|
Overhand vs. Sidearm: The effects on ball velocity and elbow and shoulder joint angles
Baseball pitching has a history of causing arm injuries, particularly
to the elbow and shoulder. The two most common throwing techniques are
the overhand throw, and the sidearm throw. These two throws differ in
arm motion and angles, and in the speed of arm segments and of the ball.
Andrews et al (2001) found that the greater the shoulder motion, the greater
the force produced, which led to the greatest ball velocity. These large
forces caused by bigger variations in arm motion, especially at the elbow
and shoulder joints, can also lead can lead to serious injury. Thus the
purpose of this study is to determine the difference in elbow and shoulder
motion, and the difference in speeds involved between the conventional
overhand and more unorthodox sidearm throws.
Methods
The only test subject was a young, healthy active male volunteer. He was
22 years old, 5'11 tall, and 195 pounds. He was right handed, and had
moderate pitching experience. He threw a wiffleball three times for both
overhand and sidearm to ensure that sufficiently good data were collected
for each type.
Data collection cosisted of two normal speed cameras with setup. [Reflective
markers on landmarks (third right metacarpel, right wrist, right shoulder,
left shoulder and right hip).] Reflective lights were used to allow reflective
markers to be more visible. A shutter wasa used to make video less blurry
for analysis. The two video cameras were synchronized by a clicker, which
when clicked mid throw, simutaneously put an identifiable notch in the
corner of the video screen. From this, the two videos could be synchronized.
Data analysis was done using Peak Motus. Only one throw was analyzed for
both overhand and sidearm. The data were digitized for each camera view,
using the synchronizing method described previously. The data were filtered
to get rid of the noise in the data, and then the 3-d coordinates were
calculated. From this, the joint angle, linear velocity, and angular velocity
were calculated for each segment.
Results
Joint Angle data
Elbow angle while thowing was significantly greater in the overhand throw
than the sidearm throw. Maximal elbow angle was aproximatly 130 degrees
in overhand, and only 110 degrees in the sidearm throw. Ball release was
at appoximatly .300 seconds after measures began.
Shoulder angle while thowing was greater during the overhand throw than
in the sidearm throw. Maximal shoulder angle in the overhand throw was
approximately 110 degrees, and only 90 degrees for the sidearm throw.
Linear
Velocity Data
The linear vleocities of arm segments in both throwing styles showed significant
increase as the segment became more distal to the body (ex. wrist faster
than elbow). The time at which maximal velocity is achieved also typically
occurs later the more distal that segment is from the body. This is an
excellent demonstration of the kinematic chain.
The maximal linear veleocity created was greater for the ball and each
arm segment in the over hand throw. The difference seen was significant
in the velocity for each of the arm segments, while the difference in
the velocities of the ball was minimal.
Discussion
A greater joint angle created while throwing leads to larger torque being
produced on the joint. If a large torque is placed on a joint, the muscles,
ligaments and tendons involved in containing the joint are stressed, and
are more likely to give way to the forces, allowing injury to occur. Since
overhand throwing led to greater maximal angle in both elbow and shoulder
joints, the overhand throw created a greater torque on these joints than
the sidearm throw.
Although
variability in arm angle was greater in sidearm throwing, the torque exerted
on the joint can be best characterized by the magnatude of joint angle.
| Maximum
overhand velocities, and time at which achieved |
| |
R.
Shoulder |
R.
Elbow |
R.
Wrist |
R.
Hand |
Ball |
| Max
Vel. (ft/s) |
14.4426 |
37.5930 |
50.6587 |
62.9871 |
88.9456 |
| Time
@ Max vel. (s) |
0.267 |
0.267 |
0.317 |
0.317 |
0.333 |
| Maximum
sidearm velocities, and time at which achieved |
| |
R.
Shoulder |
R.
Elbow |
R.
Wrist |
R.
Hand |
Ball |
| Max
Vel. (ft/s) |
12.8859 |
31.6693 |
46.8279 |
57.7887 |
87.0864 |
| Time
@ Max vel. (s) |
0.317 |
0.300 |
0.350 |
0.367 |
0.367 |
| As
you can see, the numbers speak for themselves |
One
of the major concerns of a pitch type is the linear velocity that can
be produced on the ball. High linear velocities are produced by way of
the 'kinematic chain'. Typically the greater the velocities of the individual
joints invlved in this chain, the greater the velocity of the bal, but
not necessarily. Therefore, the very similar linear ball velocities for
the two throws are the primary concern. The considerable deficiency in
arm segment linear velocity in the sidearm thow is of secondary concern,
and may be able to be corrected for by inproving sidearm throwing technique.
Conclusion
The purpose of this study was to investigate the differences between overhand
and sidearm throwing in terms of joint angles produced and the linear
velocity given to the ball. From the data collected, it can be concluded
that while ovehand throwing increases the ball'svelocity insignificantly,
it produced much greater elbow and shoulder joint angles, which may lead
to injuries. Thus, sidearm throwing reduced risk of injury while pitching
without resulting in a major loss in ball velocity.
Appendix
Andrews, J., Escamilla, R., Fleisig, G.,
Zheng, N., Barrentine, S. (2001) Kinematic comparisons of 1996 Olympic
baseball pitchers. Journal of Sports sciences,, 19 (9), 665-76.
|
