biomechanics: an integral part of sport science and sport medicine

Biomechanics: An Integral Part of Sport Science and Sport Medicine

Bruce Elliott

The Department of Human Movement ancl Exercise Science, The University of Western Australia

Elliott, B. (1999). Biomechanics: An integral part of sport science and sport medicine. Journal of Science and Medicine in Sport 2 (4): 299-310.

Biomechanics is one of the disciplines in the field of Human Movement and Exercise Science and it can be divided into three broad categories from a research perspective. Clinical biomechanics involves research in the areas of gait, neuromuscular control, tissue mechanics, and movement evaluation du~ng rehabilitation from either injury or disease. Occupational biomechanics typically involves research in the areas of ergonomics and human growth or morphology as they influence movement. While these two categories will briefly be discussed, the prhmary aim of this paper is to show the role of biomechanics in sports science and sports medicine.

Research in sports biomechanics may take the form of describing movement from a performance enhancement (such as matching of impulse curves in rowing) or injury reduction perspective (such as diving in swimming or the assessment of knee joint loading during downhill walking). However, the strength of sports biomechanics research is the ability to establish an understanding of causal mechanisms for selected movements (such as the role of internal rotation of the upper arm in hitting or striking, and the influence of elastic energy and muscle pre-stretch in stretch-shorten-cycle actions). The growth of modelling and computer simulation has further enhanced the potential use of sports biomechanics research (such as quantification of knee joint ligament forces from a dynamic model and optimising gymnastics performance through simulation of in-flight movements). Biomechanics research may also play an integral role in reducing the incidence and severity of sporting injuries (such as identification of the causes of back injuries in cricket, and the causes of knee joint injuries in sport}.

In the following discussion no attempt will be made to reference all papers published in each of these areas because of the enormity of the task. Published and current work from the biomechanics laboratory at the Department of Human Movement and Exercise Science at The University of Western Australia will generally be used to illustrate the scope of biomechanics research within that institution.

Clinical Biome©hanics Clinical b iomechanics can be categorised into four broad areas, which are p r ima r i l y c o n c e r n e d with improv ing efficiency by prov id ing a be t t e r u n d e r s t a n d i n g of the m e c h a n i s m s responsible for everyday activities.

1. Gait Gait laboratories are usua l ly found in hospital a nd univers i ty set t ings. Most gait laboratories involve a broad range of b iomechanica l a s se s smen t s r ang ing from the quant i f icat ion of k n e e jo in t loading dur ing r u n n i n g and side-stepping, to an

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BiornechanJcs: An Integral Part of Sport Science...

analysis of the walking mechanics of children with cerebral palsy. One study from our laboratory looked at knee joint loading during level and downhill (19 ° grade) walking (Kuster, Sakurai & Wood, 1995). While the general shape and temporal parameters of the ground reaction force (GRF) curves were similar for downhill and level walking, the magnitude of various maxima were different in tha t peak GRFz approximated 1.1 BW for level and 1.8 BW for downhill walking. However, the most important findings were that the bone-on-bone compressive forces and the tibio-femoral shear forces were also larger for downhill walking. This has serious implications for the elderly or for people with anterior cruciate ligament (ACL) deficiency or injured knees.

Another study investigated loading on the knee joint during volitional and unanticipated side-stepping and cross-over sporting manoeuvres (Figure 1). Greater moments at the knee joint were recorded in the unanticipated tasks. "SpLu" of the moment" changes in direction, during a game situation therefore place knee ligamentous structures at greater risk of injury thma occurs for planned manoeuvres (Lloyd, Cochrane, Besier & Ackland, 1999).

Figure la & b: Testing environment showing direction indicator lights (a) and subsequent directions of movement (b)..

2. Neuromuscu la r contro l Neuromuscular control has been an area of s tudy in biomechanics and in other disciplines for many years. For example, ff studying the ankle or knee joints, it would be appropriate to ask a n u m b e r of questions. First whether voluntary {co- activation) or involuntary (reflex) actions stabilise the joint in question, second what is the effect of this stabilisation on joint mechanics, or what is the effect of proprioceptive training on the above?

Caraffa et al. (1996) completed a prospective controlled study of 600 soccer players over three seasons and showed an incidence of 1.15 ACL injuries per team per year in the control group and 0.15 ACL injuries per team per year in the proprioceptively trained group. Besier (1999) supervised by David Lloyd developed a dynamic knee joint model capable of predicting loading in the individual ligaments. When unders tanding of loading pa t te rns is combined with neuromuscular data collected by Skoss (1999) from the same laboratory it should be possible to identify changes in "neuromuscular strategies" that occur about the

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knee and ankle joints after proprioceptive training. One could also look at changes in knee joint loading following this training in order to reduce the incidence of knee injuries.

3. Tissue mechanics Biomechanics plays a key role in the general area of tissue mechanics. Hamer (1999) for example, through a series of studies, has looked at questions related to exercise-induced muscle damage. He used an animal model, immuno- histochemistry and electronmicroscopy to show that eccentric contractions induce immediate muscle damage, However, the regeneration that followed was shown to protect the muscle against similar occurrences for up to 12 weeks. This research ~ further enhance our understanding of the role of eccentric training in preparing athletes for competition.

4. Rehabil i tation One current line of research in rehabilitation from injury involves the assessment of movement function usillg videography and dynamometry in an endeavour to re-establish pre-injury or pre-operative movement parameters. The rote of exercise is also being examined as the modality to either prepare patients for surgery or improve movement characteristics post-surgery or injury.

MeNair, Wood and Marshall (1991) examined the relationship between hamstring muscle stiffness and functional ability using the Noyes rating scale in ACL deficient subjects. They found that hamstring muscle stiffness was significantly related to functional ability and this finding has implications for the type of hamstring muscle work that should be performed in rehabilitation programs, as a stiffer muscle was functionally superior.

O¢¢upationaR Biomechamlcs 1. ~rgonorn|cs Anthropometric, kinematic and kinetic data are often collected for the purpose of impro~ng working environments by providing a clearer understanding of loading during occupational tasks. For example, an anthropometic study within the Western Australian secondary school system (4,600 students) created normative data that were used in the design of school furniture {Blanksby, Scott & Foster, 1986). Previously, school furniture dimensions were based on a British Ministry of Education report on chair heights (1953), some data from NSW and consensus of a Committee's own ideas.

A series of studies were also undertaken with a view to evaluating different sheep shea_dng techniques (Figure 2, Marshall & Burnett, 1996). The aim of this work was to compare kinematic, kinetic and electromyographic characteristics of shearing using the Australian traditional technique, the Australian modern technique, a stooped technique while using a Warrie back-aid, and the SLAMP5 sheep manipulator. The SLAMP5 manipulator significantly reduced muscle activity and loads on the body dining shearing. The overall muscle activity was generally reduced and the L 5 / S t joint compression and sheer forces were both approximately one-half of those generated using either the Australian traditional or Australian modern shearing techniques, and less than those for subjects with the back-aid. The more upright posture permitted by the SLAMP5 sheep manipulator, and the flexibility allowed in lateral and forward movement while shearing, were two major factors in this improvement.

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Figure 2: Shearer prepared for data collection.

2. Human growth/morphology In this area, researchers have investigated how morphology relates to specific movement parameters or how growth affects the ability of the body to move. A study by Carter and Ackland (1994) at the World S~_mming Championships held in Perth categorised selected morphological parameters for different swimming events. A mixed longitudinal s tudy [Richards, 1999) recorded growth and gymnastic skill levels of a group of high performance female gymnasts (trained >30 hours per week) and a group that only trained 10-15 hours per week over 3.3 years. Training intensity was shown to significantly increase the ability of the body to rotate about its longitudinal and transverse axes. However, a small whole 'body moment of inertia value about the transverse axis was shown to be the critical variable in body rotation about this ax~s.

Sports Biomechan|cs Sports biomechanists believe that an awareness of the mechanics of movement will better equip and prepare athletes to learn, teachers to teach, and coaches to detect and correct flaws in sports performance. An understanding of biomechanics is also essential for sports medicine personnel as they administer rehabilitation and prevention of injury proE, rams. Sport biomechanics research has been arbitral-fly divided into three broad areas:

1. Technique modification for movement enhancement Technique analysis and modification are a major concern of the sports biomechanist. While simply describing movement does not have a large role to play in current research, it could still be important for movements that have not previously been evaluated. However, it is imperative that studies clearly identify the key characteristics in a movement. Studies mus t look for "causative

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Biomechanics: An Integral Part of Sport Science,..

mechanisms" in sporting movements prior to using modelling and simulation based research to assist in the understanding of movement via a manipulation of key variables.

A) Descriptive Mechanics Sport biomechanists, in looking at why selected aspects of a movement are important, must remember to include research into the relationship between lead-up drills or teaching sequences and final outcome. Work by Elliott and Mitchell (1991) showed clearly tha t selected lead-up drills in the Yurchenko vault did not emphasise critical mechanical variables recorded during the vault. This is a fertile area of research for those interested in developing "good technique". (i) Suamming

The importance of the turn is apparent when one realises that it occupies 20% of the time for a 50 m event in a short-course pool. Blanksby has completed a number of studies which describe turning techniques both kinetically and kinematically in an attempt to identify key variables for the various strokes (such as Blanksby, Hodgkinson & Marshall, 1996). In general terms high performance freestylers, who produced greater force on the wall (=1.6 BW) while recording shorter contact times, produced faster turn times. Those who turned further from the wail (less knee flexion) also produced faster turn times.

Research on swim turns continues, with investigations on techniques used in various strokes and the optimal depths for streamlined gliding, currently being published. Lytfle, Blanksby, Elliott and Lloyd (1998) developed a towing arrangement (Figure 3) and demonstrated that drag at the surface was significantly higher than at 0.2, 0.4 and 0.6m depth for all velocities tested. At velocities above 1.9 ms -1, drag is significantly higher at 0.2m, than 0.4 and 0.6m, water depth.

Video Reco~_ler & Mor~or FM

FM Tr-~roJ.tter Under/rater "--. Video 1 Force Data

.._.---- Collection Corapu.ts~

Mec}~fical Winch

PulPy S~tem

S w';-r~er ~ L;ell ~ Pool Amp]iSe~

Figure 3: Drag teeing environment in swimming. 303


(ii) Rovhng The rowing stroke is a complex, dynamic interaction between athletes and the boat, with successful performance dependent upon the optimisation of the individual and the crew technique. Descriptive research into rowing has measured muscle activity over the stroke, changes that occur in boat velocity when stroke rate is modified and the time or angle histories of each rower with regard to the timing of the force-curve. "Causative mechanisms" may be investigated by relating how "seat specific" (bow or stroke) impulse curves influence boat velocity (McBride, 1998).

(iii) Di~ng A study on the lead-up drills taught to young children (6 to 8 years) learning to dive in swimming (set dive, double kneel dive, single kneel dive, crouch dive, one-foot forward standing, standing dive on edge and block dive) clearly show the dangers involved with a number of recommended techniques (Blanksby, Wearne & Elliott, 1996). Impact vertical velocity of the head with the water, the number of subjects who reached specific depths (1.2 m and 1.5 m) and the number of children who attained greater than a critical velocity for injury at specific depths, were calculated. The one-foot forward standing, standing edge and block dives were shown to need careful supervision and specific technique training if injuries were to be avoided.

B) Causative Mechanics The identification of causal relationships in movement is always an important step in identifying critical variables for performance. Two examples vail be discussed to demonstrate how an increased understanding of causal mechanisms in movement will help the coach to better prepare athletes and assist the therapist to structure better prehabilitation and rehabilitation programs. (i) Internal rotation of the upper arm

Internal rotation of the upper arm, in many over-arm and side-arm movements, has been shown to be a key factor in the development of endpoint speed. In the tennis serve (Elliott, Marshall & Noffal, 1995), squash forehand (Elliott, Marshall & Noffal, 1996), baseball pitch (Diltman, Fleisig & Andrews, 1993) and the American football pass {Rash & Shapiro, 1995), internal rotation of the upper arm has been shown to be a key variable in endpoint speed production. This movement occurs very late in the "kinematic chain" and can generate a large percentage of the distal endpoint speed at either impact or release. The ramifications for coaches, physicians and therapists are enormous, as training and rehabilitation programs must be remodelled to better prepare the shoulder region for high performance, while also protecting this area from injury.

(it) Enhancement of performance through recovery of stored elastic energy and muscle pre-load. Biomechanical research has shown tha t the use of dastic energy together with the pre-loading of muscle and associated tissue in upper limb movements have resulted in augmentation to performance. Bober, Jaskolski and NowacM (1980) reported a mean augmentation of concentric velocity in a seated upper limb pusb_ing movement of 13.7% due to prior stretch of the upper body musculature. Wilson, ERiott and Wood (1991) showed that the benefits from muscle pre-streteh and storage of elastic energy during the eccentric phase of

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the bench press lift dissipated as a function of the pause period between the eccentr ic and concentric p h a s e s of the s t r e t ch - shor ten cycle. The augmentat ion to performance was reduced by approximately 50% after a one- second delay between the eccentric and concentric phases of the action. A fur ther study b y Elliott, Baxter and Besier (1999) examined the influence of prior stretch on the augmentat ion to internal rotation at the shoulder joint with an increase in pause between the stretch-shorten cycle. The maximum velocity of the wrist decreased with increasing p a u s e time. The augmentation f rom elastic energy and muscle pre-load caused by prior stretch with no pause increased the m a x i m u m linear velocity of the wrist by 21.9% in comparison to the internal rotat ion condition which had a m e a n pause period of 1.5 s between the eccentric and concentric phases of the movement. It is therefore evident that the benefits from a pre-stretch have a significant influence on subsequent concentric motion.

Consequently, large forces can often be achieved in the early phase of the concentric motion. This may play a vital role in the early stages of movement where the inertia of an object m u s t be overcome. A sldll can then be performed with the assistance of augmentat ion from elastic energy and the commencement of concentric action with the muscles pre-stretched (and other factors influenced by musc le pre-loading and the s t re tch reflex).

C) Simulation In Sporting Movement The strength of the previously described experimentally based research designs is tha t data are gathered from actual performance of a movement. The weakness, however, is that it is almost flnpossible to have the athlete change one aspect of technique without introducing other changes. This is where descriptive data on the key mechanical variables together with computer modelling a n d simulation play an important role in movement optimisation. Computer simulation in general m e a n s using a validated computer model to car ry out "experiments" under controlled conditions, with realistic data. Wood, Marshall and Jenn ings (1987) for example filmed runner s and from kinematic and kinetic data developed an optimal control model for the lower limb during sprint running. They reported that a decreased leg recovery time is only possible when the eccentric momen t about the knee is increased jus t prior to foot-strike. Koh (1999) has recently optimised the horse impact phase of a Yurchenko style vaul t to gain a n insight into techniques at impact that lead to improved performance. As a pauci ty of research has been published in this a rea in our laboratory, examples from other laboratories are included to provide the reader with a n unders tanding of this type of biomechanies research.

Biomechanists have made some inroads towards assisting gymnast ics coaches. Nissinen, Preiss and Bmggemann (1983) constructed a model for gymnastic movements to improve existing skills and subsequent ly to develop entirely new movements . Their data from a double-back somersaul t d i smoun t on the horizontal bar provided the input for the simulat ion of the more difficult movement of the triple-back somersaul t dismount. The simulation showed that this new skill could be performed with the same initial biomechanical conditions. Coaches aware of these facts were able to teach this new skill relatively quickly, without fear that they were progressing beyond the gymnast 's capabilities, thus increas ing the possibil i ty of injury. Yeadon (1990) has enhanced our understanding of aerial movements. Somersault, tilt and twist rota t ions have all

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been evaluated using simulation techniques to gain a better understanding of how movements are either created or countered during flight.

Best and Bartlett for a n u m b e r of years have used simulation along with modelling and optimisation to improve javelin throwing. In javelin thro~_ng, the performance to be maximised is the distance thrown. Hence, the goal of research is to find a set of opt imum release conditions which serve as a reference f rom which variations can be assessed (Best, Bartlet t & Sawyer, 1995).

2.Stress and injury reduction Biomechanical research into s t ress and injury requires relationships to be drawn between the kinetics of an activity, the incidence of pain, and the site and type of injury. Potential causes of s tress such as overuse, misuse through poor technique, poor physical preparat ion a n d / o r genetic predisposition, mus t all be investigated thoroughly. The following applied research papers show how a t e a m approach to research can reduce the likelihood of injury to fast bowlers in cricket and reduce the incidence of knee injuries in ~_nter sport.

A} Bowling Teelmique and Inj~-ies in Cricket Stress fractures to the lumbar vertebra(e) of young Australian fast bowlers in cricket reached near epidemic proportions in the 1980's. A series of studies on the fast bowling action were therefore under taken in an endeavour to identify the relationship between bowling technique, the ground reaction forces associated with each delivery and back injuries in cricket. Elliott and Foster (1984) showed that, while there were obvious differences between the front-on and side-on bowling techniques, no differences were recorded in ground reaction forces. A prospective s tudy was then designed where 82 young fast bowlers were tested prior to the season and all cricket related injuries over the season were assessed by a sports physician. Computerised tomography was used to assist in the diagnosis of spinal injuries (Foster, Johns, Elliott, Ackland & Fitch, 1989). A new bowling technique (mixed technique) was identified where counter-rotation of the shoulder alignment occurred between back foot and front foot impact. This mixed technique was related to a significant increase in the incidence of bony and soft tissue injuries to the lumbar spine. Firm recommendat ions were made to coaches via a coaching paper, book, and sports medicine safety guidelines advocating the teaching of either a side-on or front-on technique but not a mixture of the two styles, along with a sensible approach to the number of overs bowled and an appropriate physical preparation. A fur ther sample of 18 year old high performance bowlers showed that pars interarticularis and intervertebral disc abnormalities were common with respect to fast bowlers (55% and 65%, respectively). Also, all players who had experienced back pain had evidence of radiologic abnormality. Furthermore, bowlers who used the mixedtechnique were more likely to present with abnormal radiologic features in the lumbar spine (Elliott, Hardcastle, Burnett & Foster, 1992).

Two studies were then designed to identify the age that disc degeneration occurred in young fast bowlers (Elliott, Davis, Khangure, Hardcastle & Foster, 1993; Burnett, Khangure, Elliott; Foster, Marshall & Hardcastle, 1996). The progression of disc degeneration for 13 year old prospective high performance fast bowlers (21% to 58% over 2.5 years) was found to be significantly related to the mixed bowling action.

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]3) Knee joint injuries in sport A population-based s tudy was designed to follow a cohort of amateur and recreational competitors (not A-grade) in hockey (382), Australian rules football (535), basketball (190), and netball (368) over two winter seasons (Hamer, Stevenson, Elliott & Finch, 1998). While a secondary aim was to determine the incidence of injury in these sports, the primary aim was to determine the possible causes of knee injuries. Kinanthropometric, strength and postural alignment parameters were measured on the non-injured lower limb of all players who suffered a knee injury. These values will be compared with data from two matched control subjects from the same sporting code. It is hoped that this nested-control study will enable causal mechanisms for knee injuries to be identified.

3. Equipment Design Biomechanists are p~nar i ly involved in equipment design from an optimisation of performance or injury prevention perspective. While design and manufacture are generally linked to the corporate sector, epidemiological assessment of design modifications and the s tudy of how design influences human performance are often undertaken in the university setting. A number of studies investigating the affect of racquet size on skill performance of young players and the relationship between string tension and resulting ball velocity have been completed in our laboratory. Research showed that 7-10 year old tennis players who used a sub- junior racquet demonstrated superior performance to the group who used aj tmior racquet (Elliott, 1981). The results of this study demonstrated the superiority of learning basic tennis skills at an early age with a racquet related to the size of the child.

The effects of stnng tension and longitudinal racquet flexibility on post-impact ball velocity were also investigated (Elliott, 1982). A significant interaction between racquet stiffness and stxing tension was recorded. String tension had no significant influence on rebound velocity for a stiff racquet, however, medium and flexible racquets produced the highest coefficients of restitution when stnlng at 245N {55 lb) compared with 289 N (65 lb) and 334 N (75 lb).

conclusions Seldom is a complex question answered by research based in a single science discipline. Hence, the biomechanist mus t combine with the exercise physiologist and biochemist, the sport psychologist and the motor development specialist to structure appropriate research design. Research into identifying key causal mechanisms associated with injury or rehabilitation processes inevitably require the knowledge and skills of the sport physician and physiotherapist. If the foot is an area of particular concern during gait research, then the podiatrist enhance the quality of the question that may be asked. The radiologist is essential if research invol~ng imaging is proposed. Winston, Schwarz and Baker (1996) proposed that biomechanics should be an integral part of epidemiological research ff injury control mechanisms were to be fully understood (Figure 4). This is essential as whatever the severity of an injury most have a mechanically related aetiology (Whiting & Zernicke, 1998). The biomechanist must therefore establish efficient models of performance that allow for individual athlete characteristics and permit performance to be enhanced without undue risk of injury.

Further research, while continuing to investigate movement in the previously designated categories, mus t also show how changes to technique or equipment design improve performance or reduce the incidence of injury.

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Biomechanics: An Integral Part of Spoil: Science...

B t ~ E C H,li~IIC,fC. I ipIn f1,10..Ct,"~' - INJU t 'Y

CO~lll l CL R F.,~..~J~ C H

Figure 4:: Biomechanicat epidemiology (Modified from Winston et a/., t996).

Ackmowtle~gmem~:s I sincerely thank my current academic colleagues [Professor Brian Blanksby, Drs Ackland, Lloyd and Hamer), Associate Professors Graeme Wood and Bob Marshall amd all my research students who have played such an important role in my university life. References Besier. T. (]999). Varus-valgus and torsional perturbations at the human knee, Unpublished

PhD Thesis, The University of Western Australia (supervisors Drs Lloyd and Acklm]d). '~%est, R.. Bartlett, R., & Sawyer, R. (1995). Optimal javelin release, Jou rna l of Applied

Biomechanics 11: 371-394. Blanksby, B., Hodgkinson, J., & Marshall, R. (1996). Force-time characteristics of freestyle

tumble tu rns by elite swimmers. The South African Journa l for Research in Sport , Physical Education and Recreation, 19: 1-15.

Blanksby, B., Scott, C., & Foster, D. {1986}. An th ropome t r i c Survey of Western Australian Secondary School Students - A Basis for the Des ign of School Furnishings and Fitt ings, ACHPER Publications: Parkside, Australia.

Blanksby, B., Wearne, F., & Elliott, B. (1996). Safe depths for teaching children to dive. The Australian Journal of Sc ience and Medicine in Sport 28: 79-85.

*Bober, T., Jaskolstd, E. & Nowacld, Z. (1980). Study on eccentric-concentric contraction of the upper body extremity muscles. Journal of B iomeehanics 13: 135-138.

Bumett, A., Khangure, M., Elliott, B., Foster, D., Marshall, R., & Hardeastle, P. (1996). Thoracolumber disc degeneration in young fast bowlers in cricket: a follow-up study. Clinical Biomeehanics 11: 305-310.

*Caraffa, A., Cerulli, G., Projetti, M., Asia, G., & Rizzo, A. (1996). Prevention of anterior cruciate ligament injuries in soccer. Knee Surgery, Sports Traumatology, Arthroscopy 4: 19-21.

Carter, J., & Ackland, T. (1994). Kinanthropometry in Aquatic Sports. Human Kinetics. Champaign, USA.

*Dillman, C., Fleisig, G., & Andrews, J. (1993). Biomechanics of pitching with emphasis upon shoulder kinematics. Journal of Orthopaedic a n d Sports Physical Therapy 18(2): 402- 4O8.

Elliott, B. (1981). Tennis racquet selection: A factor in early skill development. The Australian Journal of Sport Sc iences 1: 23-25.

Elliott, B. (1982). The influence of tennis racket flexibility and string tension on rebound velocity

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follo~-ng a dynamic impact. Research Quarterly for Exercise and Sport 53: 277-.281. Elliott, B., & Foster, D. (1984). A biomechanical analysis of the front-on and side-on fast bowling

techniques. Journa l of Human Movement Studies 10: 83-94. Elliott, B., & Mitchell, J. (1991). A biomechanical comparison of the Yurchenko vault and two

associated teaching drills. Internat ional Journa l of Sport Biomechanics 7(1): 91-107. Elliott, B., Hardcasfle, P., Burnett, A., & Foster, D. (1992). The influence of fast bowling and

physical factors in radiologic features in high performance young fast howlers. Sports Medicine Training and Rehabil i tat ion 3 :113-130 .

Elliott, B., Davis, J. , Khangure, M., Hardcasfle, P., & Eoster, D. (1993). Disc degeneration and the young fast bowler in cricket. Clinical Biomechanics 8: 227-234.

Elliott, B., Marshall, R., & Noffal, G. (1995). Contributions of upper limb segment rotations during the power serve in tennis. Journal of Applied Biomechanics 11: 433-442.

Elliott, B., Marshall, R., & Noffal, G. (1996). The role of upper limb segment rotations in the development of racket-head speed in the squash forehand. Journa l of Sports Sc iences 14: 159-165.

Elliott, B., Baxter, K., & Besier, T. (1999). Internal rotation of the upper arm during a stretch- shorten cycle movement. Journa l of Applied Biomechanics 15: 381-395.

Foster, D., Johns, D., Elliott, B., Acldand, T., & Fitch, K. (1989). Back injuries to fast bowlers in cricket: A prospective study. British Journal of Sports Medicine 23(3): 150-154.

Hamer, P. (1999). Exercise-induced muscle damage: Does apoptos i s have a role? Unpublished PhD Thesis. The University of Western Australia (supercisors Professor Grounds and Dr Lloyd).

Hamer, P., Stevenson, M., Eliiott, B., & Finch, C. (1998). The Western Australian sports injury cohort study: Results from the first year. Book of Abstracts , Australian Conference of Science and Medicine in Sport, Adelaide, p. 134.

Koh, M. (1999). Optimal control of the Yurchenko. Unpublished PhD Thesis. The University of Western Australia (supervisors Professor Elliott and Dr Lloyd).

Kuster, M, Sakurai, S., & Wood, G. (1995). A kinematic and kinetic comparison of downhill and level walking. Clinical Biomechanics 10: 79-84.

Lloyd, D., Cochraue, J., Besier, T., & Actdand, T. (1999). Unanticipated side-stepping and cross- over cutNng increases loading of the knee. In Proceedings XVlI International Society of Biomechanics Conference. Calgary, p.770. University of Calgary, Canada.

Lyltle, A., Blanksby, B., Elliott, B., & Lloyd, D. (1998). Optimal depth for streamlined gliding. In Proceedings VIII Internat ional S y m p o s i u m on Biomechanics and Medicine in Swimming. Jyvaskyla, pp85. University of Jyvaskyta, Finland.

Marshall, R., & Burnett, A. (1996). A comparison of kinematic, kinetic and EMG characteristics of subjects using stooped (traditional and modern) and SLAMP5 shearing techniques. Report to International Wool Secretariat, Australia.

McBride, M. (1998). Enhancement of boat veloci ty in rowing: The role of propulsive and transverse forces. Unpublished PhD Thesis, The University of Western Australia (supervisor Professor Elliott).

McNair, P., Wood, G., & Marshall, R. (1991). Stiffness of the hamstring muscles in anterior cruciate ligament (ACL) deficient subjects. In R. Marshall et al. (eds). Book of Abstracts, XIHth International Congress on Biomechanics, pp 548-549, The Department of Human Movement, The University of Western Australia, Australia.

*Nissinen, M., Preiss, R. & Bruggemarm, P. (1983). Simulation of human airborne movements on the horizontal bar in Biomechanics IX-B, D.A. Winter et al. (Eds.), pp 373-376, Human Kinetics: Illinios.

*Rash, G., & Shapiro, R. (1995). A three-dimensional dynamic analysis of the quarterback's throwing motion in American football. Journal of Applied Biomechanics 11(4): 443-459.

Richards, J, {1999). The effects of gymnast ic training on adolescent growth and on the b iomechanics of athletic performance. Unpublished PhD, The University of Western Australia, Australia (supervisors Professor Elliott and Dr Ackland).

Skoss, R. {1999). Factors Affect ing the Electro-mechanical Properties of Human Muscle in- Vivo, Unpublished PhD. The University of Western Australia {supervisor Dr Lloyd).

Whiting W., & Zernicke, R. (1998). Biomechanics of Musculoskeletal Injury. Human Kinetics: Champaign, USA.

Wilson, G., Elliot-t, B., & Wood, G. (1991). The effect on performance of imposing a delay dur~lg a stretch-shorten cycle movement. Medicine and Science in Sport and Exercise 2 3 : 3 6 4 - 370.

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*Winston, F., Schwarz, D., & Baker, S, (1996). Biomechanical epidemiology: a new approach to injury control. The J o u r n a l of Trauma: Injury, I n f e c t i o n and C r i t i c a l Care 40: 820-824.

Wood, G., Marshall, R., & Jennings , L. (1987). Optimal requirements and injury propensity of lower l imb mechanics in spr int running. In B. Johns son (ed), Biomechanics X-B pp 869- 874. H u m a n Kinetic: Champaign, USA.

*Yeadon, M.R. (1990). The simulation of aerial movement - I, II, III, J o u r n a l of B i o m e c h a n i c s 23(1): 59 - 84.

* Not research carried out at the Department of H u m a n Movement and Exercise Science at The University of Western Australia.

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