Skeletal muscle structure, function, and plasticity
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... Muscle architectural parameters, including muscle fiber length, physiological cross-sectional area (PCSA) and pennation angle (the angle between muscle fibers and the tendon plate), are associated with force production [4,5]. The anatomical cross-sectional area (ACSA) is simply the largest cross-section across the whole muscle, while the PCSA is the architectural parameter that is directly proportional to the maximum force generated by the muscle because it takes into account the pennation angle [6][7][8][9]. It is also the parameter that is most difficult to measure because its value is based on the entire muscle volume and includes the estimate of fiber length to reach the value for the area across the entire muscle [9]; therefore, it is indirectly determined from the muscle volume and muscle fiber length. ...
... The anatomical cross-sectional area (ACSA) is simply the largest cross-section across the whole muscle, while the PCSA is the architectural parameter that is directly proportional to the maximum force generated by the muscle because it takes into account the pennation angle [6][7][8][9]. It is also the parameter that is most difficult to measure because its value is based on the entire muscle volume and includes the estimate of fiber length to reach the value for the area across the entire muscle [9]; therefore, it is indirectly determined from the muscle volume and muscle fiber length. ...
... However, we observed that the different angles measured in the tracked fibers did not significantly alter the value of the PCSA. In fact, from all the architectural parameters, the pennation angle probably has a small influence on muscle PCSA calculations and, thus, in predicting the maximum muscle force [9]. After exercise, the pennation angle significantly decreased in the SOL muscle. ...
Proton density (PD) and diffusion tensor imaging (DTI) are imaging techniques that enable the acquisition of data from living subjects that can be used in the fine-tuning of subject-specific models’ architectural parameters. The aim of this study was to determine the in vivo 3D architectural parameters (volume, pennation angle, fiber length and physiological cross-sectional area) of the gastrocnemius medialis, gastrocnemius lateralis, soleus and tibialis anterior muscles using proton density and diffusion tensor imaging data before and after an exhaustive one-legged jump exercise. These methods were used in the in vivo 3D data acquisition of six young and physically active female subjects’ lower legs, followed by a fiber-tracking algorithm and analysis tools. No significant differences were found in the muscles’ architecture after the exercise, with the following exceptions: the anatomical cross-section area of the gastrocnemius medialis increased (p-value 0.001, effect size 0.18) after exercise; the fiber lengths of the gastrocnemius medialis, lateralis and soleus muscles were higher after exercise (p-value 0.002, 0.001 and 0.001, respectively, and effect size 2.03, 1.29 and 0.85, respectively); and the soleus mean pennation angle decreased after exercise (p-value 0.0015, effect size 2.31). These changes (or lack thereof) could be attributed to the extended acquisition time of the MRI scans to minimize noise: by increasing the acquisition time, the effect of the exercise may have been partially lost due to muscle recovery.
... postural or breathing muscles) are composed of fibres that are resistant to fatigue, termed type I fibres. The major characteristics of type I fibres are their small size, large number of mitochondria and their larger vascular supply (Lieber, 2010). These features predispose them to rely on aerobic mechanisms to produce energy (i.e. ...
... To achieve this, they rely on anaerobic pathways to produce energy (i.e. glycolysis) (Lieber, 2010). There are three different subtypes of type II fibres, from more aerobic to more anaerobic termed Type IIA, Type IIX, and Type IID fibres. ...
... Also, decreases in maximal force and increases in fatigability have been described when muscle activity is chronically decreased (e.g. sedentary states, immobilization, denervation) (Lieber, 2010). ...
Introduction: Obesity and diabetes induce structural and metabolic disturbances in insulin-sensitive tissues. Furthermore, physical exercise is one of the most prescribed lifestyle modifications to counteract these disturbances. However, comparisons of metabolic effects between different exercise modalities in an obesity context are scarce and require further investigation.
Aims: To investigate the metabolic effect of two isocaloric training programs: moderate-intensity endurance (END) or high intensity interval training (HIIT), in a mouse model of diet-induced obesity using a preventive and a treatment approach; and to investigate the effect of long-term diabetes and obesity on the skeletal muscle extracellular matrix (ECM).
Methods: Three different animal experiments were designed to achieve the aims of this thesis. 1) 72 male C57BL/6 mice were fed with standard CHOW or high-fat diet (HFD) for 10 weeks; simultaneously they underwent one of two different isocaloric exercise programs, constant-moderate (END) or high-intensity interval training (HIIT) for the same 10 weeks. 2) 72 male C57BL/6 mice were fed with standard CHOW or HFD for 10 weeks; then they underwent END or HIIT for another 10 weeks. In the third experiment, 51 male C57BL/6 mice were fed with standard CHOW or HFD for 15 weeks; then in a subset of each dietary group diabetes was induced. Subsequently, dietary intervention was continued for another 15 weeks.
Results: From a preventive perspective, END and HIIT induced similar metabolic benefits in HFD mice, however, only END normalized glucose metabolism markers. In already obese and insulin resistant mice, HIIT induced a better metabolic effect in quadriceps (skeletal muscle) and subcutaneous adipose tissue, whereas specific benefits were seen in the liver after END. Regarding the muscle ECM, diabetes induced a fibrotic profile. In contrast, HFD alone induced a dysregulation in ECM regulators.
Conclusions: Different exercise prescriptions exert differential metabolic benefits in high-fat fed mice. END induced greater desirable metabolic benefits in a preventive context, whereas HIIT appears to give greater efficacy in already obese and insulin-resistant mice. Future research should aim to explore the mechanisms behind these differential effects of exercise.
... It has been proposed that muscle fibers demonstrate different mechanical behaviors when they are weakened in the shortened rather than elongated form. The muscles that have been weakened in the long length show more weakness in their shortened length, while it may not demonstrate any dysfunction in other lengths of muscle fibers [20]. Since some muscles may be weakened in the elongated length in persons with FHP, and they are predisposed to malfunction in their short length, it seems rational to design some exercise to strengthen these muscles in the shortened length [20,21]. ...
... The muscles that have been weakened in the long length show more weakness in their shortened length, while it may not demonstrate any dysfunction in other lengths of muscle fibers [20]. Since some muscles may be weakened in the elongated length in persons with FHP, and they are predisposed to malfunction in their short length, it seems rational to design some exercise to strengthen these muscles in the shortened length [20,21]. ...
... The excessive actin to myosin filaments overlap is proposed as an explanation of the underlying mechanism of slightly more effectiveness of shortened-length training protocol [20,34]. Considering specific adaptation to imposed demands principle, it seems rational to develop exercise programs to train the weakened muscles in the shortened length, which demonstrated more weakness [35]. ...
Introduction: The purpose of this study was to investigate the effects of shortened-length versus through-range exercise training on upper quarter posture in primary school students with Forward Head Posture (FHP). Materials and Methods: Sixty pain-free participants with FHP were randomly allocated to one of three groups; shortened-length training (n=20), through-range training (n=20), and no- treatment control group (n=20). The shortened-length and through-range groups participated in training programs 3 times per week for 8 weeks. Upper quarter postures, including Craniovertebral Angle (CVA), Shoulder Angle (SA), Cranial Angle (CA), and thoracic kyphosis were measured by photogrammetry before and after the training. The confidence level was set at 95% (P<0.05). Results: After training, both exercise groups showed significant changes in CVA (P=0.001), SA (P=0.001), CA (P=0.001), and thoracic kyphosis (P=0.001) compared to the control group. Furthermore, CVA changed more in the shortened-length exercise group compared to the through-range exercise group (P=0.003) (effect size= 0.446). Conclusion: Both through-range and shortened-length exercises altered upper quarter alignment. The shortened-length training resulted in a larger change in CVA. These changes were small, and more studies are needed to investigate the effects of such training programs among people with pain.
... The outer layer of the whole muscle is the epimysium which the inner muscle fibers are surrounded by another connective tissue layer, the perimysium. Muscle fiber further could be dismembered into the level of myofibrils and is approximately 1 cm in length and 100 µm in diameter (Frontera and Ochala 2015;Lieber 2002). Satellite cells located in between the sarcolemma and the basal lamina are important in muscle growth, repair, and regeneration ( Figure 1). ...
... Sarcoplasmic reticulum is complex compared to the T tubules and stores calcium which is required in muscle activation (Lieber 2002). The muscle calcium homeostasis is maintained by SR (Calsequestrin and SERCA proteins) holding the responsibilities in the storage, release, and reuptake (Frontera and Ochala 2015). ...
... This contains all the enzymes related to the oxidation of the high-energy substrates. The resulting ATP is used for muscle contraction, ion transport, and other cellular mechanisms (Lieber 2002). Moreover, mitochondrial density is important in the determination of muscle endurance properties. ...
The fundamental basis for the human function is provided by skeletal muscle. Advancing age causes selective fiber atrophy, motor unit loss, and hybrid fiber formation resulting in hampered mass and strength, thus referred to as sarcopenia. Influence on the loss of independence of aged adults, contribute toward inclined healthcare costs conveys the injurious impact. The current understating of age-related skeletal muscle changes are addressed in this review, and further discusses mechanisms regulating protein turnover, although they do not completely define the process yet. Moreover, the reduced capacity of muscle regeneration due to impairment of satellite cell activation and proliferation with neuronal, immunological, hormonal factors were brought into the light of attention. Nevertheless, complete understating of sarcopenia requires disentangling it from disuse and disease. Nutritional intervention is considered a potentially preventable factor contributing to sarcopenia. Seafood is a crucial player in the fight against hunger and malnutrition, where it consists of macro and micronutrients. Hence, the review shed light on seafood as a nutritional intrusion in the treatment and prevention of sarcopenia. Understanding multiple factors will provide therapeutic targets in the prevention, treatment, and overcoming adverse effects of sarcopenia.
... The capacity of a muscle to generate energy is related to its functional parameters (i.e. excursion, force, contraction velocity, and fatigability), which, in turn, correlate with their structural and architectural properties, i.e. fibre type and length, physiological cross-sectional area (pCSA) and pennation angle (35). While muscle excursion is directly proportional to the length of the muscle fibre (or fascicle), it is inversely proportional to the pennation angle. ...
... Muscles with longer fibres and a higher ratio of type II to type I fibres contract faster than the others. Fatigability of a muscle is also determined by its fibre type and oxidative capacity (35). At the joint level, forces cause a rotational effect, which is the product of net force and moment arm. ...
... Muscles rich in type II fibres and with long fascicles contract faster than the others. Likewise, even with the same CSA, they can also move the body segments faster (35). Hereby, understanding the advantage of higher velocity for some physical activities would be the main concern. ...
Sarcopenia is an important public health problem, characterized by age-related loss of muscle mass and muscle function. It is a precursor of physical frailty, mobility limitation, and premature death. Although muscle loss is mainly due to the loss of type II muscle fibres, progressive loss of motor neurones is thought to be the primary underlying factor. Anterior thigh muscles undergo atrophy earlier, and the loss of anterior thigh muscle function may therefore be an antecedent finding. The aim of this review is to provide an in-depth (and holistic) neuromusculoskeletal approach to sarcopenia. In addition, under the umbrella of the International Society of Physical and Rehabilitation Medicine (ISPRM), a novel diagnostic algorithm is proposed, developed with the consensus of experts in the special interest group on sarcopenia (ISarcoPRM). The advantages of this algorithm over the others are: special caution concerning disorders related to the renin-angiotensin system at the case finding stage; emphasis on anterior thigh muscle mass and function loss; incorporation of ultrasound for the first time to measure the anterior thigh muscle; and addition of a chair stand test as a power/performance test to assess anterior thigh muscle function. Refining and testing the algorithm remains a priority for future research.
... Broadly speaking muscles can be subdivided into different types depending on 57 their speed of contraction, namely slow twitch muscles are characterized by level of oxidative 58 activity, while fast twitch muscles show high content of enzymes involved in glycolytic 59 activity. Fast-and slow-twitch muscle can be also identified based on the expression of 60 specific myosin heavy chain (MyHC) isoforms (1,2). Fast twitch muscles, also known as 61 type II fibers, are specialized for rapid movements, are mainly glycolytic contain large 62 glycogen stores and few mitochondria, fatigue rapidly and characteristically express the 63 ...
... MyHC isoforms 2X, 2B and 2A. They are also the first muscles to appear during 64 development and are more severely impacted in patients with congenital myopathies; they 65 also undergo more prominent age-related atrophy or sarcopenia (1)(2)(3)(4)(5)(6). Slow twitch muscles 66 (type 1 fibers) are mainly oxidative, contain many mitochondria and are fatigue resistant. ...
Skeletal muscles are a highly structured tissue responsible for movement and metabolic regulation, which can be broadly subdivided into fast and slow twitch muscles with each type expressing common as well as specific sets of proteins. Congenital myopathies are a group of muscle diseases leading to a weak muscle phenotype caused by mutations in a number of genes including RYR1. Patients carrying recessive RYR1 mutations usually present from birth and are generally more severely affected, showing preferential involvement of fast twitch muscles as well as extraocular and facial muscles. In order to gain more insight into the pathophysiology of recessive RYR1-congential myopathies, we performed relative and absolute quantitative proteomic analysis of skeletal muscles from wild-type and transgenic mice carrying p.Q1970fsX16 and p.A4329D RyR1 mutations which were identified in a child with a severe congenital myopathy. Our in-depth proteomic analysis shows that recessive RYR1 mutations not only decrease the content of RyR1 protein in muscle, but change the expression of 1130, 753 and 967 proteins EDL, soleus and extraocular muscles, respectively. Specifically, recessive RYR1 mutations affect the expression level of proteins involved in calcium signaling, extracellular matrix, metabolism and ER protein quality control. This study also reveals the stoichiometry of major proteins involved in excitation contraction coupling and identifies novel potential pharmacological targets to treat RyR1-related congenital myopathies.
... While each sarcomere is shortened by 1, the muscle can be shortened by 2-3 cm. Number and length of sarcomere are important for functional contraction of a muscle [13]. ...
... In the case of gravity and weight bearing, the muscle is passively stretched and the sarcomere length is prolonged. Under prolonged passive tension, the sarcomere length of the muscle increases [13]. ...
One of the most important problems in swallowing function is the risk of inadequate airway closure and aspiration. Insufficient hyolaryngeal elevation during swallowing is one of the reasons for this risk. Suprahyoid (SH) muscles are fundamental structures responsible for hyolaryngeal elevation. Inadequate activation of SH muscles causes insufficient and reduced hyolaryngeal elevation. Reduced hyolaryngeal elevation causes insufficient opening of the upper esophageal sphincter (UES), leading an increase in the amount of pharyngeal residue and a risk of aspiration. Superior hyolaryngeal excursion during swallowing contributes to airway protection and prevention of aspiration. Anterior hyolaryngeal excursion is related to the UES opening and its crucial for the safe transition of bolus to esophagus without aspiration. Our study hypothesized that the long sarcomere length of mylohyoid muscle could be a contributing or responsible factor to the reduction in the hyolaryngeal elevation. There is no study on the pathophysiology on sarcomere properties of reduced hyolaryngeal elevation. Reduced hyolaryngeal elevation emerges as a symptom that reveals the cause of aspiration. Explaining the potential mechanism of reduction in hyolaryngeal elevation may contribute to the development of new treatment approaches based on architectural features in dysphagia rehabilitation practices. Furthermore, based on our hypothesis, we recommend new therapy approaches that may contribute to reducing the hyolaryngeal elevation.
... The function of a muscle is to generate contraction and force to move or resist. The length and angle of muscle fibers depend on the architecture of the muscle (Klont et al., 1998;Lieber, 2002;Woittiez et al., 1984). Each muscle is composed of several types of muscle fibers with the contractile, metabolic, and physiological properties of each muscle differing according to their fiber characteristics (Armstrong et al., 1987;Totland and Kryvi, 1991). ...
... In addition to the muscle mechanical function, muscle fiber characteristics are influenced by the force performance (resistance vs. endurance) and energy dependence (oxidative vs. glycolytic) of individual muscles (Farup et al., 2014;Lieber, 2002 and fusiform of parallel architecture, it seems that the muscle fiber compositions (relative area) of other subtypes of parallel and pennate architectures, were not highly related to the morphological properties of the muscles. ...
This study aimed to compare the similarities, physicochemical properties, and muscle fiber characteristics of porcine skeletal muscles. Fourteen types of muscles were collected from nine pig carcasses at 24 h post-mortem and classified by muscle architecture into two main groups, namely parallel and pennate. The muscles were further differentiated into three subtypes per group. These included fan-shaped, fusiform, and strap for the parallel group, and unipennate, bipennate, and multipennate for the pennate group. Parallel-fibered muscles, which were composed of larger I, IIA, IIX, and IIXB fibers and a lower density of IIA fibers, showed higher redness and yellowness values than pennate-fibered muscles (p<0.05). However, the relative fiber area was not significantly different between the parallel and pennate groups (p>0.05). In the subtypes of parallel architecture, the strap group showed lower moisture content and higher redness values than the other subtypes and had considerably higher amounts of oxidative fibers (I and IIA; 72.3%) than the fan-shaped and fusiform groups (p<0.05). In the pennate group, unipennate showed comparatively lower moisture content and higher lightness than other pennate subtypes and was composed of smaller I, IIA, and IIX fibers than the bipennate and multipennate groups (p<0.05). Finally, a different trend of muscle clustering by hierarchical cluster analysis was found between physicochemical properties and muscle fiber characteristics. These results suggest that the physicochemical properties and muscle fiber characteristics of porcine skeletal muscles are not significantly dependent on morphological properties but are rather related to the intrinsic properties of the individual muscles.
... Res. Public Health 2022, 19, 471 2 of 14 of the knee and limits the athlete's functional capacity and, therefore, the performance of sports actions that over-solicit the tendon [8]. ...
... During eccentric contractions, the external force is greater than that being exerted by the muscle and hence lead to the muscle lengthening while tension is generated [18]. After a single session of eccentric exercise, nonadapted muscles experienced a delayed onset muscle soreness (DOMS), which produces local pain, reducing muscle functionality by decreasing maximal voluntary contraction and range of movement (ROM) [19], alters protein synthesis and degradation, and stimulates an inflammatory response [20]. However, repeated eccentric bouts (eccentric training) foster an adaption to exercise by which the muscles involved respond more efficiently to DOMS and its side effects [21]. ...
The aim of the present study was to analyze the effect of conservative non-invasive treatments based on eccentric training, stretching and extracorporeal shock wave therapy (ESWT) supplemented with β-Hydroxy β-methylbutyric (HMB) or placebo (PLAC) on body composition, pain and muscular function (jump ability, muscular power and muscular strength) in athletes with patellar tendinopathy (PT). In a double-blind randomized trial, 8 athletes (4 males and 4 females) performed a physical rehabilitation for 4 weeks. They were randomly divided into two experimental groups (two males and two females in each one) that ingested HMB (HMBG) or PLAC (PLACG). In pre- and post-intervention were assessed body composition, pain, countermovement jump (CMJ), back-squat (BS) for analyzing peak power (W) (PPPP), load (kg) associated to PPPP (PPKG) and mean velocity (m/s) (PPMV) in addition to a 5-RM leg extension tests. An interaction intervention·supplementation (p = 0.049; Ƞ2p = 0.774) was observed in the height reached in the CMJ as an intervention effect in PPPP detected for the HMBG (p = 0.049). In addition, an enhancement in PPKG (p = 0.028; Ƞ2p = 0.842) was detected in the intervention, but not in PPMV, as an increase in the intervention in the 5-RM test (p = 0.001; Ƞ2p = 0.981) was observed. No changes were noted on body composition or pain (p > 0.05). The combination of eccentric training with stretching and ESWT increased concentric muscular power and strength after 4 weeks without changes in body lean mass or pain. In addition, HMB supplementation could enhance the power muscular performance in athletes with PT, optimizing the intervention adaptions.
... The lowest values were 5.57 ± 1.05 and 4.42 ± 0.27 kPa, respectively, which are in very good agreement with previous works using the ultrasonic methods since the reported values ranging from 3.11 ± 0.42 kPa (BB) and 3.05 ± 0.52 kPa (TB) (Lacourpaille et al., 2012). Likewise, both the average rest values and their range of variation were also comparable to those obtained in previous studies carried out in vivo with magnetic resonance elastography and SSI (~10-20 kPa; Jenkyn et al., 2003;Lapole et al., 2015;Nordez & Hug, 2010;Uffmann et al., 2004;Yoshitake et al., 2014), as well as in vitro performing a stressstrain curve (~10 kPa; Lieber, 2002). As the most accurate comparison is made in resting conditions, since the contraction intensity can vary between different studies (Nordez & Hug, 2010), these results show the good agreement between NU-SWE and reference elastography methods. ...
... The inset in each figure is a magnification of the results in TB, added for better visualization. F, female; M, male agreement with those of the literature, where values between ~ 4 -20 kPa were reported by using the reference elastography and rheological methods Creze et al., 2018;Jenkyn et al., 2003;Lacourpaille et al., 2012;Lapole et al., 2015;Lieber, 2002;Nordez & Hug, 2010;Uffmann et al., 2004;Yoshitake et al., 2014). For the 40% of MVC, the literature reports values for BB ranging from ~65 to 80 kPa Nordez & Hug, 2010), as well as ~100 to 160 kPa (Lapole et al., 2015;Yoshitake et al., 2014). ...
The shear elastic modulus is one of the most important parameters to characterize the mechanical behavior of soft tissues. In biomechanics, ultrasound elastography is the gold standard for measuring and mapping it locally in skeletal muscle in vivo. However, their applications are limited to the laboratory or clinic. Thus, low-frequency elastography methods have recently emerged as a novel alternative to ultrasound elastography. Avoiding the use of high frequencies, these methods allow obtaining a mean value of bulk shear elasticity. However, they are frequently susceptible to diffraction, guided waves, and near field effects, which introduces biases in the estimates. The goal of this work is to test the performance of the non-ultrasound surface wave elastography (NU-SWE), which is portable and is based on new algorithms designed to correct the incidence of such effects. Thus, we show its first application to muscle biomechanics. We performed two experiments to assess the relationships of muscle shear elasticity versus joint torque (experiment 1) and the electromyographic activity level (experiment 2). Our results were comparable regarding previous works using the reference ultrasonic methods. Thus, the NU-SWE showed its potentiality to get wide the biomechanical applications of elastography in many areas of health and sports sciences.
... There is no reason why muscle of stroke patient cannot go from an eccentric contraction to an concentric contraction especially the muscle of the spine and the big joint because there innervation is double [6]. Lieber [7] on the contrary has investigated that concentric likes higher in the brain than eccentric and it is known that eccentric can also an muscle-reaction that occur when the muscle get an stretch that can harm the muscle. This stretch is no eccentric contraction but an reaction in the spinal cord without interference from system above. ...
... Often only the part that is closed to the Sacro Iliacal joint are working but the muscle fiber that goes further to the side including the medius are not very active. This problem is that the connection of the back and front diagonal creating the homolateral structure is according Lieber [7] an higher brain function than the both diagonal sec. Therefore there must be an boost of information that push the brain to created there tone and an concentric activation , when that is possible. ...
An important part in the treatment of person after an stroke with an "pusher" syndrome is the task-specific resistance treatment. There is always discussion about strengthening by neurological patients but when the muscle react with more coordination and power in the muscle pattern can this be only very important. That restriction was for the strengthening for an isolated muscle and then pointed at an muscle strength increase. Often was the effect an tone increase and an stimulation of the pathological synergy, but with an task specific approach the must be an task specific movement and that asked for an almost normal tone to get the movement and you still have that movement but now with load. With this increase on power and coordination will motoric learning have more effect because there are more possibilities through the increase of coordination and power. The stair in an training program is an example of the use of the stair to make an training with load that lead to increase of power and coordination and gives immediately an increase in learning. The stair is for patient with the pusher syndrome an perfect training and with load an very important part. In the mid the hypothesis around the phenomena Pusher and that support the treatment-approach of Pat. Davies and there approach to work with the back-splint. The last part is an closing part of the pusher article. There we lay the focus on the chronic stage that is often an very long period in which the level stay on the same height or makes an slow decrease. Here is for every patient possibilities to better the level but for the patient with the pusher-syndrome this chronic stage is often an delay of the subacute stage and maybe even the acute stage. And that asked for all possibilities to ensure that all is done to get the best level. That asked for variation and an treatment that never stop with assessment and searching for the best training possibility.
... (Lieber, 2002To simulate a reduced gravity environment, we fitted participants with a custom-built 99 bodyweight support system and recorded biomechanical data as they walked overground. Our in the middle of the walkway and measured ground reaction forces. ...
Bodyweight supported walking is a common gait rehabilitation method that can be used as an experimental approach to better understand walking biomechanics. Neuromuscular modeling can provide an analytical means to gain insight into how muscles coordinate to produce walking and other movements. To better understand how muscle length and velocity affect muscle force during overground walking with bodyweight support, we used an electromyography (EMG)-informed neuromuscular model to investigate changes in muscle parameters (muscle force, activation and fiber length) at varying bodyweight support levels: 0%, 24%, 45% and 69% bodyweight. Coupled constant force springs provided a vertical support force while we collected biomechanical data (EMG, motion capture and ground reaction forces) from healthy, neurologically intact participants walking at 1.20 ± 0.06 m/s. The lateral and medial gastrocnemius demonstrated a significant decrease in muscle force (lateral: p = 0.002 and medial: p < 0.001) and activation (lateral: p = 0.007 and medial: p < 0.001) through push-off at higher levels of support. The soleus, in contrast, had no significant change in muscle activation through push-off (p = 0.652) regardless of bodyweight support level even though soleus muscle force decreased with increasing support (p < 0.001). During push-off, the soleus had shorter muscle fiber lengths and faster shortening velocities as bodyweight support levels increased. These results provide insight into how muscle force can be decoupled from effective bodyweight during bodyweight supported walking due to changes in muscle fiber dynamics. The findings contribute evidence that clinicians and biomechanists should not expect a reduction in muscle activation and force when using bodyweight support to assist gait during rehabilitation.
... To this end, this article, especially the earlier sections ( § §2 and 3), is intended to provide a narrative review providing essential background and intuitive examples demonstrating the issues, rather than focusing on an exhaustive review covering all findings and models in muscle mechanics modelling. For more exhaustive reviews, we direct readers to excellent books [2][3][4][5][6] and reviews [7][8][9] published on this topic. ...
Hill-type muscle models are highly preferred as phenomenological models for musculoskeletal simulation studies despite their introduction almost a century ago. The use of simple Hill-type models in simulations, instead of more recent cross-bridge models, is well justified since computationally 'light-weight'-although less accurate-Hill-type models have great value for large-scale simulations. However, this article aims to invite discussion on numerical instability issues of Hill-type muscle models in simulation studies, which can lead to computational failures and, therefore, cannot be simply dismissed as an inevitable but acceptable consequence of simplification. We will first revisit the basic premises and assumptions on the force-length and force-velocity relationships that Hill-type models are based upon, and their often overlooked but major theoretical limitations. We will then use several simple conceptual simulation studies to discuss how these numerical instability issues can manifest as practical computational problems. Lastly, we will review how such numerical instability issues are dealt with, mostly in an ad hoc fashion, in two main areas of application: musculoskeletal biomechanics and computer animation.
... Structurally, skeletal muscle is made up of many bundles of fibres termed fasciculi that are entirely enveloped in an irregular fibrous sheath extending from the tendons, known as the epimysium, which serves to protect the muscle from friction against surrounding tissues (Lieber, 2002). Each fasciculi comprises a bundled network of muscle fibres and blood vessels surrounded by a secondary sheath called the perimysium. ...
Background: Obesity is often associated with impaired sensitivity to the effects of insulin (insulin resistance) and dietary protein (anabolic resistance) and may exacerbate the age-related decline of skeletal muscle (sarcopenia). Myostatin is a protein that negatively regulates skeletal muscle growth but its inhibition in rodents also improves insulin sensitivity. In humans, myostatin appears to be upregulated by obesity and associated with insulin resistance, but observations are confounded by lifestyle factors and ageing. Aims: To delineate between the effects of obesity and ageing on myostatin expression in human skeletal muscle; to investigate the underlying causes of these effects; and to establish the functional significance and interconnectivity of modulating insulin sensitivity and myostatin expression in human skeletal muscle cells. Methods: In Chapter 3 a cross-sectional analysis of skeletal muscle gene expression was undertaken, in conjunction with correlation analyses between serum myostatin and descriptive characteristics, to isolate the effects of obesity and ageing per se on myostatin expression and abundance. In Chapters 4 and 5, in vitro and ex vivo techniques were employed using human primary myotubes to investigate the potential involvement of lipid-induced insulin and anabolic resistance and secretory cross-talk between subcutaneous adipose tissue and muscle, in the obesity-mediated upregulation of myostatin and the associated impairment of insulin and anabolic sensitivity. In Chapter 6, the novel polyphenol metabolite Urolithin A was applied to human myotubes and a model of adipocytes, to investigate its therapeutic potential to enhance insulin and anabolic sensitivity and to suppress myostatin expression. Results: In Chapter 3 it was revealed that muscle myostatin expression is uniquely upregulated by obesity with ageing, but not by ageing in the absence of obesity, and occurs concurrently with insulin resistance and abnormal regulation of pathways involved in the maintenance of skeletal muscle mass. This association was corroborated by positive correlations between serum myostatin and multiple indices of adiposity, but not age. In Chapters 4 and 5 it was demonstrated that neither acutely elevated fatty acid availability (which induced insulin and anabolic resistance), nor chronic exposure to obese subcutaneous adipose tissue conditioned medium (which did not induce insulin or anabolic resistance but altered the expression of genes involved in myogenesis and muscle protein breakdown) recapitulated the obesity-mediated upregulation of myostatin expression. In Chapter 6 it was demonstrated for the first time that Urolithin A suppresses myostatin expression and enhances glucose transport in human myotubes (and 3T3-L1 adipocytes), the latter of which was associated with an upregulation of GLUT4 expression. Conclusions: Skeletal muscle myostatin expression is uniquely upregulated by obesity per se, but this does not appear to be mediated by lipid-induced insulin resistance, nor by the secretory milieux of obese subcutaneous adipose tissue. Nevertheless, both models perturbed factors involved in myogenesis and muscle protein breakdown, independent of an upregulation of myostatin. Thus, the factors responsible for the obesity-mediated upregulation of myostatin remain to be elucidated and future work to establish such causality is required. Furthermore, translational research to investigate the potential of Urolithin A to enhance glucose handling in peripheral tissues and to repress myostatin’s inhibitory effects on muscle growth is warranted in humans and could be of particular benefit in conditions such as sarcopenic obesity.
... During normal joint rotation, both the moment arms and muscle forces change through the range of motion and thus influence the "shape" of the torque-angle relation. It is therefore possible that the optimum joint angles for muscle force production and joint torque production do not coincide [105,106]. Not only are three of the hamstrings muscles bi-articular, so their moment arms are influenced by changes in both hip and knee joint angles, but individual muscles have different attachment sites across the hip and knee and thus a different line of action of their moment arms. ...
Temporal biomechanical and physiological responses to physical activity vary between individual hamstrings components as well as between exercises, suggesting that hamstring muscles operate differently, and over different lengths, between tasks. Nevertheless, the force-length properties of these muscles have not been thoroughly investigated. The present review examines the factors influencing the hamstrings’ force-length properties and relates them to in vivo function. A search in four databases was performed for studies that examined relations between muscle length and force, torque, activation, or moment arm of hamstring muscles. Evidence was collated in relation to force-length relationships at a sarcomere/fiber level and then moment arm-length, activation-length, and torque-joint angle relations. Five forward simulation models were also used to predict force-length and torque-length relations of hamstring muscles. The results show that, due to architectural differences alone, semitendinosus (ST) produces less peak force and has a flatter active (contractile) fiber force-length relation than both biceps femoris long head (BFlh) and semimembranosus (SM), however BFlh and SM contribute greater forces through much of the hip and knee joint ranges of motion. The hamstrings’ maximum moment arms are greater at the hip than knee, so the muscles tend to act more as force producers at the hip but generate greater joint rotation and angular velocity at the knee for a given muscle shortening length and speed. However, SM moment arm is longer than SM and BFlh, partially alleviating its reduced force capacity but also reducing its otherwise substantial excursion potential. The current evidence, bound by the limitations of electromyography techniques, suggests that joint angle-dependent activation variations have minimal impact on force-length or torque-angle relations. During daily activities such as walking or sitting down, the hamstrings appear to operate on the ascending limbs of their force-length relations while knee flexion exercises performed with hip angles 45–90° promote more optimal force generation. Exercises requiring hip flexion at 45–120° and knee extension 45–0° (e.g. sprint running) may therefore evoke greater muscle forces and, speculatively, provide a more optimum adaptive stimulus. Finally, increases in resistance to stretch during hip flexion beyond 45° result mainly from SM and BFlh muscles.
... Our group has recently shown that individuals experiencing the highest reductions in Type IIx %CSA and concomitant increases in Type IIa %CSAs are those with the greatest improvements in their lipid profile after 10 weeks of resistance training [12]. Indeed, as muscle is a highly plastic tissue [45,[56][57][58][59][60], its properties can be changed according to nutrition but mostly to training-induced metabolic, physiological and mechanical stress. Increased training volumes upregulate molecular pathways controlling the size, type and metabolic procedures of muscle fibers, which ultimately results in the transmission of Type IIx to the more metabolically efficient Type IIa muscle fibers [4,5,7,12,45,56], changes that are highly related to those of lipidemic profiles [12]. ...
The present article aims to discuss the hypothesis that skeletal muscle per se but mostly its muscle fiber composition could be significant determinants of lipid metabolism and that certain exercise modalities may improve metabolic dyslipidemia by favorably affecting skeletal muscle mass, fiber composition and functionality. It discusses the mediating role of nutrition, highlights the lack of knowledge on mechanistic aspects of this relationship and proposes possible experimental directions in this field.
... A notable example is mammalian skeletal muscles. With the ability to voluntarily generate force or produce movement, skeletal muscles are well-known for their multilevel hierarchical structures, especially the characteristic highly ordered and striated patterns at the single cell (muscle fibre) level 11 (Fig. 1a). Importantly, the actuation performance of muscles is directly related to their structural order, where disorder of the structure leads to drastic failure of function 12 . ...
High-performance actuating materials are necessary for advances in robotics, prosthetics and smart clothing. Here we report a class of fibre actuators that combine solution-phase block copolymer self-assembly and strain-programmed crystallization. The actuators consist of highly aligned nanoscale structures with alternating crystalline and amorphous domains, resembling the ordered and striated pattern of mammalian skeletal muscle. The reported nanostructured block copolymer muscles excel in several aspects compared with current actuators, including efficiency (75.5%), actuation strain (80%) and mechanical properties (for example, strain-at-break of up to 900% and toughness of up to 121.2 MJ m−3). The fibres exhibit on/off rotary actuation with a peak rotational speed of 450 r.p.m. Furthermore, the reported fibres demonstrate multi-trigger actuation (heat and hydration), offering switchable mechanical properties and various operating modes. The versatility and recyclability of the polymer fibres, combined with the facile fabrication method, opens new avenues for creating multifunctional and recyclable actuators using block copolymers. Nanostructured fibres with highly aligned and alternating crystalline and amorphous domains created from triblock copolymers exhibit excellent mechanical properties, multi-trigger actuation, high-performance contraction and on/off rotation.
... Sarcomere length is calculated along a single column of pixels as the pixel distance between pixel intensity peaks (A-bands), converted to microns (0.16 µm per pixel) and multiplied by the cosine of the detected angle to correct for angle of fiber orientation ( Figure 1C). This analysis process is repeated for distinct columns of pixels at 2 µm intervals to enable the collection of sarcomere length data from separate myofibrils (Lieber, 2002;Moo et al., 2016). ...
The lengths of a muscle’s sarcomeres are a primary determinant of its ability to contract and produce force. In addition, sarcomere length is a critical parameter that is required to make meaningful comparisons of both the force-generating and excursion capacities of different muscles. Until recently, in vivo sarcomere length data have been limited to invasive or intraoperative measurement techniques. With the advent of second harmonic generation microendoscopy, minimally invasive measures of sarcomere length can be made for the first time. This imaging technique expands our ability to study muscle adaptation due to changes in stimulus, use, or disease. However, due to past inability to measure sarcomeres outside of surgery or biopsy, little is known about the natural, anatomical variability in sarcomere length in living human subjects. To develop robust experimental protocols that ensure data provide accurate representations of a muscle’s sarcomere lengths, we sought to quantify experimental uncertainty associated with in vivo measures of sarcomere lengths. Specifically, we assessed the variability in sarcomere length measured (1) within a single image, along a muscle fiber, (2) across images captured within a single trial, across trials, and across days, as well as (3) across locations in the muscle using second harmonic generation in two upper limb muscles with different muscle architectures, functions, and sizes. Across all of our measures of variability we estimate that the magnitude of the uncertainty for in vivo sarcomere length is on the order of ∼0.25 μm. In the two upper limb muscles studied we found larger variability in sarcomere lengths within a single insertion than across locations. We also developed custom code to make measures of sarcomere length variability across a single fiber and determined that this codes’ accuracy is an order of magnitude smaller than our measurement uncertainty due to sarcomere variability. Together, our findings provide guidance for the development of robust experimental design and analysis of in vivo sarcomere lengths in the upper limb.
... Nevertheless, the potential discordance between skeletal and somatic growth highlights a possible problem for fossil analyses of size, insofar as the lack of integration between somatic, dental, and skeletal dimorphism complicates the comparison between extinct skeletal specimens and extant references. Further, soft tissue dimensions can be broken down into fat and lean muscle, which have independent patterns of distribution within the body and different causes of variation (e.g., caloric intake vs. exercise) (Cryer & Van, 2014;Lieber, 2002). The macaques used in this study are also associated with more detailed somatic measurements, including fat mass, as well as skeletons currently in preparation for museum storage. ...
Objective:
Reconstructing the social lives of extinct primates is possible only through an understanding of the interplay between morphology, sexual selection pressures, and social behavior in extant species. Somatic sexual dimorphism is an important variable in primate evolution, in part because of the clear relationship between the strength and mechanisms of sexual selection and the degree of dimorphism. Here, we examine body size dimorphism across ontogeny in male and female rhesus macaques to assess whether it is primarily achieved via bimaturism as predicted by a polygynandrous mating system, faster male growth indicating polygyny, or both.
Methods:
We measured body mass in a cross-sectional sample of 364 free-ranging rhesus macaques from Cayo Santiago, Puerto Rico to investigate size dimorphism: 1) across the lifespan; and 2) as an outcome of sex-specific growth strategies, including: a) age of maturation; b) growth rate; and c) total growth duration, using regression models fit to sex-specific developmental curves.
Results:
Significant body size dimorphism was observed by prime reproductive age with males 1.51 times the size of females. Larger male size resulted from a later age of maturation (males: 6.8-7.8 years versus females: 5.5-6.5 years; logistic model) and elevated growth velocity through the pre-prime period (LOESS model). Though males grew to larger sizes overall, females maintained adult size for longer before senescence (quadratic model).
Discussion:
The ontogeny of size dimorphism in rhesus macaques is achieved by bimaturism and a faster male growth rate. Our results provide new data for understanding the development and complexities of primate dimorphism.
... The anatomical and physiological properties of the simulated muscle fibers and their organization within the muscle were chosen so to mimic those of the biceps brachii muscle [21]. First, in each motor unit, muscle fibers were assumed to run parallel to the muscle longitudinal axis. ...
Even under isometric conditions, muscle contractions are associated with some degree of fiber shortening. The effects of muscle shortening on extracellular electromyographic potentials have not been characterized in detail. Moreover, the anatomical, biophysical, and detection factors influencing the muscle-shortening effects have been neither identified nor understood completely. Herein, we investigated the effects of muscle shortening on the amplitude and duration characteristics of single-fiber, motor unit, and compound muscle action potentials. We found that, at the single-fiber level, two main factors influenced the muscle-shortening effects: (1) the electrode position and distance relative to the myotendinous zone and (2) the electrode distance to the maxima of the dipole field arising from the stationary dipole created at the fiber-tendon junction. Besides, at the motor unit and muscle level, two additional factors were involved: (3) the overlapping between the propagating component of some fibers with the non-propagating component of other fibers and (4) the spatial spreading of the fiber-tendon junctions. The muscle-shortening effects depend critically on the electrode longitudinal distance to the myotendinous zone. When the electrode was placed far from the myotendinous zone, muscle shortening resulted in an enlargement and narrowing of the final (negative) phase of the potential, and this enlargement became less pronounced as the electrode approached the fiber endings. For electrode locations close to the myotendinous zone, muscle shortening caused a depression of both the main (positive) and final (negative) phases of the potential. Beyond the myotendinous zone, muscle shortening led to a decrease of the final (positive) phase. The present results provide reference information that will help to identify changes in MUPs and M waves due to muscle shortening, and thus to differentiate these changes from those caused by muscle fatigue.
Graphical abstract
... Sarcomere length is calculated along a single column of pixels as the pixel distance between pixel 128 intensity peaks (A-bands), converted to microns (0.16μm per pixel) and multiplied by the cosine of 129 the detected angle to correct for angle of fiber orientation ( Figure 1C). This analysis process is 130 repeated for distinct columns of pixels at 2μm intervals to enable the collection of sarcomere length 131 data from separate myofibrils (Lieber 2002, Moo, Fortuna et al. 2016. 132 ...
The lengths of a muscle's sarcomeres are a primary determinant of its ability to contract and produce force. In addition, sarcomere length is a critical parameter that is required to make meaningful comparisons of both the force-generating and excursion capacities of different muscles. Until recently, in vivo sarcomere length data have been limited to invasive or intraoperative measurement techniques. With the advent of second harmonic generation microendosopy, minimally invasive measures of sarcomere length can be made for the first time. This imaging technique expands our ability to study muscle adaptation due to changes in stimulus, use, or disease. However, due to the prior inability to measure sarcomeres outside of surgery or biopsy, little is known about the natural, anatomical variability in sarcomere length in living human subjects. To develop robust experimental protocols that ensure data provide accurate representations of a muscle's sarcomere lengths, we sought to quantify experimental uncertainty associated with in vivo measures of sarcomere lengths. Specifically, we assessed the variability in sarcomere length measured 1) within a single image, along a muscle fiber, 2) across images captured within a single trial, across trials, and across days, as well as 3) across locations in the muscle using second harmonic generation in two upper limb muscles with different muscle architectures, functions, and sizes. Across all of our measures of variability we estimate that the magnitude of the uncertainty in in vivo sarcomere length are on the order of 0.25 microns. In the two upper limb muscles studied we found larger variability in sarcomere length within a single insertion than across locations. We also developed custom code to make measures of sarcomere length variability across a single fiber and determined that this codes' accuracy is an order of magnitude smaller than our measurement uncertainty due to sarcomere variability. Together, our findings provide guidance for the development of robust experimental design and analysis of in vivo sarcomere lengths in the upper limb.
... As the PA increases, the component of force along the line of action decreases. However, pennation also allows many more muscle fibres to fit within the same muscle volume, increasing force generation (Lieber, 2011). Additionally, a higher PA is associated with a shorter FBL, reducing velocity. ...
The aim of this review was to report on the imaging modalities used to assess morphological and architectural properties of the m. triceps surae muscle in typically developing children, and the available reliability analyses. Scopus and MEDLINE (Pubmed) were searched systematically for all original articles published up to September 2020 measuring morphological and architectural properties of the m. triceps surae in typically developing children (18 years or under). Thirty eligible studies were included in this analysis, measuring fibre bundle length (FBL) (n = 11), pennation angle (PA) (n = 10), muscle volume (MV) (n = 16) and physiological cross-sectional area (PCSA) (n = 4). Three primary imaging modalities were utilised to assess these architectural parameters in vivo: two-dimensional ultrasound (2DUS; n = 12), three-dimensional ultrasound (3DUS; n = 9) and magnetic resonance imaging (MRI; n = 6). The mean age of participants ranged from 1.4 years to 18 years old. There was an apparent increase in m. gastrocnemius medialis MV and pCSA with age; however, no trend was evident with FBL or PA. Analysis of correlations of muscle variables with age was limited by a lack of longitudinal data and methodological variations between studies affecting outcomes. Only five studies evaluated the reliability of the methods. Imaging methodologies such as MRI and US may provide valuable insight into the development of skeletal muscle from childhood to adulthood; however, variations in methodological approaches can significantly influence outcomes. Researchers wishing to develop a model of typical muscle development should carry out longitudinal architectural assessment of all muscles comprising the m. triceps surae utilising a consistent approach that minimises confounding errors.
... In terms of physical exercise, it has different characteristics that are known to exert differential physiological adaptations. For instance, exercise can be prescribed with a particular modality, frequency, duration, and intensity, where the relevance of the latter has been thoroughly described [42], given that vigorous exercises (where a limited number of repetitions can be performed) activate anaerobic pathways to extract energy by skeletal muscles, which are mainly dependent on glycolysis; whereas exercise at which the intensity allows the person to sustain the effort for several minutes activates pathways dependent on nutrient oxidation in the mainly form of carbohydrates and lipids [43]. Considering the previous, aerobic exercise is frequently described in the context of obesity, specifically for its positive effects on glucose transport and insulin sensitivity in normal and pathological conditions (i.e. ...
Bariatric surgery is popular among clinicians to treat obesity because of its high impact on body weight reduction. However, the fast rate of weight loss has several consequences, such as loss of muscle mass and strength, and functional capacity. Therefore, preoperative interventions are needed to secure the surgery’s success, where physical exercise could be an effective intervention. Nevertheless, the most effective preoperative exercise prescription, along with its potential post-surgical carry-over effects, is still unclear. Recent studies have highlighted that exercise programs that differ, for instance, in intensity, induce differential metabolic benefits, that seem to be tissue-specific. This might be clinically relevant since it has been described that obesity-related metabolic impairments are not stereotypical in humans. This brief review analyses some tissue-specific disturbances derived from obesity, and how aerobic exercise programs, particularly high-intensity interval training and moderate-intensity constant training could elicit differential benefits, particularly in candidates to undergo bariatric surgery.
... No, when no movement can occur than this is no exercise to stimulated the keypoint muscles. But an eccentric movement is an movement according Dr. Lieber [22] : eccentric contraction comes from an "lower" level in the brain than concentric. It is therefore possible that the damage in the brain is so high that this is still possible. ...
Introduction: Part 4 show what the skill must be to achieve dissociation and with the hand on-facilitation we say amazing results with the possibilities to create an goal in the ADL and often with some hand possibilities. To get the hand on the right spot we need the arm therefore also the trunk and the diagonals. This part we go further with this dissociation and search for an "open "chain but we see also the possibilities that sciences have created. The science has stoke much effort in the developmental of robotic and F.E.S. stimulation techniques but still today it isn't clear of this the answer is for the recovery of the arm and especially the hand and it isn't also clear or this is an better way to get more function in the hand than the "old way". Design : But obvious there is much more possible to get an better arm-hand function by using this inventions, but than for all stroke survivors with arm and hand function decrease. An eclectic approach will use everything to get an better result but always with an good base of science and with the training and motoric learning rules in the head. To get an result in the damaged brain, there must be an amount of intensity to get the brain working on his plasticity. The question remain that we not know how much plasticity an damaged brain can obtain and obvious that is different for every stroke survivor.
... In addition, there were no significant differences in the JS between the 3/4-and 2/ 5-cut states at 0, 30, or 60 N. The muscle force was reported previously to be proportional to physiological cross-sectional area, 19 and a previous study suggested that there may be no difference between the physiological cross-sectional area of the third and fourth digits and the second and fifth digits of the FDS. 21 Considering these results, there appears to be no difference in the contribution to elbow valgus stability between the third and fourth digits and the second and fifth digits of the FDS. ...
Background
Thiel cadavers have been reported to have lifelike flexibility and mechanical properties, but whether they are useful for measurement of the ulnohumeral joint space (JS) is unclear. The contributions of the third and fourth digits and the second and fifth digits of the flexor digitorum superficialis (FDS) to elbow valgus stability are also unknown.
Purpose
To (1) clarify whether Thiel cadavers can be used for JS measurement on ultrasound and (2) identify the contributions to valgus stability of the third and fourth digits and the second and fifth digits of the FDS.
Study Design
Descriptive laboratory study.
Methods
In experiment 1 (12 elbows from human volunteers and 12 elbows from Thiel cadavers), valgus stress was increased gradually from 0 to 30 to 60 N, and the JS was compared on ultrasound between groups at each load. In experiment 2 (13 elbows from Thiel cadavers), specimens were divided into 2 groups, and the JS was measured for group 1 with the FDS intact, with tendinous insertions of the third and fourth digits cut (3/4-cut state), and with tendinous insertions of all fingers cut (all-cut state); and for group 2 at intact FDS, with tendinous insertions of the second and fifth digits cut (2/5-cut state), and at all-cut.
Results
In experiment 1, the rate of change of the JS increased significantly with elbow valgus stress in both humans and Thiel cadavers, with no significant difference between groups. In experiment 2, the JS was significantly greater in the 3/4- and 2/5-cut states compared with the intact state at both 30 N (Δ 3/4-cut vs intact = 0.23 mm [ P = .01]; Δ 2/5-cut vs intact = 0.32 mm [ P = .02]) and 60 N (Δ 3/4-cut vs intact = 0.33 mm [ P = .002]; Δ 2/5-cut vs intact = 0.37 mm [ P = .04]). There was no significant difference in JS measurements between the 3/4- and 2/5-cut states at any load.
Conclusion
Thiel cadavers showed JS changes similar to those of humans when valgus stress was applied. The third and fourth digits and the second and fifth digits of the FDS were involved in valgus stability, and there was no difference in their respective contributions.
Clinical Relevance
This study may help in identifying function of the FDS based on structure.
... These spectral sEMG characteristics probably occurred due to the predominance of type II fibers (high fatigability). 9 sEMG signal during both the imagery and attempt to take steps in the orthostatic posture can be characterized as task-specific gait training, which can be considered crucial for the motor response observed in this study. Despite the loss of supraspinal influence, the human spinal cord is responsive to task-specific sensory information and presents a potential for neuroplasticity with repetitive training. ...
Background:
Complete spinal cord injury (SCI) is characterized by permanent loss of nerve impulse propagation through the injury level leading to complete loss of voluntary muscle contraction. However, clinically undetectable top-down modulation of lower limbs might be present and can be evidenced using surface electromyography (sEMG).
Case report:
A subject with complete chronic SCI and no spasticity presents voluntary modulation of sEMG signal during a task-specific activity associated with sensory input.
Clinical rehabilitation impact:
We present for the first time the spectral characterization of sEMG signal in response to orthostatic training associated with voluntary movement attempts in complete SCI. Behavior of sEMG signal varied according to kinematic properties of movement, reinforcing the voluntary influence of efferent pathways on motor output. Our findings will contribute to elaborate evaluation protocols to investigate the preservation of corticospinal activities, and to evolve more accessible strategies in a clinical setting.
... We included only specimens whose jaws were fixed in comparable postures (i.e. at occlusion). Thus, for the purposes of this study (following Taylor & Vinyard [50]), we did not normalize fibre length by a standard sarcomere length. 1 Using our estimates of muscle mass, Lf and pinnation angle, we calculated PCSA using the following equation [110]: ...
Numerous anthropological studies have been aimed at estimating jaw-adductor muscle forces, which, in turn, are used to estimate bite force. While primate jaw adductors show considerable intra- and intermuscular heterogeneity in fibre types, studies generally model jaw-muscle forces by treating the jaw adductors as either homogeneously slow or homogeneously fast muscles. Here, we provide a novel extension of such studies by integrating fibre architecture, fibre types and fibre-specific tensions to estimate maximum muscle forces in the masseter and temporalis of five anthropoid primates: Sapajus apella ( N = 3), Cercocebus atys ( N = 4), Macaca fascicularis ( N = 3), Gorilla gorilla ( N = 1) and Pan troglodytes ( N = 2). We calculated maximum muscle forces by proportionally adjusting muscle physiological cross-sectional areas by their fibre types and associated specific tensions. Our results show that the jaw adductors of our sample ubiquitously express MHC α-cardiac, which has low specific tension, and hybrid fibres. We find that treating the jaw adductors as either homogeneously slow or fast muscles potentially overestimates average maximum muscle forces by as much as approximately 44%. Including fibre types and their specific tensions is thus likely to improve jaw-muscle and bite force estimates in primates.
... Skeletal muscle fibres contain specialised contractile machinery and thousands of mitochondria along their length (from several millimetres to centimetres) (Frontera & Ochala, 2015;Lieber, 2002). The transcriptional demands of these large, protein-rich cells are high and require hundreds of nuclei, termed myonuclei. ...
The transcriptional demands of skeletal muscle fibres are high and require hundreds of nuclei (myonuclei) to produce specialised contractile machinery and multiple mitochondria along their length. Each myonucleus spatially regulates gene expression in a finite volume of cytoplasm, termed the myonuclear domain (MND), which positively correlates with fibre cross‐sectional area (CSA). Endurance training triggers adaptive responses in skeletal muscle, including myonuclear accretion, decreased MND sizes and increased expression of the transcription co‐activator peroxisome proliferator‐activated receptor‐γ coactivator‐1α (PGC‐1α). Previous work has shown that overexpression of PGC‐1α in skeletal muscle regulates mitochondrial biogenesis, myonuclear accretion and MND volume. However, whether PGC‐1α is critical for these processes in adaptation to endurance training remained unclear. To test this, we evaluated myonuclear distribution and organisation in endurance‐trained wild‐type mice and mice lacking PGC‐1α in skeletal muscle (PGC‐1α mKO). Here, we show a differential myonuclear accretion response to endurance training that is governed by PGC‐1α and is dependent on muscle fibre size. The positive relationship of MND size and muscle fibre CSA trended towards a stronger correlation in PGC‐1a mKO versus control after endurance training, suggesting that myonuclear accretion was slightly affected with increasing fibre CSA in PGC‐1α mKO. However, in larger fibres, the relationship between MND and CSA was significantly altered in trained versus sedentary PGC‐1α mKO, suggesting that PGC‐1α is critical for myonuclear accretion in these fibres. Accordingly, there was a negative correlation between the nuclear number and CSA, suggesting that in larger fibres myonuclear numbers fail to scale with CSA. Our findings suggest that PGC‐1α is an important contributor to myonuclear accretion following moderate‐intensity endurance training. This may contribute to the adaptive response to endurance training by enabling a sufficient rate of transcription of genes required for mitochondrial biogenesis. In the present study, we aimed to test whether PGC‐1α is necessary for remodelling myonuclear number, myonuclear domain (MND) sizes and nuclear morphology after endurance training. To this end, we investigated the effects of moderate‐intensity endurance training on myonuclear distribution, organisation and shape in tibialis anterior muscle of wild‐type mice and mice lacking PGC‐1α in skeletal muscle. We found PGC‐1α governs scaling of both MND and myonuclear number with fibre CSA in larger muscle fibres of endurance‐trained mice, suggesting that PGC‐1α regulates myonuclear accretion in larger muscle fibres following endurance training
... The observed decrease in MSWD in slow walking can be regarded as a potential improvement of performance which may lead to an increase in average walking speed. It can partly be attributed to increased hamstring length (which, according to the force-velocity relationship, can increase contraction velocity) [38]. ...
Introduction: Flexibility is an essential component of muscle function, and insufficient muscle flexibility may lead to muscle injuries. Decreased hamstring flexibility is one of the frequently reported risk factors for a hamstring strain and diminished athletic performance. Stretching is a commonly used intervention for increasing muscle length. There is a lack of evidence concerning the possible effects of hamstring stretching in balance and gait biomechanics. So, this study was designed to investigate the potential effects of static hamstring stretching on the range of motion (ROM), dynamic balance, and biomechanical variables of gait in athletes with hamstring tightness.
Materials and Methods: This study is a single-group, pretest-posttest clinical trial performed on semi-professional female athletes. Twelve female athletes aged 20 to 35 years with bilateral hamstring tightness received a single session of unilateral static hamstring stretching on their randomly selected side. All subjects were assessed for straight leg raise, popliteal angle (using standard goniometry), perceived hamstring tightness (using a visual analog scale). They completed single-leg standing and 15-m walking and running tasks before and immediately after the intervention. The biomechanical parameters, including gait-line length, swing duration, and stance duration in walking tasks, maximum total force and mean total force in running task, and center of pressure (COP) displacement and standard deviation during balance task were measured using OpenGo sensor insole system. The pre-post values were compared using the paired sample t-test, and the level of significance was 0.05.
Results: The values for straight leg raise and popliteal angle significantly increased (P
... Researchers can also use different materials for warps and wefts to mimic the anisotropic property of bone [52] and cardiac tissues [102] . Heavyweight yarn is often used to create a raised rib in the fabric to mimic striated tissues such as cardiac muscles [109] and skeletal muscles [110] . ...
One of the key elements in tissue engineering is to design and fabricate scaffolds with tissue-like properties. Among various scaffold fabrication methods, textile technology has shown its unique advantages in mimicking human tissues' properties such as hierarchical, anisotropic, and strain-stiffening properties. As essential components in textile technology, textile patterns affect the porosity, architecture, and mechanical properties of textile-based scaffolds. However, the potential of various textile patterns has not been fully explored when fabricating textile-based scaffolds, and the effect of different textile patterns on scaffold properties has not been thoroughly investigated. This review summarizes textile technology development and highlights its application in tissue engineering to facilitate the broader application of textile technology, especially various textile patterns in tissue engineering. The potential of using different textile methods such as weaving, knitting, and braiding to mimic properties of human tissues is discussed, and the effect of process parameters in these methods on fabric properties is summarized. Finally, perspectives on future directions for explorations are presented.
Statement of Significance
Recently, biomedical engineers have applied textile technology to fabricate scaffolds for tissue engineering applications. Various textile methods, especially weaving, knitting, and braiding, enables engineers to customize the physical, mechanical, and biological properties of scaffolds. However, most textile-based scaffolds only use simple textile patterns, and the effect of different textile patterns on scaffold properties has not been thoroughly investigated. In this review, we cover for the first time the effect of process parameters in different textile methods on fabric properties, exploring the potential of using different textile methods to mimic properties of human tissues. Previous advances in textile technology are presented, and future directions for explorations are presented, hoping to facilitate new breakthroughs of textile-based tissue engineering.
... There are a number of muscle parameters that can be responsible for paraspinal muscle dysfunction as having direct influence on muscle force generation capacity. These parameters include physiological cross-sectional area, muscle fiber length, sarcomere length, specific tension, and passive tangent modulus (Lieber, 2011). ...
Introduction
Passive mechanical properties of the paraspinal muscles are important to the biomechanical functioning of the spine. In most computational models, the same biomechanical properties are assumed for each paraspinal muscle group, while cross sectional area or fatty infiltration in these muscles have been reported to differ between the vertebral levels. Two important properties for musculoskeletal modeling are the slack sarcomere length and the tangent modulus. This study aimed to investigate the effect of vertebral level on these biomechanical properties of paraspinal muscles in a rat model.
Methods
The left paraspinal muscles of 13 Sprague-Dawley rats were exposed under anesthesia. Six muscle biopsies were collected from each rat: three from multifidus (one per each of the L1, L3, and L5 levels) and similarly three from longissimus. Each biopsy was cut into two halves. From one half, two to three single muscle fibers and two to six muscle fiber bundles (14 ± 7 fibers surrounded in their connective tissue) were extracted and mechanically tested in a passive state. From the resulting stress-strain data, tangent modulus was calculated as the slope of the tangent at 30% strain and slack sarcomere length (beyond which passive force starts to develop) was recorded. The other half of each biopsy, which represented the muscle at the fascicle level, was snap frozen, sectioned, stained for Collagen I and its area fraction was measured. To evaluate the effect of spinal level on these biomechanical properties of multifidus and longissimus, one-way repeated measures ANOVA (p < 0.05) was performed for tangent modulus and slack sarcomere length, while for collagen I content linear mixed-models analysis was adopted.
Results
In total, 192 fibers and 262 fiber bundles were mechanically tested. For both muscle groups, no significant difference in tangent modulus of the single fibers was detected between the three spinal levels (p = 0.9 for multifidus and p = 0.08 for longissimus). Similarly, the tangent modulus values for the fiber bundles were not significantly different between the three spinal levels (p = 0.13 for multifidus and p = 0.49 for longissimus). In both muscle groups, the slack sarcomere lengths were not different among the spinal levels except for multifidus fibers (p = 0.02). Collagen I area fraction in muscle fascicles averaged 6.8% for multifidus and 5.3% for longissimus and was not different between the spinal levels.
Discussion
The results of this study highlighted that the tangent modulus, slack sarcomere length, and collagen I content of the lumbar paraspinal muscles are independent of spinal level. This finding provides the basis for the assumption of similar mechanical properties along a paraspinal muscle group.
... Concerning the architectural aspects of the skeletal musculature, the increased pennation angle and fascicle length have been accompanied by an augment in force production capacity (BLAZEVICH et al., 2003(BLAZEVICH et al., , 2007. Longer fascicle length is related to a greater number of contractile units arranged in series which may positively influence the force generation at a given shortening velocity due to a rightward shift in the isotonic force-velocity curve (LIEBER et al., 2010). In the study of Blazevich et al. (2007), the fascicle length did not increase significantly from the fifth week until the tenth of training, as occurred during the first five weeks. ...
The periodic variations in the resistance training load are more efficient for promoting muscle strength in comparison to training that does not vary the load over time. This variation occurs by manipulation of the variables presented in a resistance training program, such as the intensity, volume, muscle action speed, and exercise order. Although the pieces of evidence point to the superiority of the varied training, it’s not clear how the processes that influence the force production are affected when the training is performed with load variation through the time. Knowing the mechanics triggered by the load variation along the time could lead to training more specific to the goals desired. Thus, we aimed to discuss the central and peripheral mechanisms that influence the process of force production and to generate insights for new investigations that aim to compare the strength development between the varied and non-varied resistance training programs.
Background
When spinal stabilization exercises (SSE) are performed regularly, they may provide benefits on outcome measures in chronic nonspecific neck pain (CNNP) patients. The pandemic has made it difficult for CNNP patients to access regular physiotherapy-exercise services. This study aims to compare telerehabilitation (TR) with face-to-face rehabilitation in CNNP patients.
Methods
Neck Functional Capacity Evaluation Test (NFCET) results were the primary outcomes. Pain intensity (PI), disability, awareness, the architecture of the neck muscles, and exercise satisfaction were the secondary outcomes. Patients were randomized into the TR group (TRG) (n=15) and the control group (CG) (n=16). All patients performed SSE 3 days a week, for 8 weeks. The TRG was instructed remotely while the CG was instructed in the clinic.
Results
After 8 weeks, NFCET values increased (p<0.05). In both groups, PI and disability decreased and neck awareness increased (p<0.05). Muscle architecture parameters improved in both groups (p<0.05), except for the Right Sternocleidomastoideus in both groups and the Right Upper-Trapezius in TRG (p>0.05). There was no difference between the groups for all variables and exercise satisfaction after 8 weeks (p>0.05).
Conclusion
SSE for neck pain, whether supervised by a therapist in the clinic or by telerehabilitation, was equally effective.
Developing in vitro models that recapitulate the in vivo organization of living cells in a 3D microenvironment is one of the current challenges in the field of tissue engineering. In particular for anisotropic tissues where alignment of precursor cells is required for them to create functional structures. Herein, a new method is proposed that allows aligning in the direction of a uniform magnetic field both individual cells (muscle, stromal, and stem cells) or spheroids in a thermoresponsive collagen hydrogel. In an all‐in‐one approach, spheroids are generated at high throughput by magnetic engineering using microfabricated micromagnets and are used as building blocks to create 3D anisotropic tissue structures of different scales. The magnetic cells and spheroids alignment process is optimized in terms of magnetic cell labeling, concentration, and size. Anisotropic structures are induced to form fibers in the direction of the magnetic alignment, with the respective roles of the magnetic field, the mechanical stretching of hydrogel or co‐culture of the aligned cells with non‐magnetic stromal cells, being investigated. Over days, spheroids fuse into 3D tubular structures, oriented in the direction of the magnetic alignment. Moreover, in the case of the muscle cells model, multinucleated cells can be observed within the fibers.
This chapter focuses on the responses of various musculoskeletal tissues to the application of physical loads. It discusses some important fundamentals of materials science, the mechanical characteristics of musculoskeletal tissues, and the way they respond to different types of loading. The chapter then discusses the principles of fatigue failure. A fundamental relationship useful in understanding the effect of forces on materials is Hooke's law. All musculoskeletal and nerve tissues comprise materials that exhibit viscoelastic behavior. Tendons and ligaments are both fibrous connective tissues made primarily of bundles of collagen fibers. Peripheral nerves are tethered proximally to the spinal cord, at branch points and to the surrounding paraneural and myofascial tissues. Peripheral nerve trunks elongate proportionally to a certain point under increasing load; until this point, the nerve trunk behaves like an elastic structure and after this loading, the original shape resumes.
Anaerobic exercise is short-burst, high-intensity activity that exceeds the body's demand for oxygen and requires quick, readily available energy (sugar) that is stored in the skeletal muscle. This is known as anaerobic metabolism. During this process, lactic acid is produced faster than it can be metabolized. This study determined the effects of a topical carnosine-based gel (LactiGo) on blood lactate (HLa) production and anaerobic exercise performance variables during a 25sec. maximal sprint against a resistive force. Healthy and recreationally active men (n=10; ±SD; age=21.5±1.7 yrs, height=1.82±0.13 m, weight=82.6±11.4 kg) and women (n=10; age=19.8±1.0 yrs, height=1.71±0.05 m, weight=62.6±7.4 kg) performed the anaerobic maximal intensity resistive sprint protocol with the topical gel (LactiGo) and with placebo. Blood samples collected were analyzed with a Lactate Plus handheld blood lactate analyzer. Paired samples t-tests on performance measures (Gel vs. Placebo), and 3-way repeated measures ANOVAs (sex x condition x time) were performed on mean values for each subject. Follow-up analyses for ANOVA models were performed using paired samples t-tests with Bonferroni corrections. The level of significance was set at (p≤0.05). Comparisons indicated no sprint performance differences. However, the topical carnosine-based gel increased blood lactate accumulation following the 25 sec resistive sprint. The performance measures indicated no differences between condition (Gel vs. Placebo), however, the lactate indicated a 3-way interaction (p<0.01). Lactate measurements were significantly greater for the Post vs. Baseline (p<0.01) and Post vs. Pre (p<0.01).
Commercial aquaculture of yellowtail (Seriola quinqueradiata) is challenging, owing to deterioration of aquaculture environments. Offshore aquaculture may be a means of overcoming these problems. Here, we assessed the quality of flesh from offshore yellowtail (OY) bred for 1 year in an offshore floating flexible facility compared with coastal yellowtail (CY) cultured simultaneously in a coastal cage facility. The survival rate of the OY group was 94.46%, which was slightly lower than that of CY (98.18%). The feeding rate (feeding weight/fish weight) of CY was 0.4–0.5, whereas that of OY was only 0.3, possibly because poor weather conditions prevented feeding at the offshore facility. However, final fish weights did not differ significantly between both groups. In sensory tests, OY was inferior to CY in terms of oily taste. The lipid content in CY was significantly higher than that in OY. Hardness analysis revealed that OY muscles were harder than those of CY. There were no significant differences between OY and CY in overall sensory evaluations; thus, OY was judged as having equivalent value as a food product with CY. The redness of dark muscles was not significantly different on day 1 of refrigeration. However, the redness value of OY was significantly higher than that of CY on day 2. The inferior fattiness of OY relative to that of CY can be overcome by improving the feeding method. Therefore, offshore aquaculture with negligible environmental pollution may be effective for further development of aquaculture. Fish in the offshore floating flexible facility had lower fat contents and a harder texture. The redness of fish meat in the offshore floating flexible facility was maintained for a longer time. Offshore floating flexible culture can produce high‐quality yellowtail under eco‐friendly conditions.
This current work addresses major problems in muscle tissue engineering, via tackling the basics of materials and their processing. First, stimuli-responsive polyurethane-based copolymers were melt electrowritten (MEW) to form aligned fibers on top of a 3D printed monolayer polymer film of methacrylate hyaluronic acid (HAMA) crosslinked with Eosin Y and triethanolamine. This monolayer acts as the base for inducing self-folding, which under certain conditions in water, swells. Since a gradient in crosslinking exists from top to bottom, a bending force is generated, resulting in folding. To achieve control over cell distribution inside self-folded tubes, it was proposed to pattern polyurethane copolymers (ex. PCL-PU) on top of HA-MA. This approach was successful as it could be seen that the cells had mostly adhered on top of the copolymer fibers. Second, different polyurethane-based copolymers were synthesized, characterized, and tested for fiber formation using touch-spinning (TS). The materials exhibit highly aligned microfiber formation, biodegradability and biocompatibility, which promoted cell alignment that is an essential key for muscle tissue engineering.
Skeletal muscles are required for functional movement and force production. While it is clear that cerebral palsy (CP) results in loss of muscle strength and bodily function, and that much of this loss is caused by injury to the central nervous system, muscle is a very plastic tissue that is also dramatically affected. In many studies, it is assumed that voluntary exercise will cause the muscle to respond in the same way that typically developing muscle does, but there are scarce data demonstrating that this is true. The purpose of this review is to briefly describe muscle architectural adaptation to various forms of exercise with specific reference to voluntary exercise performed in children with CP. Exercise itself is not generic but can vary by intensity, duration, and the exact nature of the muscle length change and velocity imposed during the exercise. Our goal is to stimulate discussion in this area by pointing out salient experimental variables and, ultimately, to improve activity and participation in children with CP.
Skeletal muscles, which are the components of the locomotor system and play a primary role in the movement, produce force as a result of various biochemical and mechanical processes during contraction. Mathematical muscle models are used to simulate muscle forces in silico for various experimental or clinical purposes. The ability of muscle models to produce actual muscle forces with high accuracy is closely related to the assumptions adopted in the modeling. Huxley-type muscle models, also known as structural models, are mathematical models used to calculate various muscle characteristics as well as force based on biochemical and mechanical interactions during contraction. These models, which are based on the cross-bridge theory and the interaction of the filaments in the muscle structure, are still being modified and developed through experimental studies. Understanding the structure of muscle models, the employed assumptions, and the capabilities of these models are important for re producing the realistic muscle forces and dynamic characteristics of muscle. In this review article, the structure and properties of Huxley-type mathematical muscle models and their force responses are examined in terms of their performances in predicting experimentally obtained muscle characteristics. For this purpose, muscle forces were obtained for different contraction conditions using a Huxley model and the model performance was evaluated in the study. In addition, the changes in Huxley-type models are presented, and the kinds of works, for which are suitable, were introduced besides the advantages and disadvantages of the models.
The two types of skeletal muscle fibers are the slow-twitch (type I) and the fast-twitch (type II) fibers. Slow-twitch muscles are activated in long resistance exercise, while fast-twitch muscles are activated in forceful breakouts. Sprinters have larger type II than type I fiber areas in their leg extensor muscles because their training mainly includes fast repetitive movements. Muscle size is strongly related to better performance in the literature, with sprinters appearing to have more developed lower limb muscles. Essential elements of a high sprint performance are the ability to accelerate rapidly, the size of maximal velocity, and the ability to maintain this velocity. At the muscle level, force, velocity, and power are mainly influenced by fiber type distribution and architecture. Moreover, a strong positive correlation between fascicle length and mechanical power production applies. An increase in muscle thickness leads to a greater force production capacity of the muscle with a subsequently improved acceleration ability. It is general belief that males are faster than females because males have more muscle mass. Differences between male and female sprinters include differences in musculotendinous stiffness and greater structural compliance in females, while muscle fiber type composition and muscle fascicle length are similar. Measurement of muscle thickness is achieved with MRI and ultrasonography. In a biomechanics aspect, as a sprint begins, the generation of forward acceleration is probably the most essential factor that determines the performance. The most important muscle group, which plays a predominant role as running speed increases and reaches maximal sprint speeds, is the hip extensor/knee flexor muscles and the quality of the foot muscles.
Low back pain disorders affect more than 80% of adults in their lifetime and are the leading cause of global disability. The muscles attaching to the spine (ie, paraspinal muscles) are critical for proper spine health and play a crucial role in the functioning of the spine and whole body; however, reports of muscle dysfunction and insufficiency in chronic LBP (CLBP) patients are common. This article presents a review of the current understanding of the relationship between paraspinal muscle pathophysiology and spine‐related disorders. Human literature demonstrates a clear association between altered muscle structure/function, most notably fatty infiltration and fibrosis, and low back pain disorders; other associations, including muscle cell atrophy and fiber type changes, are less clear. Animal literature then provides some mechanistic insight into the complex relationships, including initiating factors and time courses, between the spine and spine muscles under pathological conditions. It is apparent that spine pathology can directly lead to changes in the paraspinal muscle structure, function, and biology. It also appears that changes to the muscle structure and function can directly lead to changes in the spine (eg, deformity); however, this relationship is less well studied. Future work must focus on providing insight into possible mechanisms that regulate spine and paraspinal muscle health, as well as probing how muscle degeneration/dysfunction might be an initiating factor in the progression of spine pathology. This review article details the current understanding of the relationship between paraspinal muscle pathophysiology and spine‐related disorders. Both human and animal studies are discussed, and future lines of research are recommended.
About three quarters of flying insects on Earth use the asynchronous driving mechanism in muscles to power their flights. Herein, an asynchronous flight assembly via electrostatic actuation of flapping wings in analogy to the asynchronous mechanism in natural flying insects is demonstrated. The wing motions are driven by the self‐sustained oscillation of metal beams in a steady electric field and regulated by the input voltage between two stationary electrodes, whereas the discharging process occurs repetitively as the oscillating beams hit and exchange charges with the electrodes. Several advancements in the oscillation and flight demonstrations have been achieved: 1) self‐sustainable and asynchronous oscillations for biomimetic flapping‐wing motions with high efficiency, 2) the first takeoff of an asynchronous flight assembly along the fixed electrodes, and 3) the first self‐adaptive hovering assembly via the passive modulation of the flapping frequency and amplitude when a disturbance is introduced. Currently, most of the artificial flying robots are based on the synchronous driving mechanism, whereas, herein, the feasibility of artificial flight muscle using the asynchronous driving by self‐sustained electrostatic oscillations of metal beams to power flapping wings without any AC circuits, which exhibits takeoff and self‐adaptive hovering features is demonstrated.
This experimental study aims to evaluate and validate the effectiveness of the proposed application method in the use of "focused mechanical vibrations" for the treatment of muscle spasticity. The basic concept of this study is that in spasticity, by specifically stimulating some clearly identifiable trigger points of the body, better results are obtained; in fact, with the localized mechanical-sound vibrations, by positioning the handpiece for the treatment on those specific points, immediate generalized relaxation of the entire spastic muscle is obtained through reflex pathways. To evaluate this operative reality we treated 5 subjects affected by neurological pathology with spasticity and at T0 time (before treatment) and at T1 time (immediately after treatment), they were assessed with Ashworth Scale, Passive joint evaluation, Evaluation of active motility, Test of Bahkta (for non-functioning hand), surface electromyography The subjects were treated with a 120Hz vibratory therapy handpiece for a total time of 15 minutes The data showed us a clear improvement of the parameters lost in the exam, in the less serious patients and a good improvement also in the most serious subjects.
The extracellular matrix (ECM) influences biological processes associated with tissue development and disease progression. However, robust cell‐free techniques to control fiber alignment of naturally derived ECM proteins, such as fibronectin (Fn), remain elusive. It is demonstrated that controlled hydrodynamics of Fn solutions at the air/fluid interface of porous tessellated polymer scaffolds (TPSs) generates suspended 3D fibrillar networks with alignment across multiple length scales (<1, 1–20 μm, extended to >1 mm). The direction of the fluid flow and the architecture of the polymeric supports influence protein solution flow profiles and, subsequently, the alignment of insoluble Fn fibrils. Aligned networks of fibrillar Fn characteristically alter fibroblast phenotype, indicated by increased directional orientation, enhanced nuclear and cytoskeletal polarity, and highly anisotropic and persistent cell motility when compared with nonaligned 3D networks and 2D substrates. Engineered extracellular matrices (EECMs) establish a critically needed tool for both fundamental and applied cell biology studies, with potential applications in diverse areas such as cancer biology and regenerative medicine. Herein, the production of highly aligned 3D fibrillar fibronectin (Fn) networks suspended across hyperporous polymeric scaffold supports described. Orientation of 3D protein networks is achieved through control of the fluid‐flow profiles across the scaffold supports at the air–protein solution interface during hydrodynamically induced fibrillogenesis in the absence of solution denaturants or harsh solvents. Relative to nonaligned substrates of the same composition, aligned networks promote highly directionally persistent fibroblast migration.
Fizyoterapistler, elektroterapi aletlerini özel-likle elektrik stimulasyonu güvenli ve etkili bir şekilde kullanmak istiyorlarsa temel sinir ve kas fizyolojisini iyi bir şekilde anlamaları gerek-mektedir. Bu nedenle sinir ve kas fizyolojisinde anahtar kavramlar olan hücre zarı, iyon kanalla-rı, dinlenim zar potansiyeli, aksiyon potansiyeli, sinaptik yapı ile fonksiyon, periferik sinir siste-mi, kas dokusunun yapısı, iskelet kasının uyarıl-ması/kasılması, motor ünitenin yapısı ve iskelet kas lifinin tiplerini bilmek önemlidir. Bu bölüm-de anahtar kavramların hepsinin fizyolojisini tek tek ele alacağız. Hücre Zarı Organizmalardaki hücreler; şekil, boyut ve fonk-siyon olarak birbirinden farklı olmalarına rağ-men, tüm hücreler bir zar ile çevrilmiştir. Şekil 1A'da gösterilen bu zar yapısı hücre zarı (hücre membranı) olarak adlandırılır. Yapısında %55 oranında protein, %25 fosfolipid, %13 kolesterol, %4 diğer lipitler, %3 karbonhidrat bulunurken, kalınlığı 7,5-10 nanometre arasındadır. Hücre zarı, iki katlı fosfolipit bir yapıdan oluşur ve seçi-ci geçirgendir. Lipit tabakası tüm hücre yüzeyini kaplar ve fosfolipit moleküllerinden oluşur. Fos-folipitlerin fosfat kısmı, hidrofilik (suyu seven), yağ asidi kısmı ise hidrofobiktir (suyu sevme-yen, Şekil 1B). Hücre zarının iç kısmında bulu-nan hidrofobik kısımlar, su tarafından itilirken, dış kısmında bulunan hidrofilik kısımlar da su tarafından çekilir. Yağ ve su birbirine karışmadı-ğından bu durum, zarın doğal bir dizilimde kal-masını sağlar. Hücre zarı fosfolipit yapıda olduğu için su ve suda eriyen maddelere karşı engel oluş-tururken, lipitte çözünen maddelere özellikle kü-çük molekül yapısında olan maddelere (oksijen, karbondioksit, ADEK vitaminleri, alkol vb gibi) karşı geçirgen bir yapıdadır. Yani zar yapısında-ki lipitler; yağlarda çözünmeyen suyun ve suda eriyebilir maddelerin bir hücre bölmesinden di-ğerine serbestçe gitmesini engelleyici bir bariyer görevi görürler. Bununla birlikte, zardaki protein molekülleri, zarın iç veya dış yüzündeki periferal proteinler veya zara gömülmüş ve bazıları zarı boydan boya geçen integral proteinler şeklin-dedir. Proteinler daha büyük yapıda olduğu için hücre zarının %55'ini oluştururlar. Bu proteinler çoğu kez zarı boyuna kat ederek (bu yapılar ge-nellikle por olarak adlandırılır) bazı özel madde-lerin zardan geçişine izin verir. Zar proteinlerinin diğer bir bölümü de farklı kimyasal reaksiyonları katalizleyen enzim işlevi görür. Sonuçta iyon ka-nalları, pompalar, reseptörler, taşıyıcı proteinler ve enzimler hücre zarındaki proteinlerden olu-şur. Ayrıca zardaki proteinlere gevşekçe bağlan-mış karbonhidrat molekülleri ile oluşan prete-oglikanlar vardır. Bunlar, bütün hücre yüzeyini saran bir glikokaliks adı verilen özel bir yapıyı oluştururlar. Hücrelerin birbirini tanımasında, negatif yüklerinden dolayı hücre agregasyonun önlenmesi ve tümör gelişiminin önlenmesinde glikokaliks önemli bir rol oynar. Hücre zarının yapısında yer alan kolestrol ise zar stabilizasyonu sağlar.
Introduction:
Restrictive sternal precautions intended to prevent cardiac surgery patients from damaging healing sternotomies lack supporting evidence and may decrease independence and increase post-acute care utilization. Data regarding the impact of alternative approaches on safety and outcomes are needed to guide evidence-based best practices.
Objective:
To examine whether an approach allowing greater freedom during activities of daily living than permitted under commonly-used restrictive sternal precautions can safely decrease post-acute care utilization.
Design:
Before-and-after study, using propensity score adjustment to account for differences in patient clinical and demographic characteristics, surgery type, and surgeon.
Setting:
600-bed acute care hospital.
Intervention:
Beginning March 2016, our institution replaced traditional weight- and time-based precautions given to patients who underwent median sternotomy with the "Keep Your Move in the Tube" (KMIT) approach for mindfully performing movements involved in the activities of daily living, guided by pain.
Main outcome measures:
We compared sternal wound complications, discharge disposition, 30-day readmission, and functional status between consecutive cardiac surgery patients with "independent" or "modified independent" preoperative functional status who underwent median sternotomy in the 1.5 years before (n = 627, standard precautions group) and after (n = 477, KMIT group) KMIT implementation.
Results:
The odds of discharge to home, vs to inpatient rehabilitation or skilled nursing facility, was ~3 times higher for KMIT than standard precautions patients (risk-adjusted odds ratio [rOR], 95% confidence interval [CI] = 2.90, 1.95-4.32, and 3.03, 1.57-5.86, respectively). KMIT patients also had significantly higher odds of demonstrating "independent" or "modified independent" functional status on final inpatient physical therapy treatment for bed mobility (rOR, 95%CI = 7.51, 5.48-10.30) and transfers (rOR, 95%CI = 3.40, 2.62-4.42). No significant difference was observed in sternal wound complications (in-hospital or causing readmission) (rOR, 95%CI = 1.27, 0.52-3.09) or all-cause 30-day readmissions (rOR, 95%CI = 0.55, 0.23-1.33).
Conclusions:
KMIT increases discharge-to-home for cardiac surgery patients without increasing risk for adverse events and reducing utilization of expensive institutional post-acute care. This article is protected by copyright. All rights reserved.
Coaching is one of the most common words in our modern vocabulary and has many meanings depending on the setting in which it is used. Coaching facilitates positive changes to achieve a goal, usually through indirect approaches, including improving an individual's outlook on their behaviors or attitudes. Its application has spread beyond the corporate world, and many medical specialties use coaching principles. The goals of this article are to introduce coaching as a profession, and to explore the function of a vocal coach to improve communicative and vocal performance. Moreover, differences between voice therapy and voice training are highlighted, including the principles subjacent to these interventions and the use of coaching strategies. Four strategies of professional coach practitioners adapted to the training and therapy of the voice with applications to both are described. These are: powerful questions, active listening, changing habits, and implementation intention. The use of these strategies may help individuals to achieve high voice performance. Most importantly, the speech-language pathologist voice specialist can apply these strategies particularly in cases of behavioral dysphonias, which can be resistant to traditional voice therapy.
The relative contributions of muscle force, moment arm, and tendon compliance were determined as a function of joint angle in the frog semitendinosus-hip joint system. Muscle, joint, and tendon properties were individually measured and then combined to predict the torque generated at the hip joint as a function of joint angle (i.e., the hip torque profile). Predicted torques were then compared to experimentally measured torques using a stepwise regression model to quantify the relative importance of muscle, joint, and tendon contributions to the hip torque profile. Variation in moment arm accounted for 74% of the variability observed in the hip torque profile, while addition of the muscle's intrinsic sarcomere length-tension property accounted for an additional 19% of the torque profile variability. Tendon compliance, which permitted a small amount of sarcomere shortening, accounted for only about 4% of the torque profile variability. We conclude that in this muscle-joint system, the relative fiber length-to-moment arm ratio is the major determinant of the shape of the isometric joint profile. The fiber length-to-moment arm ratio in other mammalian systems is also discussed.
The relationship between semitendinosus muscle force and knee joint kinematics during isometric torque production was examined in the frog (Rana pipiens) hindlimb. Passive muscle sarcomere length was monitored by laser diffraction during knee rotation, and joint center of rotation was determined later using principles of rigid body kinematics. Contractile force at the distal tibia, resulting from semitendinosus contraction, was also measured, and, using the kinematic data, a torque vs. joint angle curve constructed. Muscle sarcomere length varied from 3.6 micron at full knee extension to 2.0 micron at full knee flexion. Effective lever arm varied almost as a sine function, with optimal lever arm at 90 degrees of flexion. Joint torque increased linearly from 0 to 140 degrees of flexion and then sharply decreased to 160 degrees of flexion. Thus the optimal joint angle occurred at an angle (140 degrees) that was neither the angle at which muscle force was maximum (160 degrees) nor the angle at which the effective lever arm was maximum (90 degrees). These data indicate that knee torque production in the frog results from the interaction between muscular and joint properties and not either property alone.
The objective of this research was to compare the length of muscle spindles to the length of the whole muscle, during normal movements. Pairs of piezoelectric crystals were implanted near the origin and insertion of muscle fibres in the medial gastrocnemius (MG) muscle of cats. The distance between crystals was measured with pulsed ultrasound, the origin-to-insertion length of the MG muscle was measured with a transducer made of saline-filled silicone tubing, MG force was measured with a tendon force transducer and EMG activity was selectively recorded in the vicinity of implanted crystals. These signals were simultaneously recorded during posture or locomotion on a motorized treadmill. Three periods were identified in the step cycle, during which the relation between muscle length and spindle length changed dramatically. In period I (roughly corresponding to the late F and E1 phases of swing), the MG muscle and spindles followed similar length changes: both were stretched and then shortened by about 6 mm. In period II (corresponding to the stance phase, E2-E3) the MG muscle yielded under the weight of the body and was stretched by 1-3 mm, whereas the MG spindles typically continued shortening. In period III, the MG muscle shortened rapidly by 6-8 mm after the foot left the ground and then stretched again by about the same amount, whereas the spindles could remain nearly isometric. We attribute these large discrepancies in muscle and spindle length to the architecture of the MG muscle and the compliance of long tendinous elements in series with the spindles. We conclude that the length changes imposed on muscle spindles during voluntary movements are not simply related to the parent muscle length changes and cannot be estimated without taking into account the muscle architecture, the location of the spindle within the muscle, the level of muscle activation and the external load.
Surgery on the extraocular muscles of the eye is generally consisted a safe procedure which is associated with low morbidity and mortality. While infrequent, intra-operative complications occasionally occur. Tenotomy of multiple rectus muscles can result in interruption of the vascular supply to the anterior segment of the eye. Anterior segment ischemia (ASI) may result. This article reviews the complication of anterior segment ischemia as a result of strabismus surgery and its potential for producing permanent visual loss.