Slider and Curveball


So what’s harder on the arm? The Slider or the Curveball?

I would say the curveball would be harder because on releasing the curveball you have to supinate your forearm 90º, maybe even more. When throwing a slider you supinate 45º or so.
But I hear people say that the slider is the harder pitch on the arm. And you could start throwing a curve when you reach 14, but not a slider…

So what makes the slider tougher on the arm than the curveball?

I know there are some coaches that believe that no pitch puts more stress on the arm (if thrown properly) than any other pitch. (Tom House says that, and there are other believers)

But what do you think?


slider is harder on the elbow because of the torque you use to get a real slider.


The slider puts more strain on the fore arm than elbow, as i’ve been told.


The slider is harder on the arm than is the curveball because the slider is thrown with near-fastball velocity and force while the curveball is offspeed and not as much force is applied to the arm while it is supinated.


Hmm I might have misunderstood you, but shouldn’t you throw every pitch with the same arm-velocity?
I know that the curveball is a much slower pitch than the slider and fastball but why does the velocity put any more stress on the arm?
The thing that makes the curve a slower is the grip not the arm-action, right?


That is a good question. Throwing all pitches with the same arm speed is desirable because it helps fool the batter. But obviously not all pitches have the same ball speed. The reason is as follows. When throwing the fastball, the fingers stay behind the ball and apply force through the ball. When throwing a breaking pitch, the fingers apply force around the ball. Applying force through the ball produces the most force on the ball. But it also puts the most force on the arm due to the laws of physics - particularly the one that says for every force there is an equal and opposite force.

So, I believe it isn’t just the arm speed that matters but also the amount of force being applied to the ball.


Hmm thanks for the explanation Roger.
And by the way, which would be the most stressful pitch? Slider? Splitter? Sinker? Curve?


Splitters and sinkers are perfectly safe pitches… Curves and sliders can be bad on the arm, but the slider is worse in my opinion.


I agree.


[quote=“KreGg”]Hmm thanks for the explanation Roger.
And by the way, which would be the most stressful pitch? Slider? Splitter? Sinker? Curve?[/quote]
The quick answer to your question is, while all of the pitches you listed can be thrown improperly such that the all can be stressful on the arm, the slider is generally the most stressful.

Any pitch thrown with pronation (e.g. the change-up, sinker and screwball) should be safe because all rotation of the hand/wrist/forearm is in the same direction the hand/wrist rotate after release of the ball. Plus, force is imparted around the ball so less force is applied to the arm.

Pitches thrown with a twist during forward acceleration of the arm are the most stressful because the hand/wrist/forearm rotate the opposite direction as the upper arm and because there is an abrupt change of direction of the hand/wrist/forearm once the ball is released. (The arm always pronates after the ball is released regardless of which pitch was thrown.) Examples here include all improperly thrown breaking balls. The slider is the worst because in involved the most force on the arm as well.

Pitches thrown with supination that is set before forward acceleration begins such that there is no further twist are closer to the safe side of things so long as their numbers are also limited. Examples of this include all properly thrown breaking pitches. But the slider is still the worst because, again, it puts the most force in the arm.

Some pitches thrown with supination create more of a tendancy to further supinate during forward acceleration than others so these are more risky to throw. The slider is the prime example of this but I’d also include the cutter and slurve.

The splitter is unsafe only if you supinate during forward acceleration. According to Tom House, this happens when you let your thumb creep up the side of the ball towards the index finger. Keep the thumb centered below the “V” formed by the index and middle fingers and you’ll have less of a tendency to twist.


I’ve heard that the splitter is hard on the arm because of the preload due to splitting the fingers apart. I don’t know if that is true or not.

As far as curves go there is less stress imparted, but it stresses some parts of the elbow and shoulder preferentially thereby increasing the risk of damage. This is especially true for youth and adolescent players.


I’m with Roger mostly on this, the thing I haven’t seen yet is that (From my limited exerience) the slider is more commonly thrown wrong. When I see young kids attempt it I see the vast majority attempt it by casting the hand outside of the elbow and then they supinate WAY too much (The gurus all say that any supination is bad but when it’s exaggerated in an effort to get movement…way ouch!), they get the movement but as a trade-off it effects both elbow and shoulder.
Both pitches can be thrown with non-destructive consequences, they just have to learned correctly and used juditiously/responsably.
Remember that Maddux threw a grand total of 1 curve in his outing against Jason Schmidt and 0 sliders. I’ve actually seen Greg throw about 8 curves in all the years I’ve watched him (Started watching him his rookie year). I would call that responsible usage of the pitch.