Answer:
there's nothing attached..
Native Americans had grown corn for more than 2000 years. They ate it and used it to brew beer way before the Europeans landed on America on the late 15th century, led by Christopher Columbus.
When the settlers arrived to the West Indies, they were offered corn by the Native American Indians. They learned how to grow it, took seeds back with them and introduced it in Europe.
The direct object would have to be the muscle's ability because it answers the question "what".
e.g: Exercise can increase what? The muscle's ability.
