Even if you're not a basketball fan, you've probably heard of Shaquille O'Neal. He can score, pass, and block shots. In fact, Shaq has only one weakness, free throws. Put the big man on the line and he's as likely to miss as to make the shot.
There's a simple remedy for poor free throw shooting: the granny shot. You know, when you use both hands to scoop the ball underhanded towards the rim. Studies and statistics have shown that this old-fashioned shot is a much more accurate way to shoot than the overhand method.
Making a free throw, or any shot for that matter, depends on arc. A shot with an arc of 32 degrees or less has a good chance of hitting the back of the rim and bouncing out. A shot with more arc has a better chance of swishing straight through the net. The upward tossing motion of the granny shot naturally imparts the arc needed to give it a good chance to fall through the hoop.
The granny shot also makes it easier to put more backspin on the ball than you can with an overhand shot. Backspin stops the ball's forward motion when it hits the rim, similar to how a drop shot in tennis freezes the ball when it bounces.
Finally, the granny shot uses both hands, which helps keep the ball on a straight path. An overhand shot requires separate motions of the wrist, elbow, and shoulder, increasing the likelihood of sending the ball off course.
If it's so accurate, why don't players use the granny shot? Maybe because it just doesn't look cool. Even though the granny shot would mean making more free throws, it probably wouldn't sell many sneakers.