When a fore-and-aft sail is too near to the wind, it shakes. (of a sailing vessel) to be sailing so close to the wind that the sails tremble. Soccer is typically a winter sport, with registrations taking place at the end of summer and beginning of fall. Therefore, your soccer ball should be in good condition when you get it because it will determine how much fun you have while playing. The term "sail shiver" comes from the sound made by the wind blowing through the rigging of a sailboat. This sound is different for each type of sail, but generally speaking, the louder it is, the closer the sail is to the wind. When the wind blows harder, the rigging makes a more distinct sound. That's why sailors say that a boat "shivers" in a strong wind. A sail that is far enough away from the wind not to shiver but still able to drive the boat forward is called a balance sheeted sail. Soccer balls are tested to see how they react to various conditions. In particular, they are rated for size and weight. The size of the ball relates to how long a player can kick it; the heavier the ball, the more power it will put out when kicked. Balls tend to be light and spongy for use in indoor games like basketball, whereas footballs are heavy and firm for use outside.