Spinal Mechanisms for Control of Muscle Length and Force

1973 ◽

Vol 31 ◽

pp. 422-423

Author(s):

G.E. Adomian ◽

L. Chuck ◽

W.W. Pannley

Keyword(s):

Cardiac Muscle ◽

Sarcomere Length ◽

Muscle Length ◽

Contractile Force ◽

Direct Function ◽

Morphological Basis ◽

Tension Curve

Sonnenblick, et al, have shown that sarcomeres change length as a function of cardiac muscle length along the ascending portion of the length-tension curve. This allows the contractile force to be expressed as a direct function of sarcomere length. Below L max, muscle length is directly related to sarcomere length at lengths greater than 85% of optimum. However, beyond the apex of the tension-length curve, i.e. L max, a disparity occurs between cardiac muscle length and sarcomere length. To account for this disproportionate increase in muscle length as sarcomere length remains relatively stable, the concept of fiber slippage was suggested as a plausible explanation. These observations have subsequently been extended to the intact ventricle.

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Physiologic changes of compound muscle action potentials related to voluntary contraction and muscle length in carpal tunnel syndrome

Journal of Electromyography and Kinesiology ◽

10.1016/j.jelekin.2004.09.002 ◽

2005 ◽

Vol 15 (3) ◽

pp. 275-281 ◽

Cited By ~ 13

Author(s):

Byung-Jo Kim ◽

Elaine S. Date ◽

Byung Kyu Park ◽

Bryan Y. Choi ◽

Sang-Heon Lee

Keyword(s):

Carpal Tunnel Syndrome ◽

Carpal Tunnel ◽

Action Potentials ◽

Muscle Length ◽

Voluntary Contraction ◽

Muscle Action ◽

Compound Muscle Action Potentials ◽

Tunnel Syndrome

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Effect of respiratory muscle tension on lung volume

Journal of Applied Physiology ◽

10.1152/jappl.1992.73.6.2283 ◽

1992 ◽

Vol 73 (6) ◽

pp. 2283-2288 ◽

Cited By ~ 23

Author(s):

T. A. Wilson ◽

A. De Troyer

Keyword(s):

Chest Wall ◽

Lung Volume ◽

Airway Pressure ◽

Linear Prediction ◽

Muscle Tension ◽

Muscle Length ◽

Respiratory Muscles ◽

Active Tension ◽

Airway Opening ◽

Measured Change

The chest wall is modeled as a linear system for which the displacements of points on the chest wall are proportional to the forces that act on the chest wall, namely, airway opening pressure and active tension in the respiratory muscles. A standard theorem of mechanics, the Maxwell reciprocity theorem, is invoked to show that the effect of active muscle tension on lung volume, or airway pressure if the airway is closed, is proportional to the change of muscle length in the relaxation maneuver. This relation was tested experimentally. The shortening of the cranial-caudal distance between a rib pair and the sternum was measured during a relaxation maneuver. These data were used to predict the respiratory effect of forces applied to the ribs and sternum. To test this prediction, a cranial force was applied to the rib pair and a caudal force was applied to the sternum, simulating the forces applied by active tension in the parasternal intercostal muscles. The change in airway pressure, with lung volume held constant, was measured. The measured change in airway pressure agreed well with the prediction. In some dogs, nonlinear deviations from the linear prediction occurred at higher loads. The model and the theorem offer the promise that existing data on the configuration of the chest wall during the relaxation maneuver can be used to compute the mechanical advantage of the respiratory muscles.

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Influence of submaximal isometric contractions of the hamstrings on electromyography activity and force while functioning as hip extensors

Isokinetics and Exercise Science ◽

10.3233/ies-204172 ◽

2020 ◽

pp. 1-8

Author(s):

Dasom Oh ◽

Wootaek Lim

Keyword(s):

Prone Position ◽

Supine Position ◽

Isometric Contraction ◽

Muscle Length ◽

Biceps Femoris ◽

Emg Activity ◽

Isometric Contractions ◽

Significant Difference ◽

Extension Force ◽

Long Head

BACKGROUND: Although the medial and lateral hamstrings are clearly distinct anatomically and have different functions in the transverse plane, they are often considered as one muscle during rehabilitation. OBJECTIVE: The purpose of the study was to compare the electromyographic (EMG) activity between the prone position and the supine position during maximal isometric contraction and to additionally confirm the effect of submaximal isometric contractions on EMG activity of medial and lateral hamstrings, and force. METHODS: In the prone position, EMG activities of the long head of biceps femoris (BFLH) and semitendinosus (ST) were measured during the maximal isometric contraction. In the supine position, hip extension force with EMG activity were measured during the maximal and the submaximal isometric contractions. RESULTS: EMG activity in the prone position was significantly decreased in the supine position. In the supine position, there was a significant difference between the BFLH and ST during the maximal isometric contraction, but not during the submaximal isometric contractions. CONCLUSIONS: The dependence on the hamstrings could be relatively lower during hip extensions. When the medial and lateral hamstrings are considered separately, the lateral hamstrings may show a more active response, with increased muscle length, in clinical practice.

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Angle-specific impairment of elbow flexors strength after isometric exercise at long muscle length

Journal of Sports Sciences ◽

10.1080/0264041031000140356 ◽

2003 ◽

Vol 21 (10) ◽

pp. 859-865 ◽

Cited By ~ 17

Author(s):

Anastassios Philippou ◽

Maria Maridaki ◽

Gregory C. Bogdanis

Keyword(s):

Isometric Exercise ◽

Muscle Length ◽

Elbow Flexors

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Satellite cell activation in the stretch-enlarged anterior latissimus dorsi muscle of the adult quail

AJP Cell Physiology ◽

10.1152/ajpcell.1991.260.2.c206 ◽

1991 ◽

Vol 260 (2) ◽

pp. C206-C212 ◽

Cited By ~ 48

Author(s):

P. K. Winchester ◽

M. E. Davis ◽

S. E. Alway ◽

W. J. Gonyea

Keyword(s):

Satellite Cell ◽

Satellite Cells ◽

Latissimus Dorsi ◽

Tritiated Thymidine ◽

Cell Activity ◽

Muscle Length ◽

Latissimus Dorsi Muscle ◽

Cell Labeling ◽

Dorsi Muscle ◽

Anterior Latissimus Dorsi

Satellite cell activity was examined in the stretch-enlarge anterior latissimus dorsi muscle (ALD) of the adult quail. Thirty-seven birds had a weight equal to 10% of their body mass attached to one wing while the contralateral wing served as an intra-animal control. At various time intervals after application of the wing weight (from 1 to 30 days), the birds were injected with tritiated thymidine and killed 1 h later. Stretched muscle length was greater by day 1 and mass by day 3 when compared with the contralateral muscle. Satellite cells actively synthesizing DNA were quantitated in fiber segments of the control and stretched ALD. A minimum of 1,500 muscle nuclei (satellite cell nuclei and myonuclei) were counted in each muscle. Labeling in stretched muscle was expressed by the percent labeled nuclei per total nuclei counted. Satellite cell labeling was initiated by day 1, peaked between days 3 and 7, and was not statistically different from control values at day 30. These results demonstrate that satellite cells are induced to enter the cell cycle in the stretch-enlarged ALD muscle from the adult quail, and the peak of proliferative activity is within the first week of stretch.

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Muscle length and joint angle influence spinal but not corticospinal excitability to the biceps brachii across forearm postures

Journal of Neurophysiology ◽

10.1152/jn.00620.2018 ◽

2019 ◽

Vol 122 (1) ◽

pp. 413-423 ◽

Cited By ~ 2

Author(s):

Davis A. Forman ◽

Daniel Abdel-Malek ◽

Christopher M. F. Bunce ◽

Michael W. R. Holmes

Keyword(s):

Isometric Contraction ◽

Elbow Joint ◽

Joint Angle ◽

Biceps Brachii ◽

Motor Evoked Potentials ◽

Muscle Length ◽

Elbow Flexion ◽

Corticospinal Excitability ◽

Biceps Brachii Muscle ◽

Spinal Excitability

Forearm rotation (supination/pronation) alters corticospinal excitability to the biceps brachii, but it is unclear whether corticospinal excitability is influenced by joint angle, muscle length, or both. Thus the purpose of this study was to separately examine elbow joint angle and muscle length on corticospinal excitability. Corticospinal excitability to the biceps and triceps brachii was measured using motor evoked potentials (MEPs) elicited via transcranial magnetic stimulation. Spinal excitability was measured using cervicomedullary motor evoked potentials (CMEPs) elicited via transmastoid electrical stimulation. Elbow angles were manipulated with a fixed biceps brachii muscle length (and vice versa) across five unique postures: 1) forearm neutral, elbow flexion 90°; 2) forearm supinated, elbow flexion 90°; 3) forearm pronated, elbow flexion 90°; 4) forearm supinated, elbow flexion 78°; and 5) forearm pronated, elbow flexion 113°. A musculoskeletal model determined biceps brachii muscle length for postures 1–3, and elbow joint angles ( postures 4–5) were selected to maintain biceps length across forearm orientations. MEPs and CMEPs were elicited at rest and during an isometric contraction of 10% of maximal biceps muscle activity. At rest, MEP amplitudes to the biceps were largest during supination, which was independent of elbow joint angle. CMEP amplitudes were not different when the elbow was fixed at 90° but were largest in pronation when muscle length was controlled. During an isometric contraction, there were no significant differences across forearm postures for either MEP or CMEP amplitudes. These results highlight that elbow joint angle and biceps brachii muscle length can each independently influence spinal excitability. NEW & NOTEWORTHY Changes in upper limb posture can influence the responsiveness of the central nervous system to artificial stimulations. We established a novel approach integrating neurophysiology techniques with biomechanical modeling. Through this approach, the effects of elbow joint angle and biceps brachii muscle length on corticospinal and spinal excitability were assessed. We demonstrate that spinal excitability is uniquely influenced by joint angle and muscle length, and this highlights the importance of accounting for muscle length in neurophysiological studies.

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