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Walter Herzog - One of the best experts on this subject based on the ideXlab platform.
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Residual Force enhancement in human skeletal muscles a systematic review and meta analysis
Journal of Sport and Health Science, 2021Co-Authors: Daiani De Campos, Walter Herzog, Lucas B R Orssatto, Gabriel S Trajano, Heiliane De Brito FontanaAbstract:Abstract Objective We reviewed and appraised the existing evidence of in vivo manifestations of Residual Force enhancement in human skeletal muscles and assessed, through a meta-analysis, the effect of an immediate history of eccentric contraction on the subsequent torque capacity of voluntary and electrically evoked muscle contractions. Methods Our search was conducted from database inception to May 2020. Descriptive information was extracted from, and quality was assessed for, 45 studies. Meta-analyses and metaregressions were used to analyze Residual torque enhancement and its dependence on the angular amplitude of the preceding eccentric contraction. Results Procedures varied across studies with regards to muscle group tested, angular stretch amplitude, randomization of contractions, time window analyzed, and verbal command. Torque capacity in isometric (constant muscle tendon unit length and joint angle) contractions preceded by an eccentric contraction was typically greater compared to purely isometric contractions, and this effect was greater for electrically evoked muscle contractions than voluntary contractions. Residual torque enhancement differed across muscle groups for the voluntary contractions, with a significant enhancement in torque observed for the adductor pollicis, ankle dorsiflexors, ankle plantar flexors, and knee extensors, but not for the elbow and knee flexors. Meta-regressions revealed that the angular amplitude of the eccentric contraction (normalized to the respective joint's full range of motion) was not associated with the Residual torque enhancement observed. Conclusion There is evidence of Residual torque enhancement for most, but not all, muscle groups, and Residual torque enhancement is greater for electrically evoked than for voluntary contractions. Contrary to our hypothesis, and contrary to generally accepted findings on isolated muscle preparations, Residual torque enhancement in voluntary and electrically evoked contractions does not seem to depend on the angular amplitude of the preceding eccentric contraction.
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increased Force following muscle stretching and simultaneous fibre shortening Residual Force enhancement or Force depression that is the question
Journal of Biomechanics, 2021Co-Authors: Sheharzad Mahmood, Walter Herzog, Andrew SawatskyAbstract:Abstract Residual Force enhancement (rFE) describes the increase in isometric Force following muscle stretching compared to the corresponding isometric Force. Even though rFE is consistently observed in isolated muscle preparations, it is not always observed in human skeletal muscle. This inconsistency might be associated with disociations between length changes in muscle tendon units (MTUs) and fibres. This prompted the question if there is rFE for conditions where the MTU is stretched while fibres shorten. Rabbit tibialis anterior (TA) MTUs (n = 4) were stretched and the isometric Forces following stretching were compared to corresponding Forces from isometric reference contractions. Unique combinations of stretch speed and activation were used to create conditions of continuous fibre shortening during MTU stretch. Mean Force was increased (18 ± 2%) following MTU stretching compared to the isometric reference Forces. Without fibre length measurements, this result would be referred to as rFE. However, fibre shortening in the reference contractions was always greater than for the eccentric stretch contractions, suggesting that the observed increase in Force might be caused by less Residual Force depression (rFD) in the stretch tests compared to the reference contractions. However, the work performed by fibre shortening was similar between the reference and the MTU stretch contractions, suggesting that rFD was similar for both experimental conditions. Therefore, we conclude that we observed rFE in the absence of contractile element stretching. However, a lack of knowledge of the molecular mechanisms that distinguish rFE from rFD prevents an unequivocal pronouncement of what caused the enhanced Forces after active muscle stretching.
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differences in stretch shortening cycle and Residual Force enhancement between muscles
Journal of Biomechanics, 2020Co-Authors: Atsuki Fukutani, Walter HerzogAbstract:Abstract It has been suggested that cross bridge kinetics and Residual Force enhancement (RFE) affect Force in the stretch-shortening cycle (SSC). Because cross bridge kinetics and titin isoforms, which are thought to be related to RFE, differ between muscles, the SSC effect may be also muscle-dependent. Thus, we compared the SSC effect between psoas and soleus muscles, which have a distinct fiber type distribution and different titin isoforms. Four tests (SSC, SSC control, RFE, RFE control) were conducted using isolated, skinned fibers of psoas and soleus. In the SSC tests, fibers were activated at an average sarcomere length of 2.4 μm, stretched to 3.0 μm, and shortened to 2.4 μm. In the SSC control tests, fibers were activated at an average sarcomere length of 3.0 μm and then shortened to 2.4 μm. The relative increase in mechanical work obtained during shortening between tests was defined as the SSC effect. In the RFE tests, fibers were activated at an average sarcomere length of 2.4 μm and then stretched to 3.0 μm, while the RFE control tests consisted of an isometric contraction at 3.0 μm. The difference in steady-state isometric Force between tests was defined as RFE. The SSC effect was greater in soleus than in psoas, while the RFE was the same for both muscles. Since the SSC effect was greater in soleus, while the RFE was the same, the observed greater SSC effect is probably not directly caused by RFE, but may be related to differences in cross bridge kinetics.
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on sarcomere length stability during isometric contractions before and after active stretching
The Journal of Experimental Biology, 2019Co-Authors: Kaleena Johnston, Azim Jinha, Eng Kuan Moo, Walter HerzogAbstract:Sarcomere length (SL) instability and SL non-uniformity have been used to explain fundamental properties of skeletal muscles, such as creep, Force depression following active muscle shortening and Residual Force enhancement following active stretching of muscles. Regarding Residual Force enhancement, it has been argued that active muscle stretching causes SL instability, thereby increasing SL non-uniformity. However, we recently showed that SL non-uniformity is not increased by active muscle stretching, but it remains unclear if SL stability is affected by active stretching. Here, we used single myofibrils of rabbit psoas muscle and measured SL non-uniformity and SL instability during isometric contractions and for isometric contractions following active stretching at average SLs corresponding to the descending limb of the Force-length relationship. We defined isometric contractions as contractions during which mean SL remained constant. SL instability was quantified by the rate of change of individual SLs over the course of steady-state isometric Force and SL non-uniformity was defined as deviations of SLs from the mean SL at an instant of time. We found that whereas the mean SL remained constant during isometric contraction, by definition, individual SLs did not. SLs were more stable in the Force-enhanced, isometric state following active stretching compared with the isometric reference state. We also found that SL instability was not correlated with the rate of change of SL non-uniformity. Also, SL non-uniformity was not different in the isometric and the post-stretch isometric contractions. We conclude that since SL is more stable but similarly non-uniform in the Force-enhanced compared with the corresponding isometric reference contraction, it appears unlikely that either SL instability or SL non-uniformity contribute to the Residual Force enhancement property of skeletal muscle.
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Current Understanding of Residual Force Enhancement: Cross-Bridge Component and Non-Cross-Bridge Component.
International journal of molecular sciences, 2019Co-Authors: Atsuki Fukutani, Walter HerzogAbstract:Muscle contraction is initiated by the interaction between actin and myosin filaments. The sliding of actin filaments relative to myosin filaments is produced by cross-bridge cycling, which is governed by the theoretical framework of the cross-bridge theory. The cross-bridge theory explains well a number of mechanical responses, such as isometric and concentric contractions. However, some experimental observations cannot be explained with the cross-bridge theory; for example, the increased isometric Force after eccentric contractions. The steady-state, isometric Force after an eccentric contraction is greater than that attained in a purely isometric contraction at the same muscle length and same activation level. This well-acknowledged and universally observed property is referred to as Residual Force enhancement (rFE). Since rFE cannot be explained by the cross-bridge theory, alternative mechanisms for explaining this Force response have been proposed. In this review, we introduce the basic concepts of sarcomere length non-uniformity and titin elasticity, which are the primary candidates that have been used for explaining rFE, and discuss unresolved problems regarding these mechanisms, and how to proceed with future experiments in this exciting area of research.
Geoffrey A Power - One of the best experts on this subject based on the ideXlab platform.
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modifiability of Residual Force depression in single muscle fibers following uphill and downhill training in rats
Physiological Reports, 2021Co-Authors: Parastoo Mashouri, Stephen H M Brown, Jackey Chen, Alex M Noonan, Geoffrey A PowerAbstract:Following active muscle shortening, steady-state isometric Force is less than a purely isometric contraction at the same muscle length and level of activation; this is known as Residual Force depression (rFD). It is unknown whether rFD at the single muscle fiber level can be modified via training. Here we investigated whether rFD in single muscle fibers is modifiable through downhill and uphill running in the extensor digitorum longus (EDL) and soleus (SOL) muscles in rats. Rats were run uphill or downhill 5 days/week for 4 weeks. After muscles were dissected and chemically permeabilized, single fibers were tied between a length controller and Force transducer, transferred to an activating solution, with ATP and pCa of 4.2 for mechanical testing. rFD was quantified after active fiber shortening from an average sarcomere length (SL) of 3.1-2.5 µm at a relative speed of 0.15 fiber lengths/s (slow) and 0.6 fiber lengths/s (fast). rFD was calculated as the difference in Force (normalized to cross-sectional area) during the isometric steady-state phase following active shortening and the purely isometric contraction. In addition to rFD, mechanical work of shortening and stiffness depression were also calculated. rFD was present for both the EDL (6-15%) and SOL (1-2%) muscles, with no effect of training. rFD was greater for the EDL than SOL which closely corresponded to the greater stiffness depression in the EDL, indicating a greater inhibition of cross-bridge attachments. These results indicate that while rFD was observed, training did not appear to alter this intrinsic history-dependent property of single muscle fibers.
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Residual Force enhancement due to active muscle lengthening allows similar reductions in neuromuscular activation during position and Force control tasks
Journal of Sport and Health Science, 2020Co-Authors: Rhiannon Marion, Geoffrey A PowerAbstract:Abstract Background Residual torque enhancement (rTE) is the increase in torque observed during the isometric steady state following active muscle lengthening when compared with a fixed-end isometric contraction at the same muscle length and level of neuromuscular activation. In the rTE state, owing to an elevated contribution of passive Force to total Force production, less active Force is required, and there is a subsequent reduction in activation. In vivo studies of rTE reporting an activation reduction are often performed using a dynamometer, where participants contract against a rigid restraint, resisting a torque motor. rTE has yet to be investigated during a position task, which involves the displacement of an inertial load with positional control. Methods A total of 12 participants (6 males, 6 females; age = 22.8 ± 1.1 years, height = 174.7 ± 8.6 cm, mass = 82.1 ± 37.7 kg; mean ± SD) completed torque- and position-matching tasks at 60% maximum voluntary contraction for a fixed-end isometric contraction and an isometric contraction following active lengthening of the ankle dorsiflexors. Results There were no significant differences in activation between torque- and position-matching tasks (p = 0.743), with ∼27% activation reduction following active lengthening for both task types (p Conclusion These results indicate that rTE is a feature of voluntary, position-controlled contractions. These findings support and extend previous findings of isometric torque-control conditions to position-controlled contractions that represent different tasks of daily living.
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Residual Force enhancement and Force depression in human single muscle fibres
Journal of Biomechanics, 2019Co-Authors: Rhiannan A M Pinnell, Parastoo Mashouri, Nicole Mazara, Erin Weersink, Stephen H M Brown, Geoffrey A PowerAbstract:Abstract Residual Force depression (rFD) and Residual Force enhancement (rFE) are intrinsic contractile properties of muscle. rFD is characterized as a decrease in steady-state isometric Force following active shortening compared with a purely isometric contraction at the same muscle length and level of activation. By contrast, isometric Force is increased following active lengthening compared to a reference isometric contraction at the same muscle length and level of activation; this is termed rFE. To date, there have been no investigations of rFD and rFE in human muscle fibres, therefore the purpose of this study was to determine whether rFD and rFE occur at the single muscle fibre level in humans. rFD and rFE were investigated in maximally activated single muscle fibres biopsied from the vastus lateralis of healthy adults. To induce rFD, fibres were activated and shortened from an average sarcomere length (SL) of 3.2–2.6 μm. Reference isometric contractions were performed at an average SL of 2.6 μm. To induce rFE, fibres were actively lengthened from an average SL of 2.6–3.2 μm and a reference isometric contraction was performed at an average SL of 3.2 μm. Isometric steady-state Force was lower following active shortening (p
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modifiability of the history dependence of Force through chronic eccentric and concentric biased resistance training
Journal of Applied Physiology, 2019Co-Authors: Jackey Chen, Geoffrey A PowerAbstract:The history dependence of Force production is a property of muscle unexplained by current cross bridge and sliding filament theories. Whether a muscle is actively lengthened (Residual Force enhance...
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shortening induced Residual Force depression in humans
Journal of Applied Physiology, 2019Co-Authors: Jackey Chen, Daniel Hahn, Geoffrey A PowerAbstract:When an isometric muscle contraction is immediately preceded by an active shortening contraction, a reduction in steady-state isometric Force is observed relative to an isometric reference contract...
Daniel Hahn - One of the best experts on this subject based on the ideXlab platform.
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a reduction in compliance or activation level reduces Residual Force depression in human tibialis anterior
Acta Physiologica, 2019Co-Authors: Brent J Raiteri, Daniel HahnAbstract:Aim: We investigated if Residual Force depression (rFD) is present during voluntary fixed-end contractions of human tibialis anterior (TA) and whether reducing TA's activation level after active shortening could reduce rFD. Methods: Ten participants performed fixed-end dorsiflexion contractions to a low, moderate or high level while electromyography (EMG), dorsiflexion Force and TA ultrasound images were recorded. Contractions were Force- or EMG-matched and after the low or high contraction level was attained, participants respectively increased or decreased their Force/EMG to a moderate level. Participants also performed moderate level contractions while the TA muscle-tendon unit (MTU) was lengthened during the Force/EMG rise to the reference MTU length. Results: Equivalent fascicle shortening over moderate and low to moderate level contractions did not alter EMG (P = 0.45) or dorsiflexion Force (P = 0.47) at the moderate level. Greater initial fascicle shortening magnitudes (1.7 mm; P ≤ 0.01) to the high contraction level did not alter EMG (P = 0.45) or dorsiflexion Force (P = 0.30) at the subsequent moderate level compared with moderate level contractions. TA MTU lengthening during the initial Force/EMG rise reduced TA fascicle shortening (−2.5 mm; P ≤ 0.01), which reduced EMG (−3.9% MVC; P < 0.01) and increased dorsiflexion Force (3.7% MVC; P < 0.01) at the moderate level compared with fixed-end moderate level contractions. Conclusion: rFD is present during fixed-end dorsiflexion contractions because fascicles actively shorten as Force/EMG increases and rFD can be reduced by reducing the effective MTU compliance. A reduction in muscle activation level also reduces rFD by potentially triggering Residual Force enhancement-related mechanisms as Force drops and some fascicles actively lengthen.
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shortening induced Residual Force depression in humans
Journal of Applied Physiology, 2019Co-Authors: Jackey Chen, Daniel Hahn, Geoffrey A PowerAbstract:When an isometric muscle contraction is immediately preceded by an active shortening contraction, a reduction in steady-state isometric Force is observed relative to an isometric reference contract...
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Residual Force enhancement contributes to increased performance during stretch shortening cycles of human plantar flexor muscles in vivo
Journal of Biomechanics, 2018Co-Authors: Daniel Hahn, Timotheus N RiedelAbstract:Abstract It is well known that muscular Force production is history-dependent, which results in enhanced (RFE) and depressed (RFD) steady-state Forces after stretching and shortening, respectively. However, it remains unclear if Force-enhancing mechanisms can contribute to increased performance during in vivo stretch-shortening cycles (SSCs) of human locomotor muscles. The purpose of this study was to investigate whether RFE-related mechanisms contribute to enhanced Force and power output during SSCs of the human plantar flexor muscles. Net ankle torques of fourteen participants were measured during and after pure isometric, pure stretch, pure shortening, and SSC contractions when the triceps surae muscles were electrically stimulated at a submaximal level that resulted in 30% of their maximum isometric torque. Dynamic contractions were performed over an amplitude of 15°, from 5° plantar flexion to 10° dorsiflexion, at a speed of 120° s−1. External ankle work during shortening was 11.6% greater during SSCs compared to pure shortening contractions (p = .003). Additionally, RFD after SSCs (8.6%) was reduced compared to RFD after pure shortening contractions (12.0%; p
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Residual Force enhancement during multi joint leg extensions at joint angle configurations close to natural human motion
Journal of Biomechanics, 2016Co-Authors: Florian Kurt Paternoster, Wolfgang Seiberl, Daniel Hahn, Ansgar SchwirtzAbstract:The isometric steady-state Forces following lengthening are greater than those produced at the same muscle length and activation level but without prior lengthening. Although Residual Force enhancement (RFE) has been investigated across a range of conditions, its relevance for daily human movement is still poorly understood. We aimed to study RFE in a setup imitating daily activity, i.e., submaximal activation of the lower extremity's muscles with slightly flexed knee joints comparable to human walking. A motor-driven leg press dynamometer was used for randomly arranged purely isometric and isometric-eccentric-isometric contractions. Thirteen subjects performed multi-joint leg extensions, which were feedback-controlled at 30% of maximum voluntary vastus lateralis activation. Isometric-eccentric-isometric contractions incorporated a stretch from 30° to 50° knee flexion, while isometric contractions were performed at 50° knee flexion. Isometric contractions following stretch and purely isometric reference contractions were performed at 50° knee flexion. Kinematics, Forces, and muscular activity were measured using 3D optical motion tracking, Force plates, and surface EMG of 9 lower limb muscles of the right leg and joint torques were calculated by inverse dynamics. Variables of standardization (EMG, joint angles) showed no differences between contraction conditions. Eight of 13 subjects showed RFE of up to 24.8±32.5% for external Forces and joint torques. Because the remaining 5 non-responders failed to produce enhanced Forces during the stretch, we believe that RFE is functionally relevant for muscle function comparable to everyday human motion but only if there is enhanced Force during stretch that sufficiently triggers mechanisms underlying RFE.
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Residual Force enhancement in humans current evidence and unresolved issues
Journal of Electromyography and Kinesiology, 2015Co-Authors: Wolfgang Seiberl, Geoffrey A Power, Daniel HahnAbstract:Abstract Following an active lengthening contraction while maintaining activation constant, isometric Force is elevated above that of a purely isometric contraction at the same final muscle length. This fundamental property of skeletal muscle is referred to as Residual Force enhancement. While the contractile mechanisms of Residual Force enhancement are still highly-debated, from an applied perspective this review focuses on the potential physiological relevance of Residual Force enhancement in human movement. Moreover, this work aims to highlight commonalities as well as discrepancies to well accepted history-dependent properties analyzed in muscle preparations. This will help to identify aspects of Residual Force enhancement in vivo requiring further research. In the first part of this review a phenomenological description of Residual Force enhancement in vivo as observed in numerous experiments will be presented. These include voluntary as well as electrically stimulated contractions of isolated small muscles up to coordinated multi-joint contractions of humans at maximal and submaximal activation level. Secondly, we show that Residual Force enhancement during voluntary contractions is not necessarily purely mechanical in nature, but also influenced by neural control in terms of more efficient activation, increased excitability, saving of metabolic energy, and maintains muscle function in acutely and chronically altered neuromuscular states like fatigue, muscle damage and aging. Finally, this review focuses on implications of Residual Force enhancement for human movement and future directions for research on Residual Force enhancement in the context of human motor control.
Dilson E Rassier - One of the best experts on this subject based on the ideXlab platform.
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Force enhancement after stretch of isolated myofibrils is increased by sarcomere length non-uniformities.
Scientific reports, 2020Co-Authors: Ricarda M Haeger, Dilson E RassierAbstract:When a muscle is stretched during a contraction, the resulting steady-state Force is higher than the isometric Force produced at a comparable sarcomere length. This phenomenon, also referred to as Residual Force enhancement, cannot be readily explained by the Force-sarcomere length relation. One of the most accepted mechanisms for the Residual Force enhancement is the development of sarcomere length non-uniformities after an active stretch. The aim of this study was to directly investigate the effect of non-uniformities on the Force-producing capabilities of isolated myofibrils after they are actively stretched. We evaluated the effect of depleting a single A-band on sarcomere length non-uniformity and Residual Force enhancement. We observed that sarcomere length non-uniformity was effectively increased following A-band depletion. Furthermore, isometric Forces decreased, while the percent Residual Force enhancement increased compared to intact myofibrils (5% vs. 20%). We conclude that sarcomere length non-uniformities are partially responsible for the enhanced Force production after stretch.
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Residual Force enhancement is regulated by titin in skeletal and cardiac myofibrils
The Journal of Physiology, 2017Co-Authors: Nabil Shalabi, Anabelle S Cornachione, Felipe De Souza Leite, Srikar Vengallatore, Dilson E RassierAbstract:KEY POINTS When a skeletal muscle is stretched while it contracts, the muscle produces a relatively higher Force than the Force from an isometric contraction at the same length: a phenomenon referred to as Residual Force enhancement. Residual Force enhancement is puzzling because it cannot be directly explained by the classical Force-length relationship and the sliding filament theory of contraction, the main paradigms in the muscle field. We used custom-built instruments to measure Residual Force enhancement in skeletal myofibrils, and, for the first time, in cardiac myofibrils. Our data report that Residual Force enhancement is present in skeletal muscles, but not cardiac muscles, and is regulated by the different isoforms of the titin protein filaments. ABSTRACT When a skeletal muscle contracts isometrically, the muscle produces a Force that is relative to the final isometric sarcomere length (SL). However, when the same final SL is reached by stretching the muscle while it contracts, the muscle produces a relatively higher Force: a phenomenon commonly referred to as Residual Force enhancement. In this study, we investigated Residual Force enhancement in rabbit skeletal psoas myofibrils and, for the first time, cardiac papillary myofibrils. A custom-built atomic Force microscope was used in experiments that stretched myofibrils before and after inhibiting myosin and actin interactions to determine whether the different cardiac and skeletal titin isoforms regulate Residual Force enhancement. At SLs ranging from 2.24 to 3.13 μm, the skeletal myofibrils enhanced the Force by an average of 9.0%, and by 29.5% after hindering myosin and actin interactions. At SLs ranging from 1.80 to 2.29 μm, the cardiac myofibrils did not enhance the Force before or after hindering myosin and actin interactions. We conclude that Residual Force enhancement is present only in skeletal muscles and is dependent on the titin isoforms.
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Residual Force depression in single sarcomeres is abolished by mgadp induced activation
Scientific Reports, 2015Co-Authors: Neal Trecarten, Fabio C Minozzo, Felipe De Souza Leite, Dilson E RassierAbstract:The mechanisms behind the shortening-induced Force depression commonly observed in skeletal muscles remain unclear, but have been associated with sarcomere length non-uniformity and/or crossbridge inhibition. The purpose of this study was twofold: (i) to evaluate if Force depression is present in isolated single sarcomeres, a preparation that eliminates sarcomere length non-uniformities and (ii) to evaluate if Force depression is inhibited when single sarcomeres are activated with MgADP, which biases crossbridges into a strongly-bound state. Single sarcomeres (n = 16) were isolated from rabbit psoas myofibrils using two micro-needles (one compliant, one rigid), piercing the sarcomere externally adjacent to the Z-lines. The sarcomeres were contracted isometrically and subsequently shortened, in both Ca(2+)- and MgADP-activating solutions. Shortening in Ca(2+)-activated samples resulted in a 27.44 ± 9.04% Force depression when compared to isometric contractions produced at similar final sarcomere lengths (P < 0.001). There was no Force depression in MgADP-activated sarcomeres (Force depression = -1.79 ± 9.69%, P = 0.435). These results suggest that Force depression is a sarcomeric property, and that is associated with an inhibition of myosin-actin interactions.
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Residual Force enhancement in skeletal muscles: one sarcomere after the other
Journal of Muscle Research and Cell Motility, 2012Co-Authors: Dilson E RassierAbstract:The Force–length relation is one of the most prominent features of striated muscles, and predicts that the Force produced by a fully activated muscle is proportional to the overlap between myosin and actin filaments within sarcomeres. However, there are situations in which the Force–length relation deviates from predictions based purely on filament overlap. Notably, stretch of activated skeletal muscles induces a long-lasting increase in Force, which is larger than the Force produced during isometric contractions at a similar length. The mechanism behind this Residual Force enhancement and deviations from the original Force–length relation are unknown, generating heated debate in the literature. We performed a series of experiments with short segments of myofibrils and isolated sarcomeres to investigating the mechanisms of the Residual Force enhancement and the Force length-relation. In this paper, evidence will be presented showing that Force enhancement is caused by: (i) half-sarcomere non-uniformities, and (ii) a sarcomeric component, which may be associated with Ca^2+-induced stiffness of titin molecules. These mechanisms have large implications for understanding the basic mechanisms of muscle contraction.
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the mechanisms of the Residual Force enhancement after stretch of skeletal muscle non uniformity in half sarcomeres and stiffness of titin
Proceedings of The Royal Society B: Biological Sciences, 2012Co-Authors: Dilson E RassierAbstract:When activated skeletal muscles are stretched, the Force increases significantly. After the stretch, the Force decreases and reaches a steady-state level that is higher than the Force produced at the corresponding length during purely isometric contractions. This phenomenon, referred to as Residual Force enhancement, has been observed for more than 50 years, but the mechanism remains elusive, generating considerable debate in the literature. This paper reviews studies performed with single muscle fibres, myofibrils and sarcomeres to investigate the mechanisms of the stretch-induced Force enhancement. First, the paper summarizes the characteristics of Force enhancement and early hypotheses associated with non-uniformity of sarcomere length. Then, it reviews new evidence suggesting that Force enhancement can also be associated with sarcomeric structures. Finally, this paper proposes that Force enhancement is caused by: (i) half-sarcomere non-uniformities that will affect the levels of passive Forces and overlap between myosin and actin filaments, and (ii) a Ca2+-induced stiffness of titin molecules. These mechanisms are compatible with most observations in the literature, and can be tested directly with emerging technologies in the near future.
Atsuki Fukutani - One of the best experts on this subject based on the ideXlab platform.
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differences in stretch shortening cycle and Residual Force enhancement between muscles
Journal of Biomechanics, 2020Co-Authors: Atsuki Fukutani, Walter HerzogAbstract:Abstract It has been suggested that cross bridge kinetics and Residual Force enhancement (RFE) affect Force in the stretch-shortening cycle (SSC). Because cross bridge kinetics and titin isoforms, which are thought to be related to RFE, differ between muscles, the SSC effect may be also muscle-dependent. Thus, we compared the SSC effect between psoas and soleus muscles, which have a distinct fiber type distribution and different titin isoforms. Four tests (SSC, SSC control, RFE, RFE control) were conducted using isolated, skinned fibers of psoas and soleus. In the SSC tests, fibers were activated at an average sarcomere length of 2.4 μm, stretched to 3.0 μm, and shortened to 2.4 μm. In the SSC control tests, fibers were activated at an average sarcomere length of 3.0 μm and then shortened to 2.4 μm. The relative increase in mechanical work obtained during shortening between tests was defined as the SSC effect. In the RFE tests, fibers were activated at an average sarcomere length of 2.4 μm and then stretched to 3.0 μm, while the RFE control tests consisted of an isometric contraction at 3.0 μm. The difference in steady-state isometric Force between tests was defined as RFE. The SSC effect was greater in soleus than in psoas, while the RFE was the same for both muscles. Since the SSC effect was greater in soleus, while the RFE was the same, the observed greater SSC effect is probably not directly caused by RFE, but may be related to differences in cross bridge kinetics.
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Current Understanding of Residual Force Enhancement: Cross-Bridge Component and Non-Cross-Bridge Component.
International journal of molecular sciences, 2019Co-Authors: Atsuki Fukutani, Walter HerzogAbstract:Muscle contraction is initiated by the interaction between actin and myosin filaments. The sliding of actin filaments relative to myosin filaments is produced by cross-bridge cycling, which is governed by the theoretical framework of the cross-bridge theory. The cross-bridge theory explains well a number of mechanical responses, such as isometric and concentric contractions. However, some experimental observations cannot be explained with the cross-bridge theory; for example, the increased isometric Force after eccentric contractions. The steady-state, isometric Force after an eccentric contraction is greater than that attained in a purely isometric contraction at the same muscle length and same activation level. This well-acknowledged and universally observed property is referred to as Residual Force enhancement (rFE). Since rFE cannot be explained by the cross-bridge theory, alternative mechanisms for explaining this Force response have been proposed. In this review, we introduce the basic concepts of sarcomere length non-uniformity and titin elasticity, which are the primary candidates that have been used for explaining rFE, and discuss unresolved problems regarding these mechanisms, and how to proceed with future experiments in this exciting area of research.
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does stretching velocity affect Residual Force enhancement
Journal of Biomechanics, 2019Co-Authors: Atsuki Fukutani, T R Leonard, Walter HerzogAbstract:Abstract It is thought that the magnitude of Residual Force enhancement (RFE) is not affected by stretch velocity. However, the range of stretch velocities studied in previous investigations has been limited to slow and moderate velocities. High velocities of muscle stretching are associated with a loss of Force and incomplete cross-bridge attachment to actin, thus creating a unique set of eccentric conditions referred to as slippage. The purpose of this study was to extend the relationship between stretch velocity and RFE to high velocities. We hypothesized that slippage at high velocities might affect RFE. We stretched cat soleus muscles for 4 mm to the plateau of the Force-length relationship at speeds of 2, 4, 8, 16, 32, 64 mm/s to induce RFE, and slippage for the fastest condition. For each RFE test, a corresponding isometric reference test was conducted. Residual Force enhancement was quantified as the relative increase in isometric steady state Force between the experimental stretch and the isometric reference tests. Residual Force enhancement was similar for all stretch speeds, as expected, with the exception of the fastest speed (64 mm/s), which was associated with slippage and no significant RFE. These results suggest that if stretch speeds are too fast, and are associated with slippage, RFE is abolished. We conclude from these findings that proper cross-bridge engagement is required during eccentric muscle action to produce RFE.
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Residual Force enhancement is attenuated in a shortening magnitude dependent manner
Medicine and Science in Sports and Exercise, 2018Co-Authors: Atsuki Fukutani, Walter HerzogAbstract:INTRODUCTION The isometric Force attained after active stretch is greater than that attained in a purely isometric contraction. This property is referred to as Residual Force enhancement (RFE). Although RFE is thought to contribute to the enhanced Force and power in stretch-shortening cycles (SSCs), it is unclear whether shortening that occurs after active stretch eliminates the RFE induced by active stretch. Therefore, we evaluated the influence of shortening on RFE. METHODS Skinned rabbit soleus fibers (N = 43) were used for all tests. Residual Force enhancement was compared between the stretch-only condition and the SSC condition. In the SSC conditions, shortening magnitudes were either 1% or 12.5% of fiber length. The final muscle length where RFE was evaluated was 3 μm for all trials. In the SSCs with 12.5% shortening, the isometric Force before and after the SSC was also compared. RESULTS Residual Force enhancement was similar between the stretch only (7.9% ± 2.7%) and the SSC with 1% shortening condition (7.1% ± 2.9%) (P = 0.316), whereas RFE was smaller in the SSC with 12.5% shortening (3.5% ± 2.4%) than the stretch-only condition (8.4% ± 2.5%) (P < 0.001). The isometric Forces after SSCs (0.437 ± 0.103 mN) were greater than those measured before the SSC (0.422 ± 0.104 mN) (P = 0.016). CONCLUSIONS Residual Force enhancement was preserved when the shortening magnitude was small and was reduced when the shortening magnitude was large. Although RFE was attenuated by the 12.5% shortening, RFE was still observed, suggesting that RFE can contribute to SSCs.
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Residual Force Enhancement Is Preserved for Conditions of Reduced Contractile Force.
Medicine and science in sports and exercise, 2018Co-Authors: Atsuki Fukutani, Walter HerzogAbstract:INTRODUCTION The isometric muscle Force attained after active stretch is greater than that attained in a purely isometric contraction. This property is referred to as Residual Force enhancement (RFE). Because RFE is thought to be caused by a titin-based passive Force, it should be preserved in reduced contractile Force states. Therefore, we evaluated the magnitude of RFE in normal and reduced contractile Force states. METHODS Skinned fibers of rabbit psoas and soleus (N = 60) were used in all experiments. Reduced contractile Force states were induced (i) by using a low Ca concentration (N = 30), (ii) by adding 20 mM butanedione monoxime (N = 15), and (iii) by lowering the pH level (N = 15). Force enhancement and reference isometric tests were conducted for each condition. In the Force enhancement tests, fibers were actively stretched from an average sarcomere length of 2.4 to 3.0 μm. The isometric Force attained 15 s after the end of stretching was used for analysis. In the isometric reference tests, fibers were activated isometrically at an average sarcomere length of 3.0 μm, and the Force at steady state was used for analysis. The absolute and relative magnitudes of RFE were calculated. RESULTS The absolute RFE was the same for the normal and reduced contractile Force states. Because the isometric reference Force was smaller in the reduced contractile Force states, the relative RFE was greater in the reduced contractile Force than the normal states for all conditions. CONCLUSION RFE was preserved in the reduced contractile Force states.