Wyniki wyszukiwania - Biblioteka Nauki

1

An attempt to describe heart attacks via continuum damage mechanics

100%

Życzkowski M.

Archives of Mechanics

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2000

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tom Vol. 52, nr 4-5

889-910

EN

In an earlier paper the author expressed the evolution equations of classical continuum damage mechanics in terms of unit dissipated power and proposed an extension to biological materials in vivo, adding a term describing the recovery. In the present paper an analogy with evolution of the coronary artery disease is established. If we denote by S (relative stenosis) one minus the ratio of current luminal area to the initial area, then the condition S = 1 at a certain point of the artery means complete blockage at this point resulting in a heart attack (myocardial infarction). This corresponds to the condition of critical state D = 1 in damage mechanics, where D denotes a scalar measure of damage. Making use of this analogy, an evolution equation for S is proposed, with unit dissipated power replaced by unit power of flow in individual cross-sections of coronary arteries and, subsequently, by the heart power. Further, another evolution equation describes the required heart power in terms of external loadings acting on the organism as a whole. Numerical integration of the evolution equations proposed makes it possible to distinguish the loadings leading to a myocardial infarction from those subject to recovery. Also, the description of stable and unstable angina pectoris is discussed and illustrated by numerical examples.

2

Projekty i badania w biomechanice

100%

Burcan J. , Wich M.

Zeszyty Naukowe. Mechanika / Politechnika Opolska

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2001

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tom z. 68

151-158

PL

W referacie przedstawiono projekty i badania prowadzone w Zakładzie Geometrii Wykreślnej i Rysunku Technicznego PŁ dotyczące zagadnień biomechaniki.

EN

The paper presents the biomechanical projects and research work carried out in the Division of Descriptive Geometry and Engineering Drawing of the Technical University of Lodz.

3

Comparison of pre- and post-implantation mechanical behavior of composite hernia meshes

80%

Kirilova-Doneva M. , Pashkouleva D. , Sopotensky S. , Petrova G.

Journal of Theoretical and Applied Mechanics

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2020

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tom Vol. 58 nr 3

769--778

EN

Implantation of synthetic meshes provokes complications which require long-lasting follow-up. The mesh materials exposed to physiological conditions demonstrate differences in failure load, stiffness and extension. Mechanical alterations of explants made of polyester were investigated using a uni-axial tensile test and a relaxation test. The tensile strength of the explanted meshes changed in the transversal direction. The elastic modulus in the same direction increased two times. A magnified mesh image displayed mesh alteration. The relaxation tests revealed that the initial stress decreases after implantation while the reduction of stress increases in the interval 50%-96.6%.

4

Biomechanical Assessment of Three Rebar Tying Techniques

80%

Albers J. T. , Hudock S. D.

International Journal of Occupational Safety and Ergonomics

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2007

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tom Vol. 13, No. 3

279--289

EN

The National Institute for Occupational Safety and Health (NIOSH) conducted a study of ironworkers to evaluate their risk for developing back and hand injuries from hand-tying reinforcing steel bar and to investigate whether power tying tools can be an effective intervention for the prevention of work-related musculoskeletal disorders. A field investigation of biomechanical loading when using 3 techniques to tie together rebar was conducted. Researchers measured employees’ wrist and forearm movement with goniometers and videotaped and analyzed trunk postures. Manually tying rebar at ground level involved sustained deep trunk bending and rapid, repetitive, and forceful hand–wrist and forearm movements. Using a power tier significantly reduced the hand–wrist and forearm movements and allowed the ironworkers to use one free hand to support their trunk posture while tying. Adding an extension handle to the power tier allowed the ironworkers to tie rebar while standing erect, minimizing sustained trunk flexion.

5

Biomechanical Studies on Running the 400 M Hurdles

80%

Iskra J. , Coh M.

Human Movement

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2011

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tom 12

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nr 4

315-323

EN

Purpose. Biomechanical research conducted on hurdling are the basis for analysis of technique used in running disciplines. However, the 400 m hurdle run is an athletic discipline rarely subjected to individual biomechanical study. The aim of this study was to introduce the various forms of biomechanical studies on this difficult-to-quantify athletic event. Methods. In this study, 64 biomechanical articles were assessed, each covering various topics such as kinematics, dynamics, accelometrics and rhythm knowledge in the both the men's and women's 400 m hurdles. This was conducted with regard to the specificity of studies on the 400 m hurdles, including their types, methods and difficulties. The characteristics of the study were divided, among others, into: physiological effort, centrifugal force, dynamics of movement, stride rhythm, the level of abilities, laterality and type of body build. Results. Numerous sources allowed the creation of a general outline of present biomechanical studies. Conclusions. Within the context of the conducted analysis on the present state of biomechanical analysis on the 400 m hurdles, a number of basic principles were outlined that could determine the effectiveness of future research possibilities for scientists on the 400 m hurdles.

6

Biomechanical changes in pregnant women

80%

Opala-Berdzik A. , Bacik B. , Kurkowska M.

Physiotherapy

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2009

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tom 17

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nr 3

51-55

PL

Celem pracy jest przedstawienie problemów związanych z różnorodnymi biomechanicznymi zmianami w układzie mięśniowo-szkieletowym kobiet w ciąży dotyczącymi postawy ciała także w aspekcie dolegliwości bólowych, zwłaszcza w dolnym odcinku pleców. Poruszane są zagadnienia związane ze zmianą funkcjonalnego zakresu ruchomości tułowia oraz ograniczeniami i trudnościami w wykonywaniu czynności codziennych i zawodowych. W pracy przedstawiono także wpływ ciąży na stabilność posturalną i chód. Wiedza zawarta w artykule powinna być pomocna zarówno osobom prowadzącym zajęcia w szkołach rodzenia, jak też lekarzom i fizjoterapeutom w profilaktyce oraz leczeniu dolegliwości układu mięśniowo-szkieletowego u kobiet w ciąży i po porodzie.

EN

The purpose of the paper is to present the problems related to various biomechanical changes taking place in the musculoskeletal system in pregnant women concerning body posture and pain problems and especially low back pain. The changes of the functional motion range of the trunk as well as the limitations and difficulties in daily life activities and work performance are taken into consideration. The influence of pregnancy on postural stability and gait is also presented in the paper. The knowledge gathered in the article should be helpful to those who provide the child birth classes as well as to physicians and physical therapists in prevention and treatment of musculoskeletal complaints of women during pregnancy and post partum.

7

A preliminary study on the optimal choice of an implant and its orientation in ventral hernia repair

80%

Lubowiecka I. , Szepietowska K. , Szymczak C. , Tomaszewska A.

Journal of Theoretical and Applied Mechanics

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2016

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tom Vol. 54 nr 2

411--421

EN

This paper addresses the problem of ventral hernia repair. The main goals are to find an optimal surgical mesh for hernia repair and to define its optimal orientation in the abdominal wall to minimise the maximum force at the tissue-implant juncture. The optimal mesh is chosen from a set of orthotropic meshes with different stiffness ratios for typical hernia placement in the abdominal area. The implant is subjected to an anisotropic displacement field, different for the selected hernia placements. The assumed displacement fields correspond to regular human activity. Proper implantation of the mesh may determine the success of hernia repair and/or the postoperative comfort of patients. The proposed solution is based on FEM simulations of different surgical meshes behaviour. In typical hernia placements, the optimal orientation of the stiffer direction of the implant is perpendicular to the spine. However, the presented results show some cases that an oblique direction may be the optimum one.

8

Kinematic Analysis of the Take-Off and Start of the Early Flight Phase on a Large Hill (HS-134 m) during the 2009 Nordic World Ski Championships

80%

Janura M. , Cabell L. , Svoboda Z. , Elfmark M. , Zahalka F.

Journal of Human Kinetics

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2011

|

tom 27

5-16

EN

The take-off is often considered the most significant and difficult phase of a ski jump. Thus, the purpose of this study was to compare three groups of ski jumpers representing different skill levels during the execution of the take-off and start of the early flight phase in ski jumping. A total of 30 athletes, recruited from competitors performing ski jumps on an HS-134 m jumping hill, were categorized into three groups based on jump-length execution. Two-dimensional (2-D) kinematic data were collected from the lower extremities, trunk, and skis of the ski jumpers. Findings indicated that the ski jumpers with shorter jump length demonstrated significantly smaller in-run velocity (p < .05), while the elite and mediocre level ski jumpers exhibited a significantly faster shift of the thigh at the transition from take-off into the early flight of the jump (p < .05) than did the low-level ski jumpers. In addition, the centre of body mass (CoM) of the elite group shifted significantly more forward over the skis (p < .01) than did that of the other two groups. Finally, interindividual differences existed among ski jumpers at similar performance levels. The largest coefficients of variation (CVs) were found for the position changes of the trunk and shank behind the jumping hill edge.

9

The Dynamics of Human Central Arterial System

80%

Paszyński M. , Kalita P. , Schaefer R.

Schedae Informaticae

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2005

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tom Vol. 14

35-59

EN

The paper presents mathematical and numerical models of the blood flow in human arteries. We describe selected modelling techniques for the mechanical phenomena occurring in the arteries: blood flow, displacement of the wall and the fluid-structure interaction be-tween the blood and the wall. The paper concentrates on the theoretical results showing the conditions of applicability of presented models. We describe variational models for the Casson flow of blood as well as stochastic Fluid Particle Model (FPM) modified for the nonlinear flows. For the artery wali we describe the model which is the physically nonlinear Koiter shell and the Finite Element Method (FEM). We also present the simulations of the fluid-structure interaction that uses the weakly coupled approach of FPM for blood with FEM for the wall.

10

Determination of Strength Exercise Intensities Based on the Load-Power-Velocity Relationship

80%

Jandačka D. , Beremlijski P.

Journal of Human Kinetics

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2011

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tom 28

33-44

EN

The velocity of movement and applied load affect the production of mechanical power output and subsequently the extent of the adaptation stimulus in strength exercises. We do not know of any known function describing the relationship of power and velocity and load in the bench press exercise. The objective of the study is to find a function modeling of the relationship of relative velocity, relative load and mechanical power output for the bench press exercise and to determine the intensity zones of the exercise for specifically focused strength training of soccer players. Fifteen highly trained soccer players at the start of a competition period were studied. The subjects of study performed bench presses with the load of 0, 10, 30, 50, 70 and 90% of the predetermined one repetition maximum with maximum possible speed of movement. The mean measured power and velocity for each load (kg) were used to develop a multiple linear regression function which describes the quadratic relationship between the ratio of power (W) to maximum power (W) and the ratios of the load (kg) to one repetition maximum (kg) and the velocity (m•s-1) to maximal velocity (m•s-1). The quadratic function of two variables that modeled the searched relationship explained 74% of measured values in the acceleration phase and 75% of measured values from the entire extent of the positive power movement in the lift. The optimal load for reaching maximum power output suitable for the dynamics effort strength training was 40% of one repetition maximum, while the optimal mean velocity would be 75% of maximal velocity. Moreover, four zones: maximum power, maximum velocity, velocity-power and strength-power were determined on the basis of the regression function.

11

Metoda diagnozowania chodu człowieka

80%

Jaworek K. , Pauk J.

Zeszyty Naukowe Politechniki Białostockiej. Budowa i Eksploatacja Maszyn

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2002

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tom Z. 10

61--66

PL

Przedmiotem pracy jest zaprojektowanie stacji diagnostycznej, która stanie się dostępna dla wielu ośrodków klinicznych w kraju i za granicą. Jej podstawowymi elementami są: elektrogoniometr, mata chodu oraz pakiet programów do filtrowania sygnałów biomechanicznych, szacowania chwilowej wartości mocy oraz do identyfikacji modelu dynamiki lokomocji człowieka.

EN

There is presented a new diagnostic station to measuring kinematic data of human gait in this paper. The station is building from electrogoniometer, gaitrate, and software to filtering biomechanical data, estimating power developed by muscle joints, identification human gait model. The advantages of this station are simplicity and low coast.

12

Zachowanie się kręgosłupa lędźwiowego poddanego kompresji ze zginaniem w warunkach stabilizacji transpedikularnej

80%

Sajewicz E. , Sidun J. , Koronkiewicz T.

Zeszyty Naukowe Politechniki Białostockiej. Budowa i Eksploatacja Maszyn

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2002

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tom Z. 10

143--151

PL

Przedstawiono wyniki badań przemieszczeń odcinka lędźwiowego kręgosłupa, poddanego jednocześnie kompresji i zginaniu (tzw. mimośrodowe ściskanie). Badano przemieszczenia kręgu L3 dla dziewięciu preparatów ustabilizowanych za pomocą systemów Socon, Omega oraz Bial-Stab, a następnie pomiary powtarzano po wykonaniu korporektomii na poziomie L3. Wyniki badań porównywano z uzyskanymi na preparatach nieustabilizowanych. Wykazano, że brak ciągłości przedniej kolumny kręgosłupa nie wpływa na biomechaniczną jakość stabilizacji w zakresie stosowanych obciążeń.

EN

Authors described results of examinations in lumbar spine displacements during compression and flexion - eccentric compression. Displacements were measured at the level L3 in nine lumbar spine specimens stabilized with Socon, Omega or Bial-Stab System. Measurements were repeated after corporectomy at the level L3 and compared with results obtained on lumbar spine specimens without stabilization. The authors proved that break of continuity of anterior spine column had no influence on biomechanical quality of stabilization in the range of used loading.

13

Thermodynamical modelling of behavior of elasto-viscoelastic layered structure

80%

Maruszewski B. T. , Kamiński H. , Starosta R.

Applied Mechanics and Engineering

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1999

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tom Vol. 4, no 2

237-253

EN

The thermodynamical model, derivation of the field equations, proper boundary conditions, analytical and numerical solutions to an elasto-viscoelasto-elastic problem in a layered structure have been presented. Three different kinds of loading have been applied to the structure. A space-time analysis of displacements in each layer has been done.

14

Hip joint implants - survey of numerical modeling

80%

Bajer C. , Małdyk P. , Kowalczewski J.

Journal of Theoretical and Applied Mechanics

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1999

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tom nr 3

435-454

EN

In the paper the discussion of the modeling of hip joint implants is presented. the historical attempts to implant construction finally led to complex solutions. To date almost all experiences have learned from clinic observation and rather tests and trial methods than systematic research. Numerical simulations have been limited to simple stress analysis. All phenomena responsible for the damage in the treated joint are not fully explained. The comlexity of the problem is presented in the paper. The stress concentration in the region of rigid inclusion is pointed as one of the mechanical destructive factors. The change of the stem form and material rigidity cuuld reduce extremal stresses by 10-20%.

PL

W pracy omówiono modelowanie implantów stawu biodrowego. Historyczne próby ich konstruowania doprowadziły do bardzo złożonych rozwiązań. Dotąd niemal wszystkie doświadczenia zdobywano w obserwacjach klinicznych i próbach, a nie w wyniku systematycznych badań. Numeryczne symulacje ograniczono do prostej analizy stanu naprężenia. Większość zjawisk odpowiedzialnych za uszkodzenia badanych stawów nie jest w pełni wyjaśniona. W pracy zwrócono uwagę na złożoność zagadnienia. Za jeden z czynników niszczących uznano koncentracje naprężeń w strefach sztywnych wtrąceń. Zmiana kształtu trzpienia i sztywności materiału pozwala zmniejszyć ekstremalne naprężenia o 10-20%.

15

Numerical evaluation of sensitivity of stress distribution in bone to geometric parameters of endoprosthesis

80%

Kowalczyk P.

Journal of Theoretical and Applied Mechanics

|

1999

|

tom nr 3

555-577

EN

One of serious drawbacks in the bone endoprosthetics is the implant separation from bone or cement. Stress concentrations on the implant surface are deemed major factor in this process and implant shape optimization seems to be a natural way of improvement of stress disrtibution. An important tool in effective optimization algorithms is design sensitivity analysis (DSA). The discretized formulation of the problem in terms of the finite element method is presented in this paper. A three-dimensional model of femur with a cementless implant analysed. Frictionless contact and perfect bonding are assumed on the smooth and rough parts of the implant surface, respectively. Computational examples show the stress concentrations and their sensitivity to various geometric parameters of the implant.

PL

Jednym z poważnych mankamentów endoprotetyki stawów jest odrywanie się implantu od cementu lub kości. Główną przyczyną tego zjawiska są koncentracje naprężeń na powierzchni implantu. Optymalizacja kształtu implantu jest uważana za naturalną drogę do przeciwdziałania temu zjawisku. Ważnym narzędziem w algorytmach optymalizacji jest analiza wrażliwości parametrycznej (DSA). Praca przedstawia sformułowanie zagadnienia wrażliwości w zdyskretyzowanym ujęciu metody elementów skończonych. Analizowana jest kość udowa z implantem bezcementowym o powierzchni gładkiej, a w górnej części porowatej. Przykłady numeryczne przedstawiają koncentracje naprężeń w tkance kostnej i ich wrażliwość na różne parametry kształtu implantu.

16

BIomechanical aspects of artificial joint implantation in a lower limb

80%

Będziński R. , Bernakiewicz M. , Ścigała K.

Journal of Theoretical and Applied Mechanics

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1999

|

tom nr 3

455-479

EN

One of the most important trends in engineering biomechanics is experimental and numerical analysis of the stress and strain state existing in organs subject to a heavy load; e.g., the knee and hip joints. Clinical tests experimental and numerical studies on design of implants replacing damaged organs are also of crucial importance in development of biomechanics. The research is focused on determination of loads, experimental techniques as well as on simplifications assumed in measurements and applied models. The conducted investigations were concerned with estimation of mechanical behaviour of hip and knee implants after arthoplasty. The experimental tests on both the real objects and models were performed. Numerical simulation was made by using the finite element method. The tests have proved that from the biomechanical point of view proper selection of endoprothesis is of crucial importance for achieving positive long-term results of alloplasty.

PL

Jednym z najważniejszych kierunków badań w dziedzinie biomechaniki inżynierskiej jest doświadczalna i numeryczna analiza stanu odkształceń i naprężeń w organach ludzkich poddanych znacznym obciążeniom, jak chociażby staw biodrowy i kolanowy. Badania kliniczne, doświadczalne i numeryczne poświęcone konstrukcji elementów zastępujących uszkodzone elementy ciała ludzkiego stanowią jeden z najważniejszych kierunków biomechaniki. Dyskusje na tym tle skoncentrowane są na problemach beterminacji występującego stanu obciążenia, stosowanych technik pomiarowych oraz uproszczeń warunków pomiaru i przyjmowanych modeli. Przeprowadzone badania poświęcone zostały ocenie mechanicznej współpracy sztucznych elementów stawu biodrowego i kolanowego w warunkach modelowych, jak i metodą symulacji numerycznej, metodą elementów skończonych. Badania udowodniły duże znaczenie prawidłowej selekcji endoprotez z punktu widzenia biomechaniki układu na długoterminowe powodzenie alloplastyk.

17

Analiza sygnału emisji akustycznej z korowej tkanki kostnej obciążanej do złamania

80%

Zdunek A. , Trębacz H.

Prace Naukowe Politechniki Warszawskiej. Mechanika

|

2007

|

tom z. 217

145-150

EN

Acoustic emission signals (AE) were recorded during the bending test of rat femora. Bones from two adult age groups were tested: five month (A-5) and 12 months old (A-12). Bones were loaded to fracture in three-point bending. Energy of AE, number of bursts and average energy for one burst were analyzed to maximum force and to final fracture. Qualitative and quantitative differences in AE signals between two age groups were found in quasi-plastic range of deformation, while in the whole test the differences were not present. Number and energy of AE bursts in quasi-plastic range was larger in the older than in the younger bones. The fact was attributed to a larger amount of AE sources and a larger probability of growth of microfractures within the tissue before the final fracture load was achieved. The data confirm that brittleness of healthy, mature bone tissue increases with age.

18

Non-Metallic Composite Materials for Bone Surgery

80%

Chłopek J. , Kmita G.

Engineering Transactions

|

2003

|

tom Vol. 51, iss.2-3

307-323

EN

Possibility of using non-metallic materials in biomedical applications was considered. The attention was focused mainly on polymer materials and both the carbon-carbon and carbon-reinforced polymer composites, their mechanical and biological properties. The obtained results indicate that some of these materials can be successfully used instead of metallic implants for biomechanical functions.

19

Dynamical Forces Inside Facet Joints, Intervertebral Discs and Ligaments of Human Cervical Spine

80%

Gzik M. , Tejszerska D.

Engineering Transactions

|

2003

|

tom Vol. 51, iss.2-3

227-240

EN

The paper presents a dynamic spatial mathematical model in which a head, seven cervical vertebrae, a group of 19 couples of neck muscles, 6 intervertebral discs, ligaments and facet joints are taken into consideration. The created model enables simulation of dynamical forces inside anatomical parts of human neck. The behaviour of the modelled body exposed to action of a~force corresponding to the real enforcement, which occurs at a head-on collision during the road accident was simulated, and the model was verified on the basis of the data obtained from published experiments.

20

Breast Support Garments are Ineffective at Reducing Breast Motion During an Aqua Aerobics Jumping Exercise

80%

Mills C. , Ayres B. , Scurr J.

Journal of Human Kinetics

|

2015

|

tom 46

|

nr 1

49-58

EN

The buoyant forces of water during aquatic exercise may provide a form of ‘natural’ breast support and help to minimise breast motion and alleviate exercise induced breast pain. Six larger-breasted females performed standing vertical land and water-based jumps, whilst wearing three breast support conditions. Underwater video cameras recorded the motion of the trunk and right breast. Trunk and relative breast kinematics were calculated as well as exercised induced breast pain scores. Key results showed that the swimsuit and sports bra were able to significantly reduce the superioinferior breast range of motion by 0.04 and 0.05 m, respectively, and peak velocity by 0.23 and 0.33 m/s, respectively, during land-based jumping when compared to the bare-breasted condition, but were ineffective at reducing breast kinematics during water-based jumping. Furthermore, the magnitude of the swimsuit superioinferior breast range of motion during water-based jumping was significantly greater than land-based jumping (0.13 m and 0.06 m), yet there were no significant differences in exercise induced breast pain, thus contradicting previously published relationships between these parameters on land. Furthermore, the addition of an external breast support garment was able to reduce breast kinematics on land but not in water, suggesting the swimsuit and sports bras were ineffective and improvements in swimwear breast support garments may help to reduce excessive breast motion during aqua aerobic jumping exercises.