Evaluation of the internal forces on tibiofemoral joint during knee extension performance with and without load and realized and different velocities

O conhecimento das forças internas é fundamental para o entendimento das cargas impostas ao sistema musculoesquelético em situações de exercícios ou atividades físicas. Sabe-se que a articulação tibiofemoral é uma das articulações mais acometidas por doenças articulares do corpo. A técnica mais utilizada para determinação das forças internas da articulação tibiofemoral é a dinâmica inversa, entretanto, é necessário o reconhecimento de parâmetros musculares para determinação das forças articulares em situações envolvendo movimentos em cadeia cinética aberta. Um tipo de atividade extremamente desenvolvida nas academias e nas clínicas de fisioterapia para fortalecimento da musculatura extensora do joelho é o exercício de extensão de joelho em cadeia cinética aberta. Desta forma, o objetivo geral deste estudo foi avaliar as forças que envolvem a articulação tibiofemoral durante o exercício de extensão de joelho em cadeia cinética aberta e os objetivos específicos foram: desenvolver um modelo matemático que informe as forças na articulação tibiofemoral durante o exercício de extensão de joelho em cadeia cinética aberta e avaliar o efeito do aumento da velocidade de execução do exercício e o efeito do aumento da carga externa do exercício, ambos sobre a força tibiofemoral. A avaliação das forças internas da articulação tibiofemoral foi realizada com base na técnica da dinâmica inversa. O torque de resistência à extensão passiva do joelho foi acrescentado ao modelo de determinação das forças internas. Os resultados apontam que quanto menor o ângulo de flexão maior a força de compressão nas velocidades de 45°/s e 90°/s e na velocidade de 180°/s o comportamento das forças internas se alteram pelo efeito inercial da caneleira. A força de compressão apresentou seu pico máximo em torno de 1100 N durante o exercício realizado com caneleiras de 10 kg nas velocidades de 45°/s e 180°/s. A força do ligamento cruzado anterior está presente entre os ângulos de 0 à 40° e a do cruzado posterior entre 50° e 90° de flexão de joelho. O pico de força do ligamento cruzado anterior aproximadamente de 150 N durante a extensão de joelho realizada com caneleira de 10 kg nas velocidades de 45°/s e 90°/s e o pico de força do ligamento cruzado anterior foi aproximadamente de 180 N durante o exercício de extensão de joelho na velocidade de 180°/s.The knowledge of internal forces is primordial to understand the forces that are applied on the skeletal muscles system during exercises or physical activities. It's known that tibiofemoral joint is one of the most attacked by joint diseases in body. The technique that is mostly used to establish internal forces in tibiofemoral joint is inverses dinamic, however, it is necessary muscular parameter identification to determinate the joint forces in movements in which open-kinetic-chain is involved. One activity that is widly developed in academies and physiotherapy clinic for strengthening extensor muscles of the knee is the knee extension in open-kinetic-chain. Therefore, the general purpose of this study was to evaluate the involved forces in tibiofemoral joint during the knee extension exercise in open-kinetic-chain and the specific ends were: develop a mathematical model that gives the forces in tibiofemoral joint during the knee extension exercise in open-kinetic-chain and evaluate the effects of velocity's increase and the increase of external force in the exercise, both concerning tibiofemoral force. The evaluation of internal forces in tibiofemoral joint was accomplished based on inverses dynamic technique. The resistence momentum during knee passive extension was added in internal forces determination model. The results indicate that smaller the flexion angle bigger the compression forces in 45°/s and 90°/s velocities and in 180°/s velocity the function of internal forces are changed by inercial effect of ankle-weight. The compression forces indicates its maximum force around 1100 N during exercise with a 10 kg ankle-weights in 45/s and 180/s velocities. The anterior cruciate ligament's force is about 0 till 40 and the posterior cruciate ligament's force is about 50 till 90 in knee flexion. The anterior cruciate ligament's maximum force is around 150 N during knee extension with a 10kg ankle-weight in 45/s and 90/s velocities and the anterior cruciate ligament's maximum force is around 180 N during knee extension in 180/s velocity

The impact of pregnancy on postural control variables and their predictive value for pelvic girdle pain

Commonly it is acknowledged that relaxin levels and altered postural control play an important role in the development of pregnancy-related pelvic girdle pain (PPGP). However, studies are conflicting regarding the association of relaxin levels to PPGP and there is little evidence for associations between altered postural control and PPGP. Altered postural control in late pregnancy is primarily associated with alterations to the centre of mass due to anthropometric changes, related to increased body weight and foetus development. However, an increase in relaxin levels may lead to increased joint relaxation response and potentially altered somatosensory system. As relaxin levels are highest in early pregnancy there is some evidence to show that the somatosensory system might be affected and this may disturb postural control. The primary aim of this thesis was to assess postural control during early pregnancy and explore whether these variables were associated with development of PPGP. Initially two systematic reviews were conducted to explore the associations of: (a) PPGP and relaxin levels and (b) PPGP and biomechanical factors. Findings from these systematic reviews demonstrate no association between relaxin levels and PPGP; and a positive association between biomechanical factors (e.g. altered postural control and pelvic mobility) and PPGP. There were two specific aims for this thesis: (1) compare muscle onset, centre of pressure (COP) displacement and velocity as well as pelvic movement pattern of pregnant women in early stages of pregnancy with non-pregnant women and (2) assess whether muscle onset, COP displacement and velocity and pelvic movement patterns represent risk factors for developing PPGP. To investigate these aims first two further laboratory-based cross-sectional studies were conducted to assess the validity and reliability of determining initiation of heel lift during the active straight leg raise through force and centre of pressure (COP) data; and the reliability of detecting postural control parameters (muscles onsets, initiation of heel lift and weight shift) using a combination of automated and visual inspection methods. Results confirmed that the use of the medio-lateral COP displacement waveform is a valid and reliable method for identifying the initiation of heel lift. The between and within-tester reliability for identifying postural control parameters was found to be excellent. To address aim (1) of this thesis, one laboratory-based study was conducted to assess postural control differences between pregnant women in early stages of pregnancy (10th to 15th weeks) and healthy non-pregnant controls. To address aim (2) a prospective cohort study was then conducted using postural control as a risk factor for determining PPGP during pregnancy. The results from the case-control cross-sectional study showed that pregnancy affects muscle onsets of the Multifidus muscles (both sides) and the right Biceps Femoris muscle during the single leg lift task with eyes closed. In addition, increased COP displacements were observed in the pregnant group regardless of the condition (e.g. eyes open and closed). Increased pelvic mobility in the pregnancy group was associated with higher frequencies of reciprocal pelvic opening patterns in this group. After a stepwise approach four variables (right and left Biceps Femoris muscle onsets, BMI and Parity) were included in the final analysis of the prospective cohort study. Results showed that the odds of presenting PPGP during pregnancy increased between 200% to 300% when there was a 50ms delay of right and left Biceps Femoris muscle onset respectively. These findings have implications for programmes designed to prevent or manage PPGP

Evaluation of the internal forces on tibiofemoral joint during knee extension performance with and without load and realized and different velocities

O conhecimento das forças internas é fundamental para o entendimento das cargas impostas ao sistema musculoesquelético em situações de exercícios ou atividades físicas. Sabe-se que a articulação tibiofemoral é uma das articulações mais acometidas por doenças articulares do corpo. A técnica mais utilizada para determinação das forças internas da articulação tibiofemoral é a dinâmica inversa, entretanto, é necessário o reconhecimento de parâmetros musculares para determinação das forças articulares em situações envolvendo movimentos em cadeia cinética aberta. Um tipo de atividade extremamente desenvolvida nas academias e nas clínicas de fisioterapia para fortalecimento da musculatura extensora do joelho é o exercício de extensão de joelho em cadeia cinética aberta. Desta forma, o objetivo geral deste estudo foi avaliar as forças que envolvem a articulação tibiofemoral durante o exercício de extensão de joelho em cadeia cinética aberta e os objetivos específicos foram: desenvolver um modelo matemático que informe as forças na articulação tibiofemoral durante o exercício de extensão de joelho em cadeia cinética aberta e avaliar o efeito do aumento da velocidade de execução do exercício e o efeito do aumento da carga externa do exercício, ambos sobre a força tibiofemoral. A avaliação das forças internas da articulação tibiofemoral foi realizada com base na técnica da dinâmica inversa. O torque de resistência à extensão passiva do joelho foi acrescentado ao modelo de determinação das forças internas. Os resultados apontam que quanto menor o ângulo de flexão maior a força de compressão nas velocidades de 45°/s e 90°/s e na velocidade de 180°/s o comportamento das forças internas se alteram pelo efeito inercial da caneleira. A força de compressão apresentou seu pico máximo em torno de 1100 N durante o exercício realizado com caneleiras de 10 kg nas velocidades de 45°/s e 180°/s. A força do ligamento cruzado anterior está presente entre os ângulos de 0 à 40° e a do cruzado posterior entre 50° e 90° de flexão de joelho. O pico de força do ligamento cruzado anterior aproximadamente de 150 N durante a extensão de joelho realizada com caneleira de 10 kg nas velocidades de 45°/s e 90°/s e o pico de força do ligamento cruzado anterior foi aproximadamente de 180 N durante o exercício de extensão de joelho na velocidade de 180°/s.The knowledge of internal forces is primordial to understand the forces that are applied on the skeletal muscles system during exercises or physical activities. It's known that tibiofemoral joint is one of the most attacked by joint diseases in body. The technique that is mostly used to establish internal forces in tibiofemoral joint is inverses dinamic, however, it is necessary muscular parameter identification to determinate the joint forces in movements in which open-kinetic-chain is involved. One activity that is widly developed in academies and physiotherapy clinic for strengthening extensor muscles of the knee is the knee extension in open-kinetic-chain. Therefore, the general purpose of this study was to evaluate the involved forces in tibiofemoral joint during the knee extension exercise in open-kinetic-chain and the specific ends were: develop a mathematical model that gives the forces in tibiofemoral joint during the knee extension exercise in open-kinetic-chain and evaluate the effects of velocity's increase and the increase of external force in the exercise, both concerning tibiofemoral force. The evaluation of internal forces in tibiofemoral joint was accomplished based on inverses dynamic technique. The resistence momentum during knee passive extension was added in internal forces determination model. The results indicate that smaller the flexion angle bigger the compression forces in 45°/s and 90°/s velocities and in 180°/s velocity the function of internal forces are changed by inercial effect of ankle-weight. The compression forces indicates its maximum force around 1100 N during exercise with a 10 kg ankle-weights in 45/s and 180/s velocities. The anterior cruciate ligament's force is about 0 till 40 and the posterior cruciate ligament's force is about 50 till 90 in knee flexion. The anterior cruciate ligament's maximum force is around 150 N during knee extension with a 10kg ankle-weight in 45/s and 90/s velocities and the anterior cruciate ligament's maximum force is around 180 N during knee extension in 180/s velocity

The impact of pregnancy on postural control variables and their predictive value for pelvic girdle pain

Commonly it is acknowledged that relaxin levels and altered postural control play an important role in the development of pregnancy-related pelvic girdle pain (PPGP). However, studies are conflicting regarding the association of relaxin levels to PPGP and there is little evidence for associations between altered postural control and PPGP. Altered postural control in late pregnancy is primarily associated with alterations to the centre of mass due to anthropometric changes, related to increased body weight and foetus development. However, an increase in relaxin levels may lead to increased joint relaxation response and potentially altered somatosensory system. As relaxin levels are highest in early pregnancy there is some evidence to show that the somatosensory system might be affected and this may disturb postural control. The primary aim of this thesis was to assess postural control during early pregnancy and explore whether these variables were associated with development of PPGP. Initially two systematic reviews were conducted to explore the associations of: (a) PPGP and relaxin levels and (b) PPGP and biomechanical factors. Findings from these systematic reviews demonstrate no association between relaxin levels and PPGP; and a positive association between biomechanical factors (e.g. altered postural control and pelvic mobility) and PPGP. There were two specific aims for this thesis: (1) compare muscle onset, centre of pressure (COP) displacement and velocity as well as pelvic movement pattern of pregnant women in early stages of pregnancy with non-pregnant women and (2) assess whether muscle onset, COP displacement and velocity and pelvic movement patterns represent risk factors for developing PPGP. To investigate these aims first two further laboratory-based cross-sectional studies were conducted to assess the validity and reliability of determining initiation of heel lift during the active straight leg raise through force and centre of pressure (COP) data; and the reliability of detecting postural control parameters (muscles onsets, initiation of heel lift and weight shift) using a combination of automated and visual inspection methods. Results confirmed that the use of the medio-lateral COP displacement waveform is a valid and reliable method for identifying the initiation of heel lift. The between and within-tester reliability for identifying postural control parameters was found to be excellent. To address aim (1) of this thesis, one laboratory-based study was conducted to assess postural control differences between pregnant women in early stages of pregnancy (10th to 15th weeks) and healthy non-pregnant controls. To address aim (2) a prospective cohort study was then conducted using postural control as a risk factor for determining PPGP during pregnancy. The results from the case-control cross-sectional study showed that pregnancy affects muscle onsets of the Multifidus muscles (both sides) and the right Biceps Femoris muscle during the single leg lift task with eyes closed. In addition, increased COP displacements were observed in the pregnant group regardless of the condition (e.g. eyes open and closed). Increased pelvic mobility in the pregnancy group was associated with higher frequencies of reciprocal pelvic opening patterns in this group. After a stepwise approach four variables (right and left Biceps Femoris muscle onsets, BMI and Parity) were included in the final analysis of the prospective cohort study. Results showed that the odds of presenting PPGP during pregnancy increased between 200% to 300% when there was a 50ms delay of right and left Biceps Femoris muscle onset respectively. These findings have implications for programmes designed to prevent or manage PPGP

Anticipatory postural control differs between low back pain and pelvic girdle pain patients in the absence of visual feedback

Purpose The aim of this study was to examine the effect of vision on anticipatory postural control (APA) responses in two groups of clinically diagnosed chronic low back pain patients, those with Posterior Pelvic Girdle pain and those with Non-Specific Low Back Pain compared to a matched group of healthy controls during the modified Trendelenburg task. Methods Seventy-eight volunteer participants (60 females and 18 males) gave informed consent to take part in this study. 39 with confirmed LBP or PGP lasting longer than 12 weeks and 39 healthy matched controls performed 40 single leg lift tasks (hip flexion to 90° as quickly as possible) with their non-dominant lower limb. A force plate was used to determine the medial-lateral displacement of the center of pressure, and the initiation of weight shift; kinematics was used to determine initiation of leg lift; and electromyography was used to determine onset times from the external oblique (EO), internal oblique (IO) and lumbar multifidus (MF), gluteus maximus (GM) and biceps femoris (BF). Results The PGP group showed significantly longer muscle onset latencies in the BF, EO MF with visual occlusion (F2,746 = 4.51, p \u3c .0001). Conclusion The muscle onset delays identified between the two LBP sub-groups suggests that pain may not be the primary factor in alteration of APA response. The PGP group show a greater reliance on vision which may signal impairment in multiple feedback channels