Set a barbell or suspension straps at about waist height. Lie underneath with your body straight and heels on the floor. Grab the bar with an underhand (palms-up) grip shoulder-width apart. Brace your core and pull your chest up toward the bar by bending your elbows, keeping your body in a straight line. Pause at the top, then lower yourself back down with control. Repeat for reps.
Log your underhand grip inverted back row sets in 1RM.fit and watch your estimated 1RM update automatically as you get stronger.