Sit on a bench holding a dumbbell with both hands and raise it overhead with arms fully extended. Keep your elbows close to your head and upper arms stationary. Slowly bend your elbows to lower the dumbbell behind your head until your triceps are stretched, then extend your arms to bring the weight back up to the starting position. Keep the movement controlled and avoid flaring your elbows.
Log your dumbbell seated triceps extension sets in 1RM.fit and watch your estimated 1RM update automatically as you get stronger.