The sarcomere length-tension relation in skeletal muscle.

Keurs, H E ter; Iwazumi, Tatsuo; Pollack, Gerald H.

doi:10.1085/jgp.72.4.565

Cited by 155 publications

(135 citation statements)

References 28 publications

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“…Although the levels of nonuniformities and A-band displacements are larger during the experiment shown in the left, it is also present in the experiment shown in the right. muscle fibers (10,12,17,46) and myofibrils (41) and well described by the predictions of overlap between myosin and actin filaments (32,40). The forces produced by single sarcomeres in the current study are in the range of those observed with myofibrils (23,35,36), single fibers (6), and single sarcomeres (32).…”

Section: Discussionsupporting

confidence: 77%

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

Rassier

Pavlov

2012

American Journal of Physiology-Cell Physiology

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Rassier DE, Pavlov I. Force produced by isolated sarcomeres and half-sarcomeres after an imposed stretch. Am J Physiol Cell Physiol 302: C240 -C248, 2012. First published October 12, 2011 doi:10.1152/ajpcell.00208.2011.-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 ϭ 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 m·s Ϫ1 ·SL Ϫ1 ) 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 Ϯ 0.78%), and 28 sarcomeres did not show force enhancement (Ϫ0.54 Ϯ 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 halfsarcomere lengths, which significantly increases the level of force enhancement. myofibrils; myosin; titin; cross-bridges THE NOTION OF SARCOMERE LENGTH (SL) nonuniformity has played a significant role in the study of muscle contraction. It has been directly associated with several experimental observations, including the force "creep" observed at long muscle lengths (11,16), the relation between force and filament overlap (11,17,19), the kinetics of force development and relaxation (9, 43), and the effects of muscle stretch in force production (7,8,13,18,36,37). The latest is particularly important: when a stretch is applied to skeletal muscles during activation, force increases significantly while the energy consumption decreases (1, 30). The force remains elevated after the stretch to reach a steady-state level that is higher than that produced during isometric contractions at corresponding lengths (8,24,38). The mechanisms responsible for this "residual force enhancement" remain elusive and there is substantial disagreement in the literature...

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Section: Discussionsupporting

confidence: 77%

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

Rassier

Pavlov

2012

American Journal of Physiology-Cell Physiology

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“…Furthermore, the experimental points do not deviate by more than about 0-2 4um from the theoretical curve based on the amount of filament overlap. Considering that the average sarcomere length has been measured in the relaxed fibre prior to, and after activation, and taking into account that most conservative estimates indicate that sarcomeres in intact muscle fibres could shorten by up to 0-15 ,sm soon after force rises during tetanic stimulation (ter Keurs, Iwazumi & Pollack, 1978), our results strongly favour the explanation given to such force-length relations by Gordon et al (1966).…”

Section: Sarcomere Length-tension Relationssupporting

confidence: 65%

Effects of sarcomere length on the force—pCa relation in fast‐ and slow‐twitch skinned muscle fibres from the rat

Stephenson¹,

Williams²

1982

The Journal of Physiology

230

152

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SUMMARY1. Steady-state force-pCa relations were determined for mechanically skinned fibres of fast-and slow-twitch rat skeletal muscle, extensor digitorum longus (e.d.l.) and soleus respectively, at varied sarcomere lengths and temperatures (3-35 'C).2. This relation was different for the two fibre types at all sarcomere lengths, with soleus fibres having lower Ca2+ concentration threshold for activation and requiring a wider Ca2+ concentration range to reach force saturation.3. An increase in sarcomere length within the range 2-2-3-6 ,um reversibly shifted the steady-state force-pCa curves for both fast-and slow-twitch fibres toward lower Ca2+ without affecting the steepness of the curves.4. The results are consistent with the idea that the sensitivity of the contractile apparatus to Ca2+ is increased with increasing sarcomere length.5. The change in apparent Ca2+ sensitivity (measured as the change in pCa corresponding to 50 % Ca-activated force (ApCa50)) was approximately proportional to the change in sarcomere length (ASL) at all temperatures for both types of muscle fibre.6. The proportionality coefficient (ApCa50/ASL) was higher for slow-twitch fibres than for fast-twitch fibres by a factor of 1P5-2-0 at all temperatures investigated.7. The force-pCa relation was less affected by changes in sarcomere length at lower (3-5 'C) than at higher temperatures (22-35 'C).8. The sarcomere length-maximum force relation obtained with skinned fibres for sarcomere lengths between 2 10 and 4 05 jsm was similar for both fibre types at all temperatures despite large temperature dependent variations in maximum Caactivated force response. Maximum force decreased linearly to zero between ca. 2-8 and 3.95 /sm; remained high and essentially constant between ca. 2-40 and 2-80 him, and decreased significantly below 2-40 ,um.9. Myofilament-generated tension oscillations produced by partially activated soleus skinned fibres are highly length dependent, disappearing completely when sarcomere length is increased above 3-15 /sm.

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“…Sarcomere length was measured with the laser diffraction technique (ter Keurs et al 1978). A He-Ne laser beam (633 nm wavelength) was projected perpendicular to the axis of the fibre, and the sarcomere length was established in a clear region of the fibre.…”

Section: Q 2005 the Royal Societymentioning

confidence: 99%

Modulation of passive force in single skeletal muscle fibres

2005

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In this study, we investigated the effects of activation and stretch on the passive forcesarcomere length relationship in skeletal muscle. Single fibres from the lumbrical muscle of frogs were placed at varying sarcomere lengths on the descending limb of the forcesarcomere length relationship, and tetanic contractions, active stretches and passive stretches (amplitudes of ca 10% of fibre length at a speed of 40% fibre length/s) were performed. The passive forces following stretch of an activated fibre were higher than the forces measured after isometric contractions or after stretches of a passive fibre at the corresponding sarcomere length. This effect was more pronounced at increased sarcomere lengths, and the passive force-sarcomere length relationship following active stretch was shifted upwards on the force axis compared with the corresponding relationship obtained following isometric contractions or passive stretches. These results provide strong evidence for an increase in passive force that is mediated by a length-dependent combination of stretch and activation, while activation or stretch alone does not produce this effect. Based on these results and recently published findings of the effects of Ca 2C on titin stiffness, we propose that the observed increase in passive force is caused by the molecular spring titin.

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The sarcomere length-tension relation in skeletal muscle.

Cited by 155 publications

References 28 publications

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

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

Effects of sarcomere length on the force—pCa relation in fast‐ and slow‐twitch skinned muscle fibres from the rat

Modulation of passive force in single skeletal muscle fibres

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