The purpose of this study was to display increase in eccentric hamstring strength after 10-weeks training program. Secondly, if such an increase occurred, would this strength change result in altered landing kinetics and improved jumping performance? 27 recreational female athletes assigned into experimental (n = 14) and control (n = 13) groups. Baseline measures of landing kinetics were collected using a force plate, strength data and proprioceptive measurements were evaluated using an isokinetic dynamometer and vertical jump performance were determined by a jumping mat. Results indicated that NHST group increased their eccentric hamstring strength after eccentric strength training program (week-1 = 233.6&plusmn / 27.5, week-10 = 253.8&plusmn / 28.4 Nm/kgbw / p&lt / .05). The results demonstrated that there were significant differences in landing mechanics for NHST group. PVGRF (week-1 = 6.2&plusmn / 0.9, week-5 = 5.3&plusmn / 0.9 / p&lt / .05), PAPGRF (week-1 = 1.1&plusmn / 0.2 &amp / week-10 = 0.8&plusmn / 0.3 / p&lt / .05) and APImp results demonstrated significant differences in trained group (week-1 = 78.1&plusmn / 13.6 &amp / week-10 = 67.8&plusmn / 9.2 / p&lt / .05). NHST group exhibited significant increase in vertical jumping ability (week-1 = 0.25&plusmn / 0.0 &amp / week-10 = 0.27&plusmn / 0.0 cm / p&lt / .01). This study supported the following points: 1) increases in the eccentric hamstring strength were evident after NHST program, 2) the increases in isokinetic strength were sufficient to cause alterations in landing kinetics to decrease the applied joint forces, so the NHST program would be an influential factor in decreasing the lower extremity injuries, and 3) the increase in the efficiency of force transfer at the final take off phase of jumping contributed to a higher performance in vertical jump.

Orientador: Franciele Marques Vanderlei / Resumo: Estudos sobre o treinamento resistido de baixa intensidade associado à restrição de fluxo sanguíneo (RFS) atualmente tem ganhado destaque, porém ainda existem lacunas que podem ser exploradas em relação aos seus efeitos fisiológicos quando associado a treinamentos excêntricos, principalmente na força e hipertrofia muscular. Objetivo: Realizar uma revisão sistemática com metanálise e um estudo aleatorizado controlado a fim de esclarecer os reais efeitos do TRBI associado à RFS nos desfechos de força, hipertrofia muscular e desempenho funcional, e se a RFS quando associada a treinamentos excêntricos de baixa e alta intensidade é capaz de aumentar as respostas desses desfechos dos extensores de joelho em homens adultos saudáveis. Métodos: A revisão sistemática foi registrada no PROSPERO (número do registro #CRD42018104065). Os estudos foram selecionados por meio de sete bases de dados. Todos os estudos incluídos foram avaliados quanto à qualidade metodológica, utilizando a Escala PEDro, bem como foi avaliada a qualidade da evidência. Somente ensaios clínicos randomizados que avaliaram a eficácia do treinamento com RFS na força e hipertrofia muscular dos músculos extensores de joelho em adultos do sexo masculino, saudáveis e/ou fisicamente ativos, com idade de 18 a 35 anos, contra algum grupo de intervenção foram considerados elegíveis. Todas as metanálises foram conduzidas por meio do software Review Manager – RevMan e descritos como diferenças médias padronizadas (standardized ... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: Studies on low intensity resistance training associated with blood flow restriction (RFS) are currently gaining prominence, however there are still gaps that can be explored in relation to their physiological effects when associated with eccentric training, especially in muscle strength and hypertrophy. Objective: To carry out a systematic review with meta-analysis and a randomized controlled study in order to clarify the real effects of TRBI associated with RFS on the outcomes of strength, muscle hypertrophy and functional performance, and whether RFS when associated with low and high intensity eccentric training is able to increase the responses of these knee extensor outcomes in healthy adult men. Methods: The systematic review was registered in PROSPERO (registration number # CRD42018104065). The studies were selected through seven databases. All included studies were assessed for methodological quality, using the PEDro Scale, as well as the quality of evidence was assessed. Only randomized controlled trials that assessed the effectiveness of RFS training on muscle strength and hypertrophy of knee extensor muscles in healthy, male and / or physically active adults, aged 18 to 35, against any intervention group were considered eligible. All meta-analyzes were conducted using the Review Manager - RevMan software and described as standardized mean differences (SMD) or mean differences (mean difference - MD) with 95% confidence intervals (CI). The randomized controlled study ... (Complete abstract click electronic access below) / Mestre

Syftet med denna studie var att undersöka effekten av 6 veckors styrketräning med så kallad Nordic Hamstring Exercise (NHE) i jämförelse med Razor Hamstring Curl (RHC) med avseende på hamstringsmuskulaturens styrka och rörlighet hos unga fotbollsspelare.   43 fotbollsspelande ungdomar från två olika lag rekryterades till studien varav 40 slutförde den. Deltagarna var av manligt kön och hade en medelålder på 17.2 ± 0.6. De randomiserades till två olika interventionsgrupper, NHE och RHC, där de fick utföra tilldelad övning under träningstid under sex veckor. Mätning av hamstrings rörlighet och isometrisk utvärdering av hamstrings muskelstyrka i 90°-, 45°- och 0°- knävinkel utfördes innan och efter intervention. Parade t-test och Wilcoxon signed rank test användes för att testa förändringen inom grupp och ANCOVA användes för att se skillnaderna mellan grupperna.    NHE-gruppen hade en signifikant ökning av muskelstyrkan i samtliga testvinklar. RHC gruppen hade signifikant ökning i endast två av tre testvinklar. Mätningen i 0° visade ingen signifikant ökning av muskelstyrkan. Rörligheten hade en signifikant ökning i båda interventionsgrupperna. När interventionsgrupperna testades mot varandra så hade NHE gruppen en signifikant högre ökning av muskelstyrkan i 0° mätningen jämfört med RHC gruppen. Ingen signifikant skillnad uppmärksammades i de andra testvinklarna eller i ökningen av rörligheten.   Både NHE- och RHC-träning under 6 veckor resulterade i signifikant ökning av muskelstyrka och rörlighet i hamstringsmuskulaturen hos unga fotbollsspelare. NHE resulterade dock i en signifikant större ökning av muskelstyrkan i ett större rörelseomfång än RHC-övningen. Baserat på resultaten i denna studie är NHE den föredragna metoden att inkludera i framtida träningsprogram.

Performance of a series of eccentric contractions produces adverse effects including muscle weakness, delayed onset muscle soreness (DOMS), fluid accumulation and decreased muscle function. The repeated bout effect is a physiological adaptation observed when a single-bout of eccentric exercise protects against muscle damage from subsequent eccentric bouts. Similar to the repeated bout effect, increases in flexibility have been linked to attenuations in acute muscle damage, muscle fatigue and strength loss after eccentric exercise. Purpose: The purpose of this study was to examine the muscle physiological responses to eccentric strength training after first priming the muscles with either a period of static flexibility training or a single intense bout of eccentric exercise performed weeks earlier; and compare these to the responses from eccentric strength training when no prior intervention is administered. Methods: Twenty-five participants were randomly assigned to a flexibility (F) (n=8), a single-bout (SB) (n=9), or a control (C) (n=8) group. The design consisted of two 4-week phases; 1) priming intervention, 2) eccentric training. The priming intervention included static stretching (3x/week; 30mins/day) (F), a single-bout of eccentric exercise (SB) or no priming intervention (C). All groups proceeded to complete eccentric training of the knee flexors using isotonic contractions (%load progressively increased over training period) on a dynamometer following the priming intervention phase. Testing was completed at baseline, post-priming intervention and post-eccentric training, in conjunction with data being collected during the acute eccentric training phase (0hr, 24hr, 48hr; post-bout 1 and 4). Dependent measures included muscle thickness, isometric maximal voluntary contraction (MVC), eccentric and concentric MVC, optimal angle, active range of motion (ROM), passive ROM, maximal power, electromyography (EMG) and delayed onset muscle soreness (DOMS). Results: Acute data during the eccentric training phase revealed a significant reduction in DOMS for both the F and SB groups compared to the C following the first bout of eccentric exercise (p<0.05). The F also had reduced soreness in comparison to both the SB and C post fourth bout of eccentric exercise (p<0.05). The F group demonstrated attenuated loss in isometric strength (post fourth bout) and maximal power (post first bout) during eccentric training compared to the C group (p<0.05). However, there was no significant difference between groups across all dependent variables following the eccentric training phase. Conclusion: This is the first study to directly compare the protective effects observed with static flexibility training to that of a single-bout of eccentric exercise throughout a subsequent eccentric training regime. Although differences in muscle soreness, strength and maximal power occurred during the acute stages of eccentric training, there appeared to be no significant advantage of either protective priming method at the end of eccentric training.

Dans un premier temps, nous avons observé la chronologie des altérations de la biogenèse et de la fonction mitochondriale dans les ventricules droit (VD) et gauche (VG) et le muscle gastrocnémien (GAS) dans un modèle animal d’hypertension artérielle pulmonaire (HTAP). Nous avons constaté une diminution précoce des facteurs impliqués dans la biogénèse mitochondriale du GAS. Plus tard, les mêmes anomalies apparaissaient dans le VD. Au stade décompensé de l’insuffisance cardiaque droite s’ajoutaient une diminution de la protéine PGC-1 , de l’activité de la citrate-synthase et de la respiration mitochondriale. L’expression des ARNm et la respiration mitochondriale du VG n’étaient pas modifiées de façon significative.Dans un deuxième temps, nous avons étudié l’effet de l’entraînement en mode excentrique sur le même modèle d’HTAP. La survie des rats entraînés n’était pas différente de celle des rats sédentaires et la tolérance hémodynamique évaluée par échocardiographie et cathétérisme cardiaque a été bonne. Le bénéfice de l’entraînement s’est traduit par une augmentation de la vitesse maximale de course dans les deux groupes entraînés, malades et témoins. / We assessed the time courses of mitochondrial biogenesis factors and respiration in the right ventricle (RV), gastrocnemius (GAS) and left ventricle (LV) in a model of pulmonary-hypertensive (PH) rats induced by monocrotaline (MT). The expression of the studied genes was decreased early in the MT GAS. At 4 weeks, the MT GAS and MT RV showed decreased mRNA levels whatever the stage of disease, but PGC-1 protein and citrate-synthase activity were significantly reduced only atthe decompensated stage. The functional result was a significant fall in mitochondrial respiration at the decompensated stage in the RV and GAS. The mRNA expression and mitochondrial respiration were not significantly modified in the MT LV. Secondly, we assessed the effects of eccentric exercise training (ECCt) in MT rats with PH. ECCt was initiated 2 weeks after MT injection for 4 weeks. The trained MT rats survival was not different from that of sedentary rats. ECCt was not detrimental on hemodynamic condition estimated by echocardiography and right heart catheterization. Maximal speed significantly increased in trained rats. The mRNA expression of mitochondrial biogenesis factors were not significantly modified in skeletal muscle and in RV.

Currently, there are various training machines that can support training of the muscles while the muscles are lengthened, also known as eccentric training. Training machines that are widely used to train the muscles eccentrically utilize a flywheel to generate load to the user. When training the muscles eccentrically with such a machine, there is a desire to accomplish eccentric overload, which is achieved when the muscles under training are exposed to a very high load during eccentric training of these muscles. To achieve this, the user needs to activate other muscles that are not in the focus of the training or be assisted by another person. In this study, a novel, smart flywheel training machine was developed by implementing electric motor and sensors, which could identify the exercise pattern of the user and help achieve desired eccentric overload. This study focused on how the system performance of such training machine interacting with human beings was affected by various grade of sensor feedback. With an increased resolution of the sensors and a lower sample time, the cost of the system is increased, and it was therefore of interest to study what grade of sensor feedback was required. More exactly, this study evaluated how the system performance was improved when sensor resolution was improved, what resolution and sample time were required for the system to perform correct and safely and last, how noise and disturbances affected the system. The study was conducted in a simulated environment in Matlab and Simulink, and some real tests and experiments were also performed on the existing flywheel training machine. An incremental encoder was implemented in the system and resolution of the encoder, as well as sample time, were tweaked in the simulation to test different combinations of these. The results showed that both resolution and sample time had an impact on the system performance. A higher resolution resulted in a smaller tracking error to some extent, but after a certain value the system became unstable if the sample time was not small enough. Noise and disturbances had a minor impact on the system performance. It was concluded that the best choice of encoder resolution was 0.0314 radians with a sample time of 0.01 ms. Even lower resolution such as 0.628 rad, 0.126 rad or 0.0571 rad with a sample time of 0.1 ms could be allowed and should be considered safe. However, the system might not perform as desired if these alternatives are chosen, although the alternatives might decrease the cost of the system. / I nuläget finns det olika träningsmaskiner som kan stödja träning av muskler där musklerna förlängs, även känt som excentrisk träning. Träningsmaskiner som idag används i stor utsträckning för att träna musklerna excentriskt använder ett svänghjul för att generera träningsmotstånd till användaren. När musklerna tränas excentriskt med en sådan maskin finns det en önskan att åstadkomma excentrisk överbelastning; detta uppnås när musklerna som tränas utsätts för en mycket hög belastning under den excentriska träningsfasen. För att uppnå detta måste användaren aktivera andra muskler som inte står i träningens fokus eller få hjälp av en annan person. I den här studien har en ny, smart, svänghjulsträningsmaskin utvecklats genom att implementera elmotor och sensorer som kan identifiera användarens träningsmönster och hjälpa till att uppnå önskvärd excentrisk överbelastning. Denna studie fokuserade på hur systemprestanda för en sådan träningsmaskin som interagerar med människor påverkades av olika grader av sensoråterkoppling. Med en ökad upplösning av sensorerna och en lägre samplingstid ökar kostnaden för systemet och det var därför av intresse att studera vilken grad av sensoråterkoppling som krävdes. Mer exakt utvärderar denna studie hur systemets prestanda förbättrades när sensorupplösningen var högre och vilken upplösning och samplingstid som krävdes för att systemet skulle fungera korrekt och säkert. Påverkan av brus och störningar på systemet utvärderades också. Studien genomfördes i simuleringsmiljö i Matlab och Simulink och verkliga tester och experiment utfördes på den befintliga svänghjulsträningsmaskinen. En inkrementell pulsgivare (incremental encoder) implementerades i systemet och dess upplösning, såväl som samplingstid, justerades i simuleringen för att testa olika kombinationer av dessa. Resultat visade att både upplösningen och samplingstiden påverkade systemets prestanda. En högre upplösning resulterade i ett mindre reglerfel till en viss del, men efter en viss ökad upplösning blev systemet instabilt om samplingstiden inte var tillräckligt liten. Brus och störningar hade en mindre inverkan på systemprestandan. Slutsatsen var att det bästa valet av pulsgivarupplösning var 0,0314 radianer med en samplingstid på 0,01 ms. Även lägre upplösning såsom 0,628 rad, 0,126 rad eller 0,0571 rad med en samplingstid på 0,1 ms kan tillåtas och bör betraktas som säkert. Systemet kan dock komma att inte fungera som önskat om dessa alternativ väljs, dock kan alternativen sänka kostnaden för systemet.

I denna översiktsartikel granskades 17 randomiserade kontroll studier som undersökt hur excentrisk träning har påverkat hopphöjd, muskelstyrka och effektutveckling hos tränade och skadefria individer, med mål att svara på följande två frågeställningar; 1) ”Är excentrisk träning ett effektivt sätt att träna för att utveckla hopphöjd, muskelstyrka och effektutveckling för tränade och skadefria individer?” 2) ”Om det är det, hur bör denna träning i så fall se ut?”. Majoriteten av insamlade studier kunde inte urskilja några signifikanta förändringar till följd av excentrisk träning. Endast sex av 17 studier kunde påvisa akuta såväl som kortsiktiga signifikanta förbättringar av hopphöjd, muskelstyrka och effektutveckling. Dock ifrågasätts relevansen av dessa fynd då effektstorleken inte rapporterats i alla studier samt att utformningen av studierna varierat från en studie till en annan. Sammantaget lyckades inte de granskade studierna bevisa att excentrisk träning är en effektiv metod för att utveckla hopphöjd, muskelstyrka och effektutveckling hos tränade och skadefria individer. / In this review 17 randomized control studies were reviewed that had examined the effects of eccentric training regarding jump height, strength and power for trained and non-injured individuals. The purpose of the review was to answer the following two questions at issue; 1) “Is eccentric training an efficient method to enhance jump height, strength or power for trained and non-injured individuals?” 2) “If so, how should that training regime be designed?”. Most of the included studies could not distinguish any significant changes because of eccentric training. Only six out of 17 studies could show acute as well as short term significant improvements in jump height, strength and power. The relevance of these findings is questioned since effect size has not been reported in all the included studies. The variety between the different interventions in each study also makes it difficult to compare the results between one study and another. In conclusion, the reviewed studies failed to show that eccentric training is an effective method to enhance jump height, strength and power for trained and non-injured individuals.

L'objectif de ce travail de thèse est d'étudier d'une part les spécificités de la commande nerveuse lors de la contraction excentrique en explorant les mécanismes impliqués au niveau spinal et d'autre part d'examiner les mécanismes nerveux responsables de la plasticité du système neuromusculaire après un entraînement de force excentrique sous-maximal. A travers ce travail de thèse, nous mettons en évidence la contribution de l'inhibition récurrente à la réduction de l'activation musculaire classiquement observée lors de la contraction excentrique. Par ailleurs, nous montrons que l'inhibition récurrente est majorée lors des contractions sous-maximales indépendamment du mode de contraction. Ces résultats soulignent le rôle important de l'inhibition récurrente dans la spécificité de la commande nerveuse lors de la contraction excentrique. Nous confirmons que le pilotage nerveux de la contraction excentrique peut être modulé par l'entraînement de force excentrique même si les modulations de l'excitabilité spinale semblent dépendre des caractéristiques de l'entraînement. / The purpose of this PhD research is, on the one hand, to study the neural drive specificities during eccentric contractions by exploring the neural mechanisms involved at spinal level and, on the other hand, to examine the neural mechanisms responsible for the modulations of neuromuscular system following a strength submaximal eccentric training. Through this PhD research we highlight the contribution of recurrent inhibition by the Renshaw cell to the decrease of muscular activation typically observed during eccentric contraction. Furthermore, we show that recurrent inhibition is enhanced during submaximal contractions regardless of the contraction type. These results emphasize the important role of recurrent inhibition in the specificity of neural control during eccentric contractions. We confirm that the neural drive of the eccentric contraction may be modulated by eccentric strength training although modulations of spinal excitability seem to depend on the characteristics of training.