Soccer, Hockey, Tennis
A biologist could study the tennis players performance and think of ways to improve their performance. Because they study living things, such as humans... they can suggest ways tennis players can improve.
You can find worthwhile worksheets that would help your son improve his skill in skip counting at the following website..www.icanteachmychild.com/.../71-things-your-child-needs-to-know-.
It really depends on what skill you want to improve, but for any skill, the main thing would be to practice as much as you can. It could also help to get the help, tutoring, or mentoring of someone who is really good in that skill area.
They improved tennis balls because when the hand hand hit it, it would hurt. So they made the balls softer for people.
Both sports require skill, technique, and endurance. I think you would have a challenge doing either.
Cognitively speaking skill in anything is only acquired or strengthened through practice and study.
If the opponent hits a slice then you would need agility to hit the ball back.
The average tennis serve speed for a fifteen year old man would vary according to his skill and size. On average, a man serves a tennis ball at about 60 to 90 miles per hour depending on skill level.
The best place to go is the World Tennis Association's website. They are the governing body over tennis. Another good source would be Wimbledon's site or at the All England Lawn and Tennis Club.
There are many places where you can find designer tennis apparel, including online and in stores. One such website you could check out is www.tennisexpress.com.
A good way to improve the position of one's website would be to hire a company to help boost your ratings. Another way would be to hire help to raise your site to number one.