Introduction: Acute enhancements of muscle contractile properties and performance subsequent to a maximal or near maximal conditioning contraction are often termed post activation potentiation (PAP). Although still controversial, PAP is commonly linked to enhancements in the myosin regulatory light chain phosphorylation, leading to improvements in the excitation–contraction coupling. The PAP seen after a conditioning task often coexists with fatigue and is known to depend on strength level, muscle fiber type and age. Less is known about how factors such as static and dynamic changes in muscle length affect PAP, and on the relative contribution of contractile and tensile components to PAP. Aim: To enhance our understanding of how, and under what conditions, a single maximal isometric contraction affects plantar flexor muscle contractile performance, and other muscle tendon properties, in power athletes. Methods: Supramaximal twitches were evoked via electrical stimulation of the tibial nerve of athletes before and on several occasions after a 6-second maximal voluntary isometric contraction (6-s MVIC) in both static muscle, and during passive muscle lengthening and shorting at different angular velocities. Several contractile variables were measured from the twitches. The effects of a 6-s MVIC on Achilles tendon stiffness was calculated from torque and ultrasonography based measurements of tendon length at two submaximal contraction intensities. Overall stiffness index was calculated by analyzing the passive lengthening torque/angle curve.Results: A single MVIC enhanced muscle contractile properties and electromechanical delay for up to 5 minutes. Plantar flexor twitch variables such as peak twitch, rate of torque development and rate of torque relaxation were enhanced during shortening compared to lengthening muscle actions, and in an extended as compared to a flexed knee position. Achilles tendon stiffness and overall stiffness index were not significantly modulated by a single 6-s MVIC. Conclusion: The results of this thesis imply that functional enhancements from a 6-s conditioning MVIC would mainly come from improvements in contractile rather than tensile components. Stiffness changes should be monitored in future PAP-related studies since they may still occur after more extensive conditioning protocols than the current one. Improvements in contractile components subserving muscle strength after a conditioning MVIC suggests that enhancements in muscle power after a conditioning task should be greatest in fast concentric muscle actions, though still present in muscle lengthening. Conditioning should be performed in a position where full activation is easy to achieve and tailored to mach an athlete or group of athlete’s current status and characteristics, maximizing performance in a specific sport event. / <p>The project recived financial support from the Swedish National Centre for Research in Sports (CIF). Paulo Gago also wishes to thank the Fundação para a Ciência e Tecnologia (FCT), Portugal for the Ph.D. Grant (SFRH/BD/103572/2014).</p><p>New version 2015-01-25 updates the previous one by correcting the errors described in the correction list file (errata).</p> / Doctoral project: Post activation potentiation - Modulating factors and mechanisms for muscle performance.

Abstract Background. The pre-exhaustion (PE) method is a way to target a stronger muscle in a multi-joint exercise by isolating the stronger muscle immediately before the multi-joint exercise. It has been shown that this principle give greater magnitude of muscular activation in the synergistic secondary mover. There is also some indications that the PE method gives a greater neuromuscular activation of the primary mover when PE the synergist. If there are any differences between men and women in muscle activity has never been investigated before. Men have a greater absolute strength than women, especially in their upper body. There are still conflicting results if they also have greater relative strength. Aim. The purpose of the present study was to investigate if there were any neuromuscular differences between men and women when PE triceps brachii before bench press and if there was any differences in relative strength during 10RM bench press. Methods. 15 men and 15 women was randomly signed up in two different protocols. Protocol 1 started with bench press at 10 repetition maximum (10RM) and after five minutes of recovery, they performed the pre-exhaustion exercise (triceps extensions to failure) immediately before a second round of bench press with the same load on the barbell. Protocol 2 started with triceps extensions to failure immediately before bench press at their 10RM. They also had five minutes of recovery before they performed 10 repetitions of bench press. The magnitude of muscular activation were collected with surface electromyography and then processed through average root mean square (RMS). The values were normalized to muscular voluntary isometric contraction (MVIC) and expressed as percent of MVIC. The muscles that was analysed was triceps brachii (TB), pectoralis major (PM) and deltoideus anterior (DA). Results. The results showed that women had a statistically significantly higher muscular activity in all three muscles; PM (p=0.001) TB (p=0.023) and DA (p=0.047) after pre-exhaustion of TB before bench press compared to only bench press. Men showed only a statistical significant higher activation in PM (p=0.003) and a trend of higher activation in DA (p=0.061). There was a statistically significant difference in muscle activity between women and men in TB (p=0.015) but not in DA (p=0.902) and PM (p=0.436). There was no statistically significant difference between relative strength (volume load/fat free mass) (p=0.775) nor number of repetitions in bench press after PE of TB (p=0.713) between the sexes. Conclusion. The main findings in this study is that it was a statistically significant difference in neuromuscular activity in TB between men and women when PE was applied to TB before the bench press compared to bench press only, but no difference in relative strength.

Unilateral exercise can produce certain contralateral strength effects. Deleterious events can be cross-transferred as well, as illustrated by a strict symmetry in some chronic inflammatory diseases. To date, knowledge on the effects of marked overuse of skeletal muscles is limited, and there is largely no information if unilateral overuse affects the contralateral muscles. In view of this, the present study was undertaken to test the hypothesis that unilateral muscle overuse causes alterations in tissue structure and the tachykinin system, with a focus on substance P (SP), not only in the exercised muscles, but also in the contralateral muscles. SP is a well-known neuromodulator that is known to be proinflammatory. An experimental rabbit model with unilateral muscle overuse of the soleus and gastrocnemius muscles caused by exercise via electrical muscle stimulation (E/EMS) was used. In total, 40 rabbits were randomly divided into seven groups of which two groups served as controls. The rabbits were anaesthetized and then set on a “kicking machine” to perform exercise via EMS for 2h every second day. Experimental periods for groups 1-3 were 1, 3 and 6w, respectively, whereas groups 4-6 were exercised for 1w but also subjected to injections in the peritendinous tissue with SP, NaCL, Captopril (C), an ACE inhibitor, and DL-Thiorphan (Th) which inhibits the activity of neural endopeptidase. One group was not subjected to the experiment at all. The day after the last session of E/EMS, the soleus muscle and the gastrocnemius muscle from both legs were collected for analysis. Alterations in muscle structure and the tachykinin system were analyzed with enzyme and immunohistochemical techniques, in situ hybridization and EIA methods. After 1w of E/EMS, focal areas of the exercised muscles contained a mild infiltration of inflammatory cells (myositis) and small morphological changes. After 3 and 6w of E/EMS, distinct myositis and muscle changes were bilaterally present in focal areas of both muscles. The structural changes, which mainly were observed in myositis areas, consisted of increased fiber size variability, split fibers, internal myonuclei, necrotic fibers, fibrosis, fat infiltration, and small fibers containing developmental MyHCs. Bilateral morphological changes, such as loss of axons, were also observed in nerves. In addition, expressions of tachykinin and the SP-preferred receptor, the neurokinin-1 (NK-1R), were bilaterally upregulated in nerve structures and blood vessel walls.  Infiltrating white blood cells exhibited tachykinin–like and NK-1R immunoreactivity. NK-1R immunoreactions were also found in necrotic and regenerating muscle fibers. The concentration of tachykinin (SP) was significantly increased in both soleus and gastrocnemius muscles after E/EMS. There was a significant correlation between the two sides in concentration of tachykinin and in the intensity of tachykinin-like immunoreaction in blood vessel walls. The muscle fiber size and capillary supply of fibers were bilaterally decreased after 3w of EMS. The myositis areas contained an increased number of vessels with a larger size than capillaries, while areas with increased amount of connective tissue contained a very low number of capillaries. A bilateral fiber type shift against a lower proportion of slow MyHCI fibers and higher proportion of fast MyHCII fibers was observed in both muscles. The local injections of C+Th and SP+C+Th led to marked structural changes in the muscle tissue and marked increased NK-1R and tachykinin-like immunoreactivity in the myositis areas and increased tachykinin concentration in the tissue. In conclusion, the repetitive unilateral muscle overuse caused by E/EMS led overtime to muscle injury and myositis. The affected areas contained both degenerative and regenerative alterations in the muscle tissue and nerves, and an upregulation of the tachykinin system. Most interestingly, the changes not only occurred in the exercised side, but also in the homologous contralateral muscles. The tachykinin system appears to be an important factor in the processes of crossover effects.

The potential of the crural fascia to increase the articulation of the posterior thigh muscles through the in series connection of the structures, suggests that the crural fascia may influence the endpoint force direction of the muscles by partially redirecting the muscular force output. Furthermore, not only the in series connections should be considered but also how the parallel alignment of the crural fascia and the triceps surae may influence the force direction from the muscles. A redirection in force may, in turn, affect the intra-limb coordination or contribute to the selection of a task variable muscle activation pattern. The central objective was to evaluate the role of the synergistically located, posterior, distal musculature and connective tissue during locomotion. The central hypothesis was that the crural fascia would redirect the force output from the posterior thigh muscles to the endpoint and consequently increase propulsion within the limb. We selected to perform our studies in the spontaneously locomoting decerebrate cat, which allows us to investigate acute treatments applied to the hindlimb. The overall objective was accomplished by: (1) evaluating the role of the crural fascia during level walking; (2) determine the acute effect of denervating the triceps surae muscles and disrupting the crural fascia during level walking; and (3) evaluating the change in force direction output of selective stimulation of muscles in different limb configurations before and after complete fasciotomy. Our findings demonstrated that the crural fascia not only assists in propulsion but also acts to stabilize the distal limb. Furthermore, the acute denervation of the triceps surae resulted in a decrease in leg length and an increase in ankle yield during the weight acceptance phase of stance. This suggests that the conservation of the limb length as a task level variable is an adaptation rather than an immediate response.

Studying the responsiveness of specific central nervous system (CNS) pathways to electrical or magnetic stimulation can provide important information regarding fatigue processes occurring as a result of ongoing muscle activity. While there are some studies assessing CNS responsiveness during sustained maximal voluntary contractions (MVCs) few papers have examined such changes during sustained submaximal contractions, particularly in muscles of the lower limbs. The location of the underlying central fatigue process can be partially determined by assessing the responsiveness to magnetic or electrical stimulation at different sites along the CNS. This has been investigated during maximal and submaximal contractions in the upper limb muscles, however changes in corticospinal responsiveness at different CNS locations has yet to be determined during fatigue of lower limb muscles. Therefore, the focus of this study was to investigate changes in corticospinal responsiveness during a sustained submaximal contraction of the triceps surae. Comparisons were made between the size of motor evoked potentials (MEPs) elicited by motor cortical stimulation and cervicomedullary motor evoked potentials (CMEPs) elicited via magnetic stimulation of the descending tracts, in order to determine the site of any change in corticospinal responsiveness. Participants maintained an isometric contraction of triceps surae at 30% of MVC for as long as possible on two occasions. Stimulation was applied either to the motor cortex or to the cervicomedullary junction every minute during a contraction until task failure. Peripheral nerve stimulation was also applied to evoke maximal M-waves (Mmax) and a superimposed twitch. Additionally, MEPs and CMEPs were evoked during brief contractions at 80, 90 and 100% MVC as a non-fatigue control. During the sustained contractions, MEP size increased significantly in both soleus (113%; SOL) and medial gastrocnemius (108%; MG) and at endurance limit matched MEP size in the pre-fatigue MVC (≈20-25% Mmax). In contrast, CMEP size increased significantly in MG (51%) but not in SOL (63%), and at endurance limit was significantly smaller than during pre-fatigue MVC (5-6% Mmax versus 11-13% Mmax). The data indicate that cortical processes contribute substantially to the increase in corticospinal responsiveness observed during sustained submaximal contraction of triceps surae. The strength of corticospinal projections and the upper-limit of motor unit recruitment may explain differences in corticospinal responsiveness between SOL and upper arm muscles. Furthermore, differences in motor unit recruitment and firing rate may explain differences in spinal responsiveness between submaximal and maximal voluntary contractions.

京都大学 / 0048 / 新制・論文博士 / 博士(医学) / 乙第13030号 / 論医博第2112号 / 新制||医||1016(附属図書館) / 32988 / (主査)教授 三森 経世, 教授 松田 秀一, 教授 戸口田 淳也 / 学位規則第4条第2項該当 / Doctor of Medical Science / Kyoto University / DFAM

Bakgrund: Muskelbristningar i vadmuskulaturen kan vara svårrehabiliterade varför fysioterapeuter, tillsammans med andra professioner, behöver kunskap om vilka rehabiliteringsmetoder som har starkast evidens. Samstämmighet saknas, därav intresset att kartlägga olika rehabiliteringsmetoder.   Syftet med denna litteraturöversikt var att beskriva rehabiliteringsmetoder och eventuella rapporterade effekter i samband med muskelbristningar i musculus Triceps Surae samt beskriva studiekvalitet.   Metod: Fem artiklar, tre RCT-studier och två observationsstudier, granskades utifrån syfte och frågeställningar och kvalitetsgranskades enligt SBU’s (Statens beredning för medicinsk och social utvärdering) granskningsmallar. Databassökningar gjordes i PubMed, Medline och CINAHL Plus.   Resultat: Injektioner med trombocytrik plasma, is-behandling och kompression genomfördes som tillägg till ett grundläggande rehabiliteringsprogram. Huvudsakliga utfallsmått var återgång till sport/spel samt smärta. Studiekvaliteten bedömdes vara medelhög och evidensstyrkan begränsad.   Slutsats: Rehabilitering vid muskelbristningar i vadmuskulaturen ger förkortad rehabiliteringstid varav PRICE (Protection, Rest, Ice, Compression, Elevation) är betydelsefullt i det initiala skedet. Kompression och injektion av trombocytrik plasma uppvisar positiv inverkan på rehabiliteringstiden på lång sikt, isbehandling visar ingen effekt på lång sikt. Resultatet indikerar att ökad ålder förlänger rehabiliteringstiden samt ökar risken för återfall. Området är i behov av fler randomiserade kontrollerade studier för att stärka evidensen inom området.

Master's thesis topic: Influence of rheological characteristics of muscle tissue by musculus triceps surae by means of AEK practice Author: Bc. Karel Kupec Branch of study: Physiotherapy Disertation Tutor: PhDr. Petr Šifta, Ph.D. Year of Defense: 2013 Abstract: The target of this thesis was find out the effect of agistic-excentric contractions on muscle tension of musculus soleus compared with passive relaxation of musculus soleus. The assumption was, that agistic-excentric contraction reduce muscle tension of musculus soleus after anaerobic load. The contralateral lower limb was control limb for comparison agistic-excentric contraction and passive relaxation. Muscle tension was measured in laboratory in Faculty of Physical Education and Sport, Charles University: five students were measured. As a measurement method was used myotonometry, which simulated palpation. Measured data were displayed by using an analog-digital convertor and consequently evaluated. The results of this study found out positive effect of agistic-excentric contraction on muscle tension. Control form of relaxation, passive relaxation, didn't influence muscle tension so significantly. The results support the principle of hypotheses, that agisctic-exentric contraction approach affect muscle tension more positive than passive...

Master of Science / Department of Animal Sciences and Industry / Michael E. Dikeman / The longissimus lumborum (LL) muscle from 117 steers and the LL, gluteus medius (GM), and triceps brachii (TB) from 132 heifers were obtained to evaluate the effects of feeding zilpaterol hydrochloride (Zilmax®; ZH) (7.56g/907kg on a 100% DM basis) on tenderness. Both genders were blocked by initial weight into 6 blocks of 4 pens. Pens were assigned to treatments of either 0, 20, 30 or 40 d on ZH, with a 3 d withdrawal. One steak was removed from each muscle for proximate analysis and three 2.54 cm thick steaks were vacuum aged for either 7, 14 or 21 d. Steaks were cooked to 70 ˚C and six 1.27 cm diameter cores were removed for Warner-Bratzler shear force (WBSF) determinations. All muscles from steers and heifers fed 30 and 40 d with ZH, had higher (P < 0.05) WBSF compared with controls. The WBSF of steer LL and heifer TB from the 20 d treatment was higher (P < 0.05) than controls. There were no treatment by aging interactions (P > 0.05) for WBSF of steaks from steer LL, heifer LL or heifer TB, but there was a treatment by aging interaction (P < 0.05) for WBSF of steaks from heifer GM. There were no differences (P > 0.05) in percent intramuscular fat for any muscle due to treatment. When using percent intramuscular fat as a covariate, differences in WBSF of steer LL and heifer TB were not altered, but there were slight differences in heifer LL and GM WBSF due to treatment when compared with not using percent fat as a covariate. Percentages of steaks with WBSF ≥ 5 kg increased as days on ZH increased and decreased as days of aging increased. Warner-Bratzler shear force values among the three aging times for steer LL control, 20 and 40 d treatments; all heifer LL treatments, and heifer TB 20 d were all positively correlated (P < 0.01) with each other. Feeding ZH for 20 d generally increased WBSF values, but means were still acceptable. Feeding ZH for 40 d was very detrimental to tenderness.

A utilização da eletroestimulação muscular é uma estratégia utilizada para investigação da fadiga neuromuscular. Entretanto, esta técnica é pouco aplicada na musculatura extensora do cotovelo em função de limitações biomecâncias (atuação de músculos sinergistas), neurais (influência de reflexo neural) e fisiológicas (facilidade em atingir estados de potencialização pós-ativação e fadiga). Portanto, o objetivo deste estudo foi padronizar procedimentos para avaliação neuromuscular da musculatura extensora do cotovelo. Para isso, foram realizados três estudos que envolveram a adequação da técnica de eletroestimulação e um \"estudo principal\" para validar um novo protocolo de avaliação neuromuscular. Após resultados positivos em estudos complementares, a presente dissertação propôs a validação de um protocolo para análise neuromuscular com contrações submáximas para a musculatura extensora do cotovelo. Vinte participantes com idade de 25,1 ± 6,8 anos foram submetidos, em dias diferentes, a dois esforços, um a fim de promover fadiga central e fadiga periférica respectivamente. Antes e após os esforços envolvendo fadiga (periférica ou central) foram realizadas avaliações de fadiga neuromuscular para musculatura extensora do joelho (protocolo já validado) e musculatura extensora do cotovelo (protocolo proposto). Verificou-se que: (i.) o modelo de análise proposto não promove nenhum tipo de fadiga ou potencialização pós-ativação; (ii) a resposta de um pulso controle no início e no fim do modelo de análise proposto promovem respostas diferentes; (iii) o modelo proposto foi capaz de identificar redução da resposta neuromuscular; (iv) o esforço envolvendo fadiga central não promoveu fadiga central significante; (v) a utilização de um modelo matemático para investigação de fadiga neuromuscular (coeficientes resultantes de uma regressão linear) com os valores de estimulação em contrações submáximas foi sensível a fadiga mas não foi capaz de discriminar fadiga central e periférica. É possível concluir que o modelo de análise proposto para a musculatura extensora do cotovelo apresentou sensibilidade para verificar a fadiga neuromuscular. Entretanto, este não foi capaz de discriminar fadiga central e periférica. A utilização da regressão linear parece ser uma boa estratégia para diferenciar os dois modelos de fadiga e deve ser estudada com mais profundidade futuramente. / Muscular electrostimulation is a strategy used to investigate neuromuscular fatigue. However, this technique is poorly applied in the elbow extensor muscles due to the limitations of biomechanics (acting of synergistic muscles), neural (influence of neural reflex) and physiological (easiness to achieve post-activation and fatigue states of potentiation). Therefore, the purpose of this study was to standardize a neuromuscular evaluation strategy for the elbow extensor musculature. Thus, three complementary studies aimed at adjusting the electrostimulation technique and one \"main study\" to validate a new neuromuscular assessment protocol were realized. After positive results in complementary studies, the present dissertation proposed a protocol validation for neuromuscular analysis with submaximal contractions on the elbow extensor musculature. Twenty participants with 25.1 ± 6.8 years old performed, on different days, two efforts, one to promote central fatigue and peripheral fatigue respectively. Before and after the exercise involving fatigue (peripheral or central) there were realized neuromuscular fatigue evaluations for knee extensor muscles (protocol already validated) and elbow extensor musculature (protocol). The results indicate that: (i) the proposed analysis model does not promote any type of fatigue or post-activation potentiation; (ii) the response of a control pulse at the beginning and end of the proposed analysis model promotes different responses; (iii) the proposed model was able to identify reduction of neuromuscular response; (iv) the effort involving central fatigue did not promote significant central fatigue; (v) the use of a mathematical model to investigate neuromuscular fatigue (coefficients resulting from a linear regression) with the values of stimulation in submaximal contractions was sensitive after fatigue but was not able to discriminate central and peripheral fatigue. It is possible to conclude that the proposed analysis model for the elbow extensor musculature presented sensitivity to verify the neuromuscular fatigue. However, it was not able to discriminate central and peripheral fatigue. The use of linear regression seems to be a good strategy to differentiate the two models of fatigue and should be studied in more depth in the future.