Why would breeding chickens with larger breast produce tough breast meat?

The heavier the bird, and the larger the quantity of meat on it, the more likely it is to develop woody breast. Broiler chickens have been bred to strengthen the genetic markers for large breast meat, and this is thought to be a factor in the development of woody breast in recent years

Explanation:

"Woody breast" describes a quality issue stemming from a muscle abnormality in a small percentage of chicken meat in the U. S. This condition causes chicken breast meat to be hard to the touch and often pale in color with poor quality texture