Introduction: Several authors have demonstrated that, while cycling at a constant power output, EMG activity from the gastrocnemius increases systematically with increases in pedaling cadence, but that soleus EMG remains unchanged (Marsh & Martin 1995; Sanderson et al. 2006). The reason for this differential effect of cadence on the muscles of the triceps surae is unclear. Whatever factor(s) are responsible, it is assumed that, as they vary, the differential electromyographic response will vary accordingly. Decreasing the seat height has been shown to alter the kinematic characteristics of cycling (Too, 1990). The first objective of this study was to examine the effect of a decrease in seat height on the kinematics and muscle activation of the lower limb. The second objective was to investigate the effect of seat height on the relationship between cadence and triceps surae activation and, in doing so, to reveal possible factors mediating the response to changes in cadence. Methods: Participants pedaled a cycle ergometer at 200 Watts for five minutes at each of five cadences (50, 65, 80, 95, 110 rpm) and at each of two seat heights (100% and 90% trochanteric height). Kinematics of the lower limb were calculated from digitized video records of reflective markers placed on the skin over seven bony landmarks. EMG data were collected from eight lower-limb muscles. Results: The most notable findings were 1) that activation of the gastrocnemii was less in the low-seat condition and, contrary to what the findings of past research would suggest, was not associated with changes in muscle length; 2) that the medial and lateral gastrocnemii responded differently to changes in cadence at each seat height, suggesting that the functional roles of these muscles in cycling differ; 3) that several factors, including muscle length, muscle velocity, ankle angle and the direction of muscle action, were not responsible for the differential effect of cadence on activation of the soleus and gastrocnemius. Future research should investigate afferent feedback from proprioceptors in the knee joint and knee extensor muscles as possible factors mediating the effect.

Introduction: Several authors have demonstrated that, while cycling at a constant power output, EMG activity from the gastrocnemius increases systematically with increases in pedaling cadence, but that soleus EMG remains unchanged (Marsh & Martin 1995; Sanderson et al. 2006). The reason for this differential effect of cadence on the muscles of the triceps surae is unclear. Whatever factor(s) are responsible, it is assumed that, as they vary, the differential electromyographic response will vary accordingly. Decreasing the seat height has been shown to alter the kinematic characteristics of cycling (Too, 1990). The first objective of this study was to examine the effect of a decrease in seat height on the kinematics and muscle activation of the lower limb. The second objective was to investigate the effect of seat height on the relationship between cadence and triceps surae activation and, in doing so, to reveal possible factors mediating the response to changes in cadence. Methods: Participants pedaled a cycle ergometer at 200 Watts for five minutes at each of five cadences (50, 65, 80, 95, 110 rpm) and at each of two seat heights (100% and 90% trochanteric height). Kinematics of the lower limb were calculated from digitized video records of reflective markers placed on the skin over seven bony landmarks. EMG data were collected from eight lower-limb muscles. Results: The most notable findings were 1) that activation of the gastrocnemii was less in the low-seat condition and, contrary to what the findings of past research would suggest, was not associated with changes in muscle length; 2) that the medial and lateral gastrocnemii responded differently to changes in cadence at each seat height, suggesting that the functional roles of these muscles in cycling differ; 3) that several factors, including muscle length, muscle velocity, ankle angle and the direction of muscle action, were not responsible for the differential effect of cadence on activation of the soleus and gastrocnemius. Future research should investigate afferent feedback from proprioceptors in the knee joint and knee extensor muscles as possible factors mediating the effect.

Introduction: Several authors have demonstrated that, while cycling at a constant power output, EMG activity from the gastrocnemius increases systematically with increases in pedaling cadence, but that soleus EMG remains unchanged (Marsh & Martin 1995; Sanderson et al. 2006). The reason for this differential effect of cadence on the muscles of the triceps surae is unclear. Whatever factor(s) are responsible, it is assumed that, as they vary, the differential electromyographic response will vary accordingly. Decreasing the seat height has been shown to alter the kinematic characteristics of cycling (Too, 1990). The first objective of this study was to examine the effect of a decrease in seat height on the kinematics and muscle activation of the lower limb. The second objective was to investigate the effect of seat height on the relationship between cadence and triceps surae activation and, in doing so, to reveal possible factors mediating the response to changes in cadence. Methods: Participants pedaled a cycle ergometer at 200 Watts for five minutes at each of five cadences (50, 65, 80, 95, 110 rpm) and at each of two seat heights (100% and 90% trochanteric height). Kinematics of the lower limb were calculated from digitized video records of reflective markers placed on the skin over seven bony landmarks. EMG data were collected from eight lower-limb muscles. Results: The most notable findings were 1) that activation of the gastrocnemii was less in the low-seat condition and, contrary to what the findings of past research would suggest, was not associated with changes in muscle length; 2) that the medial and lateral gastrocnemii responded differently to changes in cadence at each seat height, suggesting that the functional roles of these muscles in cycling differ; 3) that several factors, including muscle length, muscle velocity, ankle angle and the direction of muscle action, were not responsible for the differential effect of cadence on activation of the soleus and gastrocnemius. Future research should investigate afferent feedback from proprioceptors in the knee joint and knee extensor muscles as possible factors mediating the effect. / Education, Faculty of / Kinesiology, School of / Graduate

Title: The influence of bicycle saddle position on muscle tone of the triceps surae muscle Objectives: The aim of this thesis is to find out what is the effect of changing the bicycle saddle position on muscle tone of triceps surae muscle. And whether the higher seat position will also increase muscle tone of the calf muscle. Methods: The thesis is divided into the theoretical part, where there is the information from the scientific literature on the subject and a practical part. The theoretical part includes anatomical descriptions and rheological properties of skeletal muscles, muscle tension and its regulation. Part of it is also the biomechanics of cycling, bike geometry and the options of bicycle seat setting and also the risk implications of the incorrect bicycle seat position. The practical part was prepared as a research by measuring of muscle tone by the myotonometer. For measurement was used the triceps surae muscle of the seven probands on the dominant lower limb. The measurement were twice two weeks apart with the different bicycle seat height. Results: The measurement results confirmed that change of bicycle saddle position has an influence on the muscle tone and that the higher saddle position will also increase muscle tone of the calf muscle. Keywords: bicycle saddle position, saddle...

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.

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.