You’ve been exercising your butt off for weeks and not seeing any results from your workout.

Maybe it’s your form, said Stacy Berman, a New York City personal trainer and founder of Stacy’s Boot Camp and Infinite Balance Yoga Fusion.

“If you’re not in the proper position, you’re probably not working on the muscles you want to work on,” she said. “If you’re doing leg lifts because you want to work on your abs but you’re lifting your lower back, you may only be working your back so you get into a negative workout pattern. It’s all about being in the right form.”

Here are five common exercises people do wrong:

1. Squats. Berman said squats are a basic exercise that people do wrong all the time.

“With squats, you work your quads, the back of your legs; butt and hamstrings,” she said.

Doing squats improperly can lead to sore knees. To avoid this, keep the body straight while bending and make sure your knees never go over your toes.

“To get the right movement, stand 6 inches in front of a bench and lower onto a bench,” Berman said. “This will ensure you’re straight. You’re body will naturally pitch forward when you squat but make sure you don’t lean forward. You should always be able to see your feet. This will ensure you’re doing them the right way.”

2. Lunges. This is another movement that can injure the knees if done improperly. Done correctly, the move can strengthen and tone the quads, butt and hamstrings, as well as the abdominals.

The movement should start with the feet apart and continue with the person moving one leg forward at a time and bending at the knee. Again, the body should stay in a straight line and the knee should remain at a 90-degree angle and never hang over the foot, Berman said.

3. Sit-ups. Proper sit-ups, as opposed to crunches, work the entire abdominal core, but often people will “cheat” using their neck and arms for better momentum.

“When you’re doing a sit-up your head should be straight; never round your shoulders and never yank your head to your chest,” Berman said. “If you’re doing a sit-up properly, you should be able to keep your hands on your head the whole time. ... You also want to breathe properly. You should exhale on the way up and inhale on the way down.”

4. Leg lifts. This is another movement that helps tone your abdominals, but if you’re placing your hands underneath your butt or back, you’re taking the stress off of the core and placing it on the lower back.

“You should keep your hands by your side the whole time,” Berman said. “You also want to make sure your legs are totally straight through the entire range of motion. If you can’t do that, try keeping both legs raised in the air and alternating the legs by lifting them one at a time.”

5. Push-ups. This exercise not only works your arms but also your core and upper back muscles. The body should remain in a straight line while you’re doing push-ups, Berman said.

“You want to imagine yourself as a plank while you’re lowering and raising back up,” she said. “If you round your shoulders while you’re doing push ups you’re only working on the neck muscle. You also want to keep the hands in line with the shoulders ... and avoid moving your hips up and down. If you’re having trouble with the movement, practice being in the plank position for one minute to get used to the movement.”