Todor I Arabadzhiev1, Vladimir G Dimitrov, George V Dimitrov. 1. Institute of Biophysics and Biomedical Engineering, Bulgarian Academy of Sciences, Acad. Georgi Bonchev Str., Block 21, 1113, Sofia, Bulgaria, todor.ia@gmail.com.
Abstract
PURPOSE: To test the validity of using the increase in surface EMG as a measure of neural adaptation during the early gains in strength. METHODS: Simulation of EMG signals detected by surface bipolar electrode with 20-mm inter-pole distance at different radial distances from the muscle and longitudinal distances from the end-plate area. The increases in the root mean square (RMS) of the EMG signal due to possible alteration in the neural drive or elevation of the intracellular negative after-potentials, detected in fast fatigable muscle fibres during post-tetanic potentiation and assumed to accompany post-activation potentiation, were compared. RESULTS: Lengthening of the intracellular action potential (IAP) profile due to elevation of the negative after-potentials could affect amplitude characteristics of surface EMG detected at any axial distance stronger than alteration in the neural drive. This was irrespective of the fact that the elevation of IAP negative after-potential was applied to fast fatigable motor units (MUs) only, while changes in frequency of activation (simulating neural drive changes) were applied to all MUs. In deeper muscles, where the fibre-electrode distance was larger, the peripheral effect was more pronounced. The normalization of EMG amplitude characteristics to an M-wave one could result only in partial elimination of peripheral factor influence CONCLUSIONS: The increase in RMS of surface EMG during the early gains in strength should not be directly related to the changes in the neural drive. The relatively small but long-lasting elevated free resting calcium after high-resistance strength training could result in force potentiation and EMG increase.
PURPOSE: To test the validity of using the increase in surface EMG as a measure of neural adaptation during the early gains in strength. METHODS: Simulation of EMG signals detected by surface bipolar electrode with 20-mm inter-pole distance at different radial distances from the muscle and longitudinal distances from the end-plate area. The increases in the root mean square (RMS) of the EMG signal due to possible alteration in the neural drive or elevation of the intracellular negative after-potentials, detected in fast fatigable muscle fibres during post-tetanic potentiation and assumed to accompany post-activation potentiation, were compared. RESULTS: Lengthening of the intracellular action potential (IAP) profile due to elevation of the negative after-potentials could affect amplitude characteristics of surface EMG detected at any axial distance stronger than alteration in the neural drive. This was irrespective of the fact that the elevation of IAP negative after-potential was applied to fast fatigable motor units (MUs) only, while changes in frequency of activation (simulating neural drive changes) were applied to all MUs. In deeper muscles, where the fibre-electrode distance was larger, the peripheral effect was more pronounced. The normalization of EMG amplitude characteristics to an M-wave one could result only in partial elimination of peripheral factor influence CONCLUSIONS: The increase in RMS of surface EMG during the early gains in strength should not be directly related to the changes in the neural drive. The relatively small but long-lasting elevated free resting calcium after high-resistance strength training could result in force potentiation and EMG increase.
Authors: Ethan C Hill; Paola M Rivera; Chris E Proppe; David H Gonzalez Rojas; Aaron M Wizenberg; Joshua L Keller Journal: J Neurophysiol Date: 2022-06-15 Impact factor: 2.974
Authors: Andrew D Vigotsky; Israel Halperin; Gregory J Lehman; Gabriel S Trajano; Taian M Vieira Journal: Front Physiol Date: 2018-01-04 Impact factor: 4.566
Authors: Nathaniel D M Jenkins; Amelia A Miramonti; Ethan C Hill; Cory M Smith; Kristen C Cochrane-Snyman; Terry J Housh; Joel T Cramer Journal: Front Physiol Date: 2017-05-29 Impact factor: 4.566
Authors: Simon Walker; Anthony J Blazevich; G Gregory Haff; James J Tufano; Robert U Newton; Keijo Häkkinen Journal: Front Physiol Date: 2016-04-27 Impact factor: 4.566