TY  - JOUR
A1  - Martinez-Valdes, Eduardo Andrés
A1  - Laine, C. M.
A1  - Falla, D.
A1  - Mayer, Frank
A1  - Farina, D.
T1  - High-density surface electromyography provides reliable estimates of motor unit behavior
JF  - Clinical neurophysiology
N2  - Objective: To assess the intra-and inter-session reliability of estimates of motor unit behavior and muscle fiber properties derived from high-density surface electromyography (HDEMG). Methods: Ten healthy subjects performed submaximal isometric knee extensions during three recording sessions (separate days) at 10%, 30%, 50% and 70% of their maximum voluntary effort. The discharge timings of motor units of the vastus lateralis and medialis muscles were automatically identified from HDEMG by a decomposition algorithm. We characterized the number of detected motor units, their discharge rates, the coefficient of variation of their inter-spike intervals (CoVisi), the action potential conduction velocity and peak-to-peak amplitude. Reliability was assessed for each motor unit characteristics by intra-class correlation coefficient (ICC). Additionally, a pulse-to-noise ratio (PNR) was calculated, to verify the accuracy of the decomposition. Results: Good to excellent reliability within and between sessions was found for all motor unit characteristics at all force levels (ICCs > 0.8), with the exception of CoVisi that presented poor reliability (ICC < 0.6). PNR was high and similar for both muscles with values ranging between 45.1 and 47.6 dB (accuracy > 95%). Conclusion: Motor unit features can be assessed non-invasively and reliably within and across sessions over a wide range of force levels. Significance: These results suggest that it is possible to characterize motor units in longitudinal intervention studies. (C) 2016 International Federation of Clinical Neurophysiology. Published by Elsevier Ireland Ltd. All rights reserved.
KW  - High-density surface EMG
KW  - Motor unit decomposition
KW  - Conduction velocity
KW  - Motor unit discharge rate
KW  - Vastus lateralis
KW  - Vastus medialis
Y1  - 2016
U6  - https://doi.org/10.1016/j.clinph.2015.10.065
SN  - 1388-2457
SN  - 1872-8952
VL  - 127
SP  - 2534
EP  - 2541
PB  - Elsevier
CY  - Clare
ER  - 
TY  - JOUR
A1  - Martinez-Valdes, Eduardo Andrés
A1  - Farina, Dario
A1  - Negro, Francesco
A1  - Del Vecchio, Alessandro
A1  - Falla, Deborah
T1  - Early motor unit conduction velocity changes to high-intensity interval training versus continuous training
JF  - Medicine and science in sports and exercise : official journal of the American College of Sports Medicine
N2  - Purpose Moderate-intensity continuous training (MICT) and high-intensity interval training (HIIT) are associated with different adjustments in motor output. Changes in motor unit (MU) peripheral properties may contribute to these adjustments, but this is yet to be elucidated. This study evaluated early changes in MU conduction velocity (MUCV) and MU action potential amplitude after 2 wk of either HIIT or MICT. Methods Sixteen men were assigned to either an MICT group or HIIT group (n = 8 each), and participated in six training sessions over 14 d. HIIT: 8 to 12 x 60-s intervals at 100% peak power output. Moderate-intensity continuous training: 90 to 120 min continuous cycling at similar to 65% VO2peak. Preintervention and postintervention, participants performed maximal voluntary contractions (MVC) and submaximal (10%, 30%, 50%, and 70% of MVC) isometric knee extensions while high-density EMG was recorded from the vastus medialis (VM) and vastus lateralis (VL) muscles. The high-density EMG was decomposed into individual MU by convolutive blind-source separation and tracked preintervention and postintervention. Results Both training interventions induced changes in MUCV, but these changes depended on the type of training (P < 0.001). The HIIT group showed higher values of MUCV after training at all torque levels (P < 0.05), MICT only displayed changes in MUCV at low torque levels (10%-30% MVC, P < 0.002). There were no changes in MU action potential amplitude for either group (P = 0.2). Conclusions Two weeks of HIIT or MICT elicit differential changes in MUCV, likely due to the contrasting load and volume used in such training regimes. This new knowledge on the neuromuscular adaptations to training has implications for exercise prescription.
KW  - Motor unit
KW  - Conduction velocity
KW  - Amplitude
KW  - Action potential
KW  - High-intensity interval training
KW  - Endurance training
Y1  - 2018
U6  - https://doi.org/10.1249/MSS.0000000000001705
SN  - 0195-9131
SN  - 1530-0315
VL  - 50
IS  - 11
SP  - 2339
EP  - 2350
PB  - Lippincott Williams & Wilkins
CY  - Philadelphia
ER  -