Whether it’s holding a plank for 60 seconds or blowing through a series of bicep curls, chances are you’ve got a few go-to exercises you feel pretty darn good about. And that’s awesome—truly—but now the bad news: Turns out, you might not be getting your favorite gym moves quiiiiite right.
You’re not alone. According to trainer extraordinaire Albert Matheny of ProMix Nutrition and co-founder of the Soho Strength Lab, the majority of gym-goers (like, more than 90 percent of them) butcher classic workout moves to some degree, valuing quantity of reps over quality of form, or getting the job done without fully engaging the muscle groups meant to be targeted.
Ready to work out the right way? Here are four of the most common mistakes Matheny sees over and over—and the super-simple tweaks you need to know to rock that perfect form.
1. The Jefferson Curl
The Jefferson Curl, which works the spine and helps lengthen tight hamstrings, is suddenly all over Instagram, but Matheny’s worried that some people are putting their bodies at risk for the sake of snapping an impressive pic. “This is meant to be a flexibility move, not a strength move,” he says.
The common mistake: Automatically reaching your hands beyond your feet and grabbing a heavier weight than necessary.
How to do it right: “If you can’t place your hands completely flat on the floor while in a hamstring stretch, don’t even think about this move,” Matheny says. If you are able to place your hands on the floor and still want more of a challenge, Matheny says it’s okay to reach beyond your feet—but work against your own body weight to see how far down you can reach, rather than automatically grabbing a weight.
You’d think a core move this beloved—used in everything from barre to bootcamp—would be pretty well understood at this point. But a lot of plank-ers essentially cheat in the position without even realizing it. “In any given class, [most] people would say they can hold a plank for 60 seconds, but 99 percent of people can’t hold a really strong plank for that long,” Matheny says.
The common mistake: Doing anything you can to keep your knees off the ground, whether that means raising or lowering your butt, or shifting your weight back on your heels. The latter is a strategy most people fall into when they get tired, Matheny says, and it means your core isn’t doing as much work as it ideally should be.
How to do it right: Actively push into the ground with your hands or forearms, keep your shoulders directly over the elbows, and make sure your abs, glutes, quads, calves, and feet are engaged the whole time. Yep, everything.
3. Bicep Curl
When it comes to crushing this arm-toning move, Matheny says it’s all about having strict form. And that means keeping the movement controlled instead of relying on momentum to bring the weight up. His rule of thumb: Fewer bicep curls done correctly is way better than higher reps done with less-than-ideal form.
The common mistake: Moving the elbow backward, which inadvertently makes the move easier.
How to do it right: Keep your back against the wall and curl the weight to your bicep. You’ll find that suddenly, that whole elbow-back habit is impossible. (Way more intense, right?)
4. Tricep extension
This is another classic, used-in-just-about-every-class move that is so good at targeting the back of the arms. But Matheny says many, many people get it wrong.
The common mistake: Matheny sees a lot of people who kind of jerk or throw their triceps back, using the momentum of the weight rather than their muscles.
How to do it right: Grip the weight really hard, then extend the arm fully being. Be deliberate, and remember: slow and steady wins the race.