Place a stability ball on the floor and get into a push-up position with your hands on the ball slightly closer than shoulder-width apart. Keep your body in a straight line and core engaged. Bend your elbows to lower your chest toward the ball, then push through your palms to extend your arms back up. Repeat for reps.
Log your narrow push up on exercise ball sets in 1RM.fit and watch your estimated 1RM update automatically as you get stronger.