We have located links that may give you full text access.
Corticospinal excitability during shortening and lengthening actions with incremental torque output.
Experimental Physiology 2018 December
NEW FINDINGS: What is the central question of this study? The relationship between motor unit recruitment and firing rate has been related to the size of the corticospinal output with variations in the nervous system gain during isometric contractions. However, corticospinal behaviour with incremental torque output might differ during anisometric contractions owing to differences in neural control of anisometric contraction types. What is the main finding and its importance? Corticospinal excitability during lengthening contractions was smaller compared with shortening but increased with incremental torque output in a similar manner between contraction types. The relationship between motor unit recruitment and firing rates is probably the main determinant of the size of an evoked response with variations in system gain.
ABSTRACT: The modulation of motor evoked potentials (MEPs), an index of corticospinal excitability, has been shown to increase during isometric contractions with incremental torque output in accordance with the contribution between motor unit recruitment and firing rate of the muscle to increases in required torque output. However, the motor unit strategy of the muscle might not be the only factor influencing this behaviour, because differences in pre- and postsynaptic control have been reported between lengthening and shortening or isometric contractions. In 30 healthy adults, MEPs were elicited in tibialis anterior during shortening and lengthening contractions at 15, 25, 50 and 80% of contraction-type-specific maximal voluntary contraction torque. Background EMG activity increased progressively with greater torque output (P < 0.001) but was similar between contraction types (P = 0.162). When normalized to the maximal muscle response, MEPs were greater during shortening compared with lengthening contractions (P = 0.004) and increased stepwise with increased contraction intensities (P = 0.001). These data show an increase in corticospinal excitability with torque output from lower to higher contraction intensities, suggesting a greater contribution of motor unit recruitment to increased nervous system gain in the tibialis anterior. Despite differences in corticospinal control of shortening and lengthening contractions, the data suggest that the corticospinal responses to increases in torque output are not dependent on contraction type, because corticospinal excitability increased to a similar extent during shortening and lengthening actions. Thus, it is likely that the relationship between motor unit recruitment and firing rate of the muscle is the main determinant of corticospinal output with variations in nervous system gain.
ABSTRACT: The modulation of motor evoked potentials (MEPs), an index of corticospinal excitability, has been shown to increase during isometric contractions with incremental torque output in accordance with the contribution between motor unit recruitment and firing rate of the muscle to increases in required torque output. However, the motor unit strategy of the muscle might not be the only factor influencing this behaviour, because differences in pre- and postsynaptic control have been reported between lengthening and shortening or isometric contractions. In 30 healthy adults, MEPs were elicited in tibialis anterior during shortening and lengthening contractions at 15, 25, 50 and 80% of contraction-type-specific maximal voluntary contraction torque. Background EMG activity increased progressively with greater torque output (P < 0.001) but was similar between contraction types (P = 0.162). When normalized to the maximal muscle response, MEPs were greater during shortening compared with lengthening contractions (P = 0.004) and increased stepwise with increased contraction intensities (P = 0.001). These data show an increase in corticospinal excitability with torque output from lower to higher contraction intensities, suggesting a greater contribution of motor unit recruitment to increased nervous system gain in the tibialis anterior. Despite differences in corticospinal control of shortening and lengthening contractions, the data suggest that the corticospinal responses to increases in torque output are not dependent on contraction type, because corticospinal excitability increased to a similar extent during shortening and lengthening actions. Thus, it is likely that the relationship between motor unit recruitment and firing rate of the muscle is the main determinant of corticospinal output with variations in nervous system gain.
Full text links
Related Resources
Trending Papers
Challenges in Septic Shock: From New Hemodynamics to Blood Purification Therapies.Journal of Personalized Medicine 2024 Februrary 4
Molecular Targets of Novel Therapeutics for Diabetic Kidney Disease: A New Era of Nephroprotection.International Journal of Molecular Sciences 2024 April 4
The 'Ten Commandments' for the 2023 European Society of Cardiology guidelines for the management of endocarditis.European Heart Journal 2024 April 18
A Guide to the Use of Vasopressors and Inotropes for Patients in Shock.Journal of Intensive Care Medicine 2024 April 14
Diagnosis and Management of Cardiac Sarcoidosis: A Scientific Statement From the American Heart Association.Circulation 2024 April 19
Essential thrombocythaemia: A contemporary approach with new drugs on the horizon.British Journal of Haematology 2024 April 9
Get seemless 1-tap access through your institution/university
For the best experience, use the Read mobile app
All material on this website is protected by copyright, Copyright © 1994-2024 by WebMD LLC.
This website also contains material copyrighted by 3rd parties.
By using this service, you agree to our terms of use and privacy policy.
Your Privacy Choices
You can now claim free CME credits for this literature searchClaim now
Get seemless 1-tap access through your institution/university
For the best experience, use the Read mobile app