Stand with feet hip-width apart, hinge at the hips with a flat back and hold a dumbbell in one hand. Let the weight hang straight down. Keeping your core braced, pull the dumbbell up toward your hip by driving your elbow back and squeezing your back muscles at the top. Slowly lower the dumbbell back down under control. Repeat on the other side.
Single arm rows work well in the 8 to 12 rep range for 3 to 4 sets per side, since the free hand bracing on a bench lets you isolate each side of the back without the lower back having to hold an unsupported hinge. Progress by adding a rep or two before moving up in dumbbell size, and always match the weaker side first if you notice an imbalance between arms. Use it after your main bilateral row or pulldown as a finisher that lets you chase a deeper stretch and a harder squeeze than a barbell row allows. It's also a solid choice for lifters with a cranky lower back, since the supported torso removes most of the spinal loading.
Should I rotate my torso as I pull? A small amount of natural rotation is fine, but if you're twisting hard to move the weight, it's too heavy; drop the load and keep the pull strict.
Why does one side feel noticeably weaker? Small side-to-side strength gaps are normal; training unilaterally like this is exactly how you close them over a few months.
Should I row to my hip or my ribs? Toward the hip targets the lats more directly, while rowing higher toward the ribs shifts emphasis onto the mid back and rear delts.
Log your dumbbell single arm bent over row sets in 1RM.fit and watch your estimated 1RM update automatically as you get stronger.