The next time you go to the gym, take a look around: you’ll probably see all kinds of exercises, some good and some not-so-good.

The unfortunate truth is that not all exercises are created equal. Some are incredibly effective at building muscle and melting fat; others are ineffective and can even do more harm than good. (Worse, the bad ones are sometimes very popular.)

Read on for our list of the worst exercises — the ones you should avoid at all costs. If you currently have them in your exercise routine, try our alternatives, which are far more effective and take your body to the next level.

1. SITUPS AND CRUNCHES

Situps and crunches are as old-school as it gets: You see them in PE class, boot camps and military training around the world. But get ready for some big news because these tummy exercises aren’t effective or good for you.

Your core — which consists of your rectus abdominis, external and internal obliques, transverse abdominis, pelvic floor, etc. — is designed to help your body stabilize and brace against twisting and bending (not generate it).

Situps and crunches, however, eliminate the bracing and put your body into bad positions: You pull your neck forward, round your shoulders, flex your spine and put a lot of stress on your lower back. (It also goes without saying that you should avoid the situp machine too for those reasons.)

Instead, choose ab exercises that help you maintain a good posture throughout the exercise. If you want to take your core strength to the next level and get washboard abs, try our super effective 14-day plank challenge: It uses many different variations to blast your midsection from different angles to test your muscles (and your mind).

2. SMITH MACHINE EXERCISES

With the exception of the inverted row, avoid all exercises on the Smith machine. It seems safe because the bar has a lock that activates when you let go, but it puts your body in unnatural positions because the bar only moves in a straight, rigid line, which is not how you move in real life.

Also, because the bar follows a straight path, you don’t get to improve your stability or balance and you won’t get the same muscle gains you’d like. Researchers found that free-weight squats and free-weight bench presses activated more muscles than doing the same exercise on a Smith machine.

Stick to the free-weight version of your exercise: barbell squat, dumbbell bench press, etc. You’ll get more overall benefits and build more muscle and strength.

3. SEATED TWIST MACHINE

Remember what we said about how the core is supposed to move? Well, the vertebrae of your spine at your lower back can only twist 13 degrees in each direction, which is tinier than one hour on a clock. But the seated twist machines actually crank your body well beyond that range-of-motion.

If you want to improve your rotational strength, try the kneeling Palloff press. Get on both knees and set a cable handle to chest height. Facing perpendicular to the cable, bring the handle to your chest, and push it straight forward. Do it facing both ways. You have to brace your trunk to resist twisting and turning, which fires your core and keeps your spine in a safe position.

4. SUPERMANS

You might see these done in gyms or even physical therapy centers in an effort to “strengthen” your lower back. But the problem is it cranks your lower back into hyperextension while putting tremendous load and compression onto your lumbar spine. (Most people have a lower back that’s already too extended, which creates something called “lordosis.”)

Substitute supermans with another exercise if it’s a part of your current fitness program. Instead of directly targeting your lower back, focus on strengthening your entire trunk — back, abs, obliques, etc. — with core exercises where you maintain great posture throughout.

Try the single-arm farmers carry: Grab a heavy dumbbell in one hand, keep your chest up and shoulder blades squeezed, then walk. Maintain a neutral lower back and don’t arch excessively.

5. BACK EXTENSIONS

The back extension machine tries to strengthen your lower back by repeatedly flexing and extending it, which can cause problems. Worse, a lot of people hold a weight plate behind their head or at their chest, which further increases the stress on your spine.

READ MORE > 10 ESSENTIAL BODYWEIGHT EXERCISES 

6. UPRIGHT ROW

This popular exercise targets your shoulders and traps. Unfortunately, it’s one of the worst exercises you can do for your shoulders because it impinges your shoulder joints. The upright row actually forces you to internally rotate your shoulders and pull a heavy weight while in a poor position, which can lead to all kinds of problems.

Instead, to build strong and wide shoulders, replace upright rows with the dumbbell overhead press. It targets your upper body without adding unnecessary (and impinging) stress to your shoulder joint.

7. BEHIND-THE-NECK LAT PULLDOWNS OR BEHIND-THE-NECK PRESSES

Avoid any upper-body exercise where you pull or push from behind your neck because it puts tremendous strain on your shoulders. In a behind-the-neck position, your shoulders are almost at their maximal limit on extension in those positions — throwing weight on top of it just adds more strain to a fragile area.

Always do lat pulldowns, chin-ups, pullups, etc. toward your collar bones; if you’re going to press a weight overhead, start with the barbell at your collar bone or use dumbbells or kettlebells.