Vários estudos têm investigado a redundância cinética dos dedos da mão por meio da análise da interdependência e interação sinérgica entre os dedos da mão durante a produção de força máxima dos dedos e controle de força dos multiplos-dedos. No entanto, pouco se sabe sobre como as mudanças no comprimento muscular dos dedos da mão poderia afetar a produção de torque máximo, assim como a interação sinérgica entre os dedos da mão. Este estudo variou o ângulo da articulação metacarpofalangeana para investigar os efeitos do comprimento muscular sobre: a) produção de torque máximo dos dedos; b) dependência dos dedos; e, c) interação de torque dos dedos. Onze adultos jovens (23,09 ± 2,63 anos) foram convidados a produzir torque isométrico máximo em flexão, com o dedo individualmente em um período de 3-s. O torque do dedo instruído e dedos não instruídos foram registrados em sete diferentes posições da articulação metacarpofalangeana (-15 °, 0 °, 15 °, 30 °, 45 °, 60 ° e 75 °). Os participantes também foram convidados a produzir torque isométrico constante, com o dedo individualmente (I, M, A e Mn) durante 12 segundos. Os resultados mostraram que a alteração no comprimento muscular proporciona efeito na capacidade dos dedos de produzir torque independente. Maior independência dos dedos (ou seja, diminuição do torque enslaving) foi encontrada em menores comprimentos musculares. Nenhum efeito do comprimento muscular foi encontrado para a tarefa de controle de torque isométrico constante. / Several studies have investigated kinetic redundancy of the hand by examining finger dependency and the synergic interactions among the hand fingers during maximum finger force production and multi-fingers force/torque control. However, little is known about how changes in the fingers' muscle length would affect the maximum torque production as well as the synergic interaction among the fingers of the hand. This study manipulated the angle of the metacarpophalangeal joint in order to investigate the effects of muscle length on: a) maximum finger torque production; b) finger dependency; and, c) finger torque interactions. Eleven young adults (23.09 ± 2.63 years) were asked to produce maximum flexion isometric torque with one finger at a time over a 3-s period. The torque of both the instructed finger and non-instructed fingers were recorded over seven different metacarpophalangeal joints positions (-15°, 0°, 15°, 30 °, 45°, 60° and 75°). Participants were also asked to produce a constant isometric torque with one finger at a time (I, M, R e L) over 12 seconds. The results showed that changes in muscle length impacted the fingers' ability to produce torque independently. Higher finger independency (i.e., decreased torque enslaving) was found for the decreased muscle lengths. No effect of muscle length was found for the constant isometric torque control task.

Vários estudos têm investigado a redundância cinética dos dedos da mão por meio da análise da interdependência e interação sinérgica entre os dedos da mão durante a produção de força máxima dos dedos e controle de força dos multiplos-dedos. No entanto, pouco se sabe sobre como as mudanças no comprimento muscular dos dedos da mão poderia afetar a produção de torque máximo, assim como a interação sinérgica entre os dedos da mão. Este estudo variou o ângulo da articulação metacarpofalangeana para investigar os efeitos do comprimento muscular sobre: a) produção de torque máximo dos dedos; b) dependência dos dedos; e, c) interação de torque dos dedos. Onze adultos jovens (23,09 ± 2,63 anos) foram convidados a produzir torque isométrico máximo em flexão, com o dedo individualmente em um período de 3-s. O torque do dedo instruído e dedos não instruídos foram registrados em sete diferentes posições da articulação metacarpofalangeana (-15 °, 0 °, 15 °, 30 °, 45 °, 60 ° e 75 °). Os participantes também foram convidados a produzir torque isométrico constante, com o dedo individualmente (I, M, A e Mn) durante 12 segundos. Os resultados mostraram que a alteração no comprimento muscular proporciona efeito na capacidade dos dedos de produzir torque independente. Maior independência dos dedos (ou seja, diminuição do torque enslaving) foi encontrada em menores comprimentos musculares. Nenhum efeito do comprimento muscular foi encontrado para a tarefa de controle de torque isométrico constante. / Several studies have investigated kinetic redundancy of the hand by examining finger dependency and the synergic interactions among the hand fingers during maximum finger force production and multi-fingers force/torque control. However, little is known about how changes in the fingers' muscle length would affect the maximum torque production as well as the synergic interaction among the fingers of the hand. This study manipulated the angle of the metacarpophalangeal joint in order to investigate the effects of muscle length on: a) maximum finger torque production; b) finger dependency; and, c) finger torque interactions. Eleven young adults (23.09 ± 2.63 years) were asked to produce maximum flexion isometric torque with one finger at a time over a 3-s period. The torque of both the instructed finger and non-instructed fingers were recorded over seven different metacarpophalangeal joints positions (-15°, 0°, 15°, 30 °, 45°, 60° and 75°). Participants were also asked to produce a constant isometric torque with one finger at a time (I, M, R e L) over 12 seconds. The results showed that changes in muscle length impacted the fingers' ability to produce torque independently. Higher finger independency (i.e., decreased torque enslaving) was found for the decreased muscle lengths. No effect of muscle length was found for the constant isometric torque control task.

Vários estudos têm investigado a redundância cinética dos dedos da mão por meio da análise da interdependência e interação sinérgica entre os dedos da mão durante a produção de força máxima dos dedos e controle de força dos multiplos-dedos. No entanto, pouco se sabe sobre como as mudanças no comprimento muscular dos dedos da mão poderia afetar a produção de torque máximo, assim como a interação sinérgica entre os dedos da mão. Este estudo variou o ângulo da articulação metacarpofalangeana para investigar os efeitos do comprimento muscular sobre: a) produção de torque máximo dos dedos; b) dependência dos dedos; e, c) interação de torque dos dedos. Onze adultos jovens (23,09 ± 2,63 anos) foram convidados a produzir torque isométrico máximo em flexão, com o dedo individualmente em um período de 3-s. O torque do dedo instruído e dedos não instruídos foram registrados em sete diferentes posições da articulação metacarpofalangeana (-15 °, 0 °, 15 °, 30 °, 45 °, 60 ° e 75 °). Os participantes também foram convidados a produzir torque isométrico constante, com o dedo individualmente (I, M, A e Mn) durante 12 segundos. Os resultados mostraram que a alteração no comprimento muscular proporciona efeito na capacidade dos dedos de produzir torque independente. Maior independência dos dedos (ou seja, diminuição do torque enslaving) foi encontrada em menores comprimentos musculares. Nenhum efeito do comprimento muscular foi encontrado para a tarefa de controle de torque isométrico constante. / Several studies have investigated kinetic redundancy of the hand by examining finger dependency and the synergic interactions among the hand fingers during maximum finger force production and multi-fingers force/torque control. However, little is known about how changes in the fingers' muscle length would affect the maximum torque production as well as the synergic interaction among the fingers of the hand. This study manipulated the angle of the metacarpophalangeal joint in order to investigate the effects of muscle length on: a) maximum finger torque production; b) finger dependency; and, c) finger torque interactions. Eleven young adults (23.09 ± 2.63 years) were asked to produce maximum flexion isometric torque with one finger at a time over a 3-s period. The torque of both the instructed finger and non-instructed fingers were recorded over seven different metacarpophalangeal joints positions (-15°, 0°, 15°, 30 °, 45°, 60° and 75°). Participants were also asked to produce a constant isometric torque with one finger at a time (I, M, R e L) over 12 seconds. The results showed that changes in muscle length impacted the fingers' ability to produce torque independently. Higher finger independency (i.e., decreased torque enslaving) was found for the decreased muscle lengths. No effect of muscle length was found for the constant isometric torque control task.

The computational musculoskeletal models that are used to study muscle moment-generating capacities of persons with movement disorders and planning treatment options must be accurate, and take into account the inter-individual variability of musculoskeletal geometry. In Paper I the methods of creating the subject-specific musculoskeletal model of the lower extremities from magnetic resonance images (MRIs) were developed. The subject-specific model was used to analyze hip, knee and ankle muscle moment arms (MALs) and muscle-tendon lengths (MTLs) during gait in a subject with unilateral cerebral palsy (CP), and to evaluate the accuracy of widespread and commonly-used scaled generic model. It was found that the scaled generic model delivered accurate values for changes in MTLs in most muscles. However, the scaled generic and the subject-specific lower extremity musculoskeletal models showed substantial differences in MALs calculated during gait. In Paper II subject-specific musculoskeletal models of nine subjects with unilateral CP were created to study muscles volumes, MTLs and MALs; and to examine the accuracy of MALs calculated by the scaled generic models. It was shown that the scaled generic model significantly underestimated hip MALs discrepancies between the affected and the non-affected sides of the lower extremities. However, it significantly overestimated hip adduction/abduction of gluteus maximus, gluteus medius, gluteus minimus, tensor fascia latae and biceps femoris long head; and hip flexion of adductor longus and rectus femoris in the affected and the non-affected sides. It was also found that muscle volumes and hip abduction MALs in gluteus medius and gluteus minimus, hip flexion MALs in iliacus and hip rotation in gluteus maximus were smaller in the affected side of lower extremities. MTLs in the affected and the non-affected sides throughout the range of hip motion were similar. This thesis suggests the need for the subject-specific musculoskeletal models that can account for variability of muscle attachments and musculoskeletal geometry of persons with movement disorders. Based on inaccuracies of the scaled generic model reported here, the generic models that are used to guide treatment decisions must be tested, and interpreted with care. / QC 20110901

Introduction The length of a muscle has been described as one of the factors contributing to the ideal movement at a joint. A decrease in the length of a muscle results in a decrease in the range of motion at the joint in direct relation to the function of that specific muscle. M Latissimus Dorsi is a muscle which undergoes length changes (loss of extensibility) and this muscle has a functional role in many aspects of sport and rehabilitation. The loss of extensibility may result in a decreased range of motion at the glenohumeral joint leading to dysfunction. Evidence-based practise requires the use of objective, valid and reliable tests for measuring the length of a muscle. No scientific evidence of reliability for any documented technique testing the length of m Latissimus Dorsi (LD) was found. Aim The aim of this study was to assess the inter-rater and intra-rater reliability of a technique adapted by Commerford and Mottram (2012) for assessing the length of LD. Study design The design of the study is a within-participant test-retest non-experimental quantitative study for reliability purposes Method Fifty-six volunteering students recruited from the Physiotherapy Department of the University of Pretoria were the participants in this study. Four qualified physiotherapists with varying numbers of years of clinical experience independently performed the test for assessing the length of LD. The test was performed twice by each physiotherapist on every participant and two measurement sessions were done. A pilot study was also done. Data Analysis and conclusion A sample of 56 participants provided an intraclass correlation coefficient (ICC) of less than 0.9 and this is regarded as poor reliability. The agreement between each rater and the differences in the two levels of experience of raters were also assessed. The ICC was used to determine the inter-rater and intra-rater reliability of the LD length test. A 0.05 level of significance was employed. The ICC between the experienced raters was found to be 0.48 with a novice rater ICC of 0.48 as well. The ICC between all the raters was 0.33. This constitutes poor reliability. The poor reliability of the technique testing the length of LD was identified and addressed in order for adequate usage thereof, in research and in practice. Recommendations of a new technique to test the length of LD was provided by the researcher. A suggestion was made regarding a manner of testing its reliability. / Dissertation (MPhysT)--University of Pretoria, 2014. / Physiotherapy / MPhysT / Unrestricted

Neuromuscular explosive strength (defined as rate of force development; RFD) is considered important during explosive functional human movements; however this association has been poorly documented. It is also unclear how different variants of strength training may influence RFD and its neuromuscular determinants. Furthermore, RFD has typically been measured in isometric situations, but how it is influenced by the types of contraction (isometric, concentric, eccentric) is unknown. This thesis compared neuromuscular function in explosive power athletes (athletes) and untrained controls, and assessed the relationship between RFD in isometric squats with sprint and jump performance. The athletes achieved a greater RFD normalised to maximum strength (+74%) during the initial phase of explosive contractions, due to greater agonist activation (+71%) in this time. Furthermore, there were strong correlations (r2 = 0.39) between normalised RFD in the initial phase of explosive squats and sprint performance, and between later phase absolute explosive force and jump height (r2 = 0.37), confirming an association between explosive athletic performance and RFD. This thesis also assessed the differential effects of short-term (4 weeks) training for maximum vs. explosive strength, and whilst the former increased maximum strength (+20%) it had no effect on RFD. In contrast explosive strength training improved explosive force production over short (first 50 ms; +70%) and long (>50 ms; +15%) time periods, due to improved agonist activation (+65%) and maximum strength (+11%), respectively. Explosive strength training therefore appears to have greater functional benefits than maximum strength training. Finally, the influence of contraction type on RFD was assessed, and the results provided unique evidence that explosive concentric contractions are 60% more effective at utilising the available force capacity of the muscle, that was explained by superior agonist activation. This work provides a comprehensive analysis of the association between athletic performance and RFD, the differential effects of maximum vs. explosive strength training, and the influence of contraction type on the capacity for RFD.

L’objectif de ce travail était de comparer l’importance de la composante nerveuse dans les différences de production de force entre les enfants et les adultes en tenant compte des conditions mécaniques qui sont susceptibles de l’influencer (longueur musculaire, mode et vitesse de contraction) et des effets de la fatigue. Trente et un garçons pré-pubères de 8-12 ans et 37 hommes de 18-30 ans ont été recrutés et répartis dans les 3 études composant ce projet. La première étude portait sur les effets de la longueur musculaire et de la fatigue sur la production de force et le niveau d’activation maximal volontaire (VA) des extenseurs du genou.La seconde traitait des effets de la longueur musculaire sur la production de force et le VA des fléchisseurs plantaires. Enfin, la troisième portait sur les effets du mode et de la vitesse de contraction sur le VA des extenseurs du genou. Les propriétés neuromusculaires ont été évaluées à l’aide de stimulations magnétiques périphériques et de contractions maximales volontaires. Les résultats montrent un VA des extenseurs du genou supérieur chez l’adulte lors de grande longueur musculaire (90°-100° de flexion) (étude 1), mais aucune différence avec l’enfant à courte longueur musculaire (20° de flexion). En revanche, sur des groupes musculaires tels que les fléchisseurs plantaires, aucun effet de la longueur sur le VA n’a été observé chez les enfants et les adultes (étude 2). En ce qui concerne les effets du mode de contraction, nos résultats montrent que le VA est inférieur en conditions excentrique et concentrique par rapport à la condition isométrique, mais aucune différence n’était observée entre les groupes (étude 3). Toutefois, l’effet de cette baisse de VA sur la production de force variait entre les groupes ; une diminution de force accompagnant la diminution de VA n’était retrouvée que chez l’adulte. Enfin,nous avons montré que la baisse du VA au cours d’un protocole de fatigue est plus conséquente chez les enfants par rapport aux adultes (étude 1), ce qui témoigne de l’existence d’une fatigue centrale majorée chez l’enfant. Une maturation inaboutie et les propriétés musculo-tendineuses particulières de l’enfant (compliance supérieure) pourraient expliquer les résultats obtenus au cours de ce travail. / The purpose of this PhD thesis was to compare the contribution of the maximal voluntary activation level (VA) of the motor units to force production differences between children and adults in various mechanical conditions that affect force production (muscle length, contraction mode and velocity), and in fatigue condition. Thirty one pre-pubertal 8 to 12-year old boys and 37 men (18-30 years) were recruited and allocated into the 3 studies ofthis project. The first study was devoted to compare the effects of muscle length and fatigue on the VA and force generating capacity of the knee extensors between children and adults. In the second study, we compared the effects of muscle length on the VA and force generating capacity of the plantar flexors between children and adults. The third study analysed the effect of contraction mode and velocity on the VA and force generating capacity of the knee extensors between children and adults. Neuromuscular properties were assessed with peripheral magnetic stimulation and maximal voluntary contractions. Results showed a higher VA of the knee extensors in adults at long muscle length (90° and 100° knee flexion) but no difference between children and adults at short length (20° knee flexion; study 1). However, the VA of the plantar flexors was not affected by muscle length changes whatever the age group considered (study 2). Results also showed a higher VA in isometric mode compared to eccentric and concentric conditions whatever the age group (study 3). However, the effect of this VA reduction on force generating capacity differed between groups, a concomitant force reduction being observed in adults, but not in children. Finally, we observed a greater VA reduction and therefore greater central fatigue in children during the fatiguing protocol (study 1). A relative immaturity and the particular musculo-tendinous properties of children (higher compliance) may account for the reported results.

Raumens adaptacija įgyta po pirmo krūvio, vadinama pakartoto krūvio efektu (PKE). PKE aiškiai reiškiasi po ekscentrinių pratimų ir yra siejamas su raumens pažeida. Raumens pažeidos dydis priklauso nuo pradinio intensyvumo, kartojimų kiekio bei raumens ištempimo amplitudės. Nėra aišku, kaip skiriasi pakartotas krūvio efektas, atliekant didėjantį ir vienodą fizinį krūvį. Tyrimo hipotezė: antro krūvio metu padidinus krūvio intensyvumą ir raumens ištempimo amplitudę sumažės pakartotas krūvio efektas. Tyrimo tikslas – nustatyti ir palyginti PKE po vienodo ir didėjančio fizinio krūvio. Uždaviniai: 1. Palyginti PKE po šuolių nuo skirtingo aukščio pakylos; 2. Palyginti PKE po šuolių su skirtinga raumens ištempimo amplitude. Praktinė darbo reikšmė: aiškesnis pakartoto krūvio efekto suvokimas gali padėti pasirinkti teisingą krūvio strategiją saugantis nuo raumenų pažeidos. Metodika: Pirmo tyrimo metu, pirma tiriamųjų grupė, šuolius atliko nuo didėjančio aukščio pakylos, pirmo krūvio metu buvo 30 cm, o antro - 60 cm aukščio pakylos. Kita tiriamųjų grupė šuolius atliko nuo vienodo 60 cm aukščio pakylos. Antro tyrimo metu, pirma tiriamųjų grupė šuolius atliko su didėjančia raumens ištempimo amplitude, pirmo krūvio metu 120º, antro - 90º kampu per kelio sąnarį. Kita grupė pirmo ir antro krūvių metu šuolius atliko su vienoda ištempimo amplitude - 90º per kelio sąnarį. Tyrimuose dalyvavo sveiki, aktyviai nesportuojantys vyrai (n=11) (amžius 19,5±1,7; ūgis 185,2±5,1 cm.; kūno masė 77,3±7... [toliau žr. visą tekstą] / Muscle’s adaptation gained after first workload is called repeated bout effect (RBF). RBF is clearly noticed after eccentric exercise and is associated with muscle damage. Muscle damage’s severity depends on the primary intensity and the extension of muscle’s amplitude. It is not clear how repeated bout effect changes performing enhanced and stable physical workload. Hypothesis. The repeated bout effect will reduce after enhancing the level of workload and the extension of muscle’s amplitude. Aim. To investigate and compare repeated bout effect after stable and enhanced physical workload. Objectives: 1. To compare RWE after jumps from different hight platforms. 2. To collate RWE with different muscles’ extension amplitude. Work significance to practice. The research results may help in choosing the right workload strategy in order to avoid muscles damage. Methods. During the first research, the first participants performed jumps from ascending height platform. During the first exercise platform was 30 cm, during the second – 60 cm height platform. Other participant group was performing jumps from stable, 60 cm height platform. During the second research, the first participant group performed jumps with enhanced muscle extension, first workload with 120°, second – 90° degrees in knee joint extension. Other group during first and second workload were performing jumps with equal – 90° degrees extension amplitude in knee joint. Healthy and not actively sporting men (n=11... [to full text]

Idiopathic clubfoot causes severe deformity of the foot and lower leg. Due to the complex anatomy and small size of the foot, the condition is difficult to define and describe. This study focused on 3D modeling of different foot positions associated with clubfoot relapse, and investigation of muscle parameters. The 3D modeling was performed in the AnyBody Modeling System to retrieve information about muscle length. Musculoskeletal modeling could provide further understanding of the condition and contribute to assessment and treatment evaluation. Five children that received clubfoot treatment as infants, and five typically developing children, serving as a control group, participated in the study. Despite treatment with the Ponseti method, Achilles tenotomy and use of an abduction orthosis, all participants of the clubfoot group showed signs of relapse. In total, seven affected legs were studied. Data from gait analyses of all participants were compiled and interpreted in the AnyBody Modeling System. The Plug-in-Gait Model for lower extremities and the Oxford Foot Model were used as marker protocol for the study. Studied lower leg muscles were Gastrocnemius Lateralis, Gastrocnemius Medialis, Soleus Lateralis and Soleus Medialis. Muscle length, defined as length of contractile element, for each leg and participant were evaluated using the AnyBody model template LowerExtremity. Compared to the control group, the models of the clubfoot group presented shorter mean muscle lengths of all investigated muscles. / Idiopatisk klumpfot orsakar allvarlig deformation av fot och underben. På grund av fotens anatomi och ringa storlek kan tillståndet vara svårt att beskriva och definiera. Denna studie innefattade 3Dmodellering av olika fotpositioner orakade av recidivklumpfot, för att undersöka muskelegenskaper. AnyBody Modeling System användes för att generera 3D-modeller och ta fram information om muskellängd. Muskuloskeletal modellering skulle kunna öka förståelsen för sjukdomen och bidra till förbättringar av initial bedömning och utvärdering av behandling. Fem barn som behandlades för klumpfot efter födseln deltog i studien. Även fem typiskt utvecklade barn medverkade och fungerade som en kontrollgrupp. Trots behandling med Ponseti-metoden, hälseneförlängning och användning av abduktionsortos, uppvisade samtliga barn i klumpfotsgruppen tecken på återfall. Totalt studerades sju ben med recidivklumpfot. Data från gånganalyser av deltagarna sammanställdes och analyserades i AnyBody Modeling System. Plug-in-Gait Model för nedre extremiteter och Oxford Foot Model användes som markörprotokoll. Under studien analyserades underbensmusklerna Gastrocnemius Lateralis, Gastrocnemius Medialis, Soleus Lateralis och Soleus Medialis. Muskellängd (längd av kontraktilelement) för varje patient och ben beräknades med hjälp av modellmallen LowerExtremity i AnyBody Modeling System. Jämfört med kontrollgruppen visade klumpfotsgruppen kortare medelmuskellängder för samtliga av de analyserade musklerna.