Magister Scientiae Dentium - MSc(Dent) / The objective of the study was to compare pain and functional limitation of temporomandibular myalgia patients, before and after low-level-laser treatment (LLLT).This was a prospective, randomized, placebo-controlled, triple-blinded clinical study. Patients diagnosed with temporomandibular myalgia according to the DC/TMD protocol were recruited from the TMD clinic of the Mitchell’s Plain Oral Health Centre. Treatment was performed using diode laser (Sirolaser, Dentsply Sirona). The 3 regions of the masseter and temporalis muscles were treated bilaterally with a dose of 8J/cm2 per region. Pain and function were assessed using pain-free opening, numeric rating scales (NRS), Characteristic Pain Intensity Scores (CPIS), Interference Score (IS), and Jaw Functional Limitation Scale (JFLS) at the first and last LLLT and at 4-week recall (intervals 1, 2, 3). Statistical analysis was done by means of explorative categorical principal and multivariate interdependent analysis.

Chronic muscle pain is a significant medical and social problem and better understanding of the pathophysiological mechanisms involved is an important requirement for further development of diagnostics, treatment and rehabilitation methods. Experimental imaging studies have investigated functional neuroanatomy of different pain components. However, several aspects of brain mechanisms underlying brain processing of muscle pain remain unclear. The general goal of the present thesis was to study functional brain anatomy of systems underlying perception of muscle pain, processing of proprioceptive information and maintenance of fatiguing muscle contractions with an emphasize on their possible interrelations. Four series of experiment were carried out. Using an injection of hypertonic saline (HS) into the m. triceps to induce pain comparable with clinical muscle pain a significant activation of insula and putamen as well as decrease of activity in the temporal and occipital cortex in comparison with control stimulation were revealed. An advanced model of prolonged muscle pain were provided by the infusion of the HS during 20 minutes into m. erector spinae A complex dynamics of brain activity during the habituation to nociceptive stimulation was shown: initial activation of insula changed to decrease of activity in this and several other cortical areas. A conjunction analysis identified activations jointly significant in both experiments (despite localization of HS nociceptive stimulation) in the right insula, occipital and left parietal cortical areas. The study of brain activity in response to different modalities of prorioceptive inputs – passive movements, kinesthetic illusions and muscle vibration showed corresponding different patterns of activation in motor and somatosenory areas and temporal areas. Finally, the study of sustained isometric muscle contractions of various force levels and durations revealed that muscle fatigue is associated with contralateral activation of the motor and somatosensory areas and temporal areas and bilateral activation in the supplementary motor areas and cingular cortex, indicating that increased efforts needed to maintain required force and its eventual breakdown with fatigue might induce activation of additional cortical areas. Analysis of data obtained in all experimental series revealed that insula, secondary somatosensory and auditory areas are activated during both perception of muscle pain and processing of somatosensory afferentation. In conclusion, this thesis has elucidated brain processing of muscle pain showing distributed, bilateral patterns comprised of activated structures predominantly attributed to the medial pain system and deactivated structures. Furthermore, initial and late phases of tonic muscle pain are associated with different brain reactions, namely initial activation of the insula followed by a significant bilateral decrease of activity at the late stage. Area of brain cortex located near lateral sulcus and comprised of secondary somatosensory cortex, posterior part of the insula and adjacent auditory cortex is engaged in the perception of muscle pain and processing of somatosensory afferentation as well as maintenance of fatiguing muscle contractions.

Nos últimos anos, os estudos de nosso grupo foram focados na área de dor, avaliando diferentes modelos experimentais de dor aguda, neuropática e muscular. A busca por mecanismos moduladores destes tipos de dores são alvo de grande estudo, uma vez que o fenômeno da dor é peculiar e torna-se de difícil tratamento em muitos casos. Distúrbios (VER) musculoesqueléticos são as principais causas de incapacidade nas pessoas durante seus anos de trabalho. Diversos estudos tem sido realizados lesionando o músculo gastrocnêmio como modelo experimental em diferentes animais para melhor entendimento deste tipo de dor. O nosso objetivo foi observar possíveis alterações histológicas no tecido muscular, avaliar a alteração na sensibilidade nociceptiva e a atividade locomotora dos animais após a indução de dor muscular crônica, bem como observar o envolvimento das células gliais na medula espinal destes animais. Em adição, avaliamos a participação de determinadas citocinas com o intuito de obter um perfil inflamatório em nosso modelo experimental. Nossos resultados demonstraram um quadro de inflamação instalada no tecido muscular de animais com miosite crônica através das analises histológicas realizadas. Os testes comportamentais tanto para hiperalgesia mecânica como térmica e alodinia confirmaram a instalação do quadro álgico uma vez que os animais com miosite apresentaram uma queda em seus limiares nociceptivos em relação aos grupos controle. A atividade locomotora dos animais também se demonstrou comprometida após a indução de miosite. Em relação à participação das células gliais neste modelo, demonstramos que houve um aumento na expressão de GFAP e OX-42, correspondentes à marcação astrócitos e células da microglia na porção lombar da medula espinal dos animais com miosite, quando comparados ao grupo controle. Quanto à participação dos mediadores sistêmicos, observamos um aumento nos níveis de IL-1β e fractalquina (FKN) no sangue dos animais, enquanto o nível de IL-10 permaneceu baixo em relação ao grupo controle. Com nossos achados esperamos colaborar com o aprimoramento de estratégias terapêuticas para tratamento de dores musculares. / In the last years, the studies of our group were focused on the area of pain, evaluating different experimental models of acute, neuropathic and muscular pain. The search for mechanisms modulating types of pain are the subject of great study, since the phenomenon of pain is peculiar and becomes difficult in many cases. Musculoskeletal (VER) disorders are the leading causes of disability in people during their working years. Several studies have been carried out with the model of experimental model in different animals to better understand this type of pain. Our objective was to observe the non-muscular histological changes, to evaluate the nociceptive sensitivity and a locomotor activity of the animals after an induction of chronic muscular pain, as well as to observe the involvement of the glial cells in the spinal cord of the animals. In addition, we evaluated the participation of certain cytokines in order to obtain an inflammatory profile in our experimental model. Our results demonstrated a picture of inflammation installed without muscle tissue of animals with chronic myositis through histological analysis. Behavioral tests for both mechanical and thermal hyperalgesia and allodynia confirmed the onset of pain since animals with myositis showed a decrease in their nociceptive thresholds in relation to the control groups. The locomotor activity of the animals was also shown to be impaired after an induction of myositis. Regarding the participation of glial cells in this model, we demonstrated that there was an increase in the expression of GFAP and OX-42, corresponding to marking astrocytes and microglia cells in the portion of the spinal cord of animals with myositis, when compared to the control group. Regarding the participation of systemic mediators, we observed an increase in the levels of IL-1β and fractalkin (FKN) in the blood of the animals, while the level of IL-10 remained low in relation to the control group. With the findings we hope to collaborate with the improvement of therapeutic strategies for the treatment of muscular pain.

A deeper understanding of both movement control and the effects of nociceptor inputs on our motor systems is critical for proper clinical diagnosis of musculo-skeletal dysfunctions and for development of novel rehabilitation schemes. In the jaw system, masticatory movements are produced by a central pattern generator (CPG) located in the brainstem. Considerable efforts have been made in deciphering this neuronal network. The present thesis contributes towards an increasingly detailed understanding of its essential elements, and presents a hypothesis of how deep somatic pain (i.e. muscle pain) may be evoked and interferes with the masticatory CPG circuitry. In Paper I, the expression of c-Fos-like protein was used as a molecular marker to visualize brainstem neurons that were active during induced fictive mastication in the anesthetized and paralyzed rabbit. Our findings provide a previously lacking detailed record of the neuronal populations that form the masticatory motor pattern. Certain cells were located in brainstem areas previously suggested to be involved in the masticatory CPG. However, it was a new finding that neurons in the dorsal part of the trigeminal main sensory nucleus (NVsnpr-d) may belong to this circuitry. Paper II focused on the discovered neurons in NVsnpr in an in vitro slice preparation from young rats.  Intracellular recordings allowed us to define two cell types based on their response to depolarizing current. Microstimulation applied to the trigeminal motor nucleus, its reticular border, the parvocellular reticular formation and the nucleus reticularis pontis caudalis, elicited postsynaptic potentials in 81% of the neurons tested. Responses obtained were predominately excitatory and sensitive to gluta-matergic antagonists DNQX or/and APV. Some inhibitory and biphasic responses were also evoked. Bicuculline methiodide or strychnine blocked the IPSPs indicating that they were mediated by GABAA or glycinergic receptors. About one third of the stimulations activated both types of neurons antidromically. Neurons in NVsnpr-d seem to gather all the conditions that can theoretically account for a role in masticatory rhythm generation. In Paper III, the masticatory model system was used to investigate the possible role of muscle spindle primary afferents in development of persistent musculoskeletal pain. Following intramuscular acidic (pH 4.0) saline injections of rat masseter muscles, in vitro whole cell recordings were done from jaw closing muscle spindle somata located in the trigeminal mesencephalic nucleus (NVmes). Compared to control neurons, the somata of afferents exposed to acid had more hyperpolarized membrane potentials, more hyperpolarized thresholds for firing, high frequency membrane oscillations and ectopic bursting of action potentials. These changes in membrane properties lasted for up to 35 days. Within the same time frame experi-mental animals showed hypersensitivity to touch on the skin covering the injected muscle. Similar saline injections also resulted in a significant increase of activity dependent c-Fos expression in NVmes neurons compared to controls. Immuno-fluorescence and lectin binding studies indicated that small-caliber muscle afferents containing known nociceptor markers (CGRP, SP, P2X3, TRPV1 and IB4) and expressing glutamate receptors are found close to the annulo-spiral endings of the NVmes afferents. Combined, our new observations support the hypothesis that excessive release of glutamate, within muscle spindles due to ectopically evoked antidromic action potentials, could lead to development of persistent musculoskeletal pain by activation and/ or sensitization of adjacent muscle afferent nociceptors.

Tyrimo tikslas: Įvertinti moterų griaučių raumenų sistemos viršutinės dalies funkcinę būklę prieš ir po pasyvios ir aktyvios kineziterapijos priemonių taikymo. Tyrimo uždaviniai: 1. Įvertinti moterų griaučių raumenų sistemos viršutinės dalies raumenų skausmo slenksčio pokyčius prieš ir po pasyvios ir aktyvios kineziterapijos. 2. Nustatyti moterų griaučių raumenų sistemos viršutinės dalies judesių amplitudės pokyčius prieš ir po pasyvios ir aktyvios kineziterapijos priemonių taikymo. 3. Įvertinti moterų griaučių raumenų sistemos viršutinės dalies raumenų jėgos pokyčius prieš ir po pasyvios ir aktyvios kineziterapijos. 4. Palyginti pasyvios ir aktyvios kineziterapijos priemonių efektyvumą moterų griaučių raumenų sistemos viršutinės dalies raumenų skausmo slenksčiui, judesių amplitudei bei raumenų jėgai. Tyrimo metodai: Buvo ištirtos 20 jauno ir vidutinio amžiaus sveikos moterys. Tiriamosios buvo suskirstytos į dvi grupes. Vienai grupei buvo taikomos pasyvios kineziterapijos priemonės, kitai – aktyvios. Prieš ir po kineziterapijos buvo vertinamas spaudimo sukeltas raumenų skausmo slenkstis (algometru), žasto judesių amplitudė (goniometru), rankų sukabinimo už nugaros ir kaklo judesių amplitudė (centimetrine juostele), pečių juostos raumenų jėga (rankos dinamometru ir „Stabilizer Pressure Biofeedback“ prietaisu). Išvados: 1. Po pasyvios kineziterapijos priemonių taikymo raumenų skausmo slenkstis statistiškai reikšmingai padidėjo 20- yje iš 22- jų vertintų miofascijinių... [toliau žr. visą tekstą] / The aim of the research: To evaluate women’s upper part of musculoskeletal system functional state before and after passive and active physical therapy. To achieve this aim the following tasks were set up: 1. To evaluate changes of muscle pain threshold in the upper part of the musculoskeletal system. 2. To assess changes of range of motion in the upper part of the musculoskeletal system. 3. To evaluate changes of muscle force in the upper part of the musculoskeletal system. 4. To compare the effect of passive and active physical therapy for the muscle pain threshold, range of motion and muscle force in the upper part of the musculoskeletal system. Method of the research: 20 young and middle-aged healthy women were tested. Subjects were divided in to two groups. We have applied passive physical therapy modalities for the first group, active physical exercises for the second group. We have assessed the muscle pain threshold (using algometer), the range of motion (goniometer and tape – measure) and muscle force (hand held dynamometer and „Stabilizer Pressure Bioffedback“) before and after passive and active physical therapy. Conclusions: 1. After the passive physical therapy the muscle pain threshold statistically significant increase in the 20 of 22 assessed myofascial trigger points (p<0,05). After active physical therapy - the muscle pain threshold a statistically significant increase in 12 of 22 assessed myofascial trigger points (p<0,05). 2. After passive physical... [to full text]

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - CAPES / Introduction: Exercise-induced muscle pain is a self-limiting condition and may have an impact on the physical activity habits of healthy individuals, patients with musculoskeletal pain and athletes. Strategies for the management of muscle pain are solely focused on controlling the symptoms after the muscle injury is already stablished. Transcutaneous Electrical Nerve Stimulation (TENS) has shown positive results for pain reduction and functional improvement in acute and chronic pain conditions. Thus, we propose that applying TENS during exercise might reduce pain and contribute to higher adherence to physical activity and better physical performance. Aim: Investigate the immediate and long-term effects of TENS applied during resisted exercise on pain intensity and physical performance of healthy subjects. Methods: This study is a randomized, double-blinded, placebo-controlled, clinical trial. The sample consists of 46 college students, of both sexes, healthy, irregularly active or sedentary, aged between 18 and 40 years. Subjects were randomly assigned into two groups: active (24) or placebo (22) TENS. The study was conducted over 5 moments: on day 1, subjects performed the one-repetition maximum test (1RM); 72 hours later, on day 2, 1RM was retested; 48 hour later, on day 3, TENS was applied during a functional resisted exercise protocol for upper limbs (bench press and rowing), with an intensity of 80% of 1RM; and 24h after, on day 4, the subjects were reevaluated. Assessment included pain intensity at rest and with movement, pressure pain threshold, temporal summation, conditioned pain modulation, infrared thermography, cardiorespiratory measures, functionality, muscle fatigue, number exercise of repetitions, muscle potency and physical tolerance. Pain measures and TENS application was on the muscle belly of the pectoralis major and latissimus dorsi. Results: TENS did not reduce pain intensity when compared to placebo (p>0.05). Active TENS increased pressure pain threshold in latissimus dorsi: p=0.02 and anterior tibial p=0.04 at the immediate reassessment. Immediate effects of TENS were significant for fatigue perception at rest (p=0.01) and with movement was similar to placebo (p<0.05). A higher number of exercise repetitions were observed in the active TENS group, starting from the 5º set of the rowing exercise (p=0.002). Reduction on physical performance was observed, with no differences between groups (p<0.05). Conclusion: Our results show that TENS did not alter pain perception in healthy individuals, but its use induced increased muscle action, contributing to a greater fatigue perception. / Introdução: A dor muscular induzida pelo exercício é uma condição auto limitante e pode ter impacto na prática de atividade física de indivíduos saudáveis, pacientes com dores musculoesqueléticas e atletas. Estratégias de tratamentos para dor muscular estão voltadas apenas para o alívio dos sintomas, após já estabelecida a lesão muscular. A Estimulação Elétrica Nervosa Transcutânea (TENS) têm mostrado resultados positivos na redução da dor e na melhora da função em condições de dor aguda e crônica. Dessa forma, propomos que utilizar a TENS durante o exercício pode reduzir a dor e contribuir para maior adesão à atividade física e melhor desempenho físico. Objetivo: Investigar os efeitos imediatos e tardios da TENS aplicada durante o exercício resistido na intensidade de dor e no desempenho físico em indivíduos saudáveis. Casuística e Métodos: Trata-se de um ensaio clínico com distribuição aleatória, duplamente encoberto e controlado por placebo. Foram incluídos no estudo, 46 sujeitos universitários, de ambos os sexos, saudáveis, irregularmente ativos ou sedentários, com idade entre 18 e 40 anos. Os sujeitos foram distribuídos aleatoriamente em 2 grupos: TENS ativa (n=24) e TENS placebo (n=22). O estudo ocorreu ao longo de cinco momentos: no dia 0, foi realizado o recrutamento da amostra, no dia 1, os sujeitos realizaram o teste de resistência máxima (1RM); após 72 horas, no dia 2, foi aplicado o reteste do 1RM; no dia 3, após 48 horas, TENS foi aplicada durante protocolo de exercícios resistidos funcionais para membros superiores (exercício de supino e remada), com intensidade de 80% de 1RM e, logo após os sujeitos foram avaliados; no dia 4, após 24 horas, foi realizada reavaliação. Foram mensuradas a intensidade de dor ao repouso e ao movimento, limiar de dor por pressão, somação temporal, modulação condicionada da dor, termografia infravermelha, medidas cardiorrespiratórias, funcionalidade, fadiga muscular ao repouso e ao movimento, número derepetições máximas das séries do exercício, potência muscular e tolerância física. A avaliação e aplicação da corrente foram realizadas no ventre muscular dos músculos peitoral maior e grande dorsal. Resultados: TENS não reduziu significativamente a intensidade de dor induzida pelo exercício em repouso e ao movimento quando comparada ao placebo (p>0,05). TENS ativa reduziu o limiar de dor por pressão no grande dorsal: p=0,02 e no tibial anterior: p=0,04 na reavaliação imediata. Efeitos imediatos da TENS foram significativos e diferentes do placebo no aumento da percepção de fadiga ao repouso na reavaliação imediata (p=0,01) e similar ao placebo na percepção de fadiga ao movimento (p<0,05). Um maior número de repetições foi observado no grupo TENS ativa, a partir da 5ª série no exercício de remada (p=0,002). A redução do desempenho físico foi observada, sem diferenças entre os grupos (p<0,05). Conclusão: Os resultados desse estudo mostram que a TENS não reduziu a percepção de dor, porém a sua utilização induziu maior trabalho muscular durante o exercício contribuindo para maior percepção de fadiga. / Aracaju

This thesis aimed to investigate the effects of experimentally induced jaw-muscle pain on the movements and electromyographic activity of jaw and head-neck during chewing in healthy subjects. Kinematic variables related were analyzed: (1) the masticatory sequence (duration, number of cycles masticatory and frequency); (2) the chewing cycle: time of opening, closing and occlusal phase; maximum range of motion and vertical, medial-lateral, anteroposterior and three-dimensional speed of jaw during the phases of opening and closing; maximum amplitude of displacement and head-neck three-dimensional speed during the phases of opening and closing jaw; maximum variation of the cervical flexion-extension angle while chewing; relationship between jaw and head-neck three-dimensional movement. The electromyography variables of the masticatory cycle analyzed were: inactive and active time of the masseter muscles in the side of work and balancing; muscle activation amplitude (MAA) of the masseter and ECM muscles, during active and inactive periods; activation symmetry of the masseter muscles and ECM; coactivation and correlation between masseter MAA and the ECM side of balancing work, during the active period. The study included 28 male volunteers, mean age of 20.6 years. Kinematic data were obtained from Qualisys System and electromyographic data via wireless sensors Delsys. Records were conducted during unilateral chewing wine gum before and after monosodium glutamate solution injections (pain-inducing substance) and normal saline (control). The order and the side of the applications were randomized and separated by a minimum of 45 min. The records before and after experimental procedures were analyzed by t test and Wilcoxon test for dependent variables and the Spearman correlation coefficient was used to analyze the relationship between mandibular and head-neck variables. As a result, it was observed that pain incited reduction on range of mid-lateral movement during the closing jaw, on vertical and three-dimensional speed during the opening and mid-lateral speed during the opening and closing of the masticatory cycle, reduction on MAA masseter muscle side job during the active period prescribed and increased activation symmetry between the masseter muscles on the side of balancing work and during the chewing cycle. However, no effect of pain was observed on the kinematic and electromyographic head-neck variables or on the movement relations and MAA or coactivation between the mandibular and head-neck systems. Moderate effect sizes were observed for results of the kinematic variables of mid-lateral amplitude and mid-lateral/vertical mandibular speed, suggesting that these may have clinical relevance in the evaluation of mastication in the presence of acute pain. Small effect sizes were observed in all results of electromyographic variables, limiting generalizability of the results to the population of patients with TMD. In conclusion, in the presence of acute pain of the stomatognathic system adaptations involve mainly local mechanisms, influencing only kinematic parameters and mandibular electromyographic without compensation on the movement and head-neck electromyographic activity. / Esta tese teve como objetivo investigar os efeitos da dor induzida experimentalmente no músculo masseter sobre os movimentos e a atividade eletromiográfica crânio-cervical e mandibular durante a mastigação em indivíduos saudáveis. Foram analisadas variáveis cinemáticas relacionadas: (1) à sequência mastigatória (duração, número de ciclos e frequência mastigatória); (2) ao ciclo mastigatório: duração das fases de abertura, fechamento e fase oclusal; amplitude máxima de movimento e velocidade vertical, médio-lateral, anteroposterior e tridimensional da mandíbula durante as fases de abertura e fechamento; amplitude máxima de deslocamento e velocidade tridimensional crânio-cervical durante as fases de abertura e fechamento mandibular; máxima variação do ângulo de flexo-extensão cervical durante a mastigação; relação entre os movimentos mandibulares e crânio-cervicais tridimensionais. As variáveis eletromiográficas analisadas, durante o ciclo mastigatório, foram: duração do tempo inativo e ativo dos músculos masseteres dos lados de trabalho e balanceio; amplitude de ativação muscular (AAM) dos músculos masseter e esternocleidomastóideo (ECM), durante os períodos ativo e inativo; simetria de ativação dos músculos masseter e ECM; coativação e correlação entre a AAM do masseter e ECM dos lados de trabalho e balanceio, durante o período ativo. Participaram do estudo 28 voluntários do sexo masculino, com média de idade de 20,6 anos. Os dados cinemáticos foram obtidos através do Sistema Qualisys e os dados eletromiográficos por meio de sensores sem fio e eletromiógrafo Delsys. Foram realizados registros em mastigação unilateral de uma bala de goma de consistência firme, antes e depois de injeções de solução de glutamato monossódico (substância indutora de dor) e de solução salina isotônica (controle). A ordem e o lado das aplicações foram randomizados e separados por um intervalo mínimo de 45 minutos. Os dados pré e pós procedimentos experimentais foram analisados pelos testes t e Wilcoxon para variáveis dependentes e o coeficiente de correlação de Spearmann foi utilizado para a análise da relação entre variáveis mandibulares e crânio-cervicais. Como resultados, observou-se que a dor ocasionou redução da amplitude de deslocamento médio-lateral durante o fechamento mandibular; redução das velocidades vertical e tridimensional durante a abertura e velocidade médio-lateral durante a abertura e fechamento do ciclo mastigatório; redução da AAM do músculo masseter do lado de trabalho durante o período ativo e aumento da simetria de ativação entre os músculos masseteres dos lados de trabalho e balanceio durante o ciclo mastigatório. Entretanto, nenhum efeito da dor foi observado sobre as variáveis cinemáticas e eletromiográficas crânio-cervicais ou sobre as relações do movimento, AAM ou coativação entre os sistemas mandibular e crânio-cervical. Tamanhos de efeito moderados foram observados para os resultados das variáveis cinemáticas de amplitude e velocidade mandibular médio-lateral e vertical, sugerindo que estas podem ter relevância clínica na avaliação da mastigação na presença de dor aguda. Tamanhos de efeito pequenos foram observados em todos os resultados das variáveis eletromiográficas, limitando sua generalização para indivíduos com DTM. Em conclusão, na presença de dor aguda, as adaptações do sistema estomatognático envolvem principalmente mecanismos locais, influenciando apenas parâmetros cinemáticos e eletromiográficos mandibulares, sem compensações sobre o movimento e atividade eletromiográfica crânio-cervical.

Background: Joint stability has been experimentally and clinically linked to mechanisms of knee injury and joint degeneration. The only dynamic, and perhaps most important, regulators of knee joint stability are contributions from muscular contractions. In participants with unstable knees, such as anterior cruciate ligament (ACL) injured, a range of neuromuscular adaptations has been observed including quadriceps weakness and increased co-activation of adjacent musculature. This co-activation is seen as a compensation strategy to increase joint stability. In fact, despite increased co-activation, instability persists and it remains unknown whether observed adaptations are the result of injury induced quadriceps weakness or the mechanical instability itself. Furthermore, there exists conflicting evidence on how and which of the neuromuscular adaptations actually improve and/or reduce knee joint stability. Purpose: The overall aim of this thesis is therefore to elucidate the role of injury and muscle weakness on muscular contributions to knee joint stability by addressing two main objectives: (1) to further our understanding of individual muscle contribution to internal knee joint moments; and (2) to investigate neuromuscular adaptations, and their effects on knee joint moments, caused by either ACL injury and experimental voluntary quadriceps inhibition (induced by pain). Methods: The relationship between individual muscle activation and internal net joint moments was quantified using partial least squares regression models. To limit the biomechanical contributions to force production, surface electromyography (EMG) and kinetic data was elicited during a weight-bearing isometric force matching task. A cross-sectional study design determined differences in individual EMG-moment relationships between ACL deficient and healthy controls (CON) groups. A crossover placebo controlled study design determined these differences in healthy participants with and without induced quadriceps muscle pain. Injections of hypertonic saline (5.8%) to the vastus medialis induced muscle pain. Isotonic saline (0.9%) acted as control. Effect of muscle pain on muscle synergies recruited for the force matching task, lunging and squatting tasks was also evaluated. Synergies were extracted using a concatenated non-negative matrix factorization framework. Results/Discussion: In CON, significant relationships of the rectus femoris and tensor fascia latae to knee extension and hip flexion; hamstrings to hip extension and knee flexion; and gastrocnemius and hamstrings to knee rotation were identified. Vastii activation was independent of moment generation, suggesting mono-articular vastii activate to produce compressive forces, essentially bracing the knee, so that bi-articular muscles crossing the hip can generate moments for the purpose of sagittal plane movement. Hip ab/adductor muscles modulate frontal plane moments, while hamstrings and gastrocnemius support the knee against externally applied rotational moments. Compared to CON, ACL had 1) stronger relationships between rectus femoris and knee extension, semitendinosus and knee flexion, and gastrocnemius and knee flexion moments; and 2) weaker relationships between biceps femoris and knee flexion, gastrocnemius and external knee rotation, and gluteus medius and hip abduction moments. Since the knee injury mechanism, is associated with shallow knee flexion angles, valgus alignment and rotation, adaptations after ACL injury are suggested to improve sagittal plane stability, but reduce frontal and rotational plane stability. During muscle pain, EMG-moment relationships of 1) semitendinosus and knee flexor moments were stronger compared to no pain, while 2) rectus femoris and tensor fascia latae to knee extension moments and 3) semitendinosus and lateral gastrocnemius to knee internal rotation moments were reduced. Results support the theory that adaptations to quadriceps pain reduces knee extensor demand to protect the joint and prevent further pain; however, changes in non-painful muscles reduce rotational plane stability. Individual muscle synergies were identified for each moment type: flexion and extension moments were respectively accompanied by dominant hamstring and quadriceps muscle synergies while co-activation was observed in muscle synergies associated with abduction and rotational moments. Effect of muscle pain was not evident on muscle synergies recruited for the force matching task. This may be due to low loading demands and/or a subject-specific redistribution of muscle activation. Similarly, muscle pain did not affect synergy composition in lunging and squatting tasks. Rather, activation of the extensor dominant muscle synergy and knee joint dynamics were reduced, supporting the notion that adaptive response to pain is to reduce the load and risk of further pain and/or injury. Conclusion: This thesis evaluated the interrelationship between muscle activation and internal joint moments and the effect of ACL injury and muscle pain on this relationship. Findings indicate muscle activation is not always dependent on its anatomical orientation as previous works suggest, but rather on its role in maintaining knee joint stability especially in the frontal and transverse loading planes. In tasks that are dominated by sagittal plane loads, hamstring and quadriceps will differentially activate. However, when the knee is required to resist externally applied rotational and abduction loads, strategies of global co-activation were identified. Contributions from muscles crossing the knee for supporting against knee adduction loads were not apparent. Alternatively hip abductors were deemed more important regulators of knee abduction loads. Both muscle pain and ACL groups demonstrated changes in muscle activation that reduced rotational stability. Since frontal plane EMG-moment changes were not present during muscle pain, reduced relationships between hip muscles and abduction moments may be chronic adaptions by ACL that facilitate instability. Findings provide valuable insight into the roles muscles play in maintaining knee joint stability. Rehabilitative/ preventative exercise interventions should focus on neuromuscular training during tasks that elicit rotational and frontal loads (i.e. side cuts, pivoting maneuvers) as well as maintaining hamstring balance, hip abductor and plantarflexor muscle strength in populations with knee pathologies and quadriceps muscle weakness.

Objectives: To assess the expression of the symptoms of jaw muscle pain and its association with alterations in biochemistry, other symptoms and the carriage of staphylococci. Methods: Three different study populations were assessed. The first was selected and examined by the author and consisted of 43 pain and 41 age and sex matched controls. The second was a study of CFS patients who were blinded to the author and the author subsequently examined the associations between jaw muscle symptom reporting and the standardised biochemistry measures. The third study was also blinded to the author but included an investigation of staphylococci and certain cytokine and biochemistry measures. Results: The three studies clearly establish an association between the carriage of toxicogenic coagulase negative staphylococci and the expression of jaw muscle pain in both males and females. These associations were homogeneous and were found whether the patients were selected on the basis of having jaw muscle pain or selected from within a population of patients selected on the basis of having Chronic Fatigue Syndrome. The studies associated the changes with variations in biochemistry and these were in turn associated with symptom expression within the jaw muscle pain patients. These biochemical alterations included the dysregulation of immune cell counts, cytokines, electrolyte and protein metabolism. These symptoms and biochemical changes were associated with pain severity and illness duration and staphylococcal toxin production. From the data a model was developed which shows the mechanisms involved in the development of chronic pain in the jaw muscles. Conclusions: The carriage of toxicogenic coagulase-negative staphylococci were found to be associated with the expression of jaw muscle pain and the alterations in biochemistry associated with these symptoms.

Objectives: To assess the expression of the symptoms of jaw muscle pain and its association with alterations in biochemistry, other symptoms and the carriage of staphylococci. Methods: Three different study populations were assessed. The first was selected and examined by the author and consisted of 43 pain and 41 age and sex matched controls. The second was a study of CFS patients who were blinded to the author and the author subsequently examined the associations between jaw muscle symptom reporting and the standardised biochemistry measures. The third study was also blinded to the author but included an investigation of staphylococci and certain cytokine and biochemistry measures. Results: The three studies clearly establish an association between the carriage of toxicogenic coagulase negative staphylococci and the expression of jaw muscle pain in both males and females. These associations were homogeneous and were found whether the patients were selected on the basis of having jaw muscle pain or selected from within a population of patients selected on the basis of having Chronic Fatigue Syndrome. The studies associated the changes with variations in biochemistry and these were in turn associated with symptom expression within the jaw muscle pain patients. These biochemical alterations included the dysregulation of immune cell counts, cytokines, electrolyte and protein metabolism. These symptoms and biochemical changes were associated with pain severity and illness duration and staphylococcal toxin production. From the data a model was developed which shows the mechanisms involved in the development of chronic pain in the jaw muscles. Conclusions: The carriage of toxicogenic coagulase-negative staphylococci were found to be associated with the expression of jaw muscle pain and the alterations in biochemistry associated with these symptoms.