scholarly journals Errors in Predicting Muscle Fiber Lengths from Joint Kinematics Point to the Need to Include Tendon Tension in Computational Neuromuscular Models

2020 ◽  
Author(s):  
Daniel A Hagen ◽  
Francisco J Valero-Cuevas
Keyword(s):  
Muscle Fiber ◽  
Fiber Length ◽  
Functional Relationship ◽  
Parametric Uncertainty ◽  
Muscle Spindles ◽  
Joint Kinematics ◽  
Effective Control ◽  
Golgi Tendon Organs ◽  
Limb Kinematics ◽  
Tendon Tension

Accurate predictions of tendon forces must consider musculotendon mechanics; specifically muscle fiber lengths and velocities. These are either predicted explicitly by simulating musculoskeletal dynamics or approximated from measured limb kinematics. The latter is complicated by the fact that tendon lengths and pennation angles vary with both limb kinematics and tendon tension. We now derive the error in kinematically-approximated muscle fiber lengths as a general equation of muscle geometry and tendon tension. This enables researchers to objectively evaluate this error’s significance—which can reach ~ 80% of the optimal muscle fiber length—with respect to the scientific or clinical question being asked. Although this equation provides a detailed functional relationship between muscle fiber lengths, joint kinematics and tendon tension, the parameters used to characterize musculotendon architecture are subject- and muscle-specific. This parametric uncertainty limits the accuracy of any generic musculoskeletal model that hopes to explain subject-specific phenomena. Nevertheless, the existence of such a functional relationship has profound implications to biological proprioception. These results strongly suggest that tendon tension information (from Golgi tendon organs) is likely integrated with muscle fiber length information (from muscle spindles) at the spinal cord to produce useful estimates of limb configuration to enable effective control of movement.

scholarly journals FINE STRUCTURE OF RAT INTRAFUSAL MUSCLE FIBERS

1971 ◽  
Vol 51 (1) ◽  
pp. 83-103 ◽  
Author(s):  
William K. Ovalle
Keyword(s):  
Muscle Fiber ◽  
Muscle Fibers ◽  
Muscle Spindles ◽  
Intrafusal Muscle ◽  
Dense Granules ◽  
Intrafusal Muscle Fibers ◽  
Sarcotubular System ◽  
Nuclear Chain ◽  
T System ◽  
Nuclear Bag

An ultrastructural comparison of the two types of intrafusal muscle fibers in muscle spindles of the rat was undertaken. Discrete myofibrils with abundant interfibrillar sarcoplasm and organelles characterize the nuclear chain muscle fiber, while a continuous myofibril-like bundle with sparse interfibrillar sarcoplasm distinguishes the nuclear bag muscle fiber. Nuclear chain fibers possess well-defined and typical M bands in the center of each sarcomere, while nuclear bag fibers contain ill-defined M bands composed of two parallel thin densities in the center of the pseudo-H zone of each sarcomere. Mitochondria of nuclear chain fibers are larger and more numerous than they are in nuclear bag fibers. Mitochondria of chain fibers, in addition, often contain conspicuous dense granules, and they are frequently intimately related to elements of the sarcoplasmic reticulum (SR). Striking differences are noted in the organization and degree of development of the sarcotubular system. Nuclear bag fibers contain a poorly developed SR and T system with only occasional junctional couplings (dyads and triads). Nuclear chain fibers, in contrast, possess an unusually well-developed SR and T system and a variety of multiple junctional couplings (dyads, triads, quatrads, pentads, septads). Greatly dilated SR cisternae are common features of nuclear chain fibers, often forming intimate associations with T tubules, mitochondria, and the sarcolemma. Such dilatations of the SR were not encountered in nuclear bag fibers. The functional significance of these structural findings is discussed.

scholarly journals Muscle Spindles in the Deep Muscles of the Human Neck: A Morphological and Immunocytochemical Study

2003 ◽  
Vol 51 (2) ◽  
pp. 175-186 ◽  
Author(s):  
Jing-Xia Liu ◽  
Lars-Eric Thornell ◽  
Fatima Pedrosa-Domellöf
Keyword(s):  
Fiber Length ◽  
Biceps Brachii ◽  
Muscle Spindles ◽  
Functional Specialization ◽  
Immunocytochemical Study ◽  
Intrafusal Fibers ◽  
Myhc Isoforms ◽  
Nuclear Chain ◽  
Human Muscles ◽  
Lumbrical Muscles

Muscle spindle density is extremely high in the deep muscles of the human neck. However, there is a paucity of information regarding the morphology and immunoreactivity of these muscle spindles. The objective of this study was to investigate the intrafusal fiber content and to assess the myosin heavy chain (MyHC) composition of muscle spindles from human deep neck muscles. In addition to the conventional spindles containing bag1, bag2, and chain fibers (b1b2c spindle), we observed a number of spindles lacking bag1 (b2c spindle) or bag2 (b1c spindle) fibers. Both bag1 and bag2 fibers contained slow tonic MyHCs along their entire fiber length and MyHCI, MyHCIIa, embryonic, and α-cardiac MyHC isoforms along a variable length of the fibers. Fetal MyHC was present in bag2 fibers but not in bag1 fibers. Nuclear chain fibers contained MyHCIIa, embryonic, and fetal isoforms with regional variations. We also compared the present data with our previous results obtained from muscle spindles in human biceps brachii and the first lumbrical muscles. The allotment of numbers of intrafusal fibers and the MyHC composition showed some muscle-related differences, suggesting functional specialization in the control of movement among different human muscles.

501 Changes of muscle fiber length in vivo during walking as revealed by ultrasound images

2008 ◽  
Vol 2007.20 (0) ◽  
pp. 165-166
Author(s):  
Naoto SASAGAWA ◽  
Tasuku MIYOSHI ◽  
Hiroyuki KOYAMA ◽  
Takashi KOMEDA ◽  
Shin-Ichiro YAMAMOTO
Keyword(s):  
Muscle Fiber ◽  
Fiber Length ◽  
Ultrasound Images

scholarly journals Dynamic left ventricular elastance: a model for integrating cardiac muscle contraction into ventricular pressure-volume relationships

2008 ◽  
Vol 104 (4) ◽  
pp. 958-975 ◽  
Author(s):  
Kenneth B. Campbell ◽  
Amy M. Simpson ◽  
Stuart G. Campbell ◽  
Henk L. Granzier ◽  
Bryan K. Slinker
Keyword(s):  
Muscle Fiber ◽  
Fiber Length ◽  
Phase 1 ◽  
Left Ventricular ◽  
Isolated Rat Heart ◽  
Rate Of Change ◽  
Lv Function ◽  
Elastic Distortion ◽  
Length Changes ◽  
Incremental Step

To integrate myocardial contractile processes into left ventricular (LV) function, a mathematical model was built. Muscle fiber force was set equal to the product of stiffness and elastic distortion of stiffness elements, i.e., force-bearing cross bridges (XB). Stiffness dynamics arose from recruitment of XB according to the kinetics of myofilament activation and fiber-length changes. Elastic distortion dynamics arose from XB cycling and the rate-of-change of fiber length. Muscle fiber stiffness and distortion dynamics were transformed into LV chamber elastance and volumetric distortion dynamics. LV pressure equaled the product of chamber elastance and volumetric distortion, just as muscle-fiber force equaled the product of muscle-fiber stiffness and lineal elastic distortion. Model validation was in terms of its ability to reproduce cycle-time-dependent LV pressure response, ΔP( t), to incremental step-like volume changes, ΔV, in the isolated rat heart. All ΔP( t), regardless of the time in the cycle at which ΔP( t) was elicited, consisted of three phases: phase 1, concurrent with the leading edge of ΔV; phase 2, a brief transient recovery from phase 1; and phase 3, sustained for the duration of systole. Each phase varied with the time in the cycle at which ΔP( t) was elicited. When the model was fit to the data, cooperative activation was required to sustain systole for longer periods than was possible with Ca2+ activation alone. The model successfully reproduced all major features of the measured ΔP( t) responses, and thus serves as a credible indicator of the role of underlying contractile processes in LV function.

Respiratory

2017 ◽  
Author(s):  
Mark Harrison
Keyword(s):  
Muscle Spindles ◽  
Pulmonary Mechanics ◽  
Carbon Dioxide Transport ◽  
Lung Volumes ◽  
Golgi Tendon Organs ◽  
Stretch Receptors ◽  
Pulmonary Stretch Receptors ◽  
Pressure Chemical ◽  
Tendon Organs ◽  
Irritant Receptors

This chapter describes the pathophysiology of the respiratory system as it applies to Emergency Medicine, and in particular the Primary FRCEM examination. The chapter outlines the key details of the control of ventilation, reflexes, pressure, chemical, and irritant receptors, J receptors, pulmonary stretch receptors, Golgi tendon organs, muscle spindles, lung volumes, pulmonary mechanics, oxygen and carbon dioxide transport, DO2/VO2 relationships, carbon monoxide, pulse oximetry, effects of altitude, and dysbarism. This chapter is laid out exactly following the RCEM syllabus, to allow easy reference and consolidation of learning.

8J-20 Measurement of Gastrocnemius muscle fiber length during passive postural modulation

2011 ◽  
Vol 2010.23 (0) ◽  
pp. 311-312
Author(s):  
Hideaki TABEI ◽  
Hiroki OBATA ◽  
Tasuku MIYOSHI ◽  
Shin-ichiroh YAMAMOTO
Keyword(s):  
Muscle Fiber ◽  
Fiber Length ◽  
Gastrocnemius Muscle
Sign in / Sign up

Export Citation Format

Share Document