Dumbbell bent-over row (single arm):
Put your left leg on the bench and grab the far side with your left hand, then bend over so your upper body is parallel with the ground. Reach down and pick up the dumbbell in your right hand with a neutral grip (palm facing you), then hold it with your arm extended, keeping your back straight.
Bring the dumbbell up to your chest, concentrating on lifting it with your back and shoulder muscles rather than your arms. Keep your chest still as you lift. At the top of the movement, squeeze your shoulder and back muscles. Lower the dumbbell slowly until your arm is fully extended again. Do all your reps on one arm before switching to the other side.
Mistakes and Recommendations:
Do not hang your head. It disrupts the natural spine position.
If you are pulling a dumbbell to your chest, it means that you took too heavy weight.
Control your movements. Any jerks will lead to injuries.
If you are rounding your back, it means that you don’t have enough stretching. Try to use an incline bench. You should also try this if your arms are weak.
Pull the dumbbell with biceps. Exhale when you lift it, inhale when you lower it.

Dumbbell bent-over row (single arm).