As you go about your business in the weight room, have you ever glanced over at a personal trainer during one of their client sessions and idly asked yourself something like, Dang, I wonder if they ever happen to notice what I'm doing over here? Good news! While your gym's fitness professionals obviously can't leave their charges to deliver you some kind of stern pro bono talking-to, they do see you, and they have a lot of feelings to share about...the myriad things you're doing wrong. (Perhaps this is, in retrospect, one of those questions to which you didn't want to know the answer.)

Fortunately, a few trainers have generously agreed to share with us the most common and most aggravating habits they see gymgoers developing—and a little free advice on how to fix them. This is, in effect, money in your pocket. Today: back rows.

Begin with the end in mind

The bent-over barbell row is one of the best mass-building exercises out there, but the most common mistake I see is people pulling the barbell high to their chest, instead of low to the top of the abdomen, and back toward the hips. Your starting position should look like this: spine flat but not parallel to the floor; shoulder blades pulled down toward the hips; and barbell hovering just an inch or two off the ground when your arms are fully extended. Be sure to initiate the row by driving your elbows toward your hips. Failure to do so will result in the lifter using the biceps and forearms to pull the weight, which can affect the degree of contraction and the range of motion in the pull. —Mike Dewar, J2FIT Strength and Conditioning

Read More6 Row Machine Alternatives to Give Your Body an Amazing Workout

Get sculpted for summer.

By Jay Willis

Don’t let the wrist list

Even people who can execute a perfect back row often subconsciously curl their wrists, especially at the top of the range of motion, for the sake of feeling like they're "doing more." Be sure your wrists are straight and immobile throughout. Remember that if your back muscles are fully contracted, bending your wrists inward—or in any other direction, really—won't provide additional benefits. —Josh Cox, Anytime Fitness

Newton’s Third Law, for the gym

Personally, I don't recommend the bent-over barbell row as a tool for gaining mass, because it leaves your entire back supported and stabilized only by the comparatively smaller core and lower-back extensor muscles. This can put an unnecessary amount of stress on the lumbar spinal region, especially for people who already experience back pain, and increase the risk for injury. To protect your lower back and prevent core-strength capacity from limiting your gains from the row, I suggest using a seated row that includes a chest support of some kind. —Devan Kline, Burn Boot Camp

If it’s not there, don’t despair

Wrists or lower back preventing you from getting the barbell row right? A dumbbell reverse fly is a great alternative for building back and rear deltoid muscles. It's especially useful if you don't have weights available that are heavy enough for a true row. Sit on the edge of a bench and lean as far forward as you can while still maintaining a flat back. Pick up the dumbbells from behind the heels and underneath your legs. With your elbows slightly bent, swing the dumbbells up by squeezing the back muscles together. —Ben Booker, Second Chance Fitness

Jay Willis is a staff writer at GQ covering news, law, and politics. Previously, he was an associate at law firms in Washington, D.C. and Seattle, where his practice focused on consumer financial services and environmental cleanup litigation. He studied social welfare at Berkeley and graduated from Harvard Law School... Read moreRelated Stories for GQFitness