Kneel on one knee near a cable machine with a low-set pulley and single handle. Grip the handle with one hand and position your upper arm close to your body. Extend your arm downward in a controlled motion until it’s straight, squeezing the triceps at the bottom. Slowly return to the start, maintaining tension and keeping your elbow steady against your thigh for isolation.
Log your cable concentration extension (on knee) sets in 1RM.fit and watch your estimated 1RM update automatically as you get stronger.