We’ve all seen people in the weight room and group fitness classes who churn out reps of various strength-training moves with questionable form. Heck, we’ve all probably been those people at some point or another, too. 

Less-than-perfect form is incredibly common amongst exercisers of all experience levels (read: stop throwing shade at that guy on the bench press) but that doesn’t mean it should go unchecked. Faulty movement patterns can not only detract from the potential benefits you reap from the exercises you do, but they can also set you up for injury.

To ensure your strength-training routine delivers all of the perks (from improved bone density to a revved metabolism to better mental health), make sure your movements aren’t falling victim to the following common strength training form mistakes.

1. Lifting with a too-narrow foot stance

Whether you’re doing standing overhead presses, lunges, or squats, a too-narrow foot position greatly reduces overall stability, which can increase the likelihood of injury and affect performance, according to CITYROW GO Instructor King Hancock, M.S., C.P.T. 

“Imagine your body is a traveling tower and your feet are the base. You want a base of support that can maintain the tower’s stability if a strong wind blows,” he explains. “The same way that a car is more stable than a motorcycle, a wider base of support provides greater stability, which not only can make exercises more effective but can also reduce your chance of injury.”

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To fix this error, look at how close or far apart your feet are before beginning a movement. Hancock recommends placing your feet about hips-width apart from one another. Then, as you press, curl, raise, snatch, swing, or lunge, aim to maintain that distance.

“Naturally, different movements require different foot positions, but, generally, most strength-training movements require a hip-width—or slightly wider—foot position,” he says.

2. Caving in your knees during squats

Ask any trainer in the world about the strength training form mistakes that make them crazy and they’re practically guaranteed to mention this one, which is known as “knee valgus” amongst the pros. 

“This is typically caused by overactive or tight adductors and underachiever abductors,” explains Caley Crawford, C.P.T., Director of Education for Row House. “Meaning, the muscles that draw your knees in are overactive or tight while the muscles that press the knees out are underactive.”

Not only does this look wonky, but “when your knees cave inward during a squat, you put excess pressure on them, which ultimately can cause pain or injury,” says HOUSEWORK founder and SoulCycle Master Trainer Sydney Miller. It also means you aren’t properly engaging your glute medius muscles (which are on the outsides of your cheeks) and getting the max benefits of this awesome exercise. 

Miller always cues exercisers to keep their weight in their heels and outer edges of their feet to help keep the glute medius engaged. Crawford meanwhile recommends squatting with a band looped around your thighs so that you have to press your knees outwards during the movement.

3. Rounding Your Spine during deadlifts

Another one of the most common strength training form mistakes pretty much all trainers are constantly on the lookout for, a rounded spine during deadlifts can also be quite dangerous.

“This is a very serious form problem that can put your spine at serious risk,” Matt Scarfo, C.P.T., C.E.S., P.E.S., F.N.S., of Lift Vault. “In fact, it’s one reason many people believe that deadlifts are a dangerous exercise.”

Important to remember here is that your lower body, not your back, should be bearing the brunt of the load during this lift. “The deadlift is the strongest lift we can do as humans, therefore there is a lot of pressure on your back if you don’t load the legs properly,” Crawford says.

Read More: How To Strength Train To Lose Weight

Your move? “When you deadlift, you want to keep your spine straight,” says Scarfo, who recommends imagining a PVC pipe or yardstick along your back. Another must-do: “Brace your lower abs and lats,” he adds. “Feeling those muscles turn on should be a big enough physical cue to help you stand with the weight.”

4. Flaring Your Elbows back during barbell back squats

Though elbows should be kept close to your ribcage and point down to the floor during barbell back squats, people often keep their elbows too high and pointing to the back. 

“This sets off a chain reaction of bad form,” says Avi Silverberg, M.S., C.S.C.S. of Feast Good. “It causes you to keep the pressure on your foot too far forward, which can cause you to lift your heels and lose balance.” According to Silverberg, it also pushes the barbell forward, which encourages you to overarch your lower back. This alone sets you up for lower back soreness and pain—and increased risk of injury.

5. Not engaging your core (during all moves)

Engaging your core is, of course, a must during abs exercises—but that doesn’t mean you should let your midsection sleep during other movements. “One of the most common strength training form mistakes I see is failing to engage your core during compound exercises like squats,” says DJ Mazzoni, M.S., C.S.C.S., medical reviewer at Illuminate Health. “This can cause postural imbalances that significantly increase the risk of injury to the back and knees.”

To protect yourself from injury and reap the full benefits of your workout, keep that spine neutral and your midsection engaged, Mazzoni. This goes for squats, deadlifts, pullups, pushups, and more. “If your core is weak, do core work to build up strength before doing heavy compound lifts,” Mazzoni adds. (Here are 18 killer moves to get started with.)

6. Scrunching Your Shoulders during upper-body moves

A major mishap that pops up during many an upper-body exercise? Shoulders that scrunch up towards your ears. Look out for this strength training no-no during moves like pullups, seated rows, and lat pulldowns, says trainer Megan Flanagan, C.P.T. 

“This can create tighter traps, along with impinged shoulders, and limits the benefits from this exercise,” she says. And if you’re like most people, your traps are already tight enough. (You can thank sitting at a desk all day for that one, folks.)

To help prevent your traps from taking over during these upper-body moves, try doing band pull-aparts to activate the shoulder blades before performing them, Flanagan suggests. “You can also think of the cue to squeeze your shoulder blades and pull your shoulders down and back.”