Task: Question Answering
Input (English): Background Paragraph: In exercises such as weight lifting, skeletal muscle contracts against a resisting force (see Figure below ). Using skeletal muscle in this way increases its size and strength. In exercises such as running, the cardiac muscle contracts faster and the heart pumps more blood. Using cardiac muscle in this way increases its strength and efficiency. Continued exercise is necessary to maintain bigger, stronger muscles. If you don’t use a muscle, it will get smaller and weaker—so use it or lose it. 
Story: Justin and Derek are accomplished competitive weight lifters. One day, Derek suffers a severe injury to his leg. Because of this injury, Derek is forced to stop exercising for several months. Justin remains injury free and continues to work out regularly on the other hand. 
Question: Who will lose less size on their muscles?
Output (English): Justin.