Lie flat on a bench holding a barbell with an overhand grip. Start with arms extended above your chest, then bend only at the elbows to slowly lower the bar behind your head. Keep your upper arms stationary and elbows close to your ears, then extend your arms back up by contracting the triceps. Maintain control throughout.
Log your barbell lying back of the head tricep extension sets in 1RM.fit and watch your estimated 1RM update automatically as you get stronger.