Kagan: The physics of catchers’ knees

From SABR member David Kagan at The Hardball Times on July 21, 2016:

Deep knee bends for a second or two ten times every evening is probably good for you. However, crouching behind the plate for five to ten seconds about one hundred and fifty times a night can’t be healthy.

If we are going to examine this from the perspective of physics, we need to realize that when you are at rest, your knees exert an upward force on the rest of your body to counter the weight of everything above them.

When Buster Posey stands up trying to understand why nobody covered third base, his knees support about 80 percent of his weight. So each knee supports about 90 lbs. Remarkably, this also is true when Posey is crouched behind the plate. When he is down waiting for the pitch, something has to keep the upper portion of his body from collapsing into the dirt. What else could it be but his knees?

Initially then, it might seem that catching shouldn’t be any more troublesome for the knees than standing. Since that is clearly not the case, we need to investigate more deeply.

Read the full article here: http://www.hardballtimes.com/the-physics-of-catchers-knees/

Originally published: July 21, 2016. Last Updated: July 21, 2016.