on the ground, many people tend to arch their back and activate their hip flexors.

“Sit-ups can be great, but if they’re not done correctly, with your back arched, they can weaken your abs,” says Petersen.

This exercise works all the major muscles of the upper back, as well as the biceps.

Here’s how to do it with good form. Stand with your feet shoulder-width apart, then bend your knees and flex your hips forward. (If you have trouble doing this exercise standing, support your weight by sitting on an incline bench, facing back.) Tilt your pelvis slightly forward, engage your abs, and extend your upper spine to add support. Hold dumbbells or barbell under your shoulders with your hands about shoulder-width apart. Bend your elbows and raise both hands to the sides of your body. Pause and then slowly lower your hands back to the starting position. (Beginners should do the movement without weights.)

These seven exercises are excellent and efficient options. But with almost any strength or resistance exercise, Petersen says, the question is not so much whether the exercise works but how well you perform it.

“All exercises, performed with good technique, do what they are supposed to do,” says Petersen.

The problem is that poor form can change the entire exercise, placing emphasis or even tension on different areas than intended. This may hurt you, rather than help you.

So, especially if you’re a beginner, it’s a good idea to seek the advice of a fitness trainer to make sure your form is safe and correct.