The video discusses the common mistake of performing pull-ups too quickly, focusing solely on moving from point A to point B. It highlights that the primary goal in the gym should be to stimulate muscle hypertrophy, which requires a focus on the eccentric (lengthening) phase of the exercise. This phase should be done slowly and with control to maximize the stimulus to the muscles, particularly the lats. The video demonstrates how pull-ups should be performed with a slow, controlled, deep stretch both upwards and downwards. Although this method will reduce the number of repetitions one can perform, it significantly enhances the muscle-building stimulus, which is the main objective of the exercise.