kinematic analysis of the sidearm throw in ultimate frisbee: motion of the wrist

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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


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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1

5

2

876

Releases3


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.

22 | P a g e


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.

23 | P a g e


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.

24 | P a g e


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


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


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


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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�

kinematic analysis of the sidearm throw in ultimate frisbee: motion of the wrist

Documents

release parameters

sidearm throw

ultimate frisbee

independent

paul taylor

test results

motion

forearm