My brother is a baseball player (He's a junior in HS on the Varsity team) and was wondering if it would be beneficial or not to have him go out with me on long rides as i hate riding alone.) He does ride sometimes but only for about 10 miles. My dad said that cycling does not use fast-twitch muscles that running fast requires and said cycling wouldn't be that great for him to develop speed. (He is a biologist/geneticist so he knows [partially] what he is talking about)
So would taking him out for 30-40 miles a day during the summer hurt him more than help? It'll definitely help his aerobic capacity but not too sure about his running.