Chapter 7 Roles of muscle activity and load on the relationship between muscle spindle length and whole muscle length in the freely walking cat

1989 ◽  
pp. 75-85 ◽  
Author(s):  
J.A. Hoffer ◽  
A.A. Caputi ◽  
I.E. Pose ◽  
R.I. Griffiths
Keyword(s):  
Muscle Spindle ◽  
Muscle Activity ◽  
Muscle Length ◽  
The Relationship ◽  
Whole Muscle

scholarly journals Position Sensitivity of Feline Paraspinal Muscle Spindles to Vertebral Movement in the Lumbar Spine

2009 ◽  
Vol 101 (4) ◽  
pp. 1722-1729 ◽  
Author(s):  
Dong-Yuan Cao ◽  
Joel G. Pickar ◽  
Weiginq Ge ◽  
Allyson Ianuzzi ◽  
Partap S. Khalsa
Keyword(s):  
Lumbar Spine ◽  
Muscle Spindle ◽  
Facet Joint ◽  
Spinous Process ◽  
Muscle Length ◽  
Muscle Spindles ◽  
Paraspinal Muscle ◽  
High Position ◽  
Position Sensitivity ◽  
The Relationship

Muscle spindles contribute to sensorimotor control by supplying feedback regarding muscle length and consequently information about joint position. While substantial study has been devoted to determining the position sensitivity of spindles in limb muscles, there appears to be no data on their sensitivity in the low back. We determined the relationship between lumbar paraspinal muscle spindle discharge and paraspinal muscle lengthening estimated from controlled cranialward movement of the L6 vertebra in anesthetized cats. Ramp (0.4 mm/s) and hold displacements (0.2, 0.4, 0.6, 0.8, and 1.2 mm for 2.5 s) were applied at the L6 spinous process. Position sensitivity was defined as the slope of the relationship between the estimated increase in muscle length and mean instantaneous frequency at each length. To enable comparisons with appendicular muscle spindles where joint angle was measured, we also calculated sensitivity in terms of the L6 and L7 intervertebral flexion angle (IVA). This angle was estimated from measurements of facet joint capsule strain (FJC) based on a previously established relationship between IVA and FJC strain in the cat lumbar vertebral column during lumbar flexion. Single-unit recordings were obtained from 12 muscle spindle afferents. Longissimus and multifidus muscles contained the receptive field of 10 and 2 afferents, respectively. Mean position sensitivity was 16.3 imp·s−1·mm−1 [10.6–22.1, 95% confidence interval (CI), P < 0.001]. Mean angular sensitivity was 5.2 imp·s−1·°−1 (2.6–8.0, P < 0.003). These slope estimates were more than 3.5 times greater compared with appendicular muscle spindles, and their CIs did not contain previous slope estimates for the sensitivity of appendicular spindles from the literature. Potential reasons for and the significance of the apparently high position sensitivity in the lumbar spine are discussed.

Spatiotemporal characteristics of 5-HT and dopamine-induced rhythmic hindlimb activity in the in vitro neonatal rat

1996 ◽  
Vol 75 (4) ◽  
pp. 1472-1482 ◽  
Author(s):  
O. Kiehn ◽  
O. Kjaerulff
Keyword(s):  
Muscle Activity ◽  
Central Pattern Generators ◽  
Rhythmic Activity ◽  
Biceps Femoris ◽  
Ventral Root ◽  
Neonatal Rat ◽  
Cycle Duration ◽  
Spatiotemporal Characteristics ◽  
The Relationship

1. Rhythmic activity was induced with either serotonin (5-HT; 10-100 microM) or dopamine (0.1-1.0 mM), in the in vitro spinal cord preparation of neonatal rats, with one intact hindlimb attached. Patterns of activity were investigated with multiple EMG recordings and the spatiotemporal characteristics of 5-HT- and dopamine-induced activity compared. 2. Dopamine-induced rhythmic activity was slow (cycle duration: 2.2-70.1 s) and irregular, whereas rhythmic activity induced by 5-HT was fast (cycle duration: 1.3-5.1 s) and regular. 3. During 5-HT- and dopamine-induced rhythmic activity, the timing of muscular activity was similar for hip flexors and hip adductors, for semimembranosus (hip extensor), and for muscles controlling the ankle and the foot. 4. In contrast, notable differences in the phase in the pattern induced by 5-HT compared with that induced by dopamine were found in the biceps femoris, semitendinosus, and quadriceps muscles. Biceps femoris and semitendinosus (functional hip extensors and knee flexors) were always extensor-like during 5-HT-induced activity, whereas in dopamine, these muscles displayed flexor-like bursts and double bursts as well as extensor-like bursts. Lack of EMG activity in biceps femoris and semitendinosus was encountered also in dopamine. In rectus femoris, vastus lateralis, and vastus medialis (main function: knee extension), the activity was dominated by flexor-like bursts in 5-HT, whereas in dopamine the activity was shifted to a predominantly extensor-like pattern. 5. The relationship between flexor and extensor burst duration and cycle duration was more variable than described for locomotor activity in adult animals. 6. The relative timing of muscle activity was stable from P0 to P4. The most important difference between rats aged 0-1 days and rats aged 2-4 days was a delayed flexor-extensor transition in older animals. 7. The complex timing of hindlimb muscle activity was relatively unchanged after transecting all dorsal roots. 8. Finally, the relationship between flexor and extensor activity and ventral root discharges was determined. It was found that the L2 ventral root burst was in phase with simple flexors while the L5 burst coincide with the extensor phase. 9. We conclude, that 5-HT and dopamine can activate spinal central pattern generators (CPGs) that already at birth are able to produce distinct patterns of motor activity. Modulatory inputs thus seems to be able to reconfigure the CPGs to produce specific motor outputs.

scholarly journals Influence of muscle length on work from trabecular muscle of frog atrium and ventricle.

1995 ◽  
Vol 198 (10) ◽  
pp. 2221-2227 ◽  
Author(s):  
D A Syme ◽  
R K Josephson
Keyword(s):  
Isometric Force ◽  
Muscle Length ◽  
Work Capacity ◽  
Linear Increase ◽  
Ventricular Muscle ◽  
Work Output ◽  
Loop Technique ◽  
Work Done ◽  
The Relationship ◽  
Work Loop

The work capacity of segments of atrial and ventricular muscle from the frog Rana pipiens was measured as a function of muscle length using the work loop technique. Both the work done during shortening and the work required to re-lengthen the muscle after shortening increased with muscle length. Net work increased with length up to a maximum, beyond which work declined. The optimum sarcomere length for work output was 2.5-2.6 microns for both atrial and ventricular muscle. Isometric force increased with muscle length to lengths well beyond the optimum for work output. Thus, the decline in work at long lengths is not simply a consequence of a reduction in the capacity of heart muscle to generate force. It is proposed that it is the non-linear increase in work required to re-lengthen muscle with increasing muscle length which limits net work output and leads to a maximum in the relationship between net work and muscle length. Extension of the results from muscle strips to intact hearts suggests that the work required to fill the ventricle exceeds that available from atrial muscle at all but rather short ventricular muscle lengths.

Transient responses and continuous behavior of active smooth muscle during controlled stretches

1982 ◽  
Vol 242 (3) ◽  
pp. C146-C158 ◽  
Author(s):  
R. A. Meiss
Keyword(s):  
Steady State ◽  
Smooth Muscles ◽  
Muscle Length ◽  
Initial Slope ◽  
Stretch Rate ◽  
Rate Dependent ◽  
Upward Slope ◽  
Length Changes ◽  
State Force ◽  
The Relationship

Controlled length changes were imposed on mesotubarium superius and ovarian ligament smooth muscles from the reproductive tracts of female rabbits in constant estrus. Stretches of up to 35% of the muscle length were applied during isometric contraction, relaxation, and steady-state force levels. Force was continuously monitored and was plotted as a function of length. During constant velocity stretches there was an initial steep rise in force, a rapid downward deviation from the initial slope, and a long region with a constant upward slope. Stretches made during contraction showed smaller initial rises in force and steeper linear portions than did identical comparison stretches made during relaxation. The value of the slope was independent of the prior developed force, but it did depend on whether the muscle was contracting or relaxing. During contraction and steady-state force levels, the slope was independent of the stretch rate, but it was strongly rate dependent during relaxation. Changes in the stretch rate during stretch caused associated changes in muscle force; the relationship was curvilinear and was exaggerated during relaxation. The findings are placed in the context of a sliding-filament--cross-bridge hypothesis.

Activity patterns in individual hindlimb primary and secondary muscle spindle afferents during normal movements in unrestrained cats

1979 ◽  
Vol 42 (2) ◽  
pp. 420-440 ◽  
Author(s):  
G. E. Loeb ◽  
J. Duysens
Keyword(s):  
Muscle Spindle ◽  
Activity Patterns ◽  
Muscle Length ◽  
Muscle Spindle Afferents ◽  
General Observation ◽  
Postural Changes ◽  
Motor Activities ◽  
Specific Muscle ◽  
Length Changes ◽  
Rapid Modulation

1. Chronically implanted microelectrode wires in the L7 and S1 dorsal root ganglia were used to record unit activity from cat hindlimb primary and secondary muscle spindle afferents. Units could be reliably recorded for several days, permitting comparison of their activity with homonymous muscle EMG and length during a variety of normal, unrestrained movements. 2. The general observation was that among both primary and secondary endings there was a broad range of different patterns of activity depending on the type of muscle involved and the type of movement performed. 3. During walking, the activity of a given spindle primary was usually consistent among similar step cycles. However, the activity was usually poorly correlated with absolute muscle length, apparently unrealted to velocity of muscle stretch, and could change markedly for similar movements performed under different conditions. 4. Spindle activity modulation not apparently related to muscle length changes was assumed to be influenced by fusimotor activity. In certain muscles, this presumption leads to the conclusion that gamma-motoneurons may be activated out of phase with homonymous alpha-motoneurons as well as by more conventional alpha-gamma-motoneuron coactivation. 5. Simultaneous recordings of two spindle primary afferents from extensor digitorum longus indicated that spindles within the same muscle may differ considerably with respect to this presumed gamma-motoneuron drive. 6. Spindle secondary endings appeared to be predominantly passive indicators of muscle length during walking, but could demonstrate apparently strong fusimotor modulation during other motor activities such as postural changes and paw shaking. 7. Both primary and secondary endings were observed to undergo very rapid modulation of firing rates in response to presumed reflexly induced intrafusal contractions. 8. It is suggested that the pattern of fusimotor control of spindles may be tailored to the specific muscle and task being performed, rather than necessarily dominated by rigid alpha-gamma coactivation.

scholarly journals Effect of mandibular position achieved using an oral appliance on genioglossus activity in healthy adults during sleep

2019 ◽  
Vol 15 (1) ◽  
Author(s):  
Michikazu Matsuda ◽  
Toru Ogawa ◽  
Ratri M. Sitalaksmi ◽  
Makiko Miyashita ◽  
Toshimi Ito ◽  
...  
Keyword(s):  
Muscle Activity ◽  
Vertical Displacement ◽  
Oral Appliance ◽  
Airway Patency ◽  
Test Conditions ◽  
Obstructive Sleep ◽  
Mandibular Position ◽  
Vertical Displacements ◽  
The Relationship ◽  
Airflow Sensor

Abstract Background Oral appliances (OAs) are generally designed to displace the mandible anteriorly and downward, to increase the airway patency. The present study aimed to examine the relationship between genioglossus (GG) muscle activity and mandibular position, considering both anterior and vertical displacements during sleep. Methods Seven healthy male adults aged 29.4 ± 1.99 years were evaluated. Maxillary and mandibular OAs were fabricated from 2-mm-thick resin plates with pressure-welding. The activity of the left GG was recorded using two silver ball electrodes attached to the lingual edge of the mandibular OA. Respiratory status and right masseter muscle activity were measured by an airflow sensor and surface electrodes, respectively. Electroencephalography was used to determine the sleep status. Stage 2 (the second stage of sleep) was defined as the state of sleeping. Four test conditions with different mandibular positions (0 and 50% anterior protrusion) and bite openings (4 mm and 12 mm) were examined. Results GG activity in SL4A (4 mm bite opening, 50% protrusion during sleep) and SL12 (12 mm bite opening, 0% protrusion during sleep) were significantly higher than that in SL4 (4 mm bite opening, 0% protrusion during sleep). Respiratory volume did not significantly differ between all test conditions. Conclusion GG activity is influenced not only by anterior protrusion of the mandible but also by vertical displacement during sleep. Thus, when determining the effectiveness of intraoral appliances in the treatment of obstructive sleep apnea, both protrusion and the size of the mandibular opening should be evaluated and taken into account.

scholarly journals The influence of training-induced sarcomerogenesis on the history dependence of force

2020 ◽  
Vol 223 (15) ◽  
pp. jeb218776 ◽  
Author(s):  
Jackey Chen ◽  
Parastoo Mashouri ◽  
Stephanie Fontyn ◽  
Mikella Valvano ◽  
Shakeap Elliott-Mohamed ◽  
...  
Keyword(s):  
Extensor Digitorum Longus ◽  
Isometric Force ◽  
Muscle Length ◽  
Force Enhancement ◽  
Active Muscle ◽  
Training Groups ◽  
Force Depression ◽  
Residual Force ◽  
Residual Force Enhancement ◽  
Whole Muscle

ABSTRACTThe increase or decrease in isometric force following active muscle lengthening or shortening, relative to a reference isometric contraction at the same muscle length and level of activation, are referred to as residual force enhancement (rFE) and residual force depression (rFD), respectively. The purpose of these experiments was to investigate the trainability of rFE and rFD on the basis of serial sarcomere number (SSN) alterations to history-dependent force properties. Maximal rFE/rFD measures from the soleus and extensor digitorum longus (EDL) of rats were compared after 4 weeks of uphill or downhill running with a no-running control. SSN adapted to the training: soleus SSN was greater with downhill compared with uphill running, while EDL demonstrated a trend towards more SSN for downhill compared with no running. In contrast, rFE and rFD did not differ across training groups for either muscle. As such, it appears that training-induced SSN adaptations do not modify rFE or rFD at the whole-muscle level.

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