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Kinematic Analysis of the Sidearm Throw in Ultimate Frisbee: Motion of the Wrist
04/04/2009
Paul Taylor
Independent Project- Paul Taylor 0601273
1.0 Table of Contents
1.0 TABLE OF CONTENTS................................................................................................................................1
1. ABSTRACT.......................................................................................................................................................3
2. INTRODUCTION.............................................................................................................................................4
2.1 BACKGROUND.................................................................................................................................................................42.1.1 Aims............................................................................................................................................................................ 6
2.2 LITERATURE REVIEW....................................................................................................................................................62.2.1 Gyroscopic Effect................................................................................................................................................... 62.2.2 Aerodynamic Lift & Pressure........................................................................................................................... 72.2.3 Use of Reflective Markers.................................................................................................................................. 8
2.6 OBJECTIVES..................................................................................................................................................................10
3. METHOD........................................................................................................................................................10
3.1 SUBJECTS...................................................................................................................................................................... 103.2 EQUIPMENT, EXPERIMENTAL SET-UP & DESIGN..................................................................................................113.3 ANGLE CALCULATION & DEFINITIONS OF MEASURED VARIABLES......................................................................12
3.3.1 Equations............................................................................................................................................................... 123.4 SAFETY..........................................................................................................................................................................133.5 PROTOCOL....................................................................................................................................................................133.6 STATISTICAL ANALYSIS..............................................................................................................................................14
4.0 RESULTS......................................................................................................................................................15
4.1 RESULT FOR RELEASE PARAMETERS.......................................................................................................................154.2 SUBJECT THROWING MOTION AND FOLLOW THROUGH........................................................................................15
5.0 DISCUSSION...............................................................................................................................................19
5.1 COCKING AND UNWINDING PHASES.........................................................................................................................195.2 THROWING MOTION AND DISC RELEASE PARAMETERS........................................................................................205.3 FUTURE CONSIDERATIONS.........................................................................................................................................23
6.0 CONCLUSION..............................................................................................................................................23
ACKNOWLEDGEMENTS.................................................................................................................................24
7.0 REFERENCES..............................................................................................................................................25
8.0 APPENDICES..............................................................................................................................................27
APPENDIX 3 RAW DATA OUTPUTS...........................................................................................................28
APPENDIX 2 T-TEST RESULTS..........................................................................................................................................30APPENDIX 2 PAIRED SAMPLES T-TEST RESULTS..........................................................................................................31APPENDIX 2 PAIRED SAMPLES T-TEST RESULTS..........................................................................................................32APPENDIX 3 TRACE 1: PRONATION 3D ANGLES..........................................................................................................33APPENDIX 4 TRACE 2: PRONATION 3D ANGULAR VELOCITIES.................................................................................35APPENDIX 5 TRACE 3: DISC LINEAR VELOCITIES.........................................................................................................37APPENDIX 6 TRACE 4: SPIN RATE..................................................................................................................................39APPENDIX 7 TRACE 5: HAND-TO-WRIST 3D ANGLE...................................................................................................41APPENDIX 8 TRACE 6: HAND-TO-WRIST 3D ANGULAR VELOCITIES........................................................................43
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Kinematic Analysis of the Sidearm Throw in Ultimate Frisbee: Motion
of the Wrist
1. Abstract
The purpose of this study was to investigate the joint kinematics during the sidearm
throwing motion. To date, little research has been conducted on the release parameters of
the sidearm throw in Ultimate Frisbee. A kinematic three-dimensional high-speed analysis
was conducted, measuring the joint angles of the forearm and wrist from the moment the
pivoting foot came into contact with the ground until post release of the sports disc. A single
male participant (Age; 20) case study was selected; with a minimum of three years of high
level competitive Ultimate experience including participation in 3 National Student
competitions. The subject was instructed to throw 35 slow (normal) and 35 fast (maximal
effort) sidearm throws. Using two gen-locked Basler high-speed cameras at 200 Hz, released
parameters were measured using reflective markers positioned at three points along the
forearm; Medial Epicondyle of the Humerus, Styloid Process of Radius, Base of Metacarpals
I-V. Mean (± standard deviation) wrist angles were found to be significantly (p<0.05) greater
for fast trials (21.030 ± 2.937) than for slow trials (16.181 ± 2.847), however no significant
difference was identified for spin rate between the two trials (fast: 6.650 ± 3.483, slow:
4.689 ± 1.730). A significant decrease in pronation angle and pronation angular velocity
during the fast trials may be an important consideration suggesting that the initiation of
throwing motion may occur from the shoulder The three-dimensional approach chosen for
this study can provide valuable information on the kinematics of the sidearm throw for
coaches and athletes, enabling training regimes and throwing techniques to be perfected.
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2. Introduction
2.1 Background
Originally introduced during the Ancient Greek Olympics, the popularity of using a flying disc
within sport has significantly increased during the last half century (Rhode, 2000). The
technologies introduced during the Second World War led to the development of novel
manufacturing procedures such as moulding. As a result, a prototype of the modern sports
disc was created, with the Wham-O Corporation, California, trade marking the new
invention as a ‘Frisbee’ based on the original ‘Frisbie Pie Tin’ (Rhode, 2000).
At the present time, there are more Frisbees sold each year than the combined number of
retailed baseballs, basketballs and footballs (Wham-O.com). The increasing demand for
Frisbees has seen the introduction of many new exciting and competitive sports such as
Ultimate and Disc Golf (Morrison, 2005).
The limited offensive space in which to receive a throw therefore enhances the need for
precision of passing required in Ultimate. This means that particular emphasis is placed on
fine motor movements, all performed at very high speed, during disc release. Ultimate is
primarily an invasion sport with the major emphasis placed on the ability of throwing. On a
playing field 100 m long and 37 m wide, Ultimate is a dynamic, non-contact, team sport with
similarities to netball, American football and basketball. The final 18 m of each end of the
playing field are end zones, with a goal being scored when a team manages to successfully
pass the disc to a team member located in the end zone that is being attacked. With no
players able to run with the disc, successive passing is the only means to move the disc up
field, whilst preventing the Frisbee from hitting the ground or being intercepted. What
makes the sport of Ultimate Frisbee unique is the lack of a referee, allowing the sport to be
based around the concept of the spirit of the game (Sasakawa & Sakurai, 2008)
An important variable when focusing on the mechanics of flight and in particular sports
focusing on throwing is the release parameters associated with each individual sport and the
athletes. As determined by Gemer, 1990; Lanka, 2000, to produce a throw in shot put at a
competitive standard, the distance achieved will be defined by the direction in which the
force is applied to the shot. Therefore ultimately the release velocity, angle of release and
the height of release will determine the achieved distance. However where the release
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velocity and release angle have to optimised, release height is not a significant variable
within Ultimate. Release height in nearly all throwing sports is very influential to the throw
outcome. In contrast, invasion sports such as American football and Ultimate are not
influenced by genetic differences such as height and mass of a performer when determining
throwing motions. The correct technique during build up and release of the sports disc
remains the same for all competitors although individuals may adapt the general technique.
Strudarus (2003) identified a variety of adapted throws used by players during a competitive
match including, the backhand throw, sidearm throw, hammer throw, scoober and blade.
Sasakawa & Sakurai (2008) additionally identified that backhand and forehand (fig 1.) as the
most frequently used throwing motions.
The Throwing action required in Ultimate has been recognised as the most important skill,
with players requiring sufficient ability to throw a variety of passes quickly and more
importantly with accuracy. Due to the limited offensive playing space available during a
match, the diversity of short passes and the occasional long pass (to accumulate points
efficiently) results in players requiring sufficient practice of both short and long throws in
training (Sasakawa & Sakurai, 2008).
Figure 1. Forehand Throwing motion (as cited in Sasakawa & Sakurai, 2008)
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2.1.1 Aims
The purpose of this study was to develop a further understanding of the forearm joint
kinetics building upon the three-dimensional analysis completed by Sasakawa & Sakurai
(2008). The variables to be identified throughout the forehand throwing motion were;
maximum and minimum values for the angle of pronation, pronation angular velocities, spin
rate, disc linear velocities, wrist angles & wrist angular velocities. In addition, the
identification of release parameters and attributes that occur between slow and fast release
throws would provide future coaches and both novice and elite players with an innovative
knowledge about forehand release mechanics.
2.2 Literature Review
Upper limb and hand movements have been reviewed, in general, as complex (Murgia,
2005). The wrist has been defined as containing two degrees of freedom (DOF): radial/ ulna
deviation and flexion/ extension (Metcalf, Notley, Chappell, Burridge &Yule, 2008).
Literature has previously tried to identify the movement of the wrist; Miyata, Kouchi,
Kurihara & Mochimaru (2004). Developing a computational model, the generation of joint
angles of the thumb, fingers, hand and wrist were produced using single markers per joint.
In addition, Small, Bryant, Dwosh, Griffiths, Pichora & Zee (1996) fabricated a surface marker
model of the wrist using six markers. The study was able to conclude that methods for
determining movement are difficult to improve in comparison to surface measurements.
From the literature, it can therefore be suggested that there is no potential method of
standardising the application of surface markers to the upper limb and forearm. As
identified in the study by Metcalf et al. (2008), measuring a wide surface area of the
forearm/ upper limb increases the potential for markers to become occluded and
indistinguishable.
2.2.1 Gyroscopic Effect
When considering the flight of the sports disc, there are two main physical considerations
determining the performance of Frisbee flight, aerodynamic lift and gyroscopic inertia
(Morrison, 2005). The aerodynamic lift is proved by the airfoil design, essentially the same
as an aircraft’s wing of smaller proportions, with the gyroscope acting as a stabilizer during
flight providing that angular velocity is occurring. Morrison (2005) identifies the origin and
importance of gyroscopic stability during the flight phase, concluding that rotation must
occur to allow the mechanics of flight to occur. Although typically literature has focused on
the fight mechanics of a backhand release, the main considerations during flight are the
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same. All the throws discussed in this study are of a right-handed forehand, resulting in an
anti-clockwise disc rotation during flight, when observed from an elevated position.
Assuming rotation is occurring, a lift force L is experienced perpendicular to the flat upper
surface and velocity v / drag forces D.
Figure 2. Frisbee in flight, off-
centre COP (Centre of Pressure) and COM (Centre of Mass) resulting in applied torque (as
cited in Morrison, 2005).
2.2.2 Aerodynamic Lift & Pressure
Lift, defined by Hummel (2003) is the perpendicular force to the flow of airstream that
opposes the downward force of gravity. It can be assumed therefore that for the disc to
travel horizontally in a balanced state, the lift force must be equal to gravity. As a disc
travels through air, a fluid, the curved shape of the Frisbee deflects the oncoming flow,
splitting the airstream above and below the disc (Panton, 1995). This separation of air, in
addition to the cambered shape of the disc, results in the air flow above the disc travelling
faster than the airflow below, causing a region of low pressure above the Frisbee (Hummel,
2003). A proportional relationship exists between increases in velocity and reduction of fluid
pressure; Potts & Crowther (2002) have conducted complex studies measuring the changes
in pressure for discs in flight. Data collected in previous studies have assumed aerodynamic
patterns for a disc in flight, due to the difference in total velocities at each side of the disc
when spinning. For example when a disc has been released from a forehand throw, due to
the rotation (anticlockwise) the motion measured on the left (posterior view) will oppose the
velocity of the disc, whereas the right will rotate in the same vector as the direction of the
disc producing a greater total velocity. Previously, literature has failed to realise that when
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assuming lift will be reduced on the opposing edge, causing an incline or roll during flight,
data repeatedly collected by Potts & Crowther (2002) significantly rejects this theory.
Due to the symmetrical design of the disc the COM will always be in the centre, however as
displayed in Fig 2. the COP can become off-centre typically as a result of the natural incline
of the front edge of the disc during flight (Hummel, 2003; Morrison, 2005).
Torque is created due to the slight lift which is experienced at the exposed edge of the disc;
when rotation does not occur, torque can cause the disc to flip upwards, effectively stopping
any controlled flight to continue (Morrison, 2005).
2.2.3 Use of Reflective Markers
Hummel & Hubbard (2001) conducted a study determining an appropriate musculoskeletal
model of the backhand throw. Conducting kinematic analysis using 180 Hz high speed
cameras, four subjects provided segment orientation data using reflective markers. Using
known orthogonal coordinates of individual body segments measures for joint torque,
motion phases and segment orientation were derived.
A more recent study by Sasakawa & Sakurai (2008) focused entirely on the forehand (right-
handed) release parameters during a maximal effort throw. Using elite and non-elite
subjects (N=17), the study tried to identify key differences in technique to provide valuable
coaching feedback for novice players. All the experiments were performed in an indoor
gymnasium, and analysis was conducted using two synchronized high-speed video cameras
set at 250 Hz and a shutter speed of 1/2000 s. Subjects performed from an elevated position
of 0.85 m allowing cameras to identify movement from beneath the disc flight, with the
additional use of reflective markers positioned on anatomical landmarks along the throwing
arm and cavity surface of the disc.
The elite subjects that were used in Sasakawa & Sakurai (2008) study were reported as 6 th
place National championship qualifiers and members of a varsity Ultimate team with
experience of 2-4 years. As the Ultimate team used in the study was based in Japan, little is
known about the actual level of ability, and on reflection may not be at an elite level in
comparison to European or American standards. In addition, little is stated about the non-
elite athletes’ backgrounds and considering the amount of playing time that is actually spent
throwing, maximal effort sidearm (forehand) throws are minimal. This therefore questions
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the study’s aim to provide coaching specific feedback for novice athletes, due to the lack of
realistic data.
A study conducted by Gordon & Dapena (2006) aimed to measure the contributions of body
segment motion in comparison to tennis racket head speed. The study conducted a 3D
analysis and specifically focussed on the use of surface markers and joint centres to calculate
accurate arm twist orientations. The researchers concluded from the research that the skin-
attached markers could not correctly identify and calculate upper arm twist orientation due
to unforeseen skin movement. In addition, joint centre calculations produced levels of error
exceeding 20%. Cappozzo, Catani, Leardini, Benedetti & Della Croce (1996); Reinschmidt,
van den Bogert, Nigg, Lundberg & Murphy (1997) acknowledged that motion of skin-
mounted markers do not follow accurately the motion of the underlying bones. This
inconsistency of accurate reflection of segment motion therefore compromises the potential
accuracy of computed outputs through digitisation.
Gordon & Dapena (2006) employed biomechanical measures of participants to calculate
elbow and wrist joint centres in contrast to the use of reflective markers. This could
therefore arguably allow for more accurate results after computational analysis. However,
the study only used a frame rate of 100 Hz; the authors did cite the need to minimise
potential errors in manual digitising and suggested that a cut off frequency of 20 Hz would
still allow high frequency detection as reasons for selecting a low frame rate.. An additional
limitation of the study was identified by the authors regarding mechanical synchronisation of
the cameras; the inability to exactly coordinate frames from different cameras may cause
error during digitising.
As identified by Grabiner (1989); Palastanga, Field & Soames (1998) and Gordon & Dapena
(2006) an important complication that may influence potential results, is the possibility of
the elbow ‘carrying angle’ effect (Fig 3). When the elbow reaches full extension, the
longitudinal axes of the upper arm and forearm may not be aligned. Potential angles of
displacement can reach 10-15° in males.
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Figure 3. Model of the arm with a carrying angle at the elbow (as cited in Gordon & Dapena,
2006).
At present, literature has only focussed on the effects of the ‘carrying angle’ and the impact
upon tennis serves. It becomes apparent that due to the unfamiliar motion during forehand
throws in Frisbee, future studies may need to consider the negative impacts that this effect
could place upon motion analysis.
2.6 Objectives
The present study specifically focuses on the correlation between disc linear velocities and
the distinction between wrist angle and spin rate between the fast and slow trials. It was
hypothesised that a direct correlation between wrist angle and spin rate would occur
between fast and slow trials. In addition, it was proposed that wrist angular velocity would
increase for the fast trials accounting for increases in disc linear velocity.
Null Hypothesis: No change would be found between fast and slow trials for spin rate, wrist
angle and wrist angular velocity.
3. Method
3.1 Subjects
A male single subject protocol was chosen for this study (age 20 years; body Mass. 74 kg;
height. 1.82 m; right-hand dominant). The subject completed both a consent and ethics
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form; he was selected due to the high level of previous competitive performance; this
specifically included participation in 3 National Student competitions, as a member of the
varsity ultimate Frisbee team based at the University of Chichester (England) and a minimum
of three years playing experience.
3.2 Equipment, Experimental Set-up & Design
Testing was completed in an indoor facility, at the University of Chichester, to eliminate the
effects of wind. All throwing trials were recorded using two gen-locked synchronised high-
speed cameras (Basler, A602fc-2, Germany) at 200 Hz. The cameras were positioned in front
of the subject, with a separation distance of 3.9m at angle of approximately 60°, and placed
on tripods at a height of 2m.
Figure 4-6 illustrate the design of the steel rods with reflective markers attached. Figures 5,
6 display the forearm marker positions (5, frontal view; 6, posterior view)
The reflective markers were securely attached to steel rods, positioned at three points along
the forearm: Medial Epicondyle of the Humerus, Styloid Process of Radius, Base of
Metacarpals I-V. To maximise the visual clarity during filming, reflective markers were
attached to either a 20ml or 40ml steel rod, resulting in a maximum of five degrees of
unwanted movement. This increase in rod length provided the maximum number of frames
displaying the reflective markers, limiting the chances of cross-over or disappearance from
view during motion. The steel rods were fastened to the skin of the forearm using high
adhesive transpore tape, maintaining a rigid form and minimising potential movement
during motion, preventing errors during filming. It is important to consider that there was no
movement restrictions caused by the rod or tape placement. The total weight of the steel
rods and reflective markers was 20g.
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Figures 7, 8, 9; reflective markers and extension arm placement on forearm and disc.
The rods attached along the forearm were aligned orthogonal to each other, with the non-
cavity surface of the disc marked with three reflective markers at 120° to each other. A pre-
test was conducted to visually assess the disc performance prior and post attachment of the
reflective markers. It was reviewed from footage that flight was not compromised by the
additional weight of the markers.
3.3 Angle calculation & definitions of measured variables
The hand (ulna-flexion) angle was measured with respect to the wrist; I.e. the angle between
planes on the anatomical landmarks (W) and (H). Forearm pronation was digitally measured
using the rotational translation between the planes (H) & (E). Setting up a datum using the
virtual line between markers 7 & 8, the angle in a second position after 5 milliseconds
(corresponding to a shutter speed of 200 Hz) was calculated.
Figure 10. displays the set up and distribution of reflective markers (O: Disc Origin, W: wrist,
H: hand & E: Elbow) and the virtual midpoints.
3.3.1 Equations
Spin Rate = 200 θ degrees/second (Figure 2.7)
θ = Sin x / H
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A
A
B Bx
C
C
θ
Independent Project- Paul Taylor 0601273
Pronation angular velocity and hand angular velocity were obtained using digitisation linear
transformation (DLT) of the 3D coordinates of anatomical landmarks (Figure 10).
Figure 11. displays the linear transformation of the disc and calculation of spin rate.
Disc linear velocity was calculated from knowledge of the distance moved with respect to
markers on the arm and change in time.
3.4 Safety
Due to the concern over equipment safety and for the prevention of impacts received from
high velocity discs, it was essential to use safety netting. All loose connecting wires were
situated away from all testing areas, with mats on all flooring providing no potential risk of
the subject tripping over exposed wires or debris. The position of the equipment was
situated away from the line of flight of the sports discs, additionally minimising risks of
impact. The high velocities throughout the movement phases resulted in all equipment such
as reflective markers that had been connected to the subject, being thoroughly checked to
ensure no possible breakdown would occur. The subject was correctly advised to wear
sports specific clothing and footwear.
3.5 Protocol
A SAQ warm-up, consisting of multiple throwing related movements and 20 trial throws was
completed prior to testing and consent provided. Both camera positions and pre-test
footage were analysed for quality and an 18-point calibration system was selected.
The subject was instructed to throw 35 slow (normal) and 35 fast (maximal effort) release
forehand throws using a 175 g, UKUA approved disc (Discraft Ultrastar, Michigan), without a
run-up. A reference plate was provided on the floor for the subject to target foot placement.
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A direct linear transformation (DLT) methodology was used, as developed by Abdel-Aziz &
Karara (1971). Three-dimensional coordinates of landmarks obtained from all video footage
were computed.
Digitising of all reflective markers (including disc) were completed for both camera angles.
Due to image clarity, an optimum 15 trials were digitised for both the normal and maximal
effort throws (Total Number = 30 trials). All 30 trials were initially cropped using an anchor
event: ground contact of the unplanted foot, during the pivoting motion, from an initial
standing position.
Figure 12. displays the experimental set-up.
All digitizing was initiated using automatic tracking, however due to markers becoming
occluded, manual digitizing had to be completed for specific frames. Manual digitizing, using
a graphics interface, was also additionally conducted due to gross digitising errors occurring
during automatic tracking. A single anchor point (disc release) was used when processing the
output data;
The mean square error for digital reconstruction was set at 0.5 cm, 0.5 cm and 0.7 cm for the
x, y and z directions respectfully.
3.6 Statistical Analysis
Paired samples t-tests were conducted to measure the differences in joint translations and
disc flight between fast and slow trials using windows SPSS version 16. Statistical significance
was set at P<0.05.
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4.0 Results
4.1 Result for Release Parameters
To explore the discrepancies between the fast and slow trials for all of the measured
variables during the sidearm release in Ultimate Frisbee, paired samples t-tests were
conducted.
Mean values (± standard deviations) for all measured release parameters are provided in
table 1. A significant difference (p< 0.05) between the fast and slow trials was recorded for
disc linear velocity which indicates a valid distinction for testing. For the seven parameters
investigated, significant differences were recorded within maximum pronation angles,
pronation angular velocity and wrist angle. No significant difference was recorded for
minimum pronation angle and wrist angular velocity however; mean values for spin rate
suggest a possible difference although no significance was observed.
Table 1. Results for release parameters
Fast Slow P-Value
Minimum Pronation Angle (°)
Maximum Pronation Angle (°)
Pronation Angular Velocity (° ¹)s̄�
Disc linear Velocity (m ¹)s̄�
Spin Rate (rps)
0.466 ± 0.712
30.460 ± 14.860
250.706 ± 150.132
12.701 ± 1.221
6.650 ± 3.483
2.788 ± 5.681
52.470 ± 21.673
459.680± 206.200
10.323 ± 0.768
4.689 ± 1.730
P=0.180
P=0.002
P=0.025
P<0.0005
P=0.220
Wrist Angle (°) 21.030 ± 2.937 16.181 ± 2.847 P=0.010
Wrist Angular Velocity (° ¹)s̄� 391. 091 ± 263.498 398. 861 ± 161.546 P=0.951
4.2 Subject throwing motion and follow through
Figures 13-18 show the changes in release parameter traces throughout the throwing
motion. Although significant differences were recorded between fast and slow trials, in
general the motions were similar. Digital analysis was initiated from the marked event
following ground contact with the pivoting foot, furthermore the forearm was observed at
an angle of flexion roughly ≥90°.
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A significant difference in maximum pronation angle was observed pre-release. However,
figure 13. clearly displays a symmetrical pattern between the fast and slow trials with a
steady increase in supination peaking approximately 0.09s (slow) and 0.015s (fast) before
release. This therefore indicates that there is an apparent cocking and unwinding phase
figure 20. (phase’s 1-3). It can be observed that supination is occurring throughout the whole
motion but the transition from maximum, prior to release and the immediate increase in
forearm pronation during release can be identified as a major contributor to disc projection.
In contrast to increased measures of pronation angle for the fast trials, statistics reported a
significant difference for pronation angular velocity (forearm swing motion); the slow trials
produced elevated levels of angular velocity in comparison to fast. Figure 14. displays the
transformation for pronation angular velocity, the most substantial difference between the
trials in addition to the increase in mean velocity (slow) is the length of time taken during
the unwinding phase. Figure 14. visibly demonstrates that although the slow trials reported
an overall increase in mean angular velocity, the unwinding phase for slow trials
approximately lasts only 0.03s in contrast to 0.12s for fast trials.
Figure 13. displays fast (red) and slow (blue) transformation of pronation angle (°).
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Figure 14. displays fast (red) and slow (blue) transformation in pronation angular velocity
(° ¹).s̄�
Figure 15. displays fast (red) and slow (blue) transformation in disc linear velocity (m ¹).s̄�
Figure 16. displays fast (red) and slow (blue) spin rates (° ¹).s̄�
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Figure 17. displays fast (red) and slow (blue) transformations in wrist angle (°).
Figure 18. displays fast (red) and slow (blue) transformations in wrist angular velocity (° ¹).s̄�
Spin rate was reported as displaying no significant difference therefore, accepting the Null
hypothesis. It is however, important to consider the mean values for the fast and slow trials
and the range of standard deviation (Figure 19).
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1 20
500
1000
1500
2000
2500
Figure 19. shows the mean (± standard deviations) of spin rate for the slow (1) & fast (2)
trials.
Due to large standard deviation within both the fast and slow trials a significant difference
could not be obtained, however the mean values indicate that a difference may have
occurred supporting the results of Sasakawa & Sakurai (2008).
5.0 Discussion
5.1 Cocking and unwinding phases
It was identified that at time of foot contact with the ground, the forearm was initially in a
supinated position with the palm facing anteriorly. The forearm was flexed at roughly 90°
with the wrist additionally in flexion and adducted approximately 14°. Due to the chosen
grip the subject’s fingers were both in a state of abduction between third and fourth
metacarpal and adduction between the second and third metacarpal/ fourth and fifth. This
positioning of the fingers allows the disc to pitch posteriorly, resulting in the frontal edge of
the disc being lifted. During the cocking phase (Figure 20), supination of the forearm was
increased in both slow and fast trials to an optimum point approximately 0.09s (slow) and
0.015s (fast) before release. Palmar flexion of the hand to a supine position occurs at the
moment of peaked supination, with the elbow remaining in flexion. More importantly, at the
peak moment of supination, due to palmar flexion and increased hand angle the disc was
observed as being parallel to the midline of the forearm. This may be a significant moment
in the build up to release of the disc, due to the disc angle of attack becoming parallel to the
plane of motion.
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5.2 Throwing motion and disc release parameters
Sasakawa & Sakurai (2008) identified an important trend for the angle of attack between
skilled and unskilled performers. They reported that for the skilled performers the angle of
attack was almost 0°, resulting in the disc being accelerated more smoothly during and post-
release due to minimal levels of air resistance. It was additionally identified that this allowed
skilled performers to increase throwing distance despite similar initial velocities. The present
study also supports the notion of disc release occurring parallel to the plane of movement
(Figure 20). Linear velocities were noted to vary from the study conducted by Sasakawa &
Sakurai (2008) who recorded initial linear velocities of 21.7 ± 1.7 (skilled); 20.7 ± 2.5
(unskilled) in contrast to 12.701 ± 1.221 for fast trials within the current study. The apparent
large variation in linear velocities cannot be identified, it is however to note that the
participants in study by Sasakawa & Sakurai (2008) were required to throw the disc as far as
possible.
Figure 20. displays the key motion phase’s: 1. (Foot contact) 2. (Cocking phase) 3.
(Unwinding phase) 4. (Release) 5-8 (follow through).
During the unwinding phase to the moment of release, pronation occurs with slow trials
displaying a faster transition time (Appendix 5) from maximal supination to minimum. This is
reflected by slow trials producing increased rates of pronation angular velocity. This would
suggest that for resultant disc linear velocities to be significantly greater for fast trials, the
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force production must have an additional source, other than pronation angle & angular
velocity.
Sasakawa & Sakurai (2008) reported small ranges of pronation angles for skilled throwers
and in addition, identified that disc spin rate was unlikely to have been produced directly
from a pronation motion of the forearm. However, indirectly it was reported that pronation
just prior to release enabled a more effective range of plantar flexion motion. This increased
plantar flexion was believed to provide greater spin rate to the disc. The current study
further identified an increase in pronation just prior to release and in fast trials identified a
significant increase in plantar flexion (hand angle), supporting the findings of Sasakawa &
Sakurai (2008). It was however found that no significant difference was reported for spin
rate between fast and slow trials. As previously identified, it is important to recognise the
results (Figure 19) clearly display spin rate having an increased mean for fast trials, however
an increase in trials may have provided clarity. No significant difference was observed for
angular velocity of the hand in relation to the wrist (plantar flexion motion) between trials.
This therefore, accepted the Null hypothesis, suggesting that disc linear velocity was not a
resultant of plantar flexion.
The series of forearm motions just prior to disc release were identified as an increase in
pronation from a supinated position, wrist extension and ulnar flexion from a radial position.
The elbow was in a motion of extension from an initial flexed position. Stancil (1975), Danna
& Poynter (1979) describe the release motion or ‘snap’ in coaching manuals as a sequential
motion consisting of supination of the forearm and ulnar deviation of the wrist. Although
this is supported by the results of the current study, it is important to recognise that positive
pronation does not occur; simply supination is decreased by a pronation motion. At the
point of release supination is reduced but still evident. Sasakawa & Sakurai (2008)
additionally describe the ‘snap’ as the sequential motion consisting of supination of the
forearm and ulnar deviation of the wrist. This evidence suggests that the sequence of
motion comprised of palmer flexion and ulnar deviation after dorsi flexion and radial
deviation, respectively.
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From the results of this study there is a clear indication that development of forward
momentum needed to project the disc linearly, at any given velocity, must be initiated in
addition to the motion of the forearm and wrist. This is due to no significant difference being
identified between the hand angular velocity and pronation angular velocity variables.
Sakurai, Ikegami, Okamoto, Yabe & Toyoshima (1993) identified the following motion during
the acceleration phase of baseball pitching: rapid shoulder internal rotation, elbow
extension, ulnar flexion and pronation. This series of sequential motions strongly reflects
those acknowledged in the both the current study and in the findings of Sasakawa & Sakurai
(2008). Therefore, it can be proposed that the Ultimate Frisbee forehand throw strongly
resembles the overhand throw in baseball pitching. Additionally, Feltner & Dapena (1986)
documented the shoulder and elbow motions, 0.2s prior to release in baseball pitching using
a 3D analysis. They reported that internal rotation of the shoulder and extensions of the
elbow were important attributes to the success of pitching motions. A more recent study by
Dillman, Fleisig & Andrews (1993) also identified internal rotation of the shoulder, extension
of the elbow, pronation of the forearm & ulnar deviation of the wrist just prior to release
when focussing on joint kinematics of the forearm during baseball pitching. From literature
it can therefore be suggested that force production and shoulder motions are key to the
differences in disc linear velocities, with the additional use of the forearm and wrist to help
provide stability during unwinding and release phases.
In contrast, Aguinaldo, Buttermore & Chambers (2007) conducted a study focussing on the
shoulder joint torques within baseball pitching. In addition to using a three-dimensional
protocol using reflective markers, it was discussed that transfer of momentum would require
less contribution of distal body segments. Additionally, Putnam (1991; 1993) and
Bahamonde (2000; 2005) concluded that baseball pitching like other throwing activities uses
momentum sequentially initiated from larger body segments. These larger body segments
collectively with smaller distal segments contribute to overall force and velocity output of a
throw. However, although applicable and accounting for most throwing motions, it is
important to note that the forehand throw in ultimate does not directly follow this rule.
Sasakawa & Sakurai (2008) conclude that although a possible analogous relationship
between baseball pitching and sidearm throwing in ultimate may occur, marked differences
in shoulder abduction/ adduction and pronation/supination of the forearm were apparent.
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However, it was additionally suggested that this may have been as a resultant of the size and
shape of the projectile and grip required to throw.
5.3 Future considerations
In the current study a single subject protocol was used to test the methodology of 3-D
kinematics, although may not be universally applicable, relevant differences between
variables should be highlighted. A future direction may be to use a cohort of athletes,
including a variation in technical ability to help identify trends between release parameters
that maybe apparent. This in turn could assist coaches in identifying correct techniques or
additionally, comprising efficient exercises in practice to progress athletes on both a team
and individual level. Furthermore, it is important to identify the differences between
coaching manuals and previous literature when regarding release parameters. It is apparent
that little or no kinematic analysis has been achieved in an outdoor environment and given
the influences of external factors such as wind, as this may have a major impact on release
parameters. This study does however provide evidence that 3-D kinematics can be
administered as an effective tool for measuring disc release techniques.
Coaches and performers may be at the risk of stress injuries caused to the medial side of the
elbow due to large tensile forces produced by shoulder internal rotation torque
(Bahamonde, 2005). Elbow injury has previously been identified within tennis forehand
strokes (Bahamonde, 2005) and baseball pitching (Sakurai et al., 1993); due to the evidence
of an analogous relationship with the sidearm throwing motion in ultimate, future
deliberation may be required. Sakurai et al. (1993) furthermore concluded that multiple
baseball pitching is thought to increase the risk of elbow injury. Additionally, if the athlete
begins throwing at an early age, which is currently occurring in Ultimate as popularity and
recognition of the sports increases, there is a greater risk (Morrison, 2005).
6.0 Conclusion
The sidearm throw in Ultimate Frisbee was explored using 3D kinematic analysis of forearm
joint angles. The findings from this research build on and are corroborative with the previous
study by Sasakawa & Sakurai (2008). Increased hand angle at the point of release, with
respect to the wrist, was shown to be significantly greater for higher disc release rates.
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Furthermore, just prior to release the forearm and wrist motions displayed pronation from
an initial supinated position, palmar flexion, extension at the elbow and plantar flexion. Spin
rate was found not to display a significant difference between fast and slow disc release
rates; however errors during the digitising process may have masked subtle differences. The
three-dimensional approach chosen for this study can provide coaches and athletes with the
capability to gain a clearer understanding of the kinematics of the sidearm throwing motion.
It is however, important to acknowledge individual differences in technique could vary and
the study was only conducted with a limited resource.
Acknowledgements
I would like to dedicate this research project to my family; Andy, Trisha, Nicola, Hollie,
Jenny, Avalon & Rupert. I wish to thank James Nairn for his participation in the study and
the support from Jenny Feakins throughout.
I would also like to thank my project supervisor Neal Smith for his guidance, support and
interest throughout the study.
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7.0 References
Aguinaldo, A.L., Buttermore, J. & Chambers, H. (2007). Effects of upper trunk rotation on
shoulder joint torque among baseball pitchers of various levels. Journal of Applied
Biomechanics, 23, 42-51.
Bahamonde, R.E. (2000). Changes in angular momentum during the tennis serve. Journal of
Sports Science, 18, 579-92.
Bahamonde, R.E. (2005). Review of the biomechanical function of the elbow joint during
tennis strokes. International Journal of Sports Medicine, 6, 42-63.
Cappozzo, A., Catani, F., Leardini, A., Benedetti, M.G. & Della Croce, U. (1996). Position and
orientation in space of bones during movement: Experimental artefacts. Clinical
Biomechanics, 11, 90-100.
Danna, M. & Poytner, D. (1979). Frisbee handbook. Quick Fox Company: Santa Barbara.
Dillman, C.J., Fleisig, G.S. & Andrews, J.R. (1993). Biomechanics of pitching with emphasis
upon shoulder kinematics. Journal of Orthopedic and Sports Therapy, 18, 402-408.
Feltner, M, & Dapena, J. (1986). Dynamics of the shoulder and elbow joints of the throwing
arm during a baseball pitch. International Journal of Sports Biomechanics, 2, 235-
259.
Gemer, G. (1990). Overview of the shot put technique. New Studies in Athletic, 5, 31-34.
Gordon, B.J. & Dapena, J. (2006). Contributions of joint rotations to racquet speed in the
tennis serve. Journal of Sports Science, 24, 31-49.
Grabiner, M.D. (1989). The elbow and radioulnar joints. In Kinesiology and applied anatomy
(edited by P.J. Rasch), pp. 136-150. Philadelphia, PA: Lea & Febiger.
Hummel, S.A. (2003). Frisbee flight simulation and throw biomechanics. Rolla: University of
Missouri.
Hummel, S.A. & Hubbard, M. (2001). A musculoskeletal model for backhand Frisbee throws.
8th Int. Symposium on Computer Simulation in Biomechanics. Milan, Italy:
Politecnico di Milano.
Lanka, J. (2000). Shot putting. In Biomechanics in sport (edited by V. Zatsiorsky), pp. 435-457.
Blackwell Sciences Ltd.
Metcalf, C.D., Notley, S.V., Chappell, P.H., Burridge, J.H. & Yule, V.T. (2008). Validation and
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application of a computational model for wrist and hand movements using surface
markers. IEEE Transactions on Biomedical Engineering, 55, 1199-1210.
Miyata, N., Kouchi, M., Kurihara, T. & Mochimaru, M. (2004). Modelling of human hand link
structure from optical motion capture data. In Proc. Int. Conf. Intelligent Robots
Systems, pp. 2129-2135. Sendai, Japan.
Morrison, V.R. (2005). The physics of Frisbees. Journal of Classical Mechanics and Relativity
,8, 1-12.
Murgia, A. (2005). A gait analysis approach to the study of upper limb kinematics using
activities of daily living. Ph.D. dissertation: University of Reading, UK.
Palastanga, N., Field, D. & Soames, R. (1998). Anatomy and human movement. Oxford:
Butterworth Heinemann.
Panton, R.L. (1995). Incompressible flow. John Wiley and Sons: London, UK.
Potts, J.R. & Crowther, W.J. (2002). Disc-wing UAV: A feasibility study in aerodynamic
control. CEAS Aerospace Aerodynamics Research Conference: Cambridge, UK.
Putnam, C.A. (1991). A segment interaction analysis of proximal-to-distal sequential segment
motion patterns, Medicine and Science in Sports and Exercise, 23, 130-144.
Putnam, C.A. (1993). Sequential motions of body segments in striking and throwing skills:
descriptions and explanations. Journal of Biomechanics, 26, 125-135.
Reinschmidt, C., van de Bogert, A.J., Nigg, B.M., Lundberg, A. & Murphy, N. (1997). Effect of
skin movement on the analysis of skeletal knee motion during running. Journal of
Biomechanics, 30, 729-732.
Rhode, A. (2000). A computational study of flow around a rotating disc in flight. Melbourne:
Florida Institute of Technology.
Sasakawa, K. & Sakurai, S. (2008). Biomechanical analysis of the sidearm throwing motion for
distance of a flying disc: A comparison of skilled and unskilled ultimate players.
Sports Biomechanics, 7, 311-321.
Sakurai, S., Ikegami, Y., Okamoto, A., Yabe, K. & Toyoshima, S. (1993). A three-dimensional
cinematographic analysis of upper limb movement during fastball and curveball
baseball pitches. Journal of Applied Biomechanics, 9, 47-65.
Small, C.F., Bryant, J.T., Dwosh, I.L., Griffiths, P.M., Pichora, D.R. & Zee, B. (1996). Validation
of a 3D optoelectronic motion analysis system for the wrist joint. Clinical
Biomechanics, 11, 481-483.
Stancil, E.D.J. (1975). Frisbee. New York: Workman Publishing.
Studarus, J. (2003). Fundamentals of ultimate. Studarus: Goleta, CA.
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8.0 Appendices
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Appendix 3 Raw Data Outputs
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Appendix 1 Raw data
Appendix 2 t-test Results
Appendix 2 Paired samples t-test Results
Paired Samples Statistics
Mean N Std. Deviation Std. Error Mean
Pair 1 S_min_pro_ang_3Dangles 2.78838 13 5.680610 1.575518
F_min_pro_ang_3Dangles .46638 13 .711979 .197467
Pair 2 S_max_pro_ang_3Dangles 52.46769 13 21.672939 6.010992
F_max_pro_ang_3Dangles 30.45985 13 14.855554 4.120189
Pair 3 S_Pro_ang_3D_angular_vel 459.67860 10 206.166476 65.195564
F_Pro_ang_3D_angular_vel 250.70620 10 150.131704 47.475813
Pair 4 S_3Dlinear_vel_Rel_Vel 10.32338 13 .767563 .212884
F_3Dlinear_vel_Rel_Vel 12.70069 13 1.220553 .338520
Pair 5 S_3D_angluar_vel_Spin_angle 1688.18588 8 622.722780 220.165750
F_3D_angular_vel_Spin_angle 2392.98012 8 1253.748548 443.267050
Pair 6 S_htw_3D_angles 16.18083 12 2.846911 .821832
F_htw_3D_angles 21.02583 12 2.937475 .847976
Pair 7 S_htw_3D_angular_vel 398.86122 9 161.546380 53.848793
F_htw_3D_angular_vel 391.09067 9 263.497630 87.832543
Paired Samples Correlations
N Correlation Sig.
Pair 1 S_min_pro_ang_3Dangles &
F_min_pro_ang_3Dangles13 -.217 .476
Pair 2 S_max_pro_ang_3Dangles &
F_max_pro_ang_3Dangles13 .476 .100
Pair 3 S_Pro_ang_3D_angular_vel &
F_Pro_ang_3D_angular_vel10 .076 .834
Pair 4 S_3Dlinear_vel_Rel_Vel &
F_3Dlinear_vel_Rel_Vel13 .096 .756
Pair 5 S_3D_angluar_vel_Spin_angle &
F_3D_angular_vel_Spin_angle8 -.151 .721
Pair 6 S_htw_3D_angles & F_htw_3D_angles 12 -.719 .008
Pair 7 S_htw_3D_angular_vel &
F_htw_3D_angular_vel9 -.477 .194
Appendix 2 Paired samples t-test Results
Mean Std. Deviation
Std. Error
Mean
95% Confidence Interval of
the Difference
t df
Sig. (2-
tailed)Lower Upper
P
ai
S_min_pro_ang_3Dangles -
F_min_pro_ang_3Dangles2.322000 5.876614 1.629879 -1.229202 5.873202 1.425 12 .180
P
a
S_max_pro_ang_3Dangles -
F_max_pro_ang_3Dangles22.007846 19.585509 5.432043 10.172442 33.843251 4.051 12 .002
P
air
S_Pro_ang_3D_angular_vel -
F_Pro_ang_3D_angular_vel208.972400 245.615687 77.670500 33.269522 384.675278 2.690 9 .025
P
air
S_3Dlinear_vel_Rel_Vel -
F_3Dlinear_vel_Rel_Vel-2.377308 1.378322 .382278 -3.210220 -1.544396 -6.219 12 .000
P
air
S_3D_angluar_vel_Spin_angle -
F_3D_angular_vel_Spin_angle-704.794250 1481.707576 523.862737 1943.532783 533.944283 -1.345 7 .220
P
air
S_htw_3D_angles - F_htw_3D_angles-4.845000 5.362584 1.548045 -8.252223 -1.437777 -3.130 11 .010
P S_htw_3D_angular_vel - 7.770556 368.959485 122.986495 -275.836811 291.377922 .063 8 .951
Appendix 3 Trace 1: Pronation 3D angles
Appendix 3 Trace 1: pronation 3D angles (°) (fast = red; slow = blue)
Appendix 4 Trace 2: Pronation 3D angular velocities
Appendix 4 Trace 2: pronation 3D angular velocities (° ¹) (fast = red; slow = blue)s̄�
Appendix 5 Trace 3: Disc linear velocities
Appendix 5 Trace 3: Disc linear velocities (m ¹) (fast = red; slow = blue)s̄�
Appendix 6 Trace 4: Spin Rate
Appendix 6 Trace 4: Spin Rate (rp ¹) (fast = red; slow = blue)s̄�
Appendix 7 Trace 5: Hand-to-wrist 3D angle
Appendix 7 Trace 5: Hand-to-wrist 3D angles (°) (fast = red; slow = blue)
Appendix 8 Trace 6: Hand-to-wrist 3D angular velocities
Appendix 8 Trace 6: Hand-to-wrist 3D angular velocities (° ¹) (fast = red; slow = blue)s̄�