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Functional Overload of the Throwing Arm: Biomechanical Testing and
Clinical Trials of a Weighted Glove
By James G. Richards, Ph.D,
Patrick W. Castagno, M.S., and
Michael J. Axe, M.D.
INTRODUCTION
Organized baseball at all levels has begun to emphasize off season
strengthening and conditioning in an effort to decrease the incidence of
rotator cuff damage. Current programs generally employ gym and
rehabilitation equipment. Exercises using weights and pulleys do not
simulate functional throwing speeds of shoulder rotation which exceed 4,000
degrees per second. In 1992, we developed and tested a weighted, fingerless,
Iycra glove (see photo) for use during indoor throwing. It was tested for
safety and effectiveness over the next two collegiate baseball seasons.
METHODS
A two-phase safety study and a two phase training study were conducted
from 1992 -1994. All players volunteered and gave informed consent Coaches
were contacted at the completion of the following baseball season to assess
incidence of injury.
Safety Phase I -Mechanics:
Nine pitchers had retro reflective markers placed in 14 anatomic locations
shown in Figure 1. All pitches were thrown from an indoor mound 63 feet away
from the catcher. Two conditions were tested loaded (with the seven once
Iycra glove) and unloaded. All pitchers threw five fastballs. Glove testing
was in randomized testing order. Video data were collected using four NAC.
cameras at an equivalent frame rate of 200 frames per second. The video data
were converted to three-dimensional data points using Motion Analysis
ExpertVision software. Data were then reduced to yield: 1) Stride length; 2)
Stride direction; 3) Distance from stride foot to midline; 4) Lateral trunk
lean (at release); 5) Ball velocity; 6) Release point relative to the front
foot; 7) Elbow kinematics/kinetic time plots; 8) Shoulder kinematics/kinetic
time plots.
Safety Phase II - Fatigue:
Five pitchers threw three. 20 pitch intervals with four minutes rest between
intervals in the loaded and unloaded conditions Marker placement and video
analysis were identical to the Safety Phase I Study.
Training Phase I - Seven Ounce:
Eighteen collegiate pitchers were involved in an off-season program. Each
pitcher threw a simulated game consisting of four, 20 pitch innings with
four minutes rest between innings. Athletes were then assigned to either the
glove (7 ounce Iycra glove) or control group by randomized block design with
velocity as the blocking factor. They then completed an eight week throwing
program. (Table 1) Post- testing was identical to pre-testing Video data
were collected from the first pitch of the simulated game and the last pitch
of each inning at both testing sessions. Velocity data were collected for
each pitch using a calibrated Decatur radar gun. Pre and post-test motion
analysis was performed similar to those used in the Safety Studies.
Training Phase II - 0.035% Bodv Weight IUc to 11 Ounces):
Fifteen collegiate pitchers with a mean weight of 864kg were randomly
assigned to a loaded or unloaded group as described above. Loading (glove
weight) in this study was 0.035% body weight which was determined from a
pilot study and represents mean mechanical breakdown minus two ounces. Phase
II was conducted identically to Phase I with glove vs. control at 8:7. Phase
II throwing program was similar in pitches to Phase I, but was extended to
10 weeks. Pre-testing post-testing were identical to Phase I.
Common Data Reduction Technique:
The three-dimensional coordinate data were smoothed with a second order
Butterworth filter with a cut-off frequency of 11 hz. Elbow and shoulder
joint centers were determined by translating the lateral humeral condyle and
acromion process markers a fixed distance into the joint structure. The
elbow joint center was determined by translating the lateral humeral condyle
marker into the joint structure five centimeters along the nexion/extension
axis of the elbow joint. The shoulder joint center was determined by
translating the acromion process marker into the joint structure seven
centimeters along the horizontal adduction/abduction axis of the shoulder
joint. The elbow and shoulder joint angular positions were calculated using
ZYX fixed axis rotations The joint angular velocities were then calculated
by differentiation of the joint angular positions. Finally, the joint
reaction forces and torques were calculated using standard inverse dynamics.
Segment centers of mass and inertial values were obtained using the methods
described by Zatsiorsky & Seluyanov (1983). Loaded and unloaded conditions
were analyzed descriptively.
RESULTS AND DISCUSSION
Mechanics:
The valgus stress on the elbow (Figure 2), that has been associated with
injury showed no increase in valgus stress from MER to ball release, but
demonstrated a 45% increase after ball release when compared to the normal
throw, (Table 2). The loaded condition resulted in a slight increase in MER
(2 degrees) and a larger ER at ball release (28 degrees). There was an
increase of 22% in shoulder abduction torque (Figure 3) and 17% increase in
horizontal adduction torque before ball release (Table 2). There was also a
20% increase in horizontal abduction torque and a 30% increase in shoulder
adduction torque after ball release. Together these suggest that the deltoid
and supraspinatus are loaded during the acceleration phase and the posterior
deltoid, posterior cuff muscles and subscapularis are loaded during the
deceleration phase, At ball release, there was no difference in compression
force but a slightly greater inferior shoulder force (15%) (Figure 4),
greater elbow flexion torque (Figure 5) and anterior shoulder force (Table
2) during acceleration suggesting that the glove loads the supraspinatus and
biceps at that time.
Fatigue:
The results of this study indicate that an overload equal to seven ounces
applied to the dorsal aspect of the hand will not create differences in
kinematics or kinetics over a 60 pitch sequence when compared to the
unloaded condition. The absence of major mechanical differences during the
use of an overload glove suggests it is safe to use in further training
studies to investigate the effects of this type of overload on training of
baseball pitchers.
Training Studies:
The results of this study indicate that training for eight or ten weeks
(Table 1) using a weighted glove produced no notable changes in the
pitcher's throwing mechanics. Furthermore, training with a weighted glove
elicIted an increase in pItch velocity of 2.2 mph which was 3.6 Standard
deviations above the pre-test mean velocity (Figure 6). This increase in
velocity occurred in spite of the fact that none of the kinematic or kinetic
parameters displayed obvious changes as a result of training with the glove.
On average, 50 pitchers each year from major league baseball make their way
to the disabled list and arguably the injury rate is even higher in amateur
baseball. None of the pitchers who completed the training program with the
overload glove suffered an injury to the throwing arm in the season
following the study. Admittedly this is anecdotal, but it is striking
nonetheless. Research involved with tracking the incidence of injury to
pitchers using various training programs need to be performed to verify this
relationship.
SUMMARY AND CONCLUSIONS:
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The rotator cuff can be safely overloaded at functional speeds with
the use of the weighted glove.
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The overload forces created on the elbow and shoulder may necessitate
a healthy inner elbow and rotator cuff prior to training with the weighted
glove.
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Glove training in the off season can improve velocity almost 2 mph
greater than training without the glove.
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Despite inclement weather and limited space, a throwing athlete can
train year round and expect fewer overuse injuries using the weighted
glove.
James G. Richards, Ph.D.
Associate Professor Physical Education
Director, Biomechanics Sports Science Laboratory
University of Delaware, Newark, DE
Patrick w. Castagno, M.S.
Instructor, Biomechanics
University of Delaware
Director, Gait Laboratory
A.I. DuPont Institute Newark, DE
Michael J. Axe, M.D.
Sports Orthopedist
Clinical Associate Professor Department of Physical Therapy
University of Delaware, Newark, DE
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In order to achieve the greatest gains from the use of Edge Power Gloves
it is best to adhere to a training regimen that is sport specific in nature.
The following programs are suggested in an effort to assist you in achieving
your goals. Keep in mind that a training regimen of at least 6 weeks is
suggested before significant gains can be attained. Enhancing your skill in
any given sport is a matter of applying Discipline, Desire and Dedication
coupled with the proper training tool. You have ordered one of the finest
training products on the market today. Now it is up to you to apply the
Discipline, Desire and Dedication to achieve your goals. Good Luck and thank
you for purchasing the Edge Power Gloves.
ARM SPEED DEVELOPMENT
Once sufficiently warmed up follow the routine below for two weeks:
MONDAY, WEDNESDAY, FRIDAY
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Begin with a distance that you are comfortable with.
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Insert a 2 oz. weight
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Throw the ball 10 times
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Gradually increase distance/Add a 2 oz. weight
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Throw the ball 8 times
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Gradually increase distance/Add a 2 oz. weight
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Throw the ball 6 times
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Gradually increase distance/Remove the 2 oz. weight
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Throw the ball 8 times
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Gradually increase distance/Remove the 4 oz. weight
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Throw 10 times
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Gradually increase distance/Remove a 2 oz. weight
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Throw 12 times
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Gradually increase distance/Remove the 4 oz. weight
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Throw 15 times
TUESDAY, THURSDAY, SATURDAY
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Follow the above throwing pattern without Edge Power Glove
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Be certain to increase your distance gradually
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Try to throw the ball on a line (one hop or two hop at great
distances)
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When throwing concentrate on putting 12 to 6 rotational spin on the
ball
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Make a habit of removing the ball from your glove in a four seam grip
The above program is a training system that incorporates the Overload/Underload
philosophy. This training regimen has been utilized in virtually all sports
with proven results in modifying the muscle fibers in an athlete. The
Overload function creates strength and endurance fibers, while the Underload
function develops and enhances the fast twitch muscle fibers. The muscle
memory created by a dedicated training program following this principle
results in enhanced strength and speed in the sport specific muscle groups
the athlete is training. In this instance greater arm strength and arm speed
will result in a ball being thrown with greater velocity.
At the conclusion of the two-week phase, assess your improvement and
ability to increase repetitions without harm to your body. If you feel you
can increase the workload, it is suggested that you perform the above
program two times per session.
BAT SPEED DEVELOPMENT
Every body knows the importance of bat speed, but few people know how to
attain it. By your purchase of the Edge Power Gloves product you realize
that the right training product and a good training program can help you
achieve greater bat speed. Mind you, the right product and training program
won't do anything for you if you don't apply them. Ultimately, your success
in attaining your goals is a result of your desire to achieve them. This
product won't do you any good lying on your desk or sitting in your bat bag.
Use them and follow the program below to see fantastic results in a few
short weeks.
MONDAY, WEDNESDAY, FRIDAY
This program can be utilized during tee work, soft toss, or dry cuts.
Concentrate on performing a well-balanced, smooth swing. When performing dry
cuts visualize a pitch in the perfect spot of the strike zone, take the knob
of the bat directly at the pitch, try to delay the release of the barrel
head into the impact zone for as long as possible. This prolonged delay is
one of the secrets to bat speed. Keep your hand path short to the ball and
long through the ball.
You can also utilize the Edge Power Gloves in single-handed improvement.
Incorporate the above 10,8,6,8,10,12,15 pattern while performing one hand
hitting drills. You may also simply weight one hand of the gloves in the
above sequence and follow a normal routine of soft toss or tee work. Top
hand and/or Bottom hand improvement will result. If you feel you are weak in
one of these areas, it wouldn't hurt to concentrate on that particular hand
for a week or so.
TUESDAY, THURSDAY, SATURDAY
Normal cage work off of live pitching or a pitching machine is suggested.
You may also perform pushups or some other form of strength conditioning
exercise. A good exercise that is sport specific for bat speed is the Wrist
Roll (performed with a light weight attached to a rope and rolled up on a
piece of wood). Another is squeezing a tennis or racquetball. These
exercises concentrate on the forearms and hands, very important factors in
the hitting process.
GOLF and TENNIS
As you can see from the above training regimens the basic pattern is to
decrease the repetitions of a given sport specific movement as the weight of
the Edge Power Glove is increased. This holds true in the golf and tennis
functions as well. The key of course is to consistently train in the program
for long enough to train the muscles involved in the movement. It is
suggested that the athlete hit golf or tennis balls without the use of the
Edge Power Gloves at least two days a week. Follow the below program and
watch your drives go farther and serves go faster in a matter of weeks.
MONDAY, WEDNESDAY, FRIDAY
Golfers may wish to follow the routine with weights added and deleted
from both gloves, or utilize only one glove for improvement with the lead or
follow hand.
Tennis players may wish to utilize both gloves while working on any two
handed impact drills, such as a two handed backhand. Make an effort to
perform the listed sequence of 10,8,6,8,10,12,15 to fully incorporate the
Overload/Underload training system.
Always use the "Soreness Rule" while training the arm and shoulder. If
you feel soreness at the next training session, go through the training
program without any weights, and only continue using weights when the
soreness is gone.
When training with weights, be patient. Begin with a comfortable weight
and slowly increase the weight used. Use proper supervision while training
with any type of weights.
Copyright © 2002
BeABetterHitter.com
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