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©Journal of Sports Science and Medicine (2007) 6, 1-20
http://www.jssm.org
Received: 09 July 2006 / Accepted: 09 February 2007 / Published (online): 01 March 2007
Baseball throwing mechanics as they relate to pathology and performance – A
review
Rod Whiteley
University of Sydney, Australia.
Abstract
It is a commonly held perception amongst biomechanists, sports
medicine practitioners, baseball coaches and players, that an
individual baseball player’s style of throwing or pitching influ-
ences their performance and susceptibility to injury. With the
results of a series of focus groups with baseball managers and
pitching coaches in mind, the available scientific literature was
reviewed regarding the contribution of individual aspects of
pitching and throwing mechanics to potential for injury and
performance. After a discussion of the limitations of kinematic
and kinetic analyses, the individual aspects of pitching mechan-
ics are discussed under arbitrary headings: Foot position at stride
foot contact; Elbow flexion; Arm rotation; Arm horizontal ab-
duction; Arm abduction; Lead knee position; Pelvic orientation;
Deceleration-phase related issues; Curveballs; and Teaching
throwing mechanics. In general, popular opinion of baseball
coaching staff was found to be largely in concordance with the
scientific investigations of biomechanists with several notable
exceptions. Some difficulties are identified with the practical
implementation of analyzing throwing mechanics in the field by
pitching coaches, and with some unquantified aspects of scien-
tific analyses.
Key words: Baseball, pitching, throwing, injury, analysis, bio-
mechanics.
Introduction
Played worldwide for over a century, baseball is a game
that involves periods of apparent inactivity punctuated by
the highest recorded angular velocities of human move-
ment. Whilst the game is a delicate balance of attack and
defense, pitching performance is integral to success on the
baseball field. The perceived importance of optimal pitch-
ing mechanics is reflected in the presence of pitching
coaches at every level of baseball’s organization. Despite
the emphasis placed on preventive care and the increasing
sophistication of medical management injury rates at the
highest level of baseball would appear to be rising (Conte,
et al., 2001; Hill, 1983). While some authorities have
found no link between ‘individual pitching traits’ and
presence of injury (Grana and Rashkin, 1980) many more
(Albright et al., 1978; Alexander, 1994; Altchek and
Hobbs, 2001; Andrews et al., 1985; Atwater, 1979; Azar,
2003; Burkhart and Morgan, 2001; Dillman et al., 1993;
Duda, 1985; Escamilla et al., 2002; Feltner, 1989; Fleisig
et al., 1996; Gainor et al., 1980; Lyman et al., 2002; Ma-
tsuo et al., 2002; Meister, 2000; Murata, 2001; Nadler,
2004; Pappas et al., 1985b; Sakurai et al., 1993; Tullos
and King, 1973; Wilk et al., 2000) believe the mechanics
of the throwing motion to be a significant contributor to
likelihood of injury. Despite this apparently commonly
held perception of a link between throwing mechanics and
pitching performance and health, few authors are specific
in their recommendations for the throwing athlete. This
paper will attempt to describe the available literature
regarding pitching and throwing mechanics as they relate
to pitching performance and health.
In concert with a literature review a request was
made of an internet biomechanics discussion group for
any further unpublished or unindexed work with several
papers and ‘works in progress’ arising. As background,
many instructional resources were viewed, and focus
groups were held with baseball and pitching coaches to
identify generally held perceptions of ‘correct’ and ‘incor-
rect’ throwing mechanics, along with their perceptions as
to the effects of these on performance and health. The
literature search and focus group results displayed a large
range of sophistication ranging from single case observa-
tions of an individual making a single throw to kinetic
comparisons of groups of subjects making groups of
throws.
Figure 1. Total number of throws made as described by
fielding position from data of Barrett and Burton (Research
Quarterly for Exercise and Sport. 73(1), 19-27, 2002). 1B
denotes first baseman; 2B': Second baseman; '3B': Third
baseman; 'SS': Shortstop; 'OF': Outfielders.
The vast majority of peer-reviewed published re-
search has been conducted into the pitching motion as
opposed to throwing in general reflecting in part the per-
ceived importance of pitching to ultimate success in base-
ball performance. In a study of 3328 throws made by 100
players during 7 collegiate games of baseball where
throws were determined ‘active’ or ‘inactive’ as to
whether the throw was made in an attempt to get a player
Review article
Throwing mechanics, pathology, and performance
2
Figure 2. Distance thrown and position of player making the throw for the data described by Barrett and Bur-
ton (Research Quarterly for Exercise & Sport. 73(1), 19-27, 2002). Note that the vast majority of throws were
made through the distance 46 to 60 feet, and that these throws were made principally by pitchers and catch-
ers. Note also that almost all of the longest throws (180 feet and above) were made by outfielders.)
out or not respectively (Barrett and Burton, 2002). This
analysis gave a quantitative breakdown of the distances
required of individual fielders, and showed that pitchers
were indeed required to make the vast majority of their
active throws over the pitching distance (1606 of 1667
throws made), and that throws made by pitchers ac-
counted for more than half of the throws made in the
game of baseball. This analysis also gave information
regarding the number of throws made and distances for
the other fielding positions. A summary of this data is
presented in Figures 1 and 2.
Whilst some authors have divided the throwing
motion into three (Pappas et al., 1985a; 1985b), four (Xue
and Masuda 1997), and five (Andrews and Wilk, 1994;
Braatz and Gogia, 1987; Walsh, 1989) stages, more
commonly the throwing motion is described as compris-
ing 6 stages (Dillman et al., 1996; 1993; Fleisig and
Escamilla, 1996; Werner et al., 1993; Werner et al., 2002,
Zheng et al., 1999). These stages are termed: wind-up,
stride, arm cocking, arm acceleration, arm deceleration,
and follow-through. A representation of these is shown in
Figure 3.
Limitations of investigations
Along with the perceived importance of pitching in base-
ball there is a perception of higher incidence of throwing
arm injury in pitchers in comparison to other position
players (McFarland and Wasik, 1998). Accordingly the
majority of investigation into throwing mechanics has
been performed on pitchers. Few reports are available
comparing pitching to throwing from the field. Norkus
(2000) investigated the 3 dimensional kinematics of
throwing sub-maximally over distances of 60, 90, and 120
feet, and throwing maximally over 120 feet. This investi-
gation found very little kinematic similarity in the sub
maximal trials and the maximum effort trials with only
maximum elbow flexion angle remaining constant across
trials. It remains to be shown if there are significant dif-
ferences between these throwing forms which warrant
further clinical investigation.
Several difficulties, theoretical and technological,
have been encountered when quantifying the timing and
forces involved in pitching. Initially, data for biomechani-
cal models were captured from film at frame rates from
67 frames per second (fps) (Atwater, 1973) to 1500 fps
(Atwater, 1979). The use of film analysis proved to be
technically demanding requiring a significant delay for
chemical development of the film, and therefore delayed
identification of any problems with the cinematography.
Increasingly high speed videotape analysis has replaced
film analysis due to its lower cost, the availability of im-
mediate feedback, the relative ease in synchronization of
individual cameras, and the increasing sophistication and
ease of computer digitization of the video analysis. The
highest recorded angular velocities of any human motion
have been displayed during a baseball pitch and this does
present some problems for kinematic analysis. For exam-
ple, during the acceleration phase of throwing, angular
velocities in excess of 10,000 °/sec have been recorded
(Werner et al., 2001). Standard NTSC videotape captures
motion at a rate of 30 frames per second, at such high
angular velocities very little information would be
gleaned from such an analysis. Even at extremely high
videotape rates of capture such as 500 frames per second,
Whiteley
3
Figure 3. Delineations of the six stages of the pitching motion are displayed here, viewed from six perspectives. The top row
shows a perspective view from the third base coaches box, the second row shows a view from home plate, the third row shows
a view from above, the fourth row shows a view from the first base side, the fifth row from second base, and the bottom row
shows a view from third base. The six stages of the pitching motion are windup, stride, arm cocking, acceleration, arm decel-
eration, and follow-through. The delineations of these stages are shown here, and are: Rest, maximum knee height, stride foot
contact, maximum arm external rotation, release, maximum internal rotation, and follow-through.
the arm would be moving through up to 20° between
frames. This apparent limitation was addressed by Fleisig
et al. (1996) who captured baseball pitchers performing
the pitching motion and American football quarterbacks
passing a football at 200 fps. Noting that the only pub-
lished data available for comparison was captured at 60
fps (Rash and Shapiro, 1995). Fleisig et al. (1996) reana-
lysed their data for several trials by viewing only every
third frame (an effective capture rate of approximately 67
fps) and compared this to their original data captured at
200 fps. They found that there was no difference in any of
the parameters measured except for shoulder internal
rotation angular velocity – the fastest recorded event.
When analyzing the truncated data (using an effective
capture rate of 67 fps) the measured angular velocities of
arm internal rotation were reduced by approximately 25%
in comparison to the original data captured at 200 fps for
the same individuals. This difference in calculated veloc-
ity (and therefore forces) between the two methods using
essentially the same data leads to speculation that differ-
ent figures may be arrived at for capture rates higher than
200 fps.
Each of the modeling studies presented considers
the shoulder to be a single multi-axial joint. This would
appear to be at least in part due to the difficulty of obtain-
ing accurate readings for the three dimensional position of
the scapula and clavicle. To date, accurate measurement
of scapular positioning has involved placement of subcu-
taneous bone pins into the scapula then recording their
position via X-Ray analysis (McClure, et al. 2001). Such
a technique whilst affording for accurate measurement of
bony position is currently impossible in the context of
analysis of maximal effort throwing mechanics. Accord-
ingly, it needs to be remembered that whilst many studies
refer to modeling and predicting forces at the ‘shoulder’,
they are referring to the glenohumeral, acromioclavicular,
sternoclavicular, and scapulothoracic joints as if they
comprised a single joint. To date, there is little in the way
of published data regarding forces at individual joints
during the throwing motion.
Much of the work regarding kinetics during the
throwing motion is used to predict potentially injurious
behavior. For example, it is shown that during the throw,
the amount of shoulder anterior force peaks at approxi-
mately 350N (Fleisig, 1994). Selecky et al. (2003) used a
force of 10N to 20 N in their measurement of passive
translation of the head of the humerus on the glenoid of
cadaveric subjects as forces greater than 25N “…often led
to marked joint subluxation and dislocation”. It is could
be erroneously inferred that the anteriorly directed force
during throwing is being borne entirely by the
glenohumeral joint, and clinical and surgical decisions
Throwing mechanics, pathology, and performance
4
(such as the strength required of surgical repair to with-
stand the rigors of throwing) may be extrapolated from
such mistaken assertions.
During motion capture, skin markers are routinely
placed over bony prominences, and then the position of
these markers is tracked and plotted in three dimensional
spaces with an inference that the position of the markers
is reflecting the position of the underlying bony promi-
nences. The accuracy of such an inference has been called
into question (Karduna et al., 2001). The data captured in
these analyses is often used to create an inverse kinetic
model from which estimations are then inferred regarding
forces and torques at individual joints. Unfortunately,
there would appear to be an inherent inaccuracy in these
models which, may be by definition unquantifiable. With
these limitations in mind, the reader should exercise cau-
tion in any interpretation of the results presented. Where
available, estimations of the inherent errors are presented,
unfortunately such data are not routinely available.
During competitive baseball pitchers are allowed to
throw from the ‘set’ or ‘windup’ positions as they choose.
In the set position, the throwing motion begins with the
thrower standing with the ipsilateral (to the throwing arm)
foot in contact with the pitching rubber, and striding to-
ward home plate with the contralateral leg. The windup
position allows for a short stride backwards or across
(with the leg contralateral to the throwing arm) before
striding toward home plate. Little work has been done in
investigating differences between these two techniques,
and it is rarely stated which technique was adopted during
analysis of pitching despite a widely held belief that
throwing from the windup position confers greater per-
formance. An exception to this was the work of Grove et
al. (1988) who documented an increased propensity to
throw strikes in a game situation for pitchers choosing the
set position (Grove et al., 1988). This group went on to
analyze the kinematics of throwing from these two posi-
tions finding the set position usually involved a reduction
in the amount of thigh rotation, and a more vertically
oriented lower leg position. It was also noted that the
direction of the stride showed less deviation when throw-
ing a curveball from a set position. These workers sug-
gested that pitchers may benefit by throwing from the set
position more often than is usually the case when dictated
by game situations (the set position is commonly used
only to limit any base-stealing opportunities by the oppo-
sition).
This paper assumes knowledge of different pitch
types (e.g. “fastball” and “curveball”) and these will not
be described further.
Kinematic factors of throwing related to injury and
performance
The review of the literature relating throwing mechanics
to health and performance uncovered work in many dif-
fering directions. This review is presented arbitrarily in
the following order:
1. Mechanical aspects
1.1. Foot position at Stride Foot Contact
1.2. Elbow flexion during throwing
1.3. Arm rotation during throwing
1.4. Arm horizontal abduction during throwing
1.5. Arm abduction during throwing
1.6. Lead knee position during throwing
1.7. Pelvic orientation during throwing
1.8. Deceleration-phase related issues
2. Curveballs
3. Teaching throwing mechanics
1. Mechanical aspects
1.1. Foot position at stride foot contact
Fleisig (1994) performed a kinematic analysis of the
pitching technique of 72 baseballers and after consultation
with pitching coaches considered eight proposed mecha-
nisms of ‘improper mechanics’. By accumulating this
data, Fleisig was able to describe average or normative
values for each individual parameter. The pitches of indi-
viduals were then compared to the accumulated means for
each of these parameters, and the kinetics calculated to
estimate variations associated with ‘improper mechanics’
or deviations from these means. Of the originally consid-
ered eight proposed mechanical faults, four were found to
be associated with increased kinetics at certain phases of
the pitching motion, including the positioning of the stride
foot.
Fleisig (1994) documented average stride foot
placement to be 87% of body height (measuring estimated
centre of the stride ankle joint back to the leading edge of
the pitching rubber). This stride was directed toward the
plate within 10cm in either direction in comparison to a
line drawn from the centre of the trailing ankle to the
centre of the home plate. The stride foot was found to be
‘closed’ or pointing toward the throwing arm side at an
angle of 15° ± 10° with reference to this line. (see Figure
4 for an explanation of these terms).
Those pitchers who were found to deviate from
these norms toward open foot position and alignment
showed increased kinetics at the shoulder. For every extra
centimeter the stride foot lands toward the ‘open’ side, an
extra 3.0N of maximum shoulder anterior force was found
during the arm cocking phase. Further, if the stride leg
was placed at an open foot angle, this too increased the
maximum shoulder anterior force during the cocking
phase at a rate of 2.1N per degree of open foot placement.
To place this data into some context, the maximum
shoulder anterior force found during the arm cocking
phase was found to be on average 350N, so if a pitcher
were to place their lead leg 10cm toward the open side
and 10° further open, then this would be associated with a
51N (or approximately 15%) increase in shoulder anterior
force during the arm cocking phase. Interestingly, those
pitchers who landed in a more ‘closed’ position (in terms
of foot angle, and placement) had no increase in stressful
parameters demonstrated.
During the assessment of the injured throwing ath-
lete, a routine finding is reported shoulder pain during the
arm cocking phase of throwing (Andrews and Fleisig,
1998; Curtis and Deshmukh 2003; Meister 2000). This
can be associated with a positive Relocation Sign (Jobe, et
al., 1989), and it has been suggested that this is indicative
of subtle anterior shoulder instability (Hamner et al.,
2000). Matsen amongst others believe that the primary
Whiteley
5
restraints to shoulder subluxation at extreme range of
motion to be the ligamentous structures (Matsen et al.,
1991). It would follow then that any increase in the
amount of shoulder anterior force during the arm cocking
phase could be directly associated with pathology at the
ligamentous restraints such as increasing anterior shoulder
instability.
Figure 4. Calculation of stride length, stride offset, and lead
foot angle at the moment of stride foot contact. Distance 'A'
measures the length from centre of the trailing ankle to the
centre of the lead ankle. Distance 'B' measures the distance
from the leading edge of the pitching rubber to the centre of
the lead ankle. Distance 'C' measures the offset of the centre
of the lead ankle from a line drawn from the centre of the
trailing ankle through to the centre of the target (home
plate). Positive values being on the non-throwing arm, or
'open' side with our example showing a positive value. Angle
Theta (Ө) measures the angle made between the long axis of
the leading foot and a parallel line drawn from the centre of
the trailing ankle to the centre of the pitching rubber. In this
case Theta measures approximately 9° toward the 'open'
side. Fleisig's (1994) PhD thesis gave normative values for
each of these variables as follows: A: 75% of height, ± SD:
4%; B: 87% ± 5%; C: 0.4cm ± 8.3cm; Theta: 15° ± 10°.
Montgomery and Knudson (2002) in an investiga-
tion of six professional baseball pitchers found that in-
creasing the stride length to 85-90% of their body height
to be associated with an increase in throwing velocity in
four of them. Contrary to some pitching instruction, this
was generally not associated with throwing the pitch
higher in the strike zone as only one of the pitchers
showed a weak trend (r = 0.54) towards doing so.
In a kinematic examination of 16 collegiate base-
ball pitchers throwing a variety of pitch types (fastball,
curveball, slider, and changeup) Escamilla et al. (1998)
found lead foot position to vary. This group found stride
length to be slightly lower than that reported by Fleisig
(1994) at 84% ± 5% for the fastball in comparison to 82%
± 4% for the curveball. This is in distinction to the work
of Elliot et al. (1986) who found no significant difference
in their group of 8 International level pitchers throwing
fastball and curveball pitches (82% ± 2% and 81% ± 6%
for the different pitches respectively). Escamilla et al.
(1998) also reported on the positioning of the lead foot
angle for each of the pitch types. They found that there
were significant differences during the fastball and curve-
ball (0cm ± 10cm versus -3cm ± 9cm); and the changeup
and curveball pitches (-3cm ± 9cm and -7cm ± 9cm). The
position of the lead foot was not significantly different for
the slider (0cm ± 9cm). Lead foot angle was not found to
be statistically significantly different for any of the trials
at -8°±12°, -7°±11°, -14°±14°, -10°±11 for the fastball,
changeup, curveball, and slider respectively.
1.2. Elbow flexion
Fleisig proposed that increased elbow flexion during the
arm cocking and acceleration phases would be associated
with an increase in kinetics, but his research did not bear
out this finding (Fleisig and Escamilla, 1996). It would
appear that this proposal is at least in part based on the
commonly held belief amongst pitching coaches that
“correct” mechanics are associated with maintaining
elbow flexion of less than 90° at the point of stride foot
contact (Figure 5). It was indeed illuminating to then see
the work of Werner who analyzed the kinetics of forty
professional pitchers during Cactus League spring Train-
ing of 1998 (Werner et al., 2001; 2002). Werner et al.
(2001; 2002) used three 120Hz cameras through at least 2
innings of pitching, choosing the best fastball in terms of
‘…location, velocity, and outcome’ from this sample for
analysis with an average displayed ball velocity of 89
mph.
In one study Werner used shoulder joint distraction
as a dependent variable (Werner et al., 2001) as it is pro-
posed that longitudinal distraction of the glenohumeral
joint can be associated with pathology commonly seen in
the throwing athlete such as shoulder instability (Altchek
and Hobb,s 2001), and traction injuries to the biceps an-
chor and superior labral complex (Andrews et al., 1985;
Andrews et al., 1985). Thirteen kinematic and kinetic
variables were chosen as independent variables for a step-
wise regression analysis. A combination of five of these
parameters explained 72% of the variance in shoulder
distraction estimated during the throwing motion. These
parameters included elbow flexion at stride foot contact
and elbow flexion at ball release. This work infers that
those pitchers who have a more flexed elbow at the point
of stride foot contact and a more flexed elbow at the point
of ball release will have a reduction in the amount of peak
longitudinal distraction force at their shoulders during the
throwing motion.
In a related study using similar materials and
methods, Werner’s group (Werner et al., 2002) performed
a stepwise regression analysis with elbow valgus as the
dependent variable. Excessive elbow joint valgus force
during throwing is considered to be the primary cause of
Valgus Extension Overload (Andrews, 1985; Andrews et
Throwing mechanics, pathology, and performance
6
Figure 5. Depiction of elbow flexion at moment of Stride Foot Contact. Commonly pitching
coaches will assert that the elbow shoulder remain at less than 90° of flexion (i.e. “straighter”)
during the throw, however the results of several investigations reveal that this may need re-
appraisal in light of reduced stressful forces at both the shoulder and elbow where a higher
amount of elbow flexion is displayed.
al., 2001; Cain et al., 2003; Wilson et al., 1983) – a spec-
trum of disorders including (but not limited to) attenua-
tion of the anterior band of the ulnar collateral ligament
(UCL) of the elbow, osteochondral damage to the postero
medial olecranon fossa, and osteochondral damage to the
radio-capitellar joint. Valgus Extension Overload is con-
sidered to be the most common elbow injury suffered by
skeletally mature throwing athletes (Azar, 2003; Joyce et
al., 1995; Pincivero et al., 1994). This study (Werner et
al., 2002) found 4 independent variables were able to
explain over 97% of the variance in elbow valgus, includ-
ing elbow flexion at the point of maximum valgus stress.
Peak valgus stress at the elbow occurs late in the cocking
phase and very early in the acceleration phase of throw-
ing, and those who displayed a greater amount of elbow
flexion at this point in the throw were associated with
lower amounts of maximum elbow valgus force during
the throw (Werner et al., 2002).
Whilst it would appear then that the commonly
held pitching coach’s maxim that the elbow should be
flexed no more than 90° at the point of stride foot contact
could bear re-examination, this notion needs to be tem-
pered in light of the findings of Levin et al (Levin et al.,
2004). This group investigated the amount of stress
placed at the UCL during valgus stress after progressive
sectioning of the posterior olecranon. Levin showed sig-
nificantly more strain occurred in the UCL at 90° than at
70° of elbow flexion (Levin et al., 2004). The highest
valgus stresses occur at late cocking and early accelera-
tion phases and perhaps assessment of elbow flexion at
this stage of the throw would be more appropriate.
In terms of pitching performance, one variable
commonly sought after is higher throwing velocity. Ma-
tsuo et al. (2001) examined 12 kinematic and 9 temporal
parameters in a group of 127 healthy college and profes-
sional pitchers (Matsuo et al., 2001). These players had an
average throwing velocity of 36.1 m·s-1 ± 1.9 m·s-1 for the
group (80.75 ± 4.2 mph). Matsuo et al. then compared the
12 kinematic and 9 temporal variables for the group who
threw more than one standard deviation greater than aver-
age (> 38.0 m·s-1, >89 mph) with the group who threw
less than one standard deviation slower then the average
(< 34.2 m·s-1, <76.5 mph). One of the variables to show a
statistically significant difference between these two sub
groups was the timing of maximum elbow extension
angular velocity during the throw. Matsuo’s group con-
sidered the throw from stride foot contact until ball re-
lease, describing these two points as 0% and 100% of the
throwing cycle respectively. Intuitively, one might expect
the higher velocity group to display peak elbow extension
angular velocity at or very close to the point of ball re-
lease. It was indeed surprising then to learn that the high
velocity group displayed the peak elbow extension angu-
lar velocity to occur at 91.1% ± 1.9% of the throw dura-
tion, whilst the slower throwing group displayed this
event slightly later at time = 93.0% ± 2.4% (Matsuo et al.,
2001). Atwater (1979) was amongst the first authors to
propose a sequential summation of kinetic links as being
critical in the production of velocity in the overhead
thrower. She describes the sequential nature of the accel-
eration of body segments moving from the lower limbs
through the trunk and then to the arm and hand. This
movement pattern typically shows each segment initially
lagging behind its preceding segment, and then accelerat-
ing to even higher angular speeds whilst the preceding
segment lagged behind. This whip-like summation of
angular velocities requires extraordinarily precise timing,
and the data of Matsuo et al. (2001) would serve to under-
score the delicacy of this balance. The throwing motion
has been modeled using a double pendulum to estimate
optimal conditions for throwing and striking (Alexander,
1991). Perhaps an alternate explanation for the seemingly
counter-intuitive finding of peak elbow extension velocity
can be found in this model. Whilst complex to describe
Whiteley
7
mathematically, a double pendulum can be constructed
simply where two solid struts (such as student’s wooden
rules) are connected at their end and swung back and forth
from one end (Cross, 2004). From this it can be appreci-
ated that maximum linear velocity of the distal end of the
distal segment is not necessarily associated with maximal
angular velocity of the proximal segment.
Werner correlated elbow joint position and elbow
kinetics with an EMG analysis of the biceps brachii, tri-
ceps brachii, and anconeus muscles in an investigation of
seven healthy college and minor league pitchers using a 2
camera 500 frames per second analysis (Werner et al.,
1993). The mean ball velocity for the subjects was 36.4
m·sec-1, and the EMG data was captured using surface
electrodes. Werner showed a sequential activity of biceps
followed by triceps activity until the moment of maximal
shoulder external rotation, and thence activity in the an-
coneus muscle as the elbow continued flexing during the
first half of the acceleration phase (Werner et al., 1993).
Active elbow extension is thought to be principally under
the control of the triceps musculature, and secondarily by
the anconeus muscle (Basmajian and Griffin, 1972). The
subsequent rapid elbow extension was not associated with
any appreciable increase in activity of either triceps
brachii or anconeus. The elbow flexion seen during the
acceleration phase was seen to be associated with a con-
current increase in the amount of predicted elbow com-
pressive force which peaked at approximately 780N
shortly before ball release (Werner et al., 1993). The rapid
elbow extension seen during the throwing motion would
therefore appear to be both a combination of active elbow
extension, and the mechanical conversion of angular
velocity of the more proximal segments (shoulder internal
rotation and horizontal adduction) into elbow extension.
In an investigation of the role of the triceps muscu-
lature during throwing, Roberts reported on the prelimi-
nary work of Dobbins who performed a radial nerve block
(thereby rendering the triceps brachii and wrist and finger
extensors inactive) and compared the kinematics of the
throws performed prior and subsequent (Roberts, 1971).
Dobbins found that the timing of the onset of elbow ex-
tension was unchanged after the radial nerve block, how-
ever prior to extending the elbow ‘collapsed’ into a
maximum elbow flexion of 145° (from the pre-nerve
block maximum of 90°). On the sixth throwing trial after
the nerve block was performed, the subject was able to
throw in excess of 80% of his original velocity despite the
absence of active triceps (and wrist extensor) contribu-
tion. This work would suggest that part of the role of the
triceps musculature is to maintain elbow flexion such that
the moment of inertia of the rotating upper arm is maxi-
mized (at 90° elbow flexion).
1.3. Arm rotation.
Investigations into the timing, magnitude, and duration of
arm rotation are shown to be related to performance and
kinetics, and are discussed below. It should be recalled
that the amount of arm rotation is usually being inferred
from the positions of skin markers on the ulna, humerus,
and trunk. Commonly this rotation (axial rotation of the
humeral component in comparison to the trunk) is termed
“shoulder rotation”, however the components of this total
arm rotation which occur at the glenohumeral, scapu-
lothoracic, acromioclavicular, and sternoclavicular joints
can only be guessed at. Accordingly, for the purposes of
this paper, this motion will be termed “arm rotation”.
1.3.1. Early external rotation: In Fleisig’s (1994) initial
investigation he found the average amount of arm rotation
to be 53° ± 26° at the point of stride foot contact (Figure
6). Those who displayed an increase in the amount of arm
external rotation at stride foot contact also displayed in-
creased kinetics at the arm and elbow, and alterations in
stride foot position.
An increase in the amount of arm rotation was
shown to be associated with increased shoulder anterior
force during the arm cocking phase at a rate of 1.3N/° of
arm rotation. The total shoulder anterior force during the
arm cocking phase was 350N, so an increase of say 40°
would be associated with an increase of 52N or almost
15%.
Figure 6. Arm external rotation at Stride Foot Contact. In
the investigation of Fleisig (1994) Arm external rotation was
found to be 53°±26°. An increase in the amount of displayed
external rotation at this point in the throwing cycle is termed
“Early External Rotation” and was shown to be associated
with increased stressful forces at both the shoulder and
elbow, whilst a reduction in external rotation is termed
“Late External Rotation” and was shown to be associated
with increased stressful forces at the elbow, but a reduction
in potentially damaging forces at the elbow.
Increased arm external rotation at stride foot con-
tact was also shown by Fleisig (1994) to be associated
with an increase in the amount of elbow medial force at a
rate of 0.7N/°. Elbow medial force averaged a peak of
280N, so an increase of 40° of arm external rotation at
stride foot contact would be associated with 28N, or 10%
of the total medial elbow force. The passive restraints
against valgus stress at the medial elbow include the
UCL, principally its anterior band. During throwing, the
load placed through this structure is thought to approach
its ultimate tensile strength. Any further increases in the
amount of valgus stress through increased arm external
rotation at stride foot contact could place this structure at
a heightened risk of tensile failure.
Throwing mechanics, pathology, and performance
8
Escamilla et al. (2002) evaluated kinetic, kine-
matic, and temporal values of 11 American and 8 Korean
healthy professional pitchers during trials of pitching a
fastball including external rotation. In this study, the Ko-
rean pitchers displayed reduced kinetics, and approxi-
mately a 10% reduction in throwing velocity in compari-
son to the American pitchers (37.1 ± 1.9 m·sec-1 vs. 34.9 ±
1.0 m·sec-1). In contrast to the findings of Fleisig (1994),
one of the variables associated with reduced kinetics at
the shoulder and elbow was an increase in the amount of
arm external rotation displayed at lead foot contact.
1.3.2. Late external rotation: A decreased amount of arm
external rotation at stride foot contact (beyond one stan-
dard deviation from the group mean) was shown by Fle-
isig (1994) to be associated with an increase in the maxi-
mum longitudinal compressive force along the humerus
during the cocking phase at a rate of 1.5 N/°. The average
maximum compressive force along the humerus being
590N for the group, an increase of 40° then could be
associated with an increase of 60N or over 10% of the
total compressive force during the arm cocking phase. It
is thought that increases of longitudinal compression
during this phase could be associated with compres-
sion/rotation injuries to the glenoid labrum, much in the
manner of proposed damage to the menisci of the knee
during weight-bearing combined with rotation.
A reduction in the amount of arm external rotation
at stride foot contact was associated with a reduction is
stressful kinetics at the elbow (Fleisig 1994). It was
shown that the elbow medial force (and varus torque) was
reduced at a rate of 0.8 N/° (0.2Nm varus torque) (Fleisig
1994). In our previous example of a 40° reduction in the
amount of arm external rotation at stride foot contact, this
would be associated with a reduction of 32N (over 10% of
the total valgus force).
1.3.3. Total arm external rotation range: Very high fig-
ures - up to 210° (Werner et al., 1993) are quoted for the
total amount of arm external rotation displayed during
throwing (Figure 7). Feltner and Dapena (1986), and
Kreighbaum and Barthels (1985) hypothesized that the
arm external rotation displayed during throwing with
simultaneous EMG activity of the horizontal adductors
and internal rotators was due to the inertial lag of the
forearm as the proximal segments rotated toward the
contralateral (to the throwing arm) side. It is not surpris-
ing then to learn of that there is no relation between the
amount of active external rotation range at the shoulder
horizontal abduction and adduction of the active arm
external rotation range and throwing skill or speed
(Clements et al., 2001). Clinically, a more useful finding
is the amount of passive arm external rotation since it
more closely reflects the nature of the movement dis-
played in the throwing motion. Whilst many authors
(Baltaci et al., 2001; Bigliani et al., 1997; Brown et al.,
1988; Crockett et al., 2002; Ellenbecker et al., 2002;
Reagan et al., 2002) have described a difference in the
total range of external and internal rotation in the domi-
nant and non dominant arms of high level baseball play-
ers, there are occasional exceptions to this finding
(Johnson, 1992).
The finding that increased range of external rota-
tion is associated with an increase in throwing speed was
originally described by Atwater (1979) who investigated
ranges of motion and throwing speed in a group of varsity
pitchers. Subsequently Wang et al. (1995) using 2 150Hz
cameras examined fastball pitches of 3 pitchers (2 col-
lege, 1 high school with an average release velocity of
32.34 m·sec-1 ± 3.63 m·sec-1). This group showed a corre-
lation between the amount of maximum external rotation
at the beginning of the acceleration phase and ball release
velocity, with the Pearson r value measuring 0.86. This
work was further expanded in the investigation of Matsuo
who found an increased maximum displayed shoulder
external rotation range (from 166.3° ± 9° to 179° ± 7.7°)
to be associated with higher throwing velocities in his
group of 127 healthy college and professional pitchers
(Matsuo et al., 2001).
Figure 7. Maximum displayed Arm External Rotation.
Maximum displayed figures for arm external rotation dur-
ing pitching have been recorded in excess of 210°, and rou-
tinely are reported in the order of 180°. The clinical assess-
ment of a thrower’s passive rotational range of motion needs
to be made with these figures in mind.
Baseball players have regularly been shown to
have both an increased passive range of external rotation
in their dominant arm, and a reduction of passive range
toward internal rotation (Donatelli et al., 2000; Ellen-
becker et al., 2002). It has been suggested that those in
whom the lost range of internal rotation exceeds their
gained external rotation are at a greater risk of subsequent
shoulder labral injury (Burkhart et al., 2003c) and that
remediation (Burkhart et al., 2003b) and prevention
(Burkhart et al., 2003b) of this lost range of motion is
curative and preventive of these injuries.
During the investigation of Werner et al. (2001),
the amount of shoulder distraction at the point of maxi-
mum external rotation was found to be proportional to the
total external rotation range displayed. Werner’s group
(2001) investigated the total shoulder distractive force as
a dependent variable in their regression analysis as it was
thought to relate to the potential for pathology at the rota-
tor cuff and glenoid labrum (Werner et al., 2001). Shoul-
der distractive forces ranging from 83% to 139% of body
weight (108% ± 16%) were found for the group of forty
professional pitchers playing in the Cactus League of
1998, which was in line with other reported data (Feltner
and Dapena, 1986; Fleisig et al., 1995) regarding the
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9
maximum distractive force at the shoulder during throw-
ing. Shoulder joint distraction during the follow-through
phase where the biceps is acting forcefully to decelerate
the extending elbow has been theoretically implicated as a
potential source of traction injury to the biceps anchor at
the superior glenoid labrum (Andrews et al., 1985). More
recently in a cadaveric study of tension on the proximal
long head of biceps at the glenoid labrum, arm external
rotation in abduction (in a simulated position of arm cock-
ing) was shown to be associated with markedly higher
amounts of strain in the proximal long head of biceps than
in any of the other simulated throwing positions (Pradhan
et al., 2001).
In the examination of American and Korean pitch-
ers by Escamilla the Korean pitchers were shown to have
a reduction in maximum arm external rotational range of
motion during arm cocking (180 ± 10° vs. 165 ± 10°), and
this was associated with a reduced kinetics at the shoulder
and elbow, and reduced ball velocity (Escamilla et al.,
2002).
When considering the total amount of arm external
rotation, and the contribution of the glenohumeral joint,
the amount of individual humeral torsion needs to be
factored into the equation. The degree of humeral torsion
an individual displays has been shown to be associated
with the total range of external rotation as well as the
propensity for anterior dislocation (Crockett et al., 2002;
Kronberg and Brostrom, 1990; 1991; 1995; Kronberg et
al., 1993; 1990; Osbahr et al., 2002; Reagan et al., 2002).
Pieper in a study of 51 male National Level Handball
players found a variation in the side to side values of
humeral torsion when measuring with longitudinal X-Ray
analysis (Pieper, 1998). Interestingly of his sample the 13
who were presently complaining of shoulder pain had an
average reduction of humeral torsion of 5.4° on their
dominant side, whilst the remaining 38 healthy players
had an average increase of 14.4° of humeral retrotorsion.
Similar conclusions were reached by Osbahr et al. (2002)
who used longitudinal X-Ray to find a 10° increase in
retroversion of the dominant side humeral head of 19
male college baseball pitchers. This figure concurs with
the findings of Crockett who used CT to investigate the
humeral torsion and glenoid version in 25 professional
baseball pitchers and 25 non-throwing controls (Crockett
et al., 2002). This group showed an average increase of
17° in the retrotorsion of the dominant arm’s humeral
head in the pitchers that was not found in the controls.
This increased humeral retroversion was found to be
associated with an increase in humeral external rotation
when measured at 90° of abduction, and would clearly
influence the amount of arm rotation which is occurring at
the glenohumeral joint. This work suggests that the in-
creased arm external rotation and concomitant reduction
in internal rotation (which has often been ascribed to
capsular and muscular adaptive changes) may well be
partly bony in origin, and a requisite for healthy perform-
ance of the extreme range of external rotation seen in
throwing athletes.
1.4. Horizontal abduction and adduction
1.4.1. Horizontal adduction: Published data show the
maximum horizontal adduction a pitcher displays to be in
the order of 14° ± 7° (Fleisig, 1994). Pitching coaches
will often see an excessive amount of arm horizontal
adduction as a mechanical fault, sometimes describing
this pattern as ‘leading with the elbow’. Fleisig (1994)
found the maximum horizontal adduction range displayed
to be proportional to the maximum elbow medial force
during arm cocking phase at a rate of 2.4 N/°. Since the
total amount of elbow medial force during the arm cock-
ing phase was 270N in Fleisig’s study, an increase of 7°
horizontal adduction would be associated with an 18N or
7% increase in this force.
1.4.2. Horizontal abduction: Escamilla et al’s (2002)
investigation of differences between a group of American
and Korean pitchers showed the higher velocity American
pitchers to have an increase in the amount of horizontal
abduction at stride foot contact (23 ± 12° vs. 14 ± 9°,
Figure 8).
Figure 8. Maximum arm horizontal abduction during pitch-
ing.
It has been theorized that an increase in the amount
of shoulder horizontal abduction range during the arm
cocking phase is associated with a propensity for shoulder
pathology. Jobe deemed this to be ‘hyperangulation’ and
thought that it would be coupled with attenuation of the
shoulder anterior capsular structures, and therefore ante-
rior shoulder instability (Jobe and Pink, 1996). These
workers state that this is seen with a throwing pattern of
the hand not being “on top of the ball” as is thought to be
preferred by pitching coaches.
Burkhart’s group (2003a) believe that in the pres-
ence of a tight and thickened postero-inferior
glenohumeral capsule, horizontal abduction combined
with external rotation as is shown in the arm cocking
phase will be associated with a postero-superior transla-
tion of the humeral head relative to the glenoid such that
it no longer contacts the posterosuperior glenoid labrum.
These researchers feel that the normal contact of the
trapped posterosuperior glenoid labrum in this position
increases tension in the anterior glenohumeral capsule in
a cam like manner, thereby enhancing
glenohumeral stability and so the failure of this mecha-
nism during postero-superior translation leads to a
failure of the shoulder’s normal stability apparatus.
1.4.3. Timing of horizontal abduction and arm external
rotation: It is seen that during the arm cocking and subse-
quent acceleration phases, the arm moves from horizontal
abduction to adduction and from extremes of external
rotation to internal rotation with extremes of external
Throwing mechanics, pathology, and performance
10
Figure 9. Comparison of glenohumeral external rotation in horizontal abduction and horizontal adduc-
tion. The image on the left depicts the proposed effect of performing the shoulder external rotation
during the cocking phase whilst the arm is “left” in horizontal abduction of the early cocking phase.
The subject on the right would be susceptible to less attenuation of the anterior capsular structures
through performing this external rotation in the plane of the scapula, and hence less horizontal abduc-
tion coupled with the required glenohumeral external rotation.
rotation displayed during concomitant shoulder horizontal
adduction (Figure 9). Clinically, it is commonly seen that
the amount of painless passive external rotation available
when measured at 90° of arm abduction will be reduced
with increased arm horizontal abduction. Whilst this has
not been formally investigated it would seem rational to
suggest that shoulder pain would be present in those indi-
viduals who aberrantly ‘leave’ their arm too long in hori-
zontal abduction during the external rotation phase of arm
cocking via a similar mechanism perhaps through attenua-
tion of the anterior capsular structures.
1.5. Arm abduction
Atwater was the first to propose that across all the throw-
ing and striking sports, the amount of arm abduction at
release/impact stayed relatively constant at 90° with ap-
parent variations being due to trunk inclination (Atwater,
1979). This has only recently been partially challenged by
Matsuo who analyzed a group of 2 submarine type pitch-
ers, 2 sidearm type pitchers, and a control group of 13 ¾
arm style pitchers (Matsuo et al., 2000). Matsuo found the
submarine style pitchers to abduct their arms to less than
75° during the arm acceleration phase, and that this style
of throwing was associated with an increased maximum
shoulder anterior force in comparison to the ¾ arm style
pitchers (Matsuo et al., 2000). This is a significant find-
ing, as it has been suggested by some pitching coaches
that submarine style pitching whilst generally capable of
lower velocity than ¾ style pitching, is less stressful on
the arms of those performing it, and has been recom-
mended to injured pitchers as a way of extending their
careers. The sidearm pitchers were noted to have an in-
creased medial elbow force in comparison to the ¾ arm
style pitchers, and this would appear to concur with the
majority of opinion of pitching instructors (see Figure
10).
Matsuo et al. (1999) modeled the effect of varying the
amount of arm abduction at ball release (through the
ranges 50° to 130°) during the throw for a number of
kinetic and performance variables. This group found that
wrist velocity was at a maximum when the shoulder was
at 90° abduction at ball release. Elbow varus torque was
at a minimum at 80° of arm abduction at release, while
peak shoulder anterior force was minimized at 110° arm
abduction at release. Shoulder compressive force was at
its lowest at 130° arm abduction at release, increasing
with all lower values investigated. This work was com-
plemented by a subsequent investigation of eleven profes-
sional pitchers by Matsuo et al. (2002) where a two cam-
era videotape analysis was conducted calculating elbow
varus torque and peak wrist velocity. Subsequently these
values were recalculated with theoretically varied levels
of arm abduction. Each pitcher was found to have
optimized their level of arm abduction to minimize the
amount of elbow varus torque and maximize the peak
wrist velocity. More recently, this work was followed up
with a 4 camera, 200Hz investigation into 33 healthy
college pitchers upon whom a two-way analysis of
variance was performed examining the effects of trunk
tilt and arm abduction on elbow varus torque through
modeling predicted forces across a range of trunk inclina-
tion and arm abduction angles (Matsuo et al., 2006). In
the simulated overhand and three-quarter arm conditions
(see section 7 for and explanation of these terms) elbow
varus torque was minimized with arm abduction of 90°,
while overall varus torque was minimized at 100° of arm
abduction with a contralateral trunk tilt of 10°. During
ipsilateral trunk tilt conditions the optimum angle of arm
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11
Figure 10. Arm abduction during pitching from the point of Stride foot contact to Maximum
External Rotation, and then to release.
abduction in terms of minimizing elbow varus torque was
generally 100° or greater.
Werner’s group (2001) found the amount of arm
abduction at stride foot contact to be 109° ± 33°, with
Flesig’s (1994) investigation showing lower values. Fle-
isig reported arm abduction at ball release to be approxi-
mately 95°, and most authors show the arm to slightly
abduct from the time of stride foot contact until maximum
external rotation, then to slightly adduct until ball release,
and then there is a sharp abduction during the decelatory
phase until maximum internal rotation of the arm is
reached. Increasing the amount of arm abduction was
shown by Werner et al. (2002) to be contributory to in-
creasing the amount of valgus stress at the elbow. In con-
trast to these findings, Escamilla’s (2002) investigation of
a group of American and Korean pitchers showed the
lower velocity (and reduced kinetics) Korean group to
have an increase in the amount of arm abduction at stride
foot contact (94 ± 11° vs. 104 ± 7°). These findings
should be considered in light of Matsuo’s (2002) more
recent modeling work in which arm abduction angle and
trunk inclination were found to be interdependent and
analyses examining only one aspect may be therefore be
superficially confounding only.
1.6. Lead knee position
At the point of stride foot contact, the lead knee has been
reported to be in varying amounts of flexion, and then
move toward more flexion, extension, or not at all (Fig-
ure11). In Matsuo’s (2001) previously described investi-
gation of a high and low velocity pitching group, the
higher velocity group displayed both a slower rate of knee
flexion on landing, and a higher rate of subsequent knee
extension. Pitching coaches will occasionally describe
this behavior as ‘firming up the front side’, and have been
reported as claiming that those throwers who
Figure 11. Lead knee position during pitching. Significant variations are seen in the amount of knee flex-
ion from the point of stride foot contact to release and then follow through. The lead knee may increase,
decrease, or remain unchanged in terms of flexion. The rate of knee extension has been shown to be asso-
ciated with an increase in ball velocity (Matsuo et al, 2001).
Throwing mechanics, pathology, and performance
12
Figure 12. Depiction of Pitching styles. Pitching style is termed according to the angle of inclination of the trunk
and the forearm of the throwing arm. The leftmost image shows a pitcher sideflexing his trunk toward the contra-
lateral (to the throwing arm) side, and an almost vertically placed forearm at release. This throwing style is termed
'overhand'. The third image shows a thrower standing erect with an almost horizontally placed forearm, this is
termed 'sidearm' throwing. The second image shows a thrower with only a small amount of contralateral sideflex-
ion and a forearm inclined between the extremes shown in sidearm and overhand throwing, this is termed 'three-
quarter' throwing. The right-most image shows a thrower displaying ipsilateral trunk sideflexion, and a lesser
amount of arm abduction than the first three images, this is termed 'submarine' throwing.
allow their ‘front side to soften’ (by letting their lead knee
move toward more flexion during the acceleration and
release phases) are not throwing to their highest potential
velocity. In agreement with these findings, Escamilla et
al. (2002) showed a reduction in the amount of knee flex-
ion at release (37 ± 14° vs. 48 ± 16°) in the higher veloc-
ity group of American pitchers in comparison to their
Korean counterparts.
In an investigation of kinematic differences be-
tween pitch types (fastball, curveball, changeup, and
slider) thrown by 16 college pitchers, Escamilla et al.,
1998) showed the changeup pitch to have the greatest
excursion of knee flexion from stride foot contact to ball
release, and the lowest ball velocity across all pitch types.
MacWilliams et al. (1998) investigated the ground
reaction forces during pitching for one high school and
six collegiate pitchers. This group placed a force platform
immediately in front of the pitching rubber (underneath
the stance leg of the pitcher) and another at the site of
stride foot landing. This enabled them to record the mag-
nitude and directions of the ‘push off’ and ‘landing’
forces during pitching. They also measured wrist linear
velocity (a good correlate of ball speed). They found that
ground reaction force directed toward the plate was highly
correlated with throwing speed (r² = 0.82) indicating that
those who pushed hardest toward the plate (from their
stance leg) and therefore were also able to decelerate most
strongly with their landing leg also displayed the highest
linear wrist velocities. The results of this study contrast
somewhat with the findings of Elliot et al. (1988) who
examined 8 International level pitchers whilst throwing
fastball and curveball pitches using a force platform
analysis of the push-off leg. In the data from the 3 highest
velocity pitchers, it was found that the timing of the force
pushing toward the plate was later in the pitch cycle but
of a similar magnitude to those three who threw slowest.
1.7. Pelvic and trunk orientation
Whilst there appear to be no strictly held definitions, it
would seem that pitchers are classified in terms of their
degree of forearm inclination at release from vertical, and
the extent and direction of trunk sideflexion. Those who
display significant trunk sideflexion away from the throw-
ing arm side with a concomitant vertically oriented fore-
arm at release will be termed ‘Overhand’ throwers. If the
same pitcher were to have their trunk vertically oriented
and the forearm almost horizontal at release then they are
termed ‘Sidearm’ pitchers. The majority of pitchers dis-
play mechanics somewhere between these two extremes
with a trunk inclined slightly toward the contralateral (to
the throwing arm) side and the forearm in between the
extremes of vertical and horizontal. This style is termed a
‘Three-Quarter arm’ throwing. Less commonly, a thrower
will inclined their trunk toward the throwing arm side
delivering the ball from a lower height. These throwers
are termed ‘Submarine’ style pitchers. (See Figure 12 for
an explanation of these terms).
Matsuo et al. (2000) investigated the kinematics
and kinetics of two sidearm and two submarine pitchers.
This group found that the sidearm style of throwing was
associated with an increase of peak medial elbow force
which concurs with the majority of opinion of pitching
instruction. Perhaps more surprisingly given the weight of
opinion of pitching instructors, the two submarine style
throwers were found to show an increase in the maximum
amount of shoulder anterior force.
In an effort to determine if variation in trunk side-
flexion influences the optimal angle of arm abduction in
terms of the sum of minimum torque squared required,
Matsuo et al. (2003) using a 4 camera 200Hz analysis
investigated the kinematics of seven professional pitchers
(throwing with an average velocity of 38.0 ± 1.3 m·sec-1).
After determining the kinematics for each of the pitchers,
torque squared was recalculated considering variations in
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13
trunk tilt angle for seven cases (-20°, -10°, 0°, 10°, 20°,
30°, and 40°) and for 6 different angles of arm abduction
at release (70°, 80°, 90°, 100°, 110°, and 120°) giving 42
possible combinations for each individual. For these sub-
jects, Matsuo found that for contralateral trunk tilt (10° to
40° conditions) optimal arm abduction angle varied from
90° to 105° whilst in the ipsilateral conditions, torque
squared decreased as arm abduction as shoulder abduction
increased, although the optimal abduction angle was not
found in the ranges of arm abduction studied (Matsuo et
al., 2003). It was concluded that on average ipsilateral
trunk tilt was associated with greater requirements of
torque squared than for the contralateral conditions, and
that the optimal condition (in terms of minimum torque
squared) was in the condition of 100° of shoulder abduc-
tion and 30° of contralateral trunk tilt. However the au-
thors hastened to point out that two of the seven subjects
did not fit this pattern in that altering their kinematics
toward this condition increased their torque squared,
suggesting that other factors (they put forward trunk in-
clination and elbow extension angular velocity as possible
candidates) may be significant contributors. A subsequent
investigation (Matsuo et al., 2006) using similar method-
ology and 33 college pitchers (average ball release veloc-
ity 36.8 ± 0.9 m·sec-1) which again modeled varied kine-
matics across the same combinations of 42 variables and
compared varus torque as a dependent variable showed
similar results in that peak elbow varus torque varied
according to both arm abduction and trunk inclination
angles. In this investigation, peak elbow varus torque
generally displayed a minimum shifted toward greater
arm abduction angles as trunk tilt angle increased ipsilat-
erally. Again, there were individual differences between
subjects however this data showed a shoulder abduction
angle minimizing elbow varus torque depending on the
trunk tilt angle with minimum varus torque at approxi-
mately 90° of arm abduction in the cases of contralateral
trunk tilt in the order of 20° to 30° - the trunk inclination
generally described as overhand and three-quarter pitch-
ers, and in accordance with the general teaching of pitch-
ing coaches.
In an EMG investigation into muscular activity
during throwing, Hirashima et al. (2002) showed activity
of the external oblique muscle contralateral to the throw-
ing arm prior to the ipsilateral external oblique. This pat-
tern of muscle activity during the axial rotation phase of
trunk movement is thought to be best disposed to assist in
the transfer of torque from the lower limb to the upper
limb. Activity in the rectus abdominus was only seen
immediately prior to release suggesting active trunk flex-
ion activity occurred quite late in the propulsive phase. In
their investigation of 127 college and professional pitch-
ers, Matsuo et al. (2001) looked at kinematic differences
between the groups which threw at 1 standard deviation
above and below the sample mean. Among their results
was the finding that higher velocity throwers tended to
display an increased forward trunk tilt at the moment of
ball release. As rectus abdominus is considered to be a
primary trunk flexor, it would appear that this EMG activ-
ity seen by Hirashima et al. (2002) late in the throwing
cycle is significant in the generation of ball speed.
Stodden et al. (2001) investigated aspects of trunk
and pelvic positioning in the horizontal plane during
pitching for a group of 19 elite level subjects (7 profes-
sional, 9 college, 3 high school). Each of the participants
displayed a variation of at least 1.8 m/sec (approximately
4.0 mph) in their trial of 10 maximal effort fastball
pitches averaging 35 ± 2 m·sec-1 (78.3 ± 4.5 mph). The
variables studied were pelvic orientation and upper torso
orientation (in the horizontal plane) at maximum knee
height; stride foot contact; instant of maximal arm exter-
nal rotation; and at the instant of ball release. They also
considered pelvic and upper torso angular velocity (in the
horizontal plane) during the arm cocking and arm accel-
eration phases. This data was then analyzed using a mixed
model analysis including all 12 pelvis and trunk related
variables, of which 5 were found to be associated with
variations in velocity. Principal findings were that during
the higher velocity trials, subjects displayed a more
‘open’ pelvis and upper torso at the point of maximum
arm external rotation, and a more open pelvis at the point
of ball release. It was also shown that the higher velocity
throws were made with higher pelvic angular velocities
during the arm cocking phase and higher upper torso
angular velocities during the arm acceleration phase.
Whilst this work was limited to the horizontal plane,
Matsuo et al. (2001) in their investigation of pitchers
throwing more than one standard deviation above and
below the mean velocity of the group of 127 pitchers
considered variables in the horizontal and sagittal planes.
Matsuo et al. (2001) investigated maximum pelvis linear
velocity, maximum pelvis and upper trunk angular veloc-
ity (in the horizontal plane), trunk forward tilt angular
velocity, and forward tilt at the instant of ball release.
With the exception of linear pelvic velocity, these entire
trunk related variables were of higher magnitude in the
high velocity group. However, only forward trunk tilt at
the instant of ball release (36.7° ± 6.7° in contrast to 28.6°
± 11.1°) reached statistical significance.
In accordance with these findings, Escamilla et al.
(2002) in their investigation of a group of American and
Korean pitchers, showed the higher velocity American
group to have a higher pelvic angular velocity during arm
cocking (660 ± 60°/s vs. 610 ± 55°/s), and an increase in
forward trunk tilt at ball release (32 ± 8° vs. 26 ± 9°).
In a 2001 investigation into 9 pitchers separated
into low and high skill level by an experienced coach,
Murata (2001) looked at the amount of non-throwing
shoulder movement. Using a two camera, 200Hz analysis,
a marker was placed over the acromion process of the
non-throwing arm, and its three dimensional motion re-
corded from stride foot contact until ball release and nor-
malized as a function of body height. The skilled group of
four pitchers threw their fastballs at 38.22 ± 1.02 m·sec-1
in comparison to the less skilled group who threw at
35.96 ± 1.45 m·sec-1. The skilled group of throwers were
found to have a reduction in the amount of non-throwing
shoulder movement in all directions for both fastball and
curveball trials during the period from stride foot contact
until ball release. A reduction in the amount of x-axis
movement was strongly associated with an increase in
fastball velocity, and perceived skill level. These findings
concur with the observations of Feltner (1989) who sug-
Throwing mechanics, pathology, and performance
14
gested that the rotation around a relatively stationary non-
throwing shoulder would give rise to higher trunk rotation
torques and therefore higher throwing velocity.
Aguinaldo et al. (2003) in a preliminary investiga-
tion looked at the timing of pelvic and trunk rotation in a
group of 37 pitchers (5 professional, 11 collegiate, 12
high school, and 9 youth level). For the purposes of the
study, the pitch cycle was normalized to Stride Foot Con-
tact = 0%, and Ball Release = 100%. Professional pitchers
were found to begin their trunk rotation significantly later
in the pitch cycle (34% ± 5%) in comparison to the rest of
the groups. Differences were also seen in the peak internal
rotation torques seen, with the youth level pitchers dis-
playing the lowest values, followed by the professional
pitchers, then the high school pitchers, and highest of all
the college pitchers. It was speculated by the authors that
the youth level pitchers had the lowest internal rotation
torques given their relative skeletal immaturity, whilst the
college and high school pitchers were speculated to have
higher internal rotation torques to compensate for their
earlier onset of trunk rotation.
Shimada et al. (2000) using a two camera 200Hz
analysis complemented with two force platforms sam-
pling at 250Hz (one at the stance foot, and one under the
landing foot) investigated the contributions of the trunk
and lower limbs to pitched ball velocity. These workers
calculated joint torques, joint torque powers, and work
done by the torso, hip, knee, and ankle joints for 10 pitch-
ers. This group found no relation between work done by
the torso and hip joints and pitched ball velocity.
Watkins et al. (1989) in an EMG investigation of
the trunk muscle activity of 15 professional baseball
pitchers showed the activation patterns to be quite similar
across each of the individual trials, and have documented
the firing pattern of muscle activity for this group.
1.8. Deceleration
Once the ball has left contact with the throwing arm, no
further action by the pitcher can alter the ball’s course.
Any alteration in mechanics of follow-through therefore,
can only be directed toward the health of the pitcher. The
force required to decelerate the throwing arm is directly
proportional to the ball speed (Fleisig, 1994). An increase
duration of the follow-through phase will result in a re-
duction in the force required while maintaining the same
impulse (by virtue of an increase in the time that force is
applied) and is recommended by most pitching authori-
ties. Some of the force required to decelerate the rapidly
internally rotating shoulder may be provided by the poste-
rior inferior glenohumeral ligament. It has been suggested
that repeated traction to this structure results in an adap-
tive shortening and thickening which subsequently alters
the centering of the humeral head during the arm cocking
phase of throwing (Burkhart et al., 2003a). These authors
believe that this alteration is critical in the formation of
superior labral tears of the glenoid associated with under-
surface fraying of the postero-superior cuff (Burkhart et
al. 2003a). The ossification seen at the postero-inferior
glenoid originally described by Bennett could be ex-
plained in terms of maladaptation to the repeated tensile
overload in this region (Bennett, 1941), and may explain
its presence in 25% of asymptomatic pitchers in Connor’s
investigation (Connor et al., 2003).
To reduce the peak forces required in deceleration
of the throwing arm, attention can be paid to all aspects of
the kinetic link, not just the throwing arm. Tempering this
desire for an extended follow-through is the practical
matter of fielding a batted ball: if the pitcher has made
such an elaborate follow-through maneuver as to render
him unable to field a ball batted back in his general direc-
tion, then his effectiveness will be diminished and his
personal safety may be at risk.
2. Curveballs
In the only published investigation of ball spin, the stan-
dard fastball pitch has been described to impart an under-
spin on the ball at a rate of 29.9 revolutions per second;
whilst the curveball has a similar rotational velocity (26.6
revolutions per second) its direction is almost exactly
opposite to that of a fastball, causing an alteration in the
flight path of the ball such that the downward and side-
ways movement is exaggerated (Escamilla et al., 1998).
Coaches regularly relate the supposed increased
stresses associated with throwing curveballs, and recom-
mendations have been made to limit the throwing of
curveballs by skeletally immature athletes (Andrews et
al., 1999; Jobe and Nuber, 1986). Lyman investigated a
group of 476 pitchers aged 9 to 14 for a single season
(Lyman et al., 2002). This group questioned the partici-
pants regarding the total number of pitches thrown in
given games, and throughout the season; the kinds of
pitches thrown; and the presence of pain or discomfort
during or after play. They also performed a videotape
analysis of 240 of the pitchers prior to the season docu-
menting 24 parameters as ‘proper, insufficient, or exces-
sive.’ The study concluded that throwing curveballs and
sliders were associated with a higher risk of shoulder and
elbow pain respectively. The group was unable to associ-
ate any of the supposed incorrect pitching mechanics with
pain. The findings of this investigation need to be consid-
ered in light of the work of Olsen et al. (2006) who com-
pared 95 adolescent pitchers who had shoulder or elbow
surgery with a group of 45 adolescent baseball pitchers
who had not complained of any shoulder or elbow pain.
This work found no effect of either frequency of pitch
type, nor age at which certain pitch types were thrown to
be related to injury occurrence. Rather the greatest indica-
tors of injury incidence were pitching frequency, pitching
with pain, and pitching with fatigue (Olsen et al., 2006).
The spin imparted on the ball will depend on the
motion path taken by the hand and fingers, and the release
pattern of the fingers on the ball. Tarbell (1971) using a
film capture rate of 1500 frames per second examined one
fastball pitch and found that the thumb was the first digit
to leave the ball but was unable to elucidate whether the
index or middle fingers left next. Ketlinski (1971) exam-
ined one curveball pitch using a capture rate of 1000
frames per second and found a finger release pattern of
thumb followed by middle finger followed by index fin-
ger for the curveball pitch. Stevenson (1985) investigated
the finger release patterns of 9 collegiate baseball pitchers
for 103 fastballs and 88 curveballs. Using 1000 frames
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15
per second cinematographic analysis, these throwers were
found to have an average release velocity of 31.8 meters
per second for the fastball trials and 25.5 m·sec-1. for the
curveballs. Stevenson (1985) found the finger release
patterns to vary between and within pitchers. For all fast-
ball trials the thumb was found to leave the ball first in
97.1% of cases [at 6.18 msec prior to release (SEM: 0.37,
SD: 3.72)], followed by the middle and index fingers
which left almost simultaneously [at 0.28 (SEM: 0.06,
SD: 0.13 msec) and 0.52 (SEM: 0.13, SD: 1.20 msec prior
to release)]. During the curveball trial, only one pitcher of
the nine demonstrated the finger release pattern docu-
mented by Ketlinski (1971). Seventy-five percent of the
curveball pitches were thrown with a release pattern of
thumb-middle-index, whilst 25% were thrown with a
pattern of middle-thumb-index (Ketlinski 1971). The
curveball trials showed five of the 9 pitchers to reliably
have a release sequence of thumb, then middle, then index
fingers whilst the remaining four pitchers showed a pat-
tern of thumb and middle fingers off almost simultane-
ously then index finger. The group data for the curveball
trials was thumb released at 6.41 (SEM: 0.63, SD: 5.86
msec prior); Index finger at 0.02 (SEM: 0.05, SD: 0.11)
and middle finger 2.48 (SEM: 0.16, SD: 1.48)
Several groups of authors have investigated kine-
matic differences between the fastball and off speed
pitches. Elliot et al. (1986) were the first to investigate
this matter in their study of 6 national level Australian
pitchers using 2 cameras recording at 200 frames per
second and one at 300 frames per second. Whilst they
found that the fastball and curveball pitches were quite
similar in many respects, there were differences in stride
length, and forearm and wrist position at release. Specifi-
cally, in the curveball group, stride length was shown to
be slightly shorter (81.4 ± 6% compared with 82.3 ± 2.3%
of body height), and the curveball was associated with a
slightly more open lead foot position (8.4 cm compared
with 7.0 cm for the fastball). The most striking differ-
ences occurred just prior to release with the forearm
placed in more supination “such that the palm of the hand
almost faces the head” and the wrist was more flexed
(188° compared with 178° for the fastball.) Higher angu-
lar velocities for the wrist joint (332.3 °/sec compared
with 177.6 °/sec) and elbow joint (986 °/sec and 969
°/sec) were seen just prior to release with the curveball
indicating higher contributions of the wrist and hand to
the total velocity (31.8% for the curveball compared with
26.5% for the fastball). In 1993, Sakurai et al. (1993)
published their findings of a kinematic analysis of 6 Japa-
nese University pitchers throwing fastball and curveball
pitches. In this analysis small sticks were placed on the
wrist and hand and two cameras capturing data at 200
frames per second were used. This group found no dif-
ferences between the pitch types for shoulder and elbow
temporal sequences, but confirmed the findings of Elliot
et al. (1986) of increased radioulnar supination and dorsi-
flexion immediately prior to release.
This kinematic data was furthered with the work of
Escamilla et al. (1998) who investigated 16 college pitch-
ers throwing fastball, curveball, changeup, and slider
pitches. For this group, Escamilla et al. (1998) examined
26 kinematic variables across each of the pitch types. In
summary, the greatest differences were shown between
the fastball and changeup groups (with 14 of the 26 pa-
rameters showing significant differences) whilst the fast-
ball and slider groups showed the least differences (only 2
of 26 parameters). In contrast to the findings of Elliot etal.
(1986) this group found that during the arm cocking and
acceleration phases, the peak values for arm internal rota-
tion and elbow extension (along with trunk rotation) were
higher in the fastball and slider groups, lower in the
curveball, and lowest in the changeup group. At ball re-
lease, the curveball group was found to have the greatest
trunk lateral tilt of the pitch types.
Using accelerometers mounted to the forearm, Sai-
tou et al. (2000) examined the pronation/supination
movements of 5 college baseball pitchers confirming the
finding of the movement of pronation before and after
release in both curveball and fastball pitch types, with no
difference in peak angular velocity between pitch types,
although the peak velocity occurred closer to ball release
in the fastball.
Escamilla et al. (1998) have published the only ki-
netic data regarding differences between throwing fast-
balls and off-speed pitches. In their preliminary examina-
tion of 18 healthy college pitchers who threw fastballs,
changeups, curveballs, and sliders, they found statistically
significant increases in medial elbow force and elbow
varus torque when throwing curveballs. Conversely, the
changeup consistently showed the lowest segmental angu-
lar speeds and forces at the shoulder and elbow.
It had been suggested that the increase in medial
elbow problems with throwing curveballs was due to an
increase in the activity of the flexor pronator muscle mass
which takes a common origin at the medial epicondyle
(Atwater, 1979). This would appear unlikely given the
findings of Sisto et al. (1987) who investigated eight
collegiate pitchers with dynamic EMG of muscles of the
forearm whilst throwing fastball and curveball pitches. No
statistically significant differences were found for any
muscle groups for either pitch, with only slight increases
in activity of the Extensor Carpi Radialis Longus and
Brevis muscles during late cocking, acceleration, and
follow-through of the curve ball as compared to the fast
ball. Saitou et al. (2001) have revisited this notion and
found an increase of activity in the Pronator Teres muscle
whilst throwing a fastball in comparison to the curveball.
Interestingly, Pomianowski et al. (2001) in a cadaveric
investigation of failure loads of the ulnar collateral liga-
ment have shown that the elbow’s resistance to valgus
stress is rotation dependent, with increasing stiffness in
supination as opposed to pronation. Given the finding that
curveballs appear to be associated with release in a posi-
tion of increased forearm supination (Elliott et al., 1986;
Saitou et al., 2000; Sakurai et al., 1993) and that the high-
est valgus torques are present at the late cocking phase of
throwing, it would seem reasonable to suggest that throw-
ers endeavor to maintain a supinated forearm throughout
the early portion of the acceleration phase in an effort to
minimize the any potentially deleterious effects of valgus
overload stress at the medial elbow.
3. Teaching throwing mechanics
Throwing mechanics, pathology, and performance
16
Long-standing motor patterns can be difficult to alter. If
aberrant mechanics can be related to pathologic forces
and diminished performance, then it stands to reason that
more correct mechanics would be best taught early in a
thrower’s career. In the only paper documenting kinemat-
ics kinetics across varying ages, Fleisig investigated 17
kinematic and 8 kinetic parameters in a group of 231
pitchers (Fleisig et al., 1999). The group was subdivided
into 4 groups based on their age: 23 youth (age range: 10-
15 years); 33 high school (15-20 years); 115 college (17-
23 years); and 60 professional (20-29 years) level ath-
letes. This investigation showed each of the 4 velocity
parameters to vary across the groups, but differences in
only one of the positional parameters and no temporal
differences were displayed in the 6 items examined. Each
of the 8 kinetic variables increased with increasing age
group which was thought to represent the increased force
generating potential of the increasingly skeletally mature
subjects. Since there were few differences in positional
and temporal parameters across this large sample of sub-
jects representing most aspects of throwing ages, it is
reasonable to suggest that teaching correct mechanics can
be performed from the earliest participation in the sport.
In light of the relatively high incidence of injury in
the throwing athlete in general (McFarland and Wasik,
1998) and the skeletally immature athlete in particular
(Gugenheim et al., 1976; Larson et al., 1976) it has been
recommended that younger athletes limit their exposure to
throwing (Olsen et al., 2006; Sabick et al., 2004). Rec-
ommendations have been made in terms of total numbers
of pitches to be made in any individual outing (Lyman et
al., 2001) and for the entire season (Lyman et al., 2002). It
has also been recommended that since increased forces at
the shoulder and elbow are shown during throwing the
curveball and slider that these pitches should be discour-
aged until skeletal maturity and discarded in preference
for the fastball and circle change-up (Andrews et al.,
1999; Nelson, 2001).
By and large, throwing mechanics is taught by
pitching coaches whose principal tool is visual inspection
of ‘live’ performance, and increasingly videotaped analy-
sis of recent performance. It is pertinent to note that the
reliability of such analysis has been called into question in
the only investigation performed thus far. Fleisig et al.
(1999) developed a checklist of key throwing parameters
which was subsequently investigated by Nicholls et al.
(2003) in a study of twenty male youth pitchers (mean age
of 12.86 ± 1.29 years). This group were filmed outdoors
using a standard video camera placed at three positions to
best view each of the identified parameters, and then
scored on a checklist to rate if the items were deemed to
be ‘proper’ (acceptable), ‘excessive’ (high), or inadequate
(low) by two raters. The results of this were then com-
pared with a 6 camera, 240Hz laboratory investigation
into the same 20 pitchers to estimate the agreement be-
tween the two methods. Unfortunately, only four of the 24
kinematic variables showed agreement between the two
methods, and inter-rater reliability showed agreement on
only 33% of the variables viewed by the two raters. Ac-
cordingly, standard videotape analysis can only be viewed
(at best) as preliminary data in the investigation of throw-
ing mechanics, and at worst routinely misleading.
Nicholls et al. (2003) identified poor lighting and subse-
quently large shutter speeds (entailing a large degree of
motion blur) as a potential confounding factor in their
analysis (Nicholls, et al. 2003).
Figure 13. Image taken from Burkhart, S.S., Morgan C.D.
and Kibler, W.B. The disabled throwing shoulder: spectrum
of pathology Part III: The SICK scapula, scapular dyskine-
sis, the kinetic chain, and rehabilitation. Arthroscopy 19(6),
649, 2003. The original caption to the image reads: 'Ideal
mechanics involve abduction in the plane of the scapula (A,
dotted line) with the elbow high enough to keep the upper
arm at or above the horizontal plane. (B) With a "dropped
elbow" (solid line), the upper arm hyperangulates posterior
to the plane of the scapula. (C) This pitcher has excellent
mechanics, with the arm abducted in the plane of the scap-
ula and positioned above the horizontal plane.' Note that this
image shows an overhand thrower at or close to maximum
external rotation of the arm.
Occasionally scholarly works will discuss the per-
ceived throwing mechanics of an individual, inferring a
potential for injury. For example, the following two im-
ages are taken from the paper of Burkhart et al. (2003b)
where they state that the pitcher in the first image dis-
plays: ‘abduction in extension, with angulation of the arm
posterior to the plane of the scapula rather than in the
plane of the scapula. Note the “dropped elbow” in this
pitcher, causing the arm-body angle to drop below the
horizontal.’ Whilst the text accompanying the second
image claims: ‘Ideal mechanics involve abduction in the
plane of the scapula (A, dotted line) with the elbow high
enough to keep the upper arm at or above the horizontal
plane. (B) With a “dropped elbow” (solid line), the upper
Whiteley
17
arm hyperangulates posterior to the plane of the scapula.
(C) This pitcher has excellent mechanics, with the arm
abducted in the plane of the scapula and positioned above
the horizontal plane (Figure 13).’
Figure 14. Image taken from Burkhart, S.S., Morgan, C.D.
and Kibler, W.B. The disabled throwing shoulder: spectrum
of pathology Part III: The SICK scapula, scapular dyskine-
sis, the kinetic chain, and rehabilitation. Arthroscopy 19(6),
650, 2003. The original caption reads: 'This pitcher has
excellent mechanics, with the arm abducted in the plane of
the scapula and positioned above the horizontal plane. This
pitcher shows abduction in extension, with angulation of the
arm posterior to the plane of the scapula rather than in the
plane of the scapula. Note the "dropped elbow" in this
pitcher, causing the arm-body angle to drop below the hori-
zontal.' Note that this image shows a pitcher soon after
stride foot contact, and before arm cocking has been under-
taken to any great extent. Therefore it is not an unusual
finding to have a reduced amount of arm abduction, and an
increased amount of arm horizontal abduction at this point
in the throwing cycle.
It is interesting to note then that the first image
(Figure 13) is taken of a pitcher in the early phase of arm
cocking whilst the second image (Figure 14) is of a
pitcher close to release. As is evidenced from many inves-
tigations into throwing mechanics, the amount of arm
horizontal abduction, and arm abduction varies substan-
tially between these two points. One can only guess that
the assumed poor mechanics are related to the first
thrower’s more vertically oriented trunk position, and
therefore since his contralateral shoulder is higher, giving
the illusion of having his throwing arm abducted less.
Conclusion
While this review of the available literature regarding
pitching and throwing of baseballs and their relation to
performance and health has shown some diversity of
opinion in several areas, and some technical difficulties
still render some of the findings as preliminary, much can
be gleaned for the coach, athlete, and treating physician
from this work. In order to maximize performance and
maintain health, ongoing research is needed to further
refine these areas of investigation in particular to investi-
gate the interaction of varying more than one of the kine-
matic variables discussed.
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Key points
• Biomechanical analyses including kinematic and
kinetic analyses allow for estimation of pitching per-
formance and potential for injury.
• Some difficulties both theoretic and practical exist
for the implementation and interpretation of such
analyses.
• Commonly held opinions of baseball pitching au-
thorities are largely held to concur with biomechani-
cal analyses.
• Recommendations can be made regarding appropri-
ate pitching and throwing technique in light of these
investigations.
AUTHOR BIOGRAPHY
Rod WHITELEY
Employment
Sports Physiotherapist in private practice who is currently
undertaking a PhD by research in physiotherapy at the Univer-
sity of Sydney, Australia.
Degree
MSc
Research interest
Baseball stems from an ongoing involvement in all aspects of
the game.
E-mail: whiteley.rod@gmail.com
Rod Whiteley
16 Spoon Bay Road, Forresters Beach, NSW, Australia, 2260.
