The barbell squat. No exercise is as dreaded yet as revered. Experts call it the best weight-training move ever invented, and nothing compares when it comes to overall strength gains, growth-hormone release and lower-body muscle-fiber stimulation. And nothing beats you down on leg day quite like a showdown at the squat rack.

To help you conquer the king of exercises, we tapped three elite training experts for their step-by-step advice on barbell squat form perfection. At the end of this master class, you will know squat.

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Anatomy of a Squat

A squat engages pretty much every part of your body, but these are the primary movers.

Quadriceps

This muscle group on the front of your thighs is made up of four heads (the vastus lateralis, vastus medialis, vastus intermedius and rectus femoris), which work together to extend your knees and flex your hips.

Hamstrings

This three-headed muscle on the back of your leg (the biceps femoris, semitendinosus and semimembranosus) is an antagonist to the quads and acts to flex your knees.

Glutes

The glutes (gluteus maximus, medius and minimus) operate synergistically with your hamstrings and work to power hip extension; the deeper the squat, the more the glutes are engaged.

Erector Spinae

This pair of lower-back muscles runs vertically on either side of your spine, flexing isometrically in concert with your abdominals to stabilize your spine and hold your upper body steady.

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9 Steps to the Perfect Squat

Here’s everything you need to know — and more! — about the world’s most effective exercise.

No. 1 | Set for Success

Adjust the supports in a power rack so the barbell rests at your mid to upper chest. Load your weight, then secure a collar on each side flush against the plates. Yes, some advanced athletes skip the collars, but for your safety and that of those around you, it’s a good practice. “It’s far too dangerous to have a weight slide off one end, then the heavy side of the bar comes slamming down,” says Zachary Long, aka The Barbell Physio, DPT, SCS, physical therapist and strength coach based in Charlotte, North Carolina. “Saving a few seconds is not worth the risk of injury.”

No. 2 | Get a Grip

Step into the center of the power rack facing the bar. Take an overhand grasp on the barbell a few inches outside shoulder width or a little beyond that — wherever you feel maximum comfort and grip security.

Crew Cue: “See” Your Set. Visualization and imagery techniques are a staple training tool for elite athletes in many sports. “Go through each step of whatever process you want to excel at,” says Angelo Grinceri, personal trainer and author of Intrinsic Strength Training: A Breakthrough Program for Real-World Functional Strength and True Athletic Power (Dragon Door Publications, 2016). “A top-level golfer visualizes each step of the golf swing. A professional snowboarder visualizes the feeling of a perfect run. In that same way, if you want to really lock in a perfect squat rep, you must first visualize yourself performing a perfect squat rep.” Take a moment, close your eyes and visualize your squat step by step, ending with a successful rep and a reracking of the bar.

No. 3 | Assume the Position

Step forward, bend your knees and dip underneath the bar. Rise up slightly so the bar rests across your upper back, just below your delts and between the tops of your shoulder blades and your trapezius (the “high-bar” position).

Crew Cue: The Highs and Lows. A high-bar or low-bar position does not matter when it comes to squatting function; it’s simply a matter of preference. “It refers to where the barbell is placed on the back,” Long explains. “In a high-bar back squat, the barbell is placed on top of the upper trapezius muscle, whereas with a low-bar back squat, the barbell rests lower on the scapulae. There are very minor changes in joint positioning and muscle activation with these variations that should not impact the average exerciser — they only become important when we discuss sport-specific effects.”

No. 4 | Get Up and Get Out

Take a deep breath in and exhale out, then brace your core to hold your spine in its natural position and stand up to lift the bar off the supports. Take a small step or two back so the bar will clear the supports as you descend for your reps.

Crew Cue: Start with Your Stack. A squat requires whole-body activation, and this cue from coach Matthew Pendola, owner of Pendola Training in Reno, Nevada, ensures top-to-bottom readiness: Start with your head and move down through your body to your feet, checking in with all your bodyparts to make sure you’re “stacked” properly. “Exhale forcefully through your mouth, squeeze your armpits down and drive your elbows [toward the floor] while gripping the bar as tightly as possible,” Pendola says. “You should feel your intercostal muscles [which run between the ribs] pulling in to cinch that ‘inner weight belt’ — the transverse abdominis and abdominal wall muscles.” Stack your body from head to toe before starting your repetitions.

No. 5 | Stand to Deliver

Position your feet about shoulder-width apart with your legs turned out slightly from your hips. “Anywhere from 0 to 20 degrees, adjusting them in or out as needed for comfort,” Long suggests. “Every athlete has their own unique combination of mobility and bone anatomy, and that means everyone has a slightly different stance.” There’s no exact level of turnout that will deliver optimal muscle stimulation or results — play with yours to ensure balance and comfort while also remaining pain-free.

No. 6 | Destination: Down

Keeping your head neutral, core braced and abs and torso upright, take a deep breath and begin to descend. “I teach individuals to ‘sit down’ rather than ‘sit back,’” Long says. “‘Sit down’ results in the knees going forward and hips going back, [leading to] a more balanced position in terms of muscle and joint loading.” On heavy-load squats, Long also suggests spinal bracing (as long as you don’t have medical issues that would preclude it): “Take a large breath in, filling your belly with air, then tighten your abdominal muscles on top of that breath. This pressurizes the abdominal cavity for maximal spinal stability during heavy lifting.”

Error Alert: Make sure to distribute your weight equally between your feet; some people are left- or right-side dominant, which could affect your movement patterns. “I do this by actively connecting to the floor with both my feet and then lowering myself slowly so I feel the weight evenly,” Grinceri says. The same level of concentration should be used on the way up.

No. 7 | Go Deep

Ideally, you should descend to a point at which your thighs are parallel with the floor or lower — e.g., ass to grass. “From a muscle-development standpoint, research has shown full-depth squats to be superior to partial-depth squats,” Long says. The reasons why are extensive but also fairly obvious: A longer range of motion stimulates more overall muscle activity and recruits a larger cross section of total muscle fibers, which in turn drives a larger hormone response during exercise and in recovery mode.

Crew Cue: Butt to Box. Pendola recommends placing a box behind you and squatting down until your glutes just lightly touch the top. “Pause there and imagine the box is a weight scale and allow only half your bodyweight to show on the scale,” Pendola says. (He credits that tidbit to world-renowned strength and conditioning coach Joe DeFranco.) For those new to squatting or who are relearning form, stack bumper plates on top of the box to shorten the range of motion and remove them incrementally as you improve.

Error Alert: Avoid a common squatting error known as “valgus collapse.” “That’s where the knees move [inward] as you squat down,” Long says. “This can come from weak glutes, ankle mobility issues and, occasionally, too wide of a stance.” Become more collapse-proof by improving your hip, ankle and upper-spine mobility.

No. 8 | All Rise

Forcefully drive through your whole foot, extending your hips and knees through the concentric (upward) portion of the lift, and exhale to return to standing.

Error Alert: Stay out of the “good morning” zone. “When you lack range of motion, your squat can start to look more like a back-loaded hip hinge (e.g., a good morning),” Grinceri says. “This is an awesome exercise on its own, but here it puts you at risk of a lower-back injury.” To determine whether you’re leaning forward when you squat, have a trainer or trusted partner watch you, or set up a phone and record your set. A good cue: “Imagine you have a wall just in front of and behind you and you’re trying not to make contact with either side,” Pendola suggests.

No. 9 | Finishing Touch

Complete your reps, then step back into the rack with both feet underneath you. Bend your knees and hips a little and set the bar in the supports, letting it settle before stepping free. Rest one to five minutes between sets, leaning toward the higher end if you’re working within 20 percent of your one-rep max and toward the lower end if you’re focused on lighter sets of 12 reps or more.

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Get Mobilized

Nearly every joint is engaged either as a primary mover or as a stabilizer during a squat. Here are some drills to mobilize some common problem areas. Perform them pre-squat to make the most of every rep.

Ankles: Exercise-Band Dorsiflexion

Secure an exercise band to a stationary object at floor level and sit facing the anchor. Bend one knee and place your foot flat on the floor; extend the other leg straight. Loop the band around your extended foot just below your toes and slide away from the anchor to create tension in the band. Slowly extend your ankle, as if pointing your toes, then flex back as far as you can. Perform 10 to 20 reps on each side.

Hips: 90-90 Hip Rotation

Sit on the floor with your legs and hips bent 90 degrees. Your front thigh should be roughly parallel to your rear calf and your rear thigh roughly parallel with your front calf. Sit up tall, keep your glutes on the floor and hold here for one to two minutes. Switch sides and repeat.

Thoracic Spine and Shoulders: Dead Hang

Take an overhand grip on a pull-up bar and allow yourself to hang freely, concentrating on elongating your body and straightening your spine. Hang 20 to 60 seconds, then drop down. Repeat two to four times.

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Quick-Fire Q&A

We asked our experts these common squatting questions.

Lifting shoes for squatting — necessary or not?

Zachary Long: “Lifting shoes are great for individuals with limited ankle mobility that impacts their squatting form or for those focusing on lifting maximal weight from a sports performance standpoint.”

What about squatting barefoot?

Long: “If an individual has exceptional ankle mobility, squatting barefoot is fine if that is their preferred method.”

What’s the consensus on knee wraps?

Angelo Grinceri: “I do not believe in teaching the body to become reliant on artificial support systems. I understand that wraps allow you to squat more weight, but I believe in improving human function over max weight lifted.”

Do women have different squatting-form issues than men?

Matthew Pendola: “The average female has about 4 percent more anterior pelvic tilt than the average male, and I’ve noticed that many women hyperextend their lower backs at the top of the squat. Fully extending the hips and squeezing the glutes at the top of a squat can lead to a disconnect in lumbar-spine stability, causing pain and potential injury. Movements like breathing hip bridges can help you first learn proper positioning for your specific biomechanics.”

Can we finally dispel the myth that squats are bad for your knees?

Long: “Research has repeatedly shown that heavy and deep squats are not only safe for your knees, but they also create adaptive changes in the body that make them effective for performance gains and in reducing injury risk.”