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.

Central nervous system stabilizes body in disturbance by means of anticipatory and compensatory postural adjustments to maintain stable position. Disturbance effects in joint are reduced by activation of agonist and antagonist forearm muscles, the muscles allow consistency by steady posture during shot. Studies showed the importance of posture in the shot, but without focus on the anticipatory and compensatory postural adjustments. The objective of this study was to analyze an electrical activity of archers during the shot an arrow with the bow. Participants consisted of 10 archers of the Brazilian National Team of archery. Electromyography captured electrical activity in 12 muscles. Accelerometer in handle indicated the beginning of the movement. Temporal pattern separated in 500 milliseconds pre and post clicker fall. Protocol started by Maximal Voluntary Isometric Contraction of 12 muscles. Archers release 3 blocks of 6-arrows in warm-up. Archers throw arrows for 12 blocks with 6-arrows with interval of 20 minutes after the block 6. One-way Analysis of Variance and Tukey Test compared temporal pattern. One-way Analysis of Variance with repeated measures compared temporal pattern and 6-arrows. Results showed that all muscles (except m. Lumbar Multifidus) increase in their demand with the proximity of the arrow release. The muscles decreased their activity due to reduced demand in compensatory and modulation phase. Comparison between 12 blocks of 6-arrows showed 3 ways of temporal pattern: 1) muscles affected by phases and muscles affected by all/any phases in the blocks of 6-arrows, 2) muscles affected by phases and muscles unaffected by all/any phases in the blocks of 6-arrows and 3) muscles unaffected by phases and muscles affected by all phases in the blocks of 6-arrows. Muscles were not affected by phases/blocks maintain muscle activity along intervals by similar muscular demand. Cross-correlation between motor muscles showed that forearm muscles obtained inverse relationship between them. Other motor muscles were strong correlation between them. Postural muscles m. Lumbar Multifidus, m. Latissimus Dorsi, m. Upper Trapezius were strong correlation with all postural muscles. Motor and postural muscles showed that m. Triceps Brachii, m. Pectoralis Major Clavicular Head and m. Posterior Deltoid showed strong correlation with all postural muscles. In conclusion, muscle activity increases in anticipatory phase and muscle activity decrease after clicker fall. There are 3 ways to compare phases and blocks: affected by phases and 1) muscles affected/2) muscles unaffected by all/any phases in the blocks of 6-arrows and 3) muscles unaffected by phases and affected by all phase in the blocks of 6-arrows. Correlation in motor muscles showed that forearm muscles obtained inverse relationship between them. Postural muscles m. Lumbar Multifidus, m. Latissimus Dorsi, m. Upper Trapezius were strong correlation with all postural muscles. Motor and postural muscles showed that m. Triceps Brachii, m. Pectoralis Major Clavicular Head and m. Posterior Deltoid showed strong correlation with all postural muscles / O sistema nervoso central estabiliza o corpo na perturbação por meio de ajustes posturais antecipatórios e compensatórios para manter a postura estável. Os efeitos da perturbação na articulação são reduzidos pela ativação dos músculos agonistas e antagonistas do antebraço, os músculos permitem a consistência no tiro pela postura estável. Os estudos mostram a importância da postura no tiro, mas não se concentrarem nos ajustes posturais antecipatórios e compensatórios. O objetivo desse estudo foi analisar a atividade elétrica muscular de arqueiros durante o atirar uma flecha com o arco. Os participantes foram 10 arqueiros da Seleção Brasileira de Tiro com Arco. A eletromiografia captou a atividade elétrica muscular de 12 músculos. O acelerômetro no punho indicou o início do movimento. As fases temporais foram separadas entre 500 milissegundos pré e pós queda do clicker. O protocolo iniciou pela Contração Isométrica Voluntária Máxima dos músculos. Arqueiros lançaram 3 séries de 6 flechas no aquecimento. Arqueiros lançaram 12 séries de 6 flechas com intervalo de 20 minutos após a série 6. Análise de Variância One-way e o Tukey compararam as fases temporais. Análise de Variância One-way com medida repetidas comparou as fases temporais e os blocos de 6 flechas. Os resultados mostraram que todos os músculos (exceção do m. Multifido Lombar) aumentaram a demanda com a proximidade de soltura da flecha. Os músculos diminuem sua atividade pela redução da sua demanda na fase compensatória e de modulação. A comparação entre blocos de 6 flechas mostrou 3 formas do padrão temporal: 1) músculos afetados pelas fases e músculos afetado por todos/alguns fases nos blocos de 6 flechas, 2) músculos afetados pelas fases e músculos não afetados por todos/alguns fases nos blocos de 6 flechas e 3) músculos não afetados pelas fases e músculos afetados por todas as fases nos blocos de 6 flechas. Os músculos não afetados fases pelas fases/blocos mantem a atividade elétrica muscular ao longo dos intervalos pela sustentação da demanda muscular. Correlação cruzada entre os músculos motores mostrou que os músculos do antebraço obtiveram relação inversa entre eles. Outros músculos motores apresentaram alta correlação entre eles. Músculos posturais m. Multifido Lombar, m. Latíssimo do Dorso, m. Trapézio Superior apresentaram alta correlação com todos os músculos posturais. Músculos motores e posturais mostraram que m. Tríceps Braquial, m. Peitoral Maior Clavicular e m. Deltoide Posterior teve alta correlação com todos os músculos posturais. Em conclusão, a atividade elétrica muscular aumenta a demanda na fase antecipatória e diminui na após queda do clicker. Existem 3 caminhos na comparação das fases e os blocos de 6 flechas: afetado pela fase e 1) músculo afetado/2) músculo não afetado por todos/algumas fases nos blocos, 3) músculo não afetado pelas fases e afetado por todos as fases nos blocos. A correlação cruzada entre os músculos motores mostrou que os músculos do antebraço obteram relação inversa entre eles. Músculos posturais m. Multifido Lombar, m. Latissimo do Dorso, m. Trapézio Superior foram altamente correlacionados com todos músculos posturais. Músculos posturais e motores mostraram que m. Triceps Brachial, m. Petoral Maior Clavicular e m. Deltoide Posterior mostraram alta correlação com todos os músculos posturais

No description available.

No description available.

Headline: Swimming technique of physically disabled swimmers with unilateral above-knee amputation Aim of the Thesis: The aim of this thesis is to describe the intra-individual differences in the swimming technique of unilateral above-knee amputees by measuring the EMG of selected muscle groups. Methods: Surface EMG measurement in combination with using synchronized video recordings. Results: Research of the observed swimmers with unilateral above-knee amputation showed that: when swimming the front crawl, the swimmers unequally balance the intense kick of right and left leg mainly using the abdominal muscles and subsequently also in the electric potential of different sizes in other observed muscles; when swimming the backstroke, the upper body muscles on the side of amputated limb do not show any different activity than the muscles of the opposite side; when swimming the breaststroke, the main propulsion muscle for locomotion through the shoulder girdle - m. latissimus dorsi is activated for a longer period of time on the side of amputated limb; thereby, electrical activity of the selected muscles is not symmetrical in the timeline. Key words: swimming step, swimming, above-knee amputation, electromyography, muscle activity, handicap, EMG.

No description available.

No description available.

Animals control locomotion through unpredictable and complex habitats using a single locomotor control system. Because of the disparate physical mechanics of different environments, behavioural plasticity, based on the complex interplay of sensory feedback and environmental constraints, is likely essential for animals moving across environments. However, few studies have investigated neuromuscular control across different environments. To fill this gap, I make use of Polypterus senegalus to address four primary objectives: (1) to explore the extent of neuromuscular plasticity across environmental gradients (viscosity and water depth), (2) to generate and test hypotheses about paramount signals for this neuromuscular plasticity, (3) to determine the neuromuscular underpinnings of locomotor transitions, and (4) to determine the neuromuscular control of developmental behavioural plasticity in novel environments. I measured the kinematic and muscle activity response of P. senegalus to gradual changes in environment forces using gradients of water viscosity and water depth. I then used a semi-intact preparation to investigate the existence and role of the mesencephalic locomotor region, a brain region that controls locomotor speed and mode in other species, for neuromuscular control in P. senegalus. Finally, I used chronic terrestrial acclimation and exercise to determine the neuromuscular underpinnings of behavioural and morphological plasticity previously seen in P. senegalus reared in a terrestrial environment. I found that in high viscosity environments, P. senegalus maintain routine swimming speed using a swimming-like muscle activity pattern with increased effort in the posterior body and the pectoral fin to generate exaggerated swimming kinematics. These results suggest that sensory feedback is essential to accommodating this novel environment. I then demonstrated that axial red muscle always carried an anterior-to-posterior wave of muscle activity in a series of discrete water depths across the aquatic-terrestrial transition. Thus, discrete changes in axial kinematics and pectoral fin coordination across this transtion are likely the result of sensory feedback and mechanical constraints of the environment. I then performed the first experiments searching for the mesencephalic locomotor region in P. senegalus and demonstrated the presence of a putative mesencephalic locomotor region that controls the frequency of swimming-like movements but does not appear to control pectoral fin movements or the transition to walking. Finally, I exposed P. senegalus to chronic terrestrial acclimation and exercise. My results suggested that while both terrestrial acclimation and exercise generate behavioural plasticity, the former results in a larger plastic repsonse. Subtle changes in the duration and timing of pectoral fin muscle activity helped reduce friction between the body and pectoral fin and the substrate below, potentially resulting in the more “effective” walking gait developed by terrestrial acclimated fish. My thesis therefore sheds light on the essential interplay of sensory feedback and mechanical constraint for generating behavioural plasticity on acute and chronic timescales, highlights the potential value of such plasticity for organismal performance and evolution, and develops study systems and experimental frameworks for further investigating the nature of plastic locomotor control in amphibious fish.

Poor control of postural muscles is a primary impairment in cerebral palsy (CP), however little is known about the activity of postural muscles during walking in individuals with CP. The objective of this study was to investigate differences in trunk and hip muscle activation patterns during the early stages of walking in children with CP compared to children with typical development (TD). Thirty-one children (16 TD, 15 CP) with an average of 28.5 months of walking experience participated. Electromyographic (EMG) data were collected from 16 trunk and hip muscles as participants walked at a self-selected pace over an instrumented walkway. Custom-written computer programs were used to identify the onset of muscle activity, and to generate instantaneous mean frequency (IMNF) curves. A functional principal component analysis was performed to determine differences in IMNF curves between groups. Linear regression analyses were performed to investigate relationships between gait parameters, muscle activation, and musculoskeletal measures. Group means were significantly lower in the CP group than the TD group for all spatiotemporal gait parameters measured. The CP group had greater percent activation and coactivation for all muscles except the external oblique. Greater hip adductor spasticity was related to increased abdominal muscle activity in the CP group. The CP group also had higher mean frequency throughout the gait cycle for all muscles. Higher IMNF can result from increased rates of motor unit activation, increased number of recruited motor units, or decreased synchrony of motor units, and may contribute to muscle fatigue in children with CP. Within the CP group, children classified as Gross Motor Function Classification System (GMFCS) level II demonstrated no differences in spatiotemporal parameters or percent muscle activation, but had greater gait symmetry and lower INMF for the trunk muscles, compared to the children classified as GMFCS level III. The potential influence of recording activity from adjacent trunk muscles is discussed, as well as the influence of the use of an assistive device by some children with CP. Postural muscle training during the early stages of walking in CP should be investigated to encourage the development of more functional and efficient movement strategies in these children. / Physical Therapy

Introduction: Musculoskeletal discomfort in the neck and shoulders is common among workers performing visually demanding near work, e.g., on a computer screen, and sustained low-level muscle activity during such work can lead to work-related pain. The relationships between visual demands and muscle activity and discomfort in the neck/shoulder region are at present unclear. Aim: The aims of this thesis were to determine whether neck/shoulder discomfort and trapezius muscle activity increases during visually demanding experimental near work, and to investigate whether eye-lens accommodation is a mediating mechanism behind increased trapezius muscle activity. Methods: The four papers included are based on two experiments with different visually demanding near work tasks (duration 5 and 7 min). Trial lenses of different diopters were used to manipulate the visual demands (i.e., induce more or less accommodation) and thereby create different viewing conditions. Monocular viewing, which does not require active convergence, was used to examine the isolated effect of accommodation. Eye-lens accommodation and trapezius muscle activity were measured continuously during the visual tasks, and in one experiment the participants rated their eye and neck/shoulder discomfort at baseline and after each visual task. Results: Neck/shoulder discomfort and trapezius muscle activity increased during the visually demanding near work and participants experiencing a greater increase in eye discomfort (compared with baseline) also developed more neck/shoulder discomfort with time. There were no significant differences in muscle activity among the viewing conditions, and no effect of isolated accommodation response within the monocular viewing conditions. Conclusion: These findings indicate that accommodation per se is unlikely to mediate trapezius muscle activity. Instead, the increase in trapezius muscle activity observed here may be due to a combination of high visual attention and enhanced requirement for eye-neck (head) stabilisation. Since these results suggest that neck/shoulder discomfort may aggravate with time when the visual demands are high, it is important to provide good visual conditions in connection with visually demanding occupations. / Introduktion: Muskelrelaterade besvär i nack- och skulderområdet är vanligt förekommande, framförallt hos individer som utför synkrävande datorarbete. En orsak till sådana besvär anses vara långvarig lågintensiv aktivitet i dessa muskler. Det är i dagsläget oklart om de belastningar som synsystemet utsätts för vid synkrävande arbete bidrar till ökad muskelaktivitet i nack/skulderregionen. Syfte: Syftet var att undersöka om experimentellt synkrävande närarbete påverkar muskelaktivitet och besvär i nack/skulderregionen, och att undersöka om aktivitet i trapezius muskeln (kappmuskeln) påverkas av ögats ackommodation, d.v.s. när linsens brytkraft förändras för att se skarpt på nära håll. Metod: De fyra delstudierna baseras på två laborativa experiment där försökspersoner (66 respektive 26 stycken) genomförde olika synkrävande uppgifter (fem och sju minuter långa). För att göra synuppgifterna mer eller mindre ansträngande för synsystemet användes linser med olika grad av brytkraft (dioptrier). Dessutom, eftersom monokulärt seende inte kräver aktiv konvergens, genomfördes tre av de fyra synuppgifterna i ena experimentet med ett öga för att undersöka den enskilda effekten av ackommodation. En autorefraktor mätte ögats ackommodation under synuppgifterna och aktiviteten i trapeziusmuskeln registreades kontinuerligt med elektromyografi (EMG). I samband med det ena experimentet skattade deltagarna sina upplevda ögon- och nack/skulderbesvär, både före experimentet (baslinje) och efter varje synuppgift. Resultat: Det synkrävande arbetet ökade både de självskattade nack/skulderbesvären och muskelaktiviteten i trapezius. De personer som upplevde en högre ökning av ögonbesvär (i förhållande till baslinjen), rapporterade också mer nack/skulderbesvär över tid. Det var varken någon signifikant skillnad i grad av muskelaktivitet mellan synuppgifterna, eller något signifikant samband mellan monokulär ackommodation och muskelaktivitet. Slutsats: Resultaten indikerar att ögats ackommodation, i sig, inte påverkar muskelaktiviteten i trapezius. Ökad muskelaktivitet i nack/skulderregionen i anslutning till synkrävande arbete kan istället bero på en kombination av höga krav på visuell uppmärksamhet och ett ökat behov av att stabilisera ögonen (huvudet) i förhållande till objektet i fokus (t.ex. texten på en bildskärm). Eftersom resultaten tyder på att synkrävande närarbete leder till ökade besvär i nack/skuldraregionen över tid, är det viktigt att utforma arbetsplatser och synkrävande arbetsuppgifter (t.ex. vid datorn) på ett sätt som främjar visuell hälsa.