Muscle mass, when gained through proper 'Weight Training For Boxing', can significantly enhance a boxer's performance by contributing to increased power and strength. However, it's important to note that the type of muscle mass matters - lean, functional muscle mass aids in delivering powerful punches and maintaining speed and agility, whereas excessive, bulky muscle mass could potentially hinder a boxer's speed, flexibility, and endurance. Therefore, weight training for boxing should be focused on building lean muscle and improving functional strength, rather than simply increasing muscle size.