Sports take the physical abilities
of our bodies to extremes. Have you ever thought about all
the science behind a serve swing? You could think
that the most important thing is just the technique,
which you obviously need, and strength, so the better the technique and strength,
the better the serve. Strength and technique are very important.
But there’s a usually ignored factor: the arm and racket length
taken together. It’s known as a second class lever.
In that move, there’s a point of origin. The shoulder is the point of origin
of force, and it is applied on the racket, which is
the point of resistance of the ball. The longer the distance,
the more angular speed the racket has. It’s true that fast servers
have long arms. They are slender and thin. A case in point is Ivo Karlović.
He’s over 6’10”. The length of his arm plus the racket
is probably more than 4 feet. The angular speed he gets
thanks to that length makes him serve faster
than 140 mph without effort. We call “moment of force” the product
of the arm and racket length, starting from the point of origin
of force, which is the shoulder, and finishing in the point of application,
which is the ball, and the total force applied.
This force is the sum of the leg impulse, the body turn, the wrist rotation,
and of course, the shoulder turn.