Why are muscles good in a fight?

Bruce Lee was very strict with his body. Muscles are very important, the term "muscle memory" the muscles remember kung fu moves to be ready in a real life application. Muscles mass can be referred to as thick skin, depending on the way you train. Muscles can be helpful with force in a fight situation, but only in the beginning. Its just one factor, you should consider the technique, the flexibility, the knowledge of the technique in the fight, and what other factors might come in.