Sit or lie on a bench holding a dumbbell in one hand with your upper arm vertical and elbow bent. Keep your upper arm stationary and extend your forearm upward to straighten the elbow, contracting the triceps. Slowly lower the dumbbell back toward the starting position under control. Focus on keeping your elbow steady and avoid using momentum.
Log your dumbbell one arm triceps extension (on bench) sets in 1RM.fit and watch your estimated 1RM update automatically as you get stronger.