scholarly journals The mechanisms of the residual force enhancement after stretch of skeletal muscle: non-uniformity in half-sarcomeres and stiffness of titin

2012 ◽  
Vol 279 (1739) ◽  
pp. 2705-2713 ◽  
Author(s):  
Dilson E. Rassier
Keyword(s):  
Skeletal Muscles ◽  
Sarcomere Length ◽  
State Level ◽  
Muscle Fibres ◽  
Force Enhancement ◽  
Considerable Debate ◽  
Residual Force ◽  
Residual Force Enhancement ◽  
Near Future ◽  
New Evidence

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 Ca 2+ -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.

scholarly journals Residual force enhancement in human skeletal muscles: A systematic review and meta-analysis

2021 ◽  
Author(s):  
Daiani de Campos ◽  
Lucas B.R. Orssatto ◽  
Gabriel S. Trajano ◽  
Walter Herzog ◽  
Heiliane de Brito Fontana
Keyword(s):  
Systematic Review ◽  
Skeletal Muscles ◽  
Meta Analysis ◽  
Force Enhancement ◽  
Residual Force ◽  
Residual Force Enhancement ◽  
Human Skeletal Muscles

scholarly journals Force enhancement after stretch of isolated myofibrils is increased by sarcomere length non-uniformities

2020 ◽  
Vol 10 (1) ◽  
Author(s):  
Ricarda M. Haeger ◽  
Dilson E. Rassier
Keyword(s):  
Steady State ◽  
Sarcomere Length ◽  
Isometric Force ◽  
Force Production ◽  
Force Enhancement ◽  
Residual Force ◽  
Residual Force Enhancement ◽  
State Force ◽  
Isometric Forces

AbstractWhen 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.

Residual force enhancement and force depression in human single muscle fibres

2019 ◽  
Vol 91 ◽  
pp. 164-169 ◽  
Author(s):  
Rhiannan A.M. Pinnell ◽  
Parastoo Mashouri ◽  
Nicole Mazara ◽  
Erin Weersink ◽  
Stephen H.M. Brown ◽  
...  
Keyword(s):  
Muscle Fibres ◽  
Single Muscle ◽  
Force Enhancement ◽  
Force Depression ◽  
Residual Force ◽  
Residual Force Enhancement

scholarly journals Effect of Active Lengthening and Shortening on Small-Angle X-ray Reflections in Skinned Skeletal Muscle Fibres

2021 ◽  
Vol 22 (16) ◽  
pp. 8526
Author(s):  
Venus Joumaa ◽  
Ian C. Smith ◽  
Atsuki Fukutani ◽  
Timothy R. Leonard ◽  
Weikang Ma ◽  
...  
Keyword(s):  
Steady State ◽  
Small Angle ◽  
Isometric Contraction ◽  
Sarcomere Length ◽  
Force Enhancement ◽  
X Ray ◽  
Cross Bridge ◽  
Residual Force ◽  
Residual Force Enhancement ◽  
Cross Bridges

Our purpose was to use small-angle X-ray diffraction to investigate the structural changes within sarcomeres at steady-state isometric contraction following active lengthening and shortening, compared to purely isometric contractions performed at the same final lengths. We examined force, stiffness, and the 1,0 and 1,1 equatorial and M3 and M6 meridional reflections in skinned rabbit psoas bundles, at steady-state isometric contraction following active lengthening to a sarcomere length of 3.0 µm (15.4% initial bundle length at 7.7% bundle length/s), and active shortening to a sarcomere length of 2.6 µm (15.4% bundle length at 7.7% bundle length/s), and during purely isometric reference contractions at the corresponding sarcomere lengths. Compared to the reference contraction, the isometric contraction after active lengthening was associated with an increase in force (i.e., residual force enhancement) and M3 spacing, no change in stiffness and the intensity ratio I1,1/I1,0, and decreased lattice spacing and M3 intensity. Compared to the reference contraction, the isometric contraction after active shortening resulted in decreased force, stiffness, I1,1/I1,0, M3 and M6 spacings, and M3 intensity. This suggests that residual force enhancement is achieved without an increase in the proportion of attached cross-bridges, and that force depression is accompanied by a decrease in the proportion of attached cross-bridges. Furthermore, the steady-state isometric contraction following active lengthening and shortening is accompanied by an increase in cross-bridge dispersion and/or a change in the cross-bridge conformation compared to the reference contractions.

scholarly journals Residual force enhancement exceeds the isometric force at optimal sarcomere length for optimized stretch conditions

2008 ◽  
Vol 105 (2) ◽  
pp. 457-462 ◽  
Author(s):  
Eun-Jeong Lee ◽  
Walter Herzog
Keyword(s):  
Steady State ◽  
Sarcomere Length ◽  
Isometric Force ◽  
Passive Component ◽  
Force Enhancement ◽  
Single Fibers ◽  
Length Relationship ◽  
Residual Force ◽  
Residual Force Enhancement ◽  
Isometric Forces

Residual force enhancement (FE) following stretch of an activated muscle is a well accepted property of skeletal muscle contraction. However, the mechanism underlying FE remains unknown. A crucial assumption on which some proposed mechanisms are based is the idea that forces in the enhanced state cannot exceed the steady-state isometric force at a sarcomere length associated with optimal myofilament overlap. Although there are a number of studies in which forces in the enhanced state were compared with the corresponding isometric forces on the plateau of the force-length relationship, these studies either did not show enhanced forces above the plateau or, if they did, they lacked measurements of sarcomere lengths confirming the plateau region. Here, we revisited this question by optimizing stretch conditions and measuring the average sarcomere lengths in isolated fibers, and we found that FE exceeded the maximal isometric reference force obtained at the plateau of the force-length relationship consistently (mean ± SD: 4.8 ± 2.1%) and by up to 10%. When subtracting the passive component of FE from the total FE, the enhanced forces remained greater than the isometric plateau force (mean ± SD: 4.3 ± 2.0%). Calcium-induced increases in passive forces, known to be present in single fibers and myofibrils, are too small to account for the FE observed here. We conclude that FE cannot be explained exclusively with a stretch-induced development of sarcomere length nonuniformities, that FE in single fibers may be associated with the recruitment of additional contractile force, and that isometric steady-state forces in the enhanced state are not uniquely determined by sarcomere lengths.

scholarly journals Residual force enhancement after stretch of contracting frog single muscle fibers.

1982 ◽  
Vol 80 (5) ◽  
pp. 769-784 ◽  
Author(s):  
K A Edman ◽  
G Elzinga ◽  
M I Noble
Keyword(s):  
Sarcomere Length ◽  
Rana Temporaria ◽  
Isometric Force ◽  
Tibialis Anterior Muscle ◽  
Control Level ◽  
Absolute Magnitude ◽  
Force Level ◽  
Force Enhancement ◽  
Residual Force ◽  
Residual Force Enhancement

Single fibers from the tibialis anterior muscle of Rana temporaria at 0.8-3.8 degrees C were subjected to long tetani lasting up to 8 s. Stretch of the fiber early in the tetanus caused an enhancement of force above the isometric control level which decayed only slowly and stayed higher throughout the contraction. This residual enhancement was uninfluenced by velocity of stretch and occurred only on the descending limb of the length-tension curve. The absolute magnitude of the effect increased with sarcomere length to a maximum at approximately 2.9 micrometers and then declined. The phenomenon was further characterized by its dependence on the amplitude of stretch. The final force level reached after stretch was usually higher than the isometric force level corresponding to the starting length of the stretch. The possibility that the phenomenon was caused by nonuniformity of sarcomere length along the fiber was examined by (a) laser diffraction studies that showed sarcomere stretch at all locations and (b) studies of 9-10 segments of approximately 0.6-0.7 mm along the entire fiber, which all elongated during stretch. Length-clamped segments showed residual force enhancement after stretch when compared with the tetanus produced by the same segment held at the short length as well as at the long length. It is concluded that residual force enhancement after stretch is a property shown by all individual segments along the fiber.

scholarly journals The role of sarcomere length non-uniformities in residual force enhancement of skeletal muscle myofibrils

2016 ◽  
Vol 3 (3) ◽  
pp. 150657 ◽  
Author(s):  
Kaleena Johnston ◽  
Azim Jinha ◽  
Walter Herzog
Keyword(s):  
Skeletal Muscle ◽  
Sarcomere Length ◽  
Isometric Force ◽  
Myosin Filament ◽  
Rabbit Muscle ◽  
Force Enhancement ◽  
Length Relationship ◽  
Reference Length ◽  
Residual Force ◽  
Residual Force Enhancement

The sarcomere length non-uniformity theory (SLNT) is a widely accepted explanation for residual force enhancement (RFE). RFE is the increase in steady-state isometric force following active muscle stretching. The SLNT predicts that active stretching of a muscle causes sarcomere lengths (SL) to become non-uniform, with some sarcomeres stretched beyond actin–myosin filament overlap (popping), causing RFE. Despite being widely known, this theory has never been directly tested. We performed experiments on isolated rabbit muscle myofibrils ( n  = 12) comparing SL non-uniformities for purely isometric reference contractions (I-state) and contractions following active stretch producing RFE (FE-state). Myofibrils were activated isometrically along the descending limb of the force–length relationship (mean ± 1 standard deviation (SD) = 2.8 ± 0.3 µm sarcomere −1 ). Once the I-state was reached, myofibrils were shortened to an SL on the plateau of the force–length relationship (2.4 µm sarcomere −1 ), and then were actively stretched to the reference length (2.9 ± 0.3 µm sarcomere −1 ). We observed RFE in all myofibrils (39 ± 15%), and saw varying amounts of non-uniformity (1 SD = 0.9 ± 0.5 µm) that was not significantly correlated with the amount of RFE, but through pairwise comparisons was found to be significantly greater than the non-uniformity measured for the I-state (0.7 ± 0.4 µm). Three myofibrils exhibited no increase in non-uniformity. Active stretching was accompanied by sarcomere popping in four myofibrils, and seven had popped sarcomeres in the I-state. These results suggest that, while non-uniformities are present with RFE, they are also present in the I-state. Furthermore, non-uniformity is not associated with the magnitude of RFE, and myofibrils that had no increase in non-uniformity with stretch still showed normal RFE. Therefore, it appears that SL non-uniformity is a normal associate of muscle contraction, but does not contribute to RFE following active stretching of isolated skeletal muscle myofibrils.

Force produced by isolated sarcomeres and half-sarcomeres after an imposed stretch

2012 ◽  
Vol 302 (1) ◽  
pp. C240-C248 ◽  
Author(s):  
Dilson E. Rassier ◽  
Ivan Pavlov
Keyword(s):  
Isometric Contraction ◽  
Sarcomere Length ◽  
Psoas Muscle ◽  
Force Measurements ◽  
Force Enhancement ◽  
In Series ◽  
Photodiode Array ◽  
Residual Force ◽  
Residual Force Enhancement ◽  
Induced Changes

When a stretch is imposed to activated muscles, there is a residual force enhancement that persists after the stretch; the force is higher than that produced during an isometric contraction in the corresponding length. The mechanisms behind the force enhancement remain elusive, and there is disagreement if it represents a sarcomeric property, or if it is associated with length nonuniformities among sarcomeres and half-sarcomeres. The purpose of this study was to investigate the effects of stretch on single sarcomeres and myofibrils with predetermined numbers of sarcomeres ( n = 2, 3. . . , 8) isolated from the rabbit psoas muscle. Sarcomeres were attached between two precalibrated microneedles for force measurements, and images of the preparations were projected onto a linear photodiode array for measurements of half-sarcomere length (SL). Fully activated sarcomeres were subjected to a stretch (5–10% of initial SL, at a speed of 0.3 μm·s−1·SL−1) after which they were maintained isometric for at least 5 s before deactivation. Single sarcomeres showed two patterns: 31 sarcomeres showed a small level of force enhancement after stretch (10.46 ± 0.78%), and 28 sarcomeres did not show force enhancement (−0.54 ± 0.17%). In these preparations, there was not a strong correlation between the force enhancement and half-sarcomere length nonuniformities. When three or more sarcomeres arranged in series were stretched, force enhancement was always observed, and it increased linearly with the degree of half-sarcomere length nonuniformities. The results show that the residual force enhancement has two mechanisms: 1) stretch-induced changes in sarcomeric structure(s); we suggest that titin is responsible for this component, and 2) stretch-induced nonuniformities of half-sarcomere lengths, which significantly increases the level of force enhancement.

scholarly journals Calcium sensitivity of residual force enhancement in rabbit skinned fibers

2014 ◽  
Vol 307 (4) ◽  
pp. C395-C401 ◽  
Author(s):  
V. Joumaa ◽  
W. Herzog
Keyword(s):  
Lattice Spacing ◽  
Sarcomere Length ◽  
Isometric Force ◽  
Calcium Sensitivity ◽  
Skinned Fibers ◽  
Passive Force ◽  
Force Enhancement ◽  
Osmotic Compression ◽  
Residual Force ◽  
Residual Force Enhancement

Isometric force after active stretch of muscles is higher than the purely isometric force at the corresponding length. This property is termed residual force enhancement. Active force in skeletal muscle depends on calcium attachment characteristics to the regulatory proteins. Passive force has been shown to influence calcium attachment characteristics, specifically the sarcomere length dependence of calcium sensitivity. Since one of the mechanisms proposed to explain residual force enhancement is the increase in passive force that results from engagement of titin upon activation and stretch, our aim was to test if calcium sensitivity of residual force enhancement was different from that of its corresponding purely isometric contraction and if such a difference was related to the molecular spring titin. Force-pCa curves were established in rabbit psoas skinned fibers for reference and residual force-enhanced states at a sarcomere length of 3.0 μm 1) in a titin-intact condition, 2) after treatment with trypsin to partially eliminate titin, and 3) after treatment with trypsin and osmotic compression with dextran T-500 to decrease the lattice spacing in the absence of titin. The force-pCa curves of residual force enhancement were shifted to the left compared with their corresponding controls in titin-intact fibers, indicating increased calcium sensitivity. No difference in calcium sensitivity was observed between reference and residual force-enhanced contractions in trypsin-treated and osmotically compressed trypsin-treated fibers. Furthermore, calcium sensitivity after osmotic compression was lower than that observed for residual force enhancement in titin-intact skinned fibers. These results suggest that titin-based passive force regulates the increase in calcium sensitivity of residual force enhancement by a mechanism other than reduction of the myofilament lattice spacing.

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