Using
K Vest to Compare Rotational Velocities During The Pitching Motion
There
are many aspects of the throwing motion that get talked about as being impactful
to throwing velocity. One such thing
that has caught my attention lately is the idea of rotational velocities. Clearly, baseball is a rotational sport and
requires very fast rotational movements.
I was given access to a K-Vest for a few weeks so I wanted to collect a
bunch of data to see if rotational velocities alone could give insight into
throwing velocity.
K-Vest
uses 4 sensors to capture data: a vest with a sensor on the upper back, a belt
with a sensor on the tail bone, an upper arm strap with a sensor just above the
elbow & a lower arm strap with a sensor on the wrist. Rotational velocities of each show up as Pelvis,
Torso, Upper Arm and Hand. The
measurements for each are Degrees Per Second.
I
collected data on 10 different pitchers ranging in age from 10-21 years old. 2 are current college pitchers, 1 is an incoming
college freshman, 3 are High School D1 commits, 2 are current High School
Freshman and 2 are youth level players.
Each threw between 6&8 pitches while using the K-Vest. Below are the average results for each
pitcher, along with their peak indoor mound velocity and a ranking (1-10) in
each individual category.
|
Current Level
|
Peak Indoor Velo (MPH)
|
Avg Pelvis Speed (deg/sec)
|
Avg Trunk Speed (deg/sec)
|
Avg Upper Arm Speed (deg/sec)
|
Avg Hand Speed (deg/sec)
|
|
D3 Junior (D1 Transfer)
|
90.7 (1)
|
835 (2)
|
1,220.2 (5)
|
1,357.8 (7)
|
2,768 (8)
|
|
HS Sr D1 Commit
|
90.3 (2)
|
598.7 (8)
|
944.3 (9)
|
1,489.5 (5)
|
2,953.8 (3)
|
|
D1 Junior
|
88.4 (3)
|
612.7 (7)
|
1,273 (4)
|
1,623.7 (3)
|
2,926.7 (5)
|
|
HS Sr D1 Commit
|
82.1 (4)
|
840.8 (1)
|
1,238.5 (3)
|
1,347.3 (8)
|
2,504 (9)
|
|
D3 Freshman
|
81.3 (5)
|
743 (6)
|
1,404.8 (2)
|
1,553.8 (4)
|
2,975.3 (2)
|
|
HS Sr D1 Commit
|
77.7 (6)
|
596.4 (9)
|
1,208.6 (7)
|
1,218.7 (10)
|
2,790 (7)
|
|
HS Freshman
|
71.9 (7)
|
795.2 (3)
|
1,149.2 (8)
|
1,447.5 (6)
|
2,855.5 (6)
|
|
HS Freshman
|
69.1 (8)
|
794 (4)
|
1,415.8 (1)
|
1,739.6 (2)
|
2,403.2 (10)
|
|
Youth Level
|
60 (9)
|
514.5 (10)
|
805.2 (10)
|
1,281.6 (9)
|
2,982.3 (1)
|
|
Youth Level
|
54.2 (10)
|
793.5 (5)
|
1,217.8 (6)
|
1,886.5 (1)
|
2,943.5 (4)
|
The chart below shows the correlation (R Value)
between velocity and each rotational speed.
Velocity vs Pelvis Speed
|
Velocity vs Trunk Speed
|
Velocity vs Upper Arm Speed
|
Velocity vs Hand Speed
|
.0136
|
.1683
|
-.3419
|
-.0513
|
Wrap
Up
From
the charts above, it’s fair to say that there is no correlation between any of
the 4 rotational speeds being directly linked to velocity.
There are several thoughts that I have after
conducting this test. The K-Vest calculates
K Angle, which is the difference between pelvis and trunk within the playback
animation. This should allow for actual
numbers on shoulder/hip separation. I will go back and calculate each throws
maximum K Value and compare that to throwing velocity. That being said, the idea of shoulder/hip
separation isn’t as cut and dry as just shoulder/hip separation at any part of
the throwing motion. The timing of it
should be very important. Also, the
amount of bend in the trunk will impact shoulder/hip separation. The K Vest also measures that, but I’m not
certain on how to calculate it into a separation number. When looking at other studies and trying to
compare their findings with the data from the K Vest, I don’t know exactly how
the measurements themselves differ. This
could lead to errors in comparison due to different ways the measurements are
taken. I also don’t have anything to test its accuracy against. Even though
there were no correlations to velocity, the K Vest has huge potential benefits
for pitchers due to its ability to take the guesswork out of numerous angles
throughout the entire delivery.
Questions
to Ponder
1. Could
the differences from metric to metric (pelvis to trunk, trunk to upper arm,
upper arm to hand) give us real insight as to where guys are efficiently
gaining their current velo and where they have inefficiencies?
2. Does
weight play a role in all of this? If 2
guys have similar trunk rotational speeds but one weighs 200 pounds while the other
weighs 150 pounds, will the 200 pound guy benefit more from that rotational speed?
3. If
there was a way to determine force into the ground while maximum rotational
velocities were occurring, how much better would that insight give us into ball
velocity?
4. If
we know when maximum negative trunk rotation occurs, would the K Value at that
moment have a strong correlation with velocity?
