Three "stupid" things you might be doing at the gym, and the best ways to fix them.

1. You skip squats because they're bad for your knees.

Squats don't ruin your knees; the way you're squatting does. Many men butcher the move, and then complain of knee pain. And that's a shame, because the squat is one of the most effective exercises you can do. It works nearly every muscle in your body, and burns a ton of calories. In fact, physiologists at the Mayo Clinic have found that squats place less stress on your knees than leg extensions, a popular machine alternative.

There are some guys who have past injuries or musculoskeletal issues who should stay away from the exercise, but they're rare. So stop skipping it, and start reaping the benefits of this classic. If you properly execute a good squat pattern, your knees shouldn't hurt. Here's a brief breakdown on how to properly back squat.

SETUP

1. Squeeze your shoulder blades together to create a "shelf” along your upper back. This is where the bar will sit. Maintain this "shelf" throughout the entire exercise.

2. Before unracking the weight, step under the bar so it's across your shelf, and pull down on it. This will help engage your lats—which are the largest muscles in your back—and provide more tension and stability in the spine.

3. Unrack the bar, and take two steps away.

4. Brace your abs, squeeze your glutes, and keep a neutral spine.

DESCENT

1. Push your hips back like you're sitting in a chair.  (To maintain proper form as you lower, I tell clients to pretend as if they're crushing a can between their butt and hamstrings.)

2. As you sit back, open up your hips by pushing your knees out. Your kneecaps should stay in line with your middle toes.

3. Your knees may glide forward over your toes a bit, and that's fine. It's impossible to squat without that happening. You just want to minimize this glide as much as possible.

4. Push your hips back until your quadriceps are parallel to the floor or slightly past parallel. Going past parallel (110 degrees) puts no added joint stress on your knees than staying above parallel (70 degrees) or going to parallel (90 degrees), according to a study in Clinical Biomechanics. 

ASCENT

1. Stand up by thrusting your hips forward and squeezing your glutes. That's it. 

2. You bench press with your feet on the bench. 

When it comes to bench pressing, proper technique ensures steady gains and fewer injuries. Unfortunately, I see a lot of guys doing the lift wrong. One of the biggest mistakes: Putting up your feet on the bench. While many guys say it helps them work their pectoral muscles harder, I'm here to tell you that's just not the case.

Sure, it might help isolate them a little more than the standard version, but benching with your feet up makes you unstable. That means you can't lift as much weight.

Instead, keep your feet flat on the floor, and drive through your heels as you press up the weight. This creates a solid foundation and allows you to press as much weight as you possibly can. Progressive overload is what builds a stronger bench press and, subsequently, larger pecs—not lifting lighter loads with your feet on the bench. 

Other guys put their feet on the bench to flatten their backs. For some reason, they falsely believe benching with a curved back is a bad thing. But have you ever seen a powerlifter bench? They arch their back every single time! It gives them a mechanical advantage to lift more pounds.

Now, I'm not saying you should bend your back until it looks like St. Louis' Gateway Arch. But your lower back has a natural inward curve that you can maintain throughout the lift.

3. You work your biceps with curls.

Your biceps are the size of tennis balls, yet you'll work them with 17 different variations for more than half an hour. Stop! There are tons of other exercises that work your biceps while also targeting a ton of other muscles groups. It's time to get more bang for your buck.

That's why I have a strict rule in my gym that if you can't perform at least five strict chinups (sternum to bar), then you can't do a bicep curl. The chinup not only hammers your biceps, but it's one of the best ways to work your latissimus dorsi, the biggest muscle group in your upper body.

Strong, wide lats give you the coveted V-shaped torso. And if vanity alone won't compel you to work your back muscles, maybe this will: You'll increase your gains at the gym. That's because your lats and the other muscles of your upper- and mid-back are key to stabilizing your shoulder joints. Stable shoulders allow you to lift heavier weights. If those muscles are weak, however, almost every upper-body lift—including your precious arm curls—will suffer.

If you can't perform chinups with perfect form, concentrate on the eccentric, or lowering, portion of the move instead. There's greater potential for growth during this phase if you go slowly and under control.

DO THIS: Stand on a bench, box, or step under a pullup bar. Jump up and grab the bar so that your sternum touches the bar. Hold this position a couple seconds as you try to keep your body from swinging back and forth. Slowly lower yourself until your arms are fully extended. Drop down onto the bench, box, or step. That's 1 rep. Perform 3 to 5 sets of 3 to 5 reps 3 times a week.