Title: Reliability of isometric and isokinetic strength testing in the knee flexion and extension Objectives: To compare the reliability of isometric and isokinetic testing of the knee strength in flexion and extension Methods: I used intraclass correlation coefficient and Pearson's correlation coefficient. Results: I have discovered that the reliability measured on isokinetic and isometric dynamometer is high. Furthermore the reliability of the maximum strength measurement was higher with-using the isokinetic dynamometer. Keywords: reliability, intraclass correlation coefficient, isometric dynamometry, maximal isometric strength, isokinetic dynamometry, knee strength, Cybex Humac Norm

Title: The effect of alcohol drinking on the isokinetic knee strength Objectives: The objective of this thesis is to assess the effect of alcohol on isokinetic knee strength during extension and flexion. Methods: Fifteen volunteers participated in this study. Their age was 23,9 ± 1,9 years, height 179,5 ± 7,2cm and weight 78,5 ± 7,95kg. They were all students from sports faculty. One group of volunteers was given alcohol with juice (0,8g of alcohol to 1kg of fat-free mass), the second group drank only juice. We used the switch design study. We measured isokinetic knee strenght on dynamometer Cybex Humac Norm (Cybex NORM ®, Humac, CA, USA) in three types of angular velocity (6Oř/s, 180ř/s, 240ř/s). The parametrs were peak torque, muscular work, average muscular power and time to peak. Results: We registered statistically significant increase of peak torque, muscular work and average muscular powers when measuring flexion in all the three angular velocities (60ř/s, 180ř/s, 240ř/s). We did not register statistically or effect size significant diference readings of time needed for maximal peak torque when measuring flexion and extension. The only exception was angular speed 240ř/s where we registered a factually significant change in time needed for extensors to reach the maximal peak torque....

Atualmente, alguns pesquisadores tem se dedicado ao estudo do efeito da manipulação do treinamento de força sobre a ativação das vias de sinalização intracelular para hipertrofia. Tem-se sugerido que o grau de tensão muscular desempenhe um papel importante nesta sinalização. Dentre os diferentes tipos de ações musculares, as ações excêntricas (AE) reconhecidamente proporcionam maior grau de tensão à estrutura do músculo esquelético. Em particular, AE de alta velocidade parecem exercer um efeito interessante sobre os ganhos de hipertrofia muscular. Porém, pouco se sabe sobre o efeito da manipulação da velocidade sobre as vias de sinalização da hipertrofia. Assim, o presente estudo teve como objetivo verificar o efeito agudo da AE de alta e baixa velocidade sobre a sinalização para hipertrofia muscular. Vinte sujeitos foram aleatoriamente divididos em dois grupos. Um realizou cinco séries de oito AE máximas à 20º/s (EXC20) e o outro à 210o/s (EXC210) do exercício extensão de joelhos. Amostras do músculo vasto lateral foram obtidas antes, imediatamente após e duas horas após o exercício. As análises de quantificação protéica de Akt e p70S6K totais não apresentaram diferenças significantes intra ou inter grupos. A avaliação da fosforilação das mesmas proteínas revelou um efeito principal de tempo, indicando um aumento da fosforilação nos tempos imediatamente após e duas horas após o término do exercício em relação à amostra controle (p<0,05), porém não foram observadas diferenças entre os grupos. Para os dados de expressão gênica de MGF e mTOR, não foram observadas diferenças intra ou inter grupos. Em conclusão, a manipulação aguda da velocidade das AE parece não influenciar a fosforilação ou expressão gênica das proteínas em questão / Recently, many studies have focused on the effects of strength training variables manipulation on the activation of intracellular signaling pathways for skeletal muscle hypertrophy. It has been suggested that the muscle tension plays a major role in such process. Eccentric muscle actions (EE) are notorious for imposing a greater amount of tension on the active muscle. In particular, EE performed at high velocities seems to exert an interesting effect on hypertrophy gains. However, little is known about the effect of EE velocity manipulation on hypertrophy pathways signaling. Thus, the present study aimed to investigate the acute effect of low and high velocity EE on muscle hypertrophy signaling. Twenty subjects were randomly assigned to either a slow velocity group 20o/s (ECC20) or fast group 210o/s (ECC210). Muscle biopsy samples were taken before, immediately after and two hours after the completion of five sets of eight maximal repetitions at the designated velocity, knee extension exercise. Akt and p70S6K analysis did not reveal any differences inter or intra groups. Akt and p70S6K phosphorylation results indicated a main effect for time (p<0,05), with increased phosphorylation values for immediately after and two hours after time points in comparison to control samples. MGF and mTOR mRNA analysis did not return any inter or intra groups differences. In conclusion, the acute manipulation of EE velocity does not seem to differently influence the phosphorylation or expression of the proteins studied

A dinamometria isocinética é um método seguro e fidedigno de avaliação da força, trabalho e potência dos grupos musculares e representa o padrão ouro na avaliação em cadeia cinética aberta. Com os avanços tecnológicos, a avaliação isocinética tornou-se uma ferramenta muito utilizada para avaliação do desempenho muscular tanto em estudos biomecânicos como clínicos. O objetivo deste estudo foi realizar revisão sistemática da literatura sobre avaliação isocinética do quadril, com ênfase nos parâmetros metodológicos associados e melhor reprodutibilidade, especificamente: posicionamento do paciente, do eixo do dinamômetro e do braço de alavanca no momento do exame; velocidade angular e tipo de contração. Foi realizada uma pesquisa bibliográfica sistematizada nas bases de dados eletrônicas Cochrane, LILACS, PEDro, PubMed e SciELO. Os critérios de inclusão foram: artigos que avaliaram a força da musculatura do quadril com o dinamômetro isocinético e que continham análise de reprodutibilidade ICC ou PCC dos testes. Foram encontrados 148 artigos selecionados nas bases de dados eletrônicas, deste total foram selecionados 20 estudos que avaliaram isocineticamente a musculatura do quadril, após a pré-seleção dos artigos, os mesmos foram subdivididos em 3 grupos de acordo com o movimento realizado pelo quadril: Grupo 1 treze artigos avaliaram o movimento de flexão e extensão; Grupo 2 nove artigos avaliaram abdução e adução; Grupo 3 seis artigos avaliaram rotação interna e externa, um total de 1137 indivíduos foram submetidos à avaliação isocinética do quadril. Em cada Grupo selecionaram-se os artigos que obtiveram melhor resultado de reprodutibilidade, cujos parâmetros metodológicos foram avaliados. Conclusão: Para obter melhor reprodutibilidade da avaliação isocinética da musculatura flexora e extensora do quadril, o indivíduo deve ser posicionado em decúbito dorsal com o eixo do dinamômetro alinhado no trocânter maior do fêmur. A fixação do braço de alavanca posicionada na região mais distal possível da coxa. A velocidade angular utilizada para análise de pico de torque e trabalho muscular 60°/s e para avaliação da potência muscular 180°/s e as contrações analisadas concêntricas e excêntricas. Na avaliação isocinética da musculatura abdutora e adutora do quadril, o indivíduo deve ser posicionado em decúbito lateral com as costas voltada para o dinamômetro, o eixo do dinamômetro posicionado na intersecção de duas linhas retas, sendo a primeira linha a partir da EIPS até o joelho e a segunda linha medial ao trocânter maior do fêmur em direção à linha média do corpo. A fixação do braço de alavanca posicionada na região distal da coxa. A velocidade angular utilizada para análise de pico de torque e trabalho muscular 30°/s e para avaliação de potência muscular 210°/s. As contrações analisadas foram concêntricas e excêntricas. Na avaliação isocinética dos rotadores internos e externos, o indivíduo testado posicionou-se sentado com eixo do dinamômetro alinhado com a linha articular do joelho, com a fixação do braço de alavanca na região distal da tíbia. A velocidade angular mais utilizada para análise de pico de torque e trabalho muscular foi de 30°/s e para avaliação da potência muscular foi 210°/s, as contrações analisadas também foram concêntricas e excêntricas. / Isokinetic dynamometry is a safe and reliable method for assessing the force, work and power of muscle groups and is the \"gold standard\" in the evaluation of muscle strength in the open kinetic chain. With technological advances, isokinetic evaluation has become a widely used tool to evaluate muscle performance in biomechanical as well as in clinical studies. The objective of this study was to systematically review the literature on isokinetic evaluation of the hip, with emphasis on methodological parameters associated to better reproducibility, specifically: patient positioning, dynamometer axis and lever arm during the evaluation; angular speed and type of contraction. A literature search was carried out systematically in electronic databases Cochrane, LILACS, PEDro, PubMed and SciELO. The inclusion criteria were papers on the evaluation of the hip muscles strength with an isokinetic dynamometer and papers that analyzed the ICC or PCC reproducibility test. 148 papers were found in electronic databases and of this total were selected 20 studies that evaluated isokinetically the muscles of the hip, after pre-selection, they were divided into 3 groups according to the movement performed by the hip: Group 1 - thirteen papers evaluated the flexion and extension; Group 2 - nine papers evaluated abduction and adduction; Group 3 - six papers evaluated internal and external rotation, a total of 1137 subjects underwent isokinetic evaluation of the hip. In each Group were selected items that obtained better results reproducibility, whose methodological parameters were evaluated. In conclusion: in order to obtain better reproducibility of isokinetic evaluation of the flexor and extensor muscles of the hip: the individual must be positioned in the supine position and the dynamometer axis must be aligned in the greater trochanter of the femur. The positioning of the lever arm must be in the most distal region of the thigh possible. The angular speed used to analyze torque peak and muscle work was 60°/s, and to evaluate the muscle power was 180°/s, and contractions analyzed concentric and eccentric. In isokinetic evaluation of the abductor and adductor muscles: the individual must be positioned in the side-lying position with your back toward the dynamometer and the dynamometer axis must be aligned with the intersection of two straight lines, with the 1st line from the posterior-superior iliac spine to the knee and the 2nd line medial to the greater trochanter of the femur toward the midline of the body. The positioning of the level arm must be in the most distal region of the thigh. The speed used to analyze torque peak and muscle work was 30°/s, and to evaluate the muscle power it was 210°/s, with concentric and eccentric contractions being analyzed. In isokinetic evaluation of internal and external rotators: the individual must be positioned in the sitting position and the dynamometer axis must be aligned with the line knee joint. The positioning of the level arm must be in the distal region of the tibia. The speed used to analyze torque peak and muscle work was 30°/s, and to evaluate the muscle power it was 210°/s, with concentric and eccentric contractions being analyzed.

O treinamento isocinético é uma alternativa eficaz para incrementos neuromusculares e na performance de torque muscular dos flexores e extensores do joelho. No entanto, o treinamento mais efetivo para aumentar o equilíbrio de torque muscular entre isquiotibiais e quadríceps (I/Q) ainda parece desconhecido. Portanto, o objetivo deste estudo foi comparar os efeitos de três diferentes tipos de treinamentos isocinéticos nas razões I/Q convencional (Rcon) e funcional (Rfun). Adicionalmente, foram avaliados os efeitos desses treinamentos nas variáveis de pico de torque (PT) concêntrico e excêntrico, pico de torque isométrico (PTI) taxa de produção de torque (TPT), ativação muscular (EMG), atraso eletromecânico (AE), espessura muscular (EM) e echo-intensity (EI) dos músculos flexores e extensores do joelho, bem como no desempenho funcional através dos testes squat jump (SJ), counter movement jump (CMJ), drop jump (DJ) e sprint 40m. Quarenta sujeitos homens destreinados (22,87 ± 2,28 anos, 70,66 ± 11,04 kg, 174,29 ± 6,9 cm) realizaram 6 semanas de treinamento para flexores e extensores do joelho em um dinamômetro isocinético Biodex. Eles foram selecionados de forma randomizada em 3 grupos de treinamento: modo concêntrico de extensão e concêntrico de flexão de joelhos (CON/CON); modo excêntrico de extensão e excêntrico de flexão de joelhos (EXC/EXC); modo concêntrico de extensão e excêntrico de flexão de joelhos (CON/EXC); e um grupo controle que não realizou nenhum treinamento (CNTRL). Todas as sessões de treinamento foram separadas por pelo menos 48h e as variáveis analisadas foram testadas em 2 dias, sendo realizadas 72h antes e depois da realização dos treinamentos. O grupo que treinou no modo EXC/EXC obteve maiores resultados na RFun, assim como aumentos significativos em PT excêntrico, PTI, CMJ e DJ comparado aos demais grupos (p<0,05), enquanto o grupo que treinou no modo CON/CON aumentou TPF em relação aos demais (p>0.05). Todos os grupos aumentaram EM do quadríceps e isquiotibiais de forma similar (p<0,05). Não houve diferença entre os grupos para PT concêntrico, EMG, AE, EI, RCon, SJ ou Sprint 40m (p>0,05). Portanto, o modo de treinamento EXC/EXC pode ser o mais efetivo para aumentar equilíbrio de torque muscular funcional I/Q. Treinamento excêntrico aumenta o torque excêntrico, influenciando nos aumentos na RFun e em saltos verticais que envolvem torque excêntrico (CMJ e DJ). O modo de treinamento CON/CON pode ser o mais efetivo em aumentos na potencia muscular. / Isokinetic dynamometers may be a viable alternative for improvements in neuromuscular and strength performance of knee flexors and extensors. However, the most advantages training protocol to elicit the greatest increases in hamstrings to quadriceps (H/Q) muscle balance is unknown. Therefore, the aim of this study was to compare three different isokinetic training protocols on H/Q strength balance, calculated by conventional and functional ratios. A secondary aim was to compare the training protocols across varied quadriceps and hamstrings muscle actions on concentric and eccentric peak torque (PT), isometric peak torque (IPT), rate of torque development (RTD), muscle activation (EMG), electromechanical delay (EMD), muscle thickness (MT) and echo-intensity (EI), as well functional performance tested by squat jump (SJ), counter movement jump (CMJ), drop jump (DJ) and 40m sprint tests. Forty untrained male subjects (22.87 ± 2.28 yrs, 70.66 ± 11.04 kg, 174.29 ± 6.9 cm) performed 6 weeks of training of their dominant and non-dominant knees on a Biodex isokinetic dynamometer. They were randomly assigned to 3 training groups; concentric quadriceps and concentric hamstrings (CON/CON), eccentric quadriceps and eccentric hamstrings (ECC/ECC), concentric quadriceps and eccentric hamstrings (CON/ECC) or no training (CNTRL). All training sessions were separated by at least 48 hours, and all variables were tested in 2 days 72h before and after training. Results revealed that the ECC/ECC group showed significant increases in functional ratio, as well as hamstrings and quadriceps eccentric PT, IPT, CMJ and DJ, compared to all other groups while the CON/CON group increased RTD (p<0.05). In addition, all training groups increased MT of quadriceps and hamstrings similarly (p<0.05). There were no differences between groups for concentric PT, EMG, ED, EI, SJ, conventional ratio or 40m sprint (p>0.05). Our findings suggest that ECC/ECC training may be the most effective at increasing functional H/Q strength ratio. Eccentric training increases eccentric strength, thereby increasing the functional H/Q strength ratio. Eccentric training also improves vertical jumps involving eccentric strength. CON/CON training may be more effective at increasing muscle power.

The aim of the study was to determine and to compare the trunk extensor and flexor muscles isocinetic contraction properties of adolescent wrestlers and non-athletes. To meet the target set the following tasks have been formulated: 1. To determine the trunk extensor muscles isocinetic contraction indices of wrestlers and non-athletes performing movements at different rate. 2. To determine the trunk flexor muscles isocinetic contraction indices of wrestlers and non-athletes performing movements at different rate. 3. To compare the ratio of trunk extensors and flexors muscles isocinetic contraction indices of wrestlers and non-athletes.. Six 16 years-old Greco-Roman wrestlers and nine non-athletes of the same age participated in the research. By means of the isokinetic dynamometer of the Biodex System 3 Pro type such functional indices of trunk muscles (extensors and flexors), as maximal and mean peak torque (PT), power, time up to developing maximal PT, as well as the ratio of these indices between trunk muscles (extensors and flexors) have been determined, All these indices were established performing trunk extension and flexion at 3 different angular rates, at 60, 90 and 120 degrees/sec. 1. Trunk extension indices (maximal and mean PT, power) of 16 year-old wrestlers are higher than those of non-athletes of the same age, irrespective of trunk extensors rate that was 60, 90 and 120 degrees/sec, except for the values of power indices performing trunk extensor at the rate... [to full text]

The goals of the pelvis include maintaining the center of mass of the body, assisting in foot clearance and absorb forces from the lower extremities using muscles and ligaments to stabilize the joint. A better understanding of the influence of muscle strength on controlling pelvic obliquity in a healthy population will help in understanding low back pain and overuse lower extremity injuries. Thirteen females (22 ±2 yrs) participated in isokinetic strength testing of the hip abductors, adductors, internal rotators and external rotators on a Biodex dynamometer. The subjects also underwent gait analysis during self selected pace walking and stair descent. For each muscle group subjects were divided into weaker and stronger groups based on the mean. Independent t-test revealed a significantly greater amount of pelvic obliquity in the stronger group for abductors, adductors, and internal rotators during stair descent. Subjects may be compensating for more pelvic obliquity with less movement of the hip, knee and ankle. During walking weaker external rotators was the only muscle group that significantly increased pelvic obliquity. Our study supports the finding of other studies that the external rotators contribute to pelvic stabilization during walking (Powers, 2003).

To examine the effect of acute beetroot juice supplementation on the rate of fatigue as measured by changes in peak torque. Placebo-controlled, double-blind, cross-over study, 35 recreationally active subjects consumed beetroot (BR) juice or black currant juice (PL) 12 and 2.5 hours before the exercise procedure. Peak torque was measured on the BIODEX dynamometer by performing 50, maximal effort, concentric knee extensions at 90°/s. Blood pressure (BP) was recorded before and after exercise. No significant difference between BR and PL in the rate of fatigue measured by change in peak torque. By stage 3, subjects retained 87.6±6.9% of strength with BR and 86.7±6.3% with PL (p= 0.363). Stages 10 was as follows: BR 47.9±12.6 vs. PL 46.9±12.9% (p= 0.419). The rate of work fatigue showed no significant differences. By stage 4, mean percent work fatigue showed 20.6±9% with BR and 21.8±10.1% with PL (p= 0.224). Stage 10 was as follows: BR 52.5±12.6% vs. PL 53.2±13% (p= 0.571). Post-exercise diastolic BP (BR: 67.2±9.8 vs. PL: 64.5±7.9mmHg, p= 0.039) and MAP (BR: 91.6±9.3 vs. PL: 88.8±8.2mmHg, p= 0.011) were higher with BR supplementation. Acute bouts of beetroot juice supplementation had no significant effect on knee extensor muscle fatigue measured during isokinetic contractions

Fourteen college softball players were recruited to participate in this study to determine if a strength imbalance between the lower extremities, how significant this difference this may be and of any correlations existed among all the functional tests. Subjects took part in isokinetic flexion and extension at 60 and 240 deg/sec, parallel squats, 2-legged vertical jump, single leg vertical jump, and a five-hop test. Peak and average torque was recorded for isokinetic testing and revealed significant differences between the dominant and non-dominant limbs (13.00%- 16.00%). Peak and average force was analyzed for squats and all vertical jumps. Significance was found among all activities between dominant and non-dominant legs, other than average force for single leg vertical jump. A significant difference was also exhibited for the five-hop test between the lower extremities. Significant correlations were also found at the 0.05 and 0.01 levels amongst the various functional tests. Overall findings revealed a significant strength imbalance between the dominant and non-dominant limbs. Further research needs to be conducted in determining how detrimental these differences could be in daily performance for athletes. / School of Physical Education

The game of rugby union has evolved over the years into a professional sport in which an increased incidence of injury is evident. This also applies to the shoulder joint. It appears that certain risk factors are associated with shoulder pathology among rugby players as well as among the general population. In a competitive sporting environment where high stress loads are placed upon the body and joints, this association may be even more pronounced. Despite the fact that numerous studies have investigated the various factors that potentially play a role in the occurrence of shoulder injuries among sports participants generally, similar studies involving rugby union players in particular are limited. Previous studies have investigated and profiled rugby players with regards to posture, shoulder isokinetic muscle strength and electromyographic patterns, but no study has yet investigated the relationship between these factors and the role they may play in the risk of being injured. It would be beneficial to have a better understanding of the interplay between these factors and to identify the most likely factors to predict and/or prevent shoulder injuries in rugby players. With this information at hand, it might be possible to identify players who are at risk of shoulder injuries in order that they may potentially benefit from effective “pre-habilitation” protocols. The aim of this study was to determine what the relationship between thoracic posture, isokinetic shoulder strength and scapulae muscle activation patterns in injured and uninjured rugby players was, and to determine which of these variables might predict shoulder injuries. Methods Ninety-one (91) uninjured semi-professional rugby union players’ shoulder joint range of motion differences (ROM) were manually tested with the hand-behind-the-neck and hand- behind-the-back method. The profiling and classification of the thoracic posture was performed using the New York Posture Test. Scapular muscle activation patterns were determined by means of electromyography (EMG) measuring the activation of the upper and lower trapezius, serratus anterior and infrapinatus muscles. The isokinetic muscle strength of the rotator cuff muscles was determined at 60°/sec (Kin-Com 500H) measuring concentric and eccentric forces during internal and external rotation. Results Some participants presented with non-ideal or unsatisfactory shoulder internal rotators (59%) and external rotators (85%) bilateral ROM differences. Of all the participants, 68% presented with an abnormal shoulder position in the lateral view, and the sequence of muscle activation of the scapula stabiliser muscles was found to be: serratus anterior; lower trapezius; infraspinatus and then upper trapezius. The isokinetic antagonist/agonist strength ratio for shoulder rotation during concentric muscle contraction was 64% for the non-dominant and 54% for the dominant shoulder. The corresponding ratios for the eccentric muscle contraction of the non-dominant and dominant shoulders were 67% and 61% respectively. The median muscle onset times of the backline players’ non-dominant infraspinatus muscles were 35.90 ms for ideal, 95.20 ms for non-ideal, and 93.90 ms for the unsatisfactory external rotators’ range of motion (ROM) differences. The median firing orders of the forwards’ dominant lower trapezius muscle was 3 for ideal, 1 for non-ideal, and 2 for unsatisfactory external rotators’ ROM differences. Among the forward shoulder group and the normal shoulder position group of the forwards respectively, the median muscle onset time of their non-dominant infraspinatus muscle was 113 milliseconds (ms) and 42 ms. Their non- dominant serratus anterior muscles’ median onset time was 78.85 ms among the players with a rounded back, and 31.90 ms among the players with a normal thoracic curvature. The backline players displayed a median non-dominant serratus anterior onset time of 47.45 ms (in the uneven shoulder group) versus 32.75 ms (in the even shoulder group). The median firing order of the backline players’ non-dominant infraspinatus muscle was third in the normally curved back group. Among the players with an abnormally rounded back, however, the median firing order changed to second. The median external rotation/internal rotation isokinetic strength ratio of the forward players was 63% (forward shoulders), versus 56.50% (normal shoulder position). This was for their non-dominant shoulders. Certain isokinetic shoulder strength ratios displayed statistically significant correlations with scapular muscle activation patterns but they were not clinically significant. Players who had sustained shoulder injuries during the season differed significantly from those who had not sustained injuries with regards to the following baseline measurements: age (the injured were older), height (the injured were taller) and non-dominant/dominant concentric external rotation ratio (the injured had a higher ratio). Among the backline players baseline differences occurred within age (the injured were older), weight (the injured were heavier), height (the injured were taller) and the body mass index (BMI) (the injured had a higher BMI). The variables that displayed statistically significant predictive values towards future injury were age (1.34 times increase for each year older), insufficient shoulder external rotator ROM differences (16.15 times increase if an unsatisfactory ROM difference occurs), uneven shoulders (4.43 times increase if shoulders were abnormally uneven) and the non- dominant/dominant concentric external rotation strength ratio (a 1.42 times increase for every 10% that the ratio increases). Conclusion Profiling of the group of players revealed that their non-ideal or unsatisfactory flexibility of shoulder external rotators, their forward shoulders in the lateral view, and their weakness of the shoulder external rotators did not result in abnormal scapular muscle activation patterns. Positive relationships were found between certain postural abnormalities (forward shoulders, a rounded back and uneven shoulders) and the delay of muscle onset times of infraspinatus and serratus anterior, as well as the firing order of infraspinatus. Forward shoulders increased antagonist/agonist isokinetic shoulder rotation strength ratios. Non-ideal or unsatisfactory flexibility of shoulder external rotators displayed positive relationships with altered infraspinatus muscle onset times and an altered lower trapezius muscle firing order. No clinically significant correlations were found between isokinetic shoulder strength ratios and scapulae muscle activation patterns. It appears that posture (uneven shoulders), has a higher predictive ability than shoulder strength imbalance (non-dominant/dominant concentric external rotation ratio) regarding future shoulder injury. However, age and especially external rotator ROM deficiency proved to be strong predictors of future shoulder injury in semi-professional rugby players. / Thesis (PhD (Human Movement Science))--North-West University, Potchefstroom Campus, 2013.