Do you have a straight back?

Consider the following:

The average human head weighs 8 pounds. If your chin is jutting forward about 3 inches—which is often the case when you work at a computer—the muscles in your neck, shoulders, and upper back have to support a weight of 11 pounds. That’s a 38 percent increase in weight—often over the course of several hours. If you don’t take action, sitting at a desk all the time can lead to postural dysfunction, which you might know as slouching.

The result isn’t just a poor appearance; the condition is a common cause of weight-lifting failure, pain, and injury. If you regularly work at a desk or lift weights, there’s a good chance you already have—or will soon have—sinistral syndrome. Your risk is higher if you do both.

With our test, you can determine whether you are a victim of this syndrome. Then check your posture again with our guide. It will tell you what to do if you have already encountered this problem, as well as how to prevent it in the future.

Bonus: Your shoulders will be bigger, stronger and healthier than ever.

Self-test: Do you suffer from slouching?

Place two fingers on the top of your right shoulder and feel the bony process. This is your acromion. Now take a ruler and lie down on your back on the floor, with your right arm close to your body. Use your left hand to measure the distance between your right acromion and the floor, being careful not to raise or lower your right shoulder when measuring. If the distance is more than 3 cm, you have problems with your posture.

Need more confirmation? Ask a friend to take a photo of you – shirtless – from the side. Stand up straight, but in a relaxed position, as you normally would without thinking about your posture. In the photo, check that the middle of your ear is in line with the middle of your shoulder, hip, and ankle. If you can’t draw a straight line through these points, then the diagnosis is correct.

Problem #1: Your Exercises

The shoulder is the most complex and unstable joint in the human body. For it to function properly, you must train all the muscles that help stabilize it. The problem is that many guys think that the shoulder muscles are just the deltoids, the superficial muscles of the shoulder. They reason like this: if I can’t see this muscle, why should I train it?

This means they do a lot of overhead presses and lateral raises—exercises that target the front and middle deltoids—but they don’t engage the smaller, less visible muscles at the back of the shoulder joint at all. The result: a strength imbalance that reduces shoulder stability.

Not only does poor stability increase your risk of injury—rotator cuff dislocation and tears—it also reduces your strength capabilities in almost all upper-body lifting movements. In fact, weak shoulder muscles are the most common cause of long-term weightlifting plateaus.

Another problem: bench presses and high-pulley rows, two of the most popular exercises in any gym (other than, say, biceps curls). The former targets the pectoralis major—the main muscle in your chest—and the latter targets the latissimus dorsi. Both of these large muscles attach to the inside of your upper arm, meaning they internally rotate it. If you do these exercises more often than externally rotating movements—like bent-over rows and low-pulley rows—the pectoralis major and latissimus dorsi will pull your arms inward, causing your shoulders to roll forward.

Here's how to train the "other" shoulder muscles. You'll need to count the total number of sets of bench presses, shoulder presses, and pulldowns you do in a week, and make sure you're doing an equal number of sets of exercises that work the following muscle groups:

• Rear deltoids

The deltoid muscle is made up of three distinct bundles: the anterior, middle, and posterior. While shoulder presses and lateral raises work the anterior and middle deltoids, they ignore the posterior deltoids.

Suggested Exercises: Try bent-over dumbbell rows and dumbbell curls using a wide grip. Perform the rows while seated, pulling the rope handle toward your neck, not your lower chest.

• Rotator cuff

The rotator cuff is made up of the tendons of the supraspinatus, infraspinatus, teres minor, and suprascapularis muscles, which stabilize the humerus, allowing you to rotate your arm in any direction.

Suggested Exercises: Strengthen your rotator cuff by working it at least twice a week with external rotation exercises and a movement called PNF (proprioceptive neuromuscular release).

• Scapular muscles

These muscles—the trapezius, serratus anterior, pectoralis minor, rhomboid major, and rhomboid minor—move and stabilize your shoulder blades. According to research, 100 percent of people with shoulder problems have unstable shoulder blades.

Suggested Exercises: Focus on rowing movements such as bent-over rows and low-pulley rows. Squeeze your shoulder blades together at the beginning of these exercises.

Problem #2: Your Work

If you suffer from poor posture, changing your exercise routine will not guarantee that the problem will be solved. 30 minutes a day spent exercising will not compensate for all the time you spend sitting in one position.

If your shoulders are hunched forward for long periods of time, your chest muscles become shortened. Because these muscles are attached to your arms, the distance they need to stretch when you slouch is less than when your shoulders are pulled back.

Over time, the chest muscles adapt to this position as if it were their natural state. As a result, many of the shoulder stabilizing muscles become overstretched, making them weaker.

Recommended exercises: Do stretching exercises every day. They stretch your chest muscles, which prevents them from becoming permanently shortened.

If you work at a computer, do 10 standing shoulder rolls every hour. Stand up and roll your shoulders back, squeezing your shoulder blades together. Hold each rep for 3 seconds. And remember to keep your head and shoulders in line with your pelvis—it’s an easy way to ensure your body is in the right position.

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