The tapering distribution of segment masses in the human arm helps in the generation of high ball release speeds in overarm throwing. However, the masses of the individual arm segments might not be optimal; arm segment masses could be optimised in order to improve throwing performance. The aim of this project was to identify and understand the optimal upper arm mass that results in the highest ball release speed in overarm throwing. The first study was a theoretical study, using a simple two-segment model of the arm to determine the optimal combination of arm segment masses that maximises ball release speed. This simplified throw was chosen to identify the basic mechanism causing changes in ball release speed with a heavier upper arm mass. The study identified that there is an optimal upper arm mass, but this optimum depends on the forearm mass and the shoulder torque. Furthermore, the study showed that a heavier forearm mass produces a lower ball release speed. An experimental approach was used in the second study to analyse the effect of additional upper arm mass on ball release speed and throwing mechanics in an overarm throw similar to that used by baseball pitchers. However, group analysis of the ball release speed did not reveal an optimal upper arm mass, and most of the kinematic, kinetic, and temporal variables were not affected by additional upper arm mass. However, analysing the ball release speed of each participant individually revealed that most participants increased their ball release speed, although there was considerable variation in the optimal upper arm mass. As the optimal upper arm masses in this study did not agree with those predicted in the first theoretical study, a more realistic three-dimensional model is needed to simulate the effect of upper arm mass on ball release speed. The third study was a combination of a theoretical and experimental approach. A three-dimensional model of the throwing arm was used to predict the participant's optimal upper arm mass and to determine the kinematic and kinetic variables that determine the optimal upper arm mass in overarm throwing. Even though the simulations did not accurately predict an athlete's optimal upper arm mass, the results highlighted that throwing athletes can benefit from a heavier upper arm mass as long as their ability to produce a high internal shoulder rotation angular velocity is not restricted. In summary, the findings of this project highlight that some athletes can benefit from a heavier upper arm mass to maximise their ball release speed without increasing the risk of injuries. However, as the optimal upper arm varies between athletes it is important to analyse each athlete individually.

Darbo tikslas: įvertinti pilvo giliųjų ir paviršinių raumenų elektrinį aktyvumą atliekant uždaros ir atviros kinetinės grandinės pratimus. Uždaviniai: 1. Įvertinti pilvo giliųjų ir paviršinių raumenų elektrinį aktyvumą atliekant pratimus ant stabilios atramos. 2. Įvertinti pilvo giliųjų ir paviršinių raumenų elektrinį aktyvumą atliekant pratimus ant nestabilios atramos. 3. Įvertinti pilvo giliųjų ir paviršinių raumenų elektrinį aktyvumą atliekant atviros kinetinės grandinės pratimus. 4. Įvertinti pilvo giliųjų ir paviršinių raumenų elektrinį aktyvumą atliekant uždaros kinetinės grandinės pratimus. 5. Įvertinti skirtingų, pilvo raumenims lavinti skirtų pratimų atlikimo metu gautą pilvo giliųjų ir paviršinių raumenų elektrinį aktyvumą. Tyrimo metodai: Tyrime dalyvavo 20 darbingo amžiaus vyrų, per tris mėnesius neturėjusių nusiskundimų dėl apatinės nugaros dalies skausmo. Tyrimo pradžioje tiriamajam buvo duodama 15 minučių apšilimo programa, po kurios sekė 8 testuojant naudotų pratimų atlikimas. Ant tiriamojo priklijuotais paviršiniais elektrodais, elektromiografu Myotrace 400 buvo registruojamas ir užrašomas raumenų elektrinis aktyvumas. Išvados: 1. Didžiausias raumenų elektrinis aktyvumas buvo atliekant liemens lenkimą kulnais spaudžiant dėžutę sėdmenų link ant stabilios atramos (p<0,05). Didžiausias santykinis giliųjų-paviršinių pilvo raumenų aktyvumas buvo atliekant liemens lenkimo atremtyje ant delnų ir kelių pratimą. 2. Atliekant pratimus ant nestabilios atramos... [toliau žr. visą tekstą] / The aim: to assess deep and superficial abdominal muscles electrical activity during open and closed kinetic chain exercises. Objectives: 1. To evaluate the surface and deep abdominal muscle electrical activity during exercise on a stable support. 2. To evaluate the surface and deep abdominal muscle electrical activity during the exercises on unstable supports. 3. To evaluate the surface and deep abdominal muscle electrical activity during a open kinetic chain exercises. 4. To evaluate the surface and deep abdominal muscle electrical activity during closed kinetic chain exercises. 5. To evaluate the surface and deep abdominal muscle electrical activity in variation of the abdominal exercises. Research metods: A total of 20 working-age men during the three months had no complaints of lower back pain. In the beginning of study the research was given 15 minutes to warm-up program, which was followed by eight testing exercises performance. Electromyograph Myotrace 400 has been registered and recorded muscles electrical activity by glued onto the skin surface electrodes. Conclusions: 1. The maximum muscle electrical activity was during trunk flexion with pressing the box by the heels toward the buttocks on the stable surface (p<0,05). The highest ratio of surface-deep abdominal muscle activity was during trunk flexion facing on the palms and knees. 2. During the exercises on unstable surface the highest muscle electrical activity was in trunk flexion exercise with pressing the... [to full text]

The purpose of this study was to determine if a firefighter's fundamental movement patterns can act as predictors for occupational injury and performance during the firefighter academy training. The study consisted of 23 firefighter candidates entering the 16-week firefighter academy training. The firefighter candidates', VO2Max, 1.5 mile-run and Firefighter Physical Conditioning Course and movement patterns were assessed at the on-set of the 16-week training. The firefighter movement patterns were assessed utilizing the Functional Movement Screen, which was designed to identify flaws in fundamental movement patterns. The firefighter candidates were then observed and their injuries documented during the firefighter academy training. The injury results as well as the initial performance tests were then compared to the results obtained by the Functional Movement Screen. There were no significant findings when comparing the Functional Movement Screen to the performance tests. The only significant correlation was with the Functional Movement Screen asymmetry score and the Firefighter Physical Conditioning Course. The relationship between the injuries recorded and Functional Movement Screen scores were inconclusive. The results of this study were unable to determine if a movement-based assessment such as the Functional Movement Screen can be utilized as an injury or performance predictor tool. The findings determined that further research needs to be performed with efforts placed on larger population groups and more emphasis placed on the scoring and analysis criteria used by the movement-based assessment. / Ph. D.

Exercícios em cadeia cinética aberta e fechada tem sido propostos para a reabilitação no pós operatório de reconstrução do ligamento cruzado anterior. Não há consenso na literatura sobre qual o tipo de exercício é mais apropriado e ao mesmo tempo seguro, não pondo em risco o procedimento cirúrgico. O propósito deste estudo foi verificar os efeitos da utilização de protocolos de reabilitação em cadeia cinética aberta e fechada de indivíduos em pós operatório de reconstrução do ligamento cruzado anterior, através de respostas comportamentais verificadas por indicadores biomecânicos. A amostra experimental foi constituída de trinta indivíduos, divididos em três grupos amostrais independentes: (CON) dez indivíduos normais que não sofreram nenhum tipo de intervenção; (CCF) dez pacientes submetidos ao programa de reabilitação em cadeia cinética fechada e (CCA) dez pacientes submetidos ao programa de reabilitação em cadeia cinética aberta. Os testes para avaliar os parâmetros biomecânicos selecionados foram realizados em duas etapas: avaliação clínica (deslocamento tibial anterior e escore de Lysholm) e avaliação da marcha (análise dinâmica, cinemática e eletromiográfica). O tratamento foi realizados três vezes por semana, durante doze semanas. Os pacientes foram submetidos a três testes; o primeiro no pré-operatório; o segundo após quatro semanas da cirurgia e o terceiro após quatro meses de cirurgia. O grupo controle realizou apenas um teste e não foi submetido a nenhum tipo de tratamento. Para a xx análise do deslocamento tibial anterior foi utilizado o aparelho KT1000. A análise da marcha foi realizada através da esteira rolante Gaitway Kistler, a análise da atividade eletromiográfica através do sistema Bagnoli 8, composta de eletrodos de superfície e a análise da variação angular do joelho através do eletrogoniômetro Elgon-Burns. Os dados foram registrados, armazenados, processados e analisados estatisticamente, levando-se em consideração o nível de significância de 0,05. As variáveis relativas à força de reação do solo foram analisadas através da determinação de componentes principais. O deslocamento tibial anterior diminuiu ao final do tratamento e o escore de Lysholm aumentou em ambos os grupos, sem diferença significativa entre eles. Das variáveis analisadas relativas à marcha o tempo de apoio simples, as taxas de crescimento para os picos da força vertical, a deflexão da força mínima, a força mínima e o segundo pico parecem-nos serem as variáveis mais sensíveis para identificar diferenças na forma de andar em função do protocolo de reabilitação. Ao analisar a amplitude de movimento percebe-se que esta variável é sensível a mudanças expressivas na variação angular do joelho, como ocorreram no teste após quatro semanas de pós-operatório. Pela análise descritiva, diferenças angulares menores devem ser analisadas através dos ângulos em momentos específicos da marcha. Em relação à atividade elétrica muscular o M.bíceps femoral foi o que apresentou maior variação na sua atividade. E os valores de simetria demonstram que o grupo cadeia cinética aberta foi o que apresentou maiores diferenças entre as pernas no teste após quatro semanas de cirurgia, o que demonstra maior instabilidade no andar. O presente estudo permite concluir que as alterações da marcha são mais expressivas um mês após a cirurgia do que no período pré-operatório. O escore de Lysholm, os componentes principais das variáveis relativas a força de reação do solo e a variação angular do joelho indicam que os exercícios em cadeia cinética fechada são mais eficientes para a recuperação da marcha do que os de cadeia cinética aberta. No entanto, os dois tipos de exercícios propiciam melhora dos parâmetros da marcha e parecem ser eficientes na recuperação da marcha dos pacientes submetidos à reconstrução do ligamento cruzado anterior. O período de quatro meses de reabilitação assegura uma marcha sem riscos para o paciente, mas ainda distinta da característica da marcha de indivíduos não acometidos pela lesão / Open kinetic chain and closed kinetic chain exercises have been proposed for rehabilitation protocol in the reconstruction of the anterior cruciate ligament. There is no consensus in the literature regarding which exercise is more appropriate and at the same time safe without putting in risk the surgical procedure. The purpose of this study was to evaluate the results of the open kinetic chain and closed kinetic chain protocols in the rehabilitation of those individuals that were subject to the reconstruction of the anterior cruciate ligament based on biomechanical indicatives. The sample was made of thirty individuals, divided in three independent groups: (CON) ten normal individuals that were not submitted to the surgical intervention; (CCF) ten patients submitted to the closed kinetic chain rehabilitation program, and (CCA) ten patients submitted to the open kinetic chain rehabilitation program. Tests to evaluate the desired biomechanical parameters had been carried out through two stages: clinical evaluation (anterior tibial displacement and Lysholm`s score) as well as gait evaluation (dynamic, kinematic and electromyografic analysis). The treatment was carried out three times per week, during twelve weeks. Each patient had been evaluated in three occasions: before the surgery; four weeks after the surgery; and four months after the surgery. The group control was submitted to only one evaluation test and no treatment at all. KT1000 equipament was used for evaluating the tibial displacement. The gait analysis was carried out through the Gaitway Kistler treadmill; the electromyography analysis was evaluated through xxii the System Bagnoli 8 composed of surface electrodes and the analysis of the angular variation of the knee through Elgon-Burns electrogoniometer. Data had been collected and analyzed considering the 0,05 significance level. The ground reaction force variable had been analyzed through of the determination of main components. The anterior tibial displacement diminished at the end of the treatment and the Lysholm`s score increased in both groups without significant difference between them. From the analyzed variables regarding gait, the time of simple support, the taxes of growth for peaks of the vertical force, the deflection of the minimum force, the minimum force and as the peak, seem to be the most sensible variables to identify gait differences due to the rehabilitation protocol. Upon analyzing the amplitude of movement it was noticed that this variable was sensible to huge changes in the angular variation, as those observed after four weeks from the surgery. By the descriptive analysis, lesser angular differences must be analyzed through the angles at specific moments of the gait. Regarding the muscular activity the femoral biceps femoris (long head) presented greater variation in its activity. And, the symmetry values demonstrate that the open kinetic chain group presented greater differences between both legs in the test four weeks after the surgery, demonstrating greater instability in walking. The current study permit to conclude that the variations in the gait are higher in one month after the surgery than in the pre-surgery period. The Lysholm`s score, the ground reaction force, variable the main components and the angular variation of the knee indicates that the exercises in closed kinetic chain are more efficient than opened kinetic chain for recovering the gait. However, the two exercises improved the parameters of gait and seem to be efficient in recovering the gait pattern of patients submitted to the anterior cruciate ligament reconstruction. Although the four months period of rehabilitation is enough to reinstate a harmless gait pattern to patients, it is still not sufficient to return the patients` gait standards to those of individuals without injury

Exercícios em cadeia cinética aberta e fechada tem sido propostos para a reabilitação no pós operatório de reconstrução do ligamento cruzado anterior. Não há consenso na literatura sobre qual o tipo de exercício é mais apropriado e ao mesmo tempo seguro, não pondo em risco o procedimento cirúrgico. O propósito deste estudo foi verificar os efeitos da utilização de protocolos de reabilitação em cadeia cinética aberta e fechada de indivíduos em pós operatório de reconstrução do ligamento cruzado anterior, através de respostas comportamentais verificadas por indicadores biomecânicos. A amostra experimental foi constituída de trinta indivíduos, divididos em três grupos amostrais independentes: (CON) dez indivíduos normais que não sofreram nenhum tipo de intervenção; (CCF) dez pacientes submetidos ao programa de reabilitação em cadeia cinética fechada e (CCA) dez pacientes submetidos ao programa de reabilitação em cadeia cinética aberta. Os testes para avaliar os parâmetros biomecânicos selecionados foram realizados em duas etapas: avaliação clínica (deslocamento tibial anterior e escore de Lysholm) e avaliação da marcha (análise dinâmica, cinemática e eletromiográfica). O tratamento foi realizados três vezes por semana, durante doze semanas. Os pacientes foram submetidos a três testes; o primeiro no pré-operatório; o segundo após quatro semanas da cirurgia e o terceiro após quatro meses de cirurgia. O grupo controle realizou apenas um teste e não foi submetido a nenhum tipo de tratamento. Para a xx análise do deslocamento tibial anterior foi utilizado o aparelho KT1000. A análise da marcha foi realizada através da esteira rolante Gaitway Kistler, a análise da atividade eletromiográfica através do sistema Bagnoli 8, composta de eletrodos de superfície e a análise da variação angular do joelho através do eletrogoniômetro Elgon-Burns. Os dados foram registrados, armazenados, processados e analisados estatisticamente, levando-se em consideração o nível de significância de 0,05. As variáveis relativas à força de reação do solo foram analisadas através da determinação de componentes principais. O deslocamento tibial anterior diminuiu ao final do tratamento e o escore de Lysholm aumentou em ambos os grupos, sem diferença significativa entre eles. Das variáveis analisadas relativas à marcha o tempo de apoio simples, as taxas de crescimento para os picos da força vertical, a deflexão da força mínima, a força mínima e o segundo pico parecem-nos serem as variáveis mais sensíveis para identificar diferenças na forma de andar em função do protocolo de reabilitação. Ao analisar a amplitude de movimento percebe-se que esta variável é sensível a mudanças expressivas na variação angular do joelho, como ocorreram no teste após quatro semanas de pós-operatório. Pela análise descritiva, diferenças angulares menores devem ser analisadas através dos ângulos em momentos específicos da marcha. Em relação à atividade elétrica muscular o M.bíceps femoral foi o que apresentou maior variação na sua atividade. E os valores de simetria demonstram que o grupo cadeia cinética aberta foi o que apresentou maiores diferenças entre as pernas no teste após quatro semanas de cirurgia, o que demonstra maior instabilidade no andar. O presente estudo permite concluir que as alterações da marcha são mais expressivas um mês após a cirurgia do que no período pré-operatório. O escore de Lysholm, os componentes principais das variáveis relativas a força de reação do solo e a variação angular do joelho indicam que os exercícios em cadeia cinética fechada são mais eficientes para a recuperação da marcha do que os de cadeia cinética aberta. No entanto, os dois tipos de exercícios propiciam melhora dos parâmetros da marcha e parecem ser eficientes na recuperação da marcha dos pacientes submetidos à reconstrução do ligamento cruzado anterior. O período de quatro meses de reabilitação assegura uma marcha sem riscos para o paciente, mas ainda distinta da característica da marcha de indivíduos não acometidos pela lesão / Open kinetic chain and closed kinetic chain exercises have been proposed for rehabilitation protocol in the reconstruction of the anterior cruciate ligament. There is no consensus in the literature regarding which exercise is more appropriate and at the same time safe without putting in risk the surgical procedure. The purpose of this study was to evaluate the results of the open kinetic chain and closed kinetic chain protocols in the rehabilitation of those individuals that were subject to the reconstruction of the anterior cruciate ligament based on biomechanical indicatives. The sample was made of thirty individuals, divided in three independent groups: (CON) ten normal individuals that were not submitted to the surgical intervention; (CCF) ten patients submitted to the closed kinetic chain rehabilitation program, and (CCA) ten patients submitted to the open kinetic chain rehabilitation program. Tests to evaluate the desired biomechanical parameters had been carried out through two stages: clinical evaluation (anterior tibial displacement and Lysholm`s score) as well as gait evaluation (dynamic, kinematic and electromyografic analysis). The treatment was carried out three times per week, during twelve weeks. Each patient had been evaluated in three occasions: before the surgery; four weeks after the surgery; and four months after the surgery. The group control was submitted to only one evaluation test and no treatment at all. KT1000 equipament was used for evaluating the tibial displacement. The gait analysis was carried out through the Gaitway Kistler treadmill; the electromyography analysis was evaluated through xxii the System Bagnoli 8 composed of surface electrodes and the analysis of the angular variation of the knee through Elgon-Burns electrogoniometer. Data had been collected and analyzed considering the 0,05 significance level. The ground reaction force variable had been analyzed through of the determination of main components. The anterior tibial displacement diminished at the end of the treatment and the Lysholm`s score increased in both groups without significant difference between them. From the analyzed variables regarding gait, the time of simple support, the taxes of growth for peaks of the vertical force, the deflection of the minimum force, the minimum force and as the peak, seem to be the most sensible variables to identify gait differences due to the rehabilitation protocol. Upon analyzing the amplitude of movement it was noticed that this variable was sensible to huge changes in the angular variation, as those observed after four weeks from the surgery. By the descriptive analysis, lesser angular differences must be analyzed through the angles at specific moments of the gait. Regarding the muscular activity the femoral biceps femoris (long head) presented greater variation in its activity. And, the symmetry values demonstrate that the open kinetic chain group presented greater differences between both legs in the test four weeks after the surgery, demonstrating greater instability in walking. The current study permit to conclude that the variations in the gait are higher in one month after the surgery than in the pre-surgery period. The Lysholm`s score, the ground reaction force, variable the main components and the angular variation of the knee indicates that the exercises in closed kinetic chain are more efficient than opened kinetic chain for recovering the gait. However, the two exercises improved the parameters of gait and seem to be efficient in recovering the gait pattern of patients submitted to the anterior cruciate ligament reconstruction. Although the four months period of rehabilitation is enough to reinstate a harmless gait pattern to patients, it is still not sufficient to return the patients` gait standards to those of individuals without injury

Neuromuscular control is believed to play an essential role during dynamic knee joint stabilisation. Evaluation of voluntary muscle action can be delineated as support strategies against external loading moments (Lloyd & Buchanan, 2001). The aim of this study was to determine if males and females exhibit differences in knee muscle action and cocontraction during voluntary isometric closed kinetic chain force generation in various directions in the horizontal plane representative of applied loads transverse to the long axis of the shank. Twenty-six healthy young adults (13 male, 13 female) stood with their dominant leg in a boot fixed to a force platform. A force target matching protocol required subjects to position a cursor (projected on a video screen) over a target and maintain the position for one second. To control the cursor, loads were applied against the force platform with their dominant leg to produce various combinations of anterior-posterior, medial-lateral loads while maintaining constant inferior-superior loads. A successful target match required a normalised force magnitude of equal effort for each subject and target location which triggered the recording of electromyography (EMG) for eight muscles crossing the knee joint. EMG was normalised to percent maximum voluntary isometric contraction. A mean magnitude of muscle activation, mean direction of muscle activation and a muscle specificity index was determined using EMG vectors. In addition, cocontraction indices were also computed for antagonist muscle pairs. Based on similar previous research, it was hypothesised that females would have greater quadriceps and hamstrings coactivation, greater muscle activation magnitudes, lower specificity for the quadriceps than males and no difference in hamstring characteristics. In our study, females significantly cocontracted their vastus lateralis and lateral gastrocnemius muscles to a greater degree than males (p=0.001). No significant differences were observed across sexes for the cocontraction of quadriceps and hamstrings or the lateral quadriceps and gastrocnemius muscles. Females displayed significantly lower specificity than males in their semitendinosus (p=0.025) and tensor fascia lata (p=0.012) activity patterns, greater magnitude of muscle activation in their lateral gastrocnemius (p=0.002) and tensor fascia lata (p<0.003) and no statistical difference in the other muscles. Furthermore, the activation patterns in our study grossly differed from previous open kinetic chain force target matching. These findings indicate that healthy young males and females have differences in their knee muscle control strategies and that knee muscle recruitment patterns differ during weight bearing and non-weight bearing tasks.

Neuromuscular control is believed to play an essential role during dynamic knee joint stabilisation. Evaluation of voluntary muscle action can be delineated as support strategies against external loading moments (Lloyd & Buchanan, 2001). The aim of this study was to determine if males and females exhibit differences in knee muscle action and cocontraction during voluntary isometric closed kinetic chain force generation in various directions in the horizontal plane representative of applied loads transverse to the long axis of the shank. Twenty-six healthy young adults (13 male, 13 female) stood with their dominant leg in a boot fixed to a force platform. A force target matching protocol required subjects to position a cursor (projected on a video screen) over a target and maintain the position for one second. To control the cursor, loads were applied against the force platform with their dominant leg to produce various combinations of anterior-posterior, medial-lateral loads while maintaining constant inferior-superior loads. A successful target match required a normalised force magnitude of equal effort for each subject and target location which triggered the recording of electromyography (EMG) for eight muscles crossing the knee joint. EMG was normalised to percent maximum voluntary isometric contraction. A mean magnitude of muscle activation, mean direction of muscle activation and a muscle specificity index was determined using EMG vectors. In addition, cocontraction indices were also computed for antagonist muscle pairs. Based on similar previous research, it was hypothesised that females would have greater quadriceps and hamstrings coactivation, greater muscle activation magnitudes, lower specificity for the quadriceps than males and no difference in hamstring characteristics. In our study, females significantly cocontracted their vastus lateralis and lateral gastrocnemius muscles to a greater degree than males (p=0.001). No significant differences were observed across sexes for the cocontraction of quadriceps and hamstrings or the lateral quadriceps and gastrocnemius muscles. Females displayed significantly lower specificity than males in their semitendinosus (p=0.025) and tensor fascia lata (p=0.012) activity patterns, greater magnitude of muscle activation in their lateral gastrocnemius (p=0.002) and tensor fascia lata (p<0.003) and no statistical difference in the other muscles. Furthermore, the activation patterns in our study grossly differed from previous open kinetic chain force target matching. These findings indicate that healthy young males and females have differences in their knee muscle control strategies and that knee muscle recruitment patterns differ during weight bearing and non-weight bearing tasks.

Neuromuscular control is believed to play an essential role during dynamic knee joint stabilisation. Evaluation of voluntary muscle action can be delineated as support strategies against external loading moments (Lloyd & Buchanan, 2001). The aim of this study was to determine if males and females exhibit differences in knee muscle action and cocontraction during voluntary isometric closed kinetic chain force generation in various directions in the horizontal plane representative of applied loads transverse to the long axis of the shank. Twenty-six healthy young adults (13 male, 13 female) stood with their dominant leg in a boot fixed to a force platform. A force target matching protocol required subjects to position a cursor (projected on a video screen) over a target and maintain the position for one second. To control the cursor, loads were applied against the force platform with their dominant leg to produce various combinations of anterior-posterior, medial-lateral loads while maintaining constant inferior-superior loads. A successful target match required a normalised force magnitude of equal effort for each subject and target location which triggered the recording of electromyography (EMG) for eight muscles crossing the knee joint. EMG was normalised to percent maximum voluntary isometric contraction. A mean magnitude of muscle activation, mean direction of muscle activation and a muscle specificity index was determined using EMG vectors. In addition, cocontraction indices were also computed for antagonist muscle pairs. Based on similar previous research, it was hypothesised that females would have greater quadriceps and hamstrings coactivation, greater muscle activation magnitudes, lower specificity for the quadriceps than males and no difference in hamstring characteristics. In our study, females significantly cocontracted their vastus lateralis and lateral gastrocnemius muscles to a greater degree than males (p=0.001). No significant differences were observed across sexes for the cocontraction of quadriceps and hamstrings or the lateral quadriceps and gastrocnemius muscles. Females displayed significantly lower specificity than males in their semitendinosus (p=0.025) and tensor fascia lata (p=0.012) activity patterns, greater magnitude of muscle activation in their lateral gastrocnemius (p=0.002) and tensor fascia lata (p<0.003) and no statistical difference in the other muscles. Furthermore, the activation patterns in our study grossly differed from previous open kinetic chain force target matching. These findings indicate that healthy young males and females have differences in their knee muscle control strategies and that knee muscle recruitment patterns differ during weight bearing and non-weight bearing tasks.

Patellofemoral pain (PFP) is believed to be associated with deficits in coordination between the different heads of the quadriceps muscle; however, considerable debate exists in the literature regarding the presence of such a deficit. Discrepancies between studies may be explained by differences in experimental tasks, such as whether the task is performed with open (OKC) or closed kinetic chain (CKC), or whether the activity is voluntary or triggered. Particular interest has been directed toward the function of the vastus medialis obliquus (VMO), which is a short muscle with limited ability to exert torque across the knee joint, but probably has a particular role in controlling patellofemoral joint position. Another short muscle that may influence knee joint position control is popliteus (POP), which is located in the back of the knee. This thesis investigates task specific activity of quadriceps in CKC versus OKC and studies the relative activity between the four heads of the quadriceps in PFP subjects compared to controls without knee pain in voluntary activity (CKC and OKC) and postural responses to balance perturbations. In addition, this thesis investigates the presumed function of POP for control of joint position in postural tasks in healthy individuals. All subjects were of normal weight and height and between 18 and 40 years. Quadriceps activity was tested for isometric with identical joint configuration in CKC and OKC, and it was performed as a reaction time task. Balance perturbations were elicited by unpredictable anterior and posterior translations of the support surface. Function of POP was investigated in unpredictable support surface translations and in self induced provocations to balance by moving the arms. Muscle activity was recorded with electromyography (EMG). Optic kinematic analysis was used to obtain specific movement responses to perturbations of balance. The quadriceps muscles were activated differently in CKC and OKC. VMO was activated earlier and to a greater degree in CKC. Rectus femoris was activated earlier and to a greater degree in OKC. PFP subjects reacted slower in both CKC and OKC, but there was no difference between groups in the relative activity between the different heads of the quadriceps. In the unpredictable support surface translation in the anterior direction, PFP subjects responded with earlier onset of VMO and with greater trunk and hip flexion in the anterior translation. POP activation in response to support surface translations in both directions occurred before all other muscles measured. In the self-initiated provocations of balance, POP was activated after the initiation of the balance provocation. This thesis concludes that quadriceps activity was task specific. The lack of difference between groups in OKC and CKC, and the difference between groups in postural responses suggest that variations in motor behaviour may occur only in tasks habitually performed. Differences in muscle activation patterns may be related to compensatory strategies to unload the quadriceps muscles and the patellofemoral joint. Furthermore, this thesis suggests that POP muscle may have a particular role in active control of the knee joint.

Darbo tikslas – įvertinti nugaros giliųjų ir paviršinių raumenų elektrinį aktyvumą atliekant pratimus atviroje kinetinėje grandinėje. Pasirinktam darbo tikslui įgyvendinti buvo iškelti šie uždaviniai: 1. Įvertinti nugaros giliųjų ir paviršinių raumenų elektrinį aktyvumą atliekant pratimus atviroje kinetinėje grandinėje ant stabilios atramos. 2. Įvertinti nugaros giliųjų ir paviršinių raumenų elektrinį aktyvumą atliekant pratimus atviroje kinetinėje grandinėje ant nestabilios atramos. 3. Palyginti giliųjų raumenų elektrinį aktyvumą su paviršinių raumenų elektriniu aktyvumu kiekvieno pratimo metu. 4. Palyginti raumenų elektrinį aktyvumą tarp identiškų pratimų, atliekamų ant stabilios atramos, su atliekamais ant nestabilios atramos. 5. Palyginti raumenų elektrinį aktyvumą tarp identiškų pratimų, kurių atlikimas skiriasi judesyje dalyvaujančių apatinių galūnių skaičiumi. Tyrime dalyvavo 20 darbingo amžiaus vyrų, per tris mėnesius neturėjusių nusiskundimų dėl nugaros apatinės dalies skausmo. Tyrimą sudarė dvi dalys: 15 minučių trukmės tiriamųjų apšilimas (5 minutės veloergometro mynimui ir 10 minučių tempimo pratimams) ir tiriamųjų testavimas. Tiriamųjų testavimą sudarė 11 pratimų ir 2 testavimo padėtys maksimaliam valingam testuojamų raumenų susitraukimui išgauti. Išvados: 1. Dauginio raumens elektrinis aktyvumas buvo didesnis nuo 19,5 % iki 27,8 % nei tiesiamojo nugaros raumens krūtininės dalies elektrinis aktyvumas penkiuose iš septynių pratimų, atliekamų ant stabilios... [toliau žr. visą tekstą] / The purpose of this research: To evaluate electric activity of deep and superficial back muscles during open kinetic chain exercises. Goals of this research: 1. To evaluate electric activity of deep and superficial back muscles during open kinetic chain exercises performed on stable support. 2. To evaluate electric activity of deep and superficial back muscles during open kinetic chain exercises performed on labile support. 3. To compare electric activity of deep and superficial back muscles during each exercise. 4. To compare electric activity of back muscles between the same exercise pairs performed on different support type. 5. To compare electric activity of back muscles during exercise performed with one lower limb with exercise performed with both lower limbs. During this research 20 men, who had no recent complaints about low back pain (>3 months), were tested. The testing consisted of two parts: 15 min. for warm up exercises (5 min. – cardio respiratory warm up and 10 min. – stretching exercises) and the main testing. The main testing consisted of 11 exercises and 2 exercise to determine maximum voluntary contraction. Conclusion: 1. Electric activity of multifidus muscle was statistically significant higher than electric activity of thoracic part of erector spinae muscle during 5 from 7 exercises performed on stable support (p<0,05). 2. Electric activity of multifidus muscle was statistically significant higher than electric activity of thoracic part of erector spinae... [to full text]