Chin-up

Hang from a pull-up bar with your palms facing towards you and your hands shoulder-width apart.

Engage your core and pull your body up towards the bar, leading with your chest.

Continue pulling until your chin is above the bar.

Pause for a moment at the top, then slowly lower your body back down to the starting position.

Repeat for the desired number of repetitions.

Losing tension in the core or lower back partway through the movement — because Chin-up loads multiple joints at once, a small breakdown in bracing at the hips or spine compounds through the whole chain.

Rounding the upper back or shrugging the shoulders up toward the ears at the start of the pull instead of initiating with the target muscle.

Rushing through reps using momentum rather than controlling both the lifting and lowering phase, which is especially important since there's no external load to force good tempo.

Attempting this exercise before building sufficient base strength and control — it has a low margin for error, so technique breakdown under fatigue is a common cause of injury.