Stand beside a rack or bench and place one hand and knee on it for support. Hold a dumbbell in your free hand with your arm extended toward the floor. Keep your back flat and core braced. Pull the dumbbell up toward your hip by driving your elbow back and up, squeezing your back muscles at the top. Slowly lower the dumbbell back to the starting position under control.
Log your dumbbell one arm row (rack support) sets in 1RM.fit and watch your estimated 1RM update automatically as you get stronger.