Isolates the lats with zero biceps involvement.
Keep your arms locked straight and pull from your lats, not your hands.
Sweeping a bar from overhead to your thighs with locked arms trains the lats through their pure function, pulling the arm down and back, without the biceps helping the way they do in rows and pulldowns. The long head of the triceps assists because it also crosses the shoulder, which is why your upper arms feel it too. Its cable arc keeps tension on the lats through the whole path, making it a favourite for building the mind-muscle connection and finishing back sessions.
Because the long head of the triceps crosses the shoulder joint and helps pull the arm down. Some triceps involvement is baked in. If it dominates, lighten the load and think about driving your elbows down rather than pushing the bar with your hands.
The lat pulldown lets you go heavier and builds more overall size, the straight-arm version isolates the lats by removing the biceps from the pull. They are teammates, use the straight-arm move to feel the lats, then the heavy pulldown to load them.
A slight hinge, roughly 20 to 30 degrees, gives the lats a longer stretch overhead without turning the exercise into a bow. Set the hinge once and hold it, if your torso pumps up and down you are using momentum.
