There's an old fitness joke that goes like this: You know your workout is terrible if you do arm curls in the squat rack. Okay, this isn't really a joke. It’s a "nice" way of telling people that they shouldn't curl in the squat rack. (See, it makes the strong dudes really mad. Is this on? Tap, tap, tap.)

But seriously folks, no routine is perfect. And I've found three not-so obvious ways to tell if your workout needs work. Will your exercise plan pass -- or fail?

(And if you're still wondering why you shouldn't curl in the squat rack, just trust me and don't do it.)

1. You sit or lie down for more than two exercises

Most gyms are filled with places to park your butt. But a funny thing: The benches and seats aren't there so you can rest between exercises. (Most people do.) Apparently, they're there so that you can rest as you exercise. For example, the leg press, leg extension, and leg curl all require you to sit or lie down so that you can work your lower body muscles. "It doesn't make sense," says Alwyn Cosgrove, C.S.C.S., co-owner of Results Fitness in Santa Clarita, California. "People sit all day, and then they go to the gym and sit there, too."

Cosgrove says most of his clients want to undo the effects of their desk job. Think: belly-fat, poor posture, and tight muscles. "Sitting contributes to all of those problems," he says. "That's why we keep people on their feet. There are always exceptions, but I don't want anyone sitting or lying for more than two exercises. And for fat loss, I prefer that our clients don't sit at all." Yes, you have to lie down if you want to do bench press. But for most exercises, sitting is completely optional. (If you're still not convinced you spend too much time in a chair, find out Why Your Desk Job Could Be Killing You.)

2. You're not playing the right percentages

Here's a quick quiz:

Question 1: How many total sets of exercises do you do for your lower body each week? For instance, if you do three sets of the squat on Monday, and three sets of the lunge on Friday, that's six total sets. (Duh.)

Question 2: How many total sets of all exercises do you do each week? This includes everything: lunges, squats, bench presses, pullups, curls -- you name it.

Now divide your answer in Question 1 by your answer in Question 2. Keep that number in mind.

Question 3: What percentage of your body's muscle resides below your waist? Hint: Probably around 50 percent or more, right?

Final question: How does the percentage you calculated earlier compare to your answer in Question 3? "If there's a big difference, your workout is probably way out of balance," says Cosgrove. "Whether you're trying to lose fat or build muscle, you're missing out on a huge opportunity to improve your results."

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This isn't the only version of the quiz you should take, though. What about the time you spend working the front side of your body compared to the back side of your body? How many sets of exercises do you do for you chest, arms, and quads, compared to your back, glutes, and hamstrings? "I know guys who spend 90 percent of their time working 50 percent of their body," says Cosgrove. "This slows their results, and over time, can lead to injury due to strength imbalances." (Are you out of balance? Use these simple self-tests to find and fix your posture problems.)

Now this isn't an exact way to determine if your workout is balanced. But it'll help you determine whether or not you're even if in the ballpark. If you're closer to 90-10 than you are to 50-50, your workout is probably horrible.

3. You can’t pass this core test

Even if you don't have an ounce of fat, you could be soft in the middle. Watch the video to see a cool test of core of strength that you can try right now, courtesy of Gray Cook, P.T., author of Movement: Functional Movement Systems. It's a simple way to determine if your midsection isn't as strong as it should be.

Warning: The fact that you regularly do ab exercises doesn't guarantee you'll pass this test. "You can do lots of crunches and situps and still have a weak core," says Mike Wunsch, co-creator of 24-Hour Abs, Men's Health's newest ab-sculpting diet and exercise plan. "I see that all the time." The reason: Classic ab moves like crunches and situps work the muscles that allow you to flex (that is, round) your lower spine. True core exercises, on the other hand, train the muscles that prevent your spine from rounding.

The bottom line: If you can’t pass this test, you need to upgrade your ab workout to focus on stability exercises like the plank and side plank. The perfect solution: The Best Ab Workout You've Never Done.

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