If you’re struggling with pull ups the reason may not be your back and shoulder muscles or your biceps. This is more so true if you can do chin ups (palms facing you). With most guys and girls who struggle with one of the best compound bodyweight exercises the reason is weak brachioradialis muscle.
This forearm muscle flexes the forearm at the elbow and it’s the one muscle that carries a lot of the load as you pull yourself to the bar with palms facing away from you. If you switch to the chin up position, your biceps take more of the load and since they are a lot stronger muscles you can pull yourself up easier.
How to Improve?
You can of course use assisted pull ups such as the pull up machine, or use rubber bands over the bar to help pull you up and slowly improve your strength. After all, doing the exercise will naturally work the required muscles.
But you can improve a lot faster if you target the muscles with other exercises. So what exercises target brachioradialis? You might be doing them already but perhaps not enough of them and they’re overlooked in your workout.
The first most obvious exercise is the reverse bicep curl. As you lift a dumbbell with your pronated hand you work brachioradialis the way you want. So doing more of this exercise will increase your forearm strength for the pull up.
Another exercise is a hammer curl which also works the muscles the way you want.
Finally, as an improved variation, you can combine the two exercises by starting with a hammer curl, then pronating your hand and finishing with the bicep curl in the eccentric movement.
Simply add this combined exercise to your workout routine and you will improve your pull up rather quickly.