Sit at a cable pulldown machine with your thighs secured under the pads and grasp the bar with a slightly wider than shoulder-width overhand grip. Keep your chest up and core engaged as you pull the bar down toward your upper chest by driving your elbows downward. Squeeze your shoulder blades together at the bottom, then slowly return the bar to the starting position with control. Focus on smooth movement and avoiding excessive leaning to effectively target the back muscles.
Pulldowns work well in the 8 to 12 rep range for 3 to 4 sets, since the seated, supported position lets you chase a deep stretch and a hard squeeze without the fatigue of a free-standing pull like the pull up. Progress by adding a small amount of weight once you can complete every set with a full stretch at the top and a strict squeeze at the bottom, rather than swinging heavier weight through a partial range. Use it as the main vertical pull on days when pull ups are too advanced, or as a second, higher-rep vertical pull after pull ups on a heavier back day.
Is the pulldown a good substitute for pull ups? Yes, especially for building toward your first strict pull up, since you can dial in the exact resistance rather than fighting full bodyweight from day one.
Should I pull to my chest or behind my neck? To the chest; pulling behind the neck forces the shoulders into a position most lifters don't have the mobility for and adds little extra benefit.
Why do I feel this in my arms more than my back? Grip too tight or too narrow shifts the work onto the biceps and forearms; use a slightly wider, relaxed grip and focus on driving the elbows down and back.
Log your cable pulldown sets in 1RM.fit and watch your estimated 1RM update automatically as you get stronger.