The slider is one of the most dangerous pitches in baseball. Nasty, dirty, hard...its one of my favorite pitches to throw, heck my car's license plate reads "SLIDPCE". So why don't I teach it on my website?
Simple. The slider is one of the most dangerous pitches...for the arm.
The slider is thrown just as hard as a fastball, but at the last moment, the index and middle finger "cut" across the front of the baseball, forcing a spin that induces the ball to slide hard down and away from their throwing hand side.
Why is this so dangerous? In order to create this spin and force, the hand must SUPINATE upon release. Think of turning a doorknob clockwise. "Supination refers to the lateral rotation of the radius, a simple forearm twist at the radioulnar joint." Pitchers who try to do too much to the slider will supinate their wrists forcefully, exposing themselves to a greater risk for injuries.
Supination during release leaves the arm subject to forearm flyout, which results in a collision between the ulna and the humerus as the elbow slams closed.
Pronation on the other hand, involves the thumb turning downward (palm down). This is the longest path the arm can take to slow itself down and any overhand throw of an object where the arm doesn't force supination ends with the pronation of the arm/hand. Fastballs, changeups, sinkers, screwballs and even curveballs end in a pronation of the hand.
In simple terms, think of driving a car towards a stop sign. Supinating your arm would be the equivalent of slamming your brakes to a stop, while pronating would be the equivalent of slowly coasting to a stop. After a while, your car eventually breaks down. Without proper strengthening, maintenance and throwing mechanics, your arm will do the same.
I've seen teammates blow out elbows entirely just weeks after learning a slider. I've seen kids 12 years old and younger, snapping off sliders thinking they're curveballs. To sum up, there are entirely too many people teaching a pitch without teaching the proper responsibility attached to strengthening and caring for the arms they're destroying.
So how do we teach sliders? Quite frankly, I think there are too many of the YOUTUBE crowd that like to teach pitches without understanding HOW to teach it properly...nevermind teaching arm strengthening exercises.
Soon, I will post a video on How To Throw A Slider, however with a HUGE disclaimer attached, but with all the pertinent information present. In this information age of Monkey See, Monkey Do, we should realize what we sometimes teach often can do more harm than good.