Which practice is aimed at developing internal focus in martial arts?

The practice of Muk Yum is specifically focused on fostering internal awareness and concentration in martial arts. This meditation practice emphasizes calming the mind and centering oneself, which is essential for developing mental clarity and enhancing one's ability to connect with both the body and spirit. By engaging in Muk Yum, practitioners learn to quiet their thoughts and distractions, enabling them to achieve a deeper understanding of themselves and their martial arts training. This internal focus is crucial for improving techniques, enhancing performance, and cultivating a strong sense of presence during training and sparring.

While the other practices listed have their own significance within martial arts, they are not primarily aimed at developing internal focus in the same way that Muk Yum is. Thus, Muk Yum stands out as the correct choice for this question.