@article{MartinezValdesGuzmanVenegasSilvestreetal.2016,
  author    = {Martinez-Valdes, Eduardo Andr{\´e}s and Guzman-Venegas, R. A. and Silvestre, R. A. and Macdonald, J. H. and Falla, D. and Araneda, O. F. and Haichelis, D.},
  title     = {Electromyographic adjustments during continuous and intermittent incremental fatiguing cycling},
  series = {Psychotherapeut},
  volume    = {26},
  journal   = {Psychotherapeut},
  publisher = {Wiley-Blackwell},
  address   = {Hoboken},
  issn      = {0905-7188},
  doi       = {10.1111/sms.12578},
  pages     = {1273 -- 1282},
  year      = {2016},
  abstract  = {We studied the sensitivity of electromyographic (EMG) variables to load and muscle fatigue during continuous and intermittent incremental cycling. Fifteen men attended three laboratory sessions. Visit 1: lactate threshold, peak power output, and VO2max. Visits 2 and 3: Continuous (more fatiguing) and intermittent (less fatiguing) incremental cycling protocols [20\%, 40\%, 60\%, 80\% and 100\% of peak power output (PPO)]. During both protocols, multichannel EMG signals were recorded from vastus lateralis: muscle fiber conduction velocity (MFCV), instantaneous mean frequency (iMNF), and absolute and normalized root mean square (RMS) were analyzed. MFCV differed between protocols (P<0.001), and only increased consistently with power output during intermittent cycling. RMS parameters were similar between protocols, and increased linearly with power output. However, only normalized RMS was higher during the more fatiguing 100\% PPO stage of the continuous protocol [continuous-intermittent mean difference (95\% CI): 45.1 (8.5\% to 81.7\%)]. On the contrary, iMNF was insensitive to load changes and muscle fatigue (P=0.14). Despite similar power outputs, continuous and intermittent cycling influenced MFCV and normalized RMS differently. Only normalized RMS was sensitive to both increases in power output (in both protocols) and muscle fatigue, and thus is the most suitable EMG parameter to monitor changes in muscle activation during cycling.},
  language  = {en}
}
@article{MartinezValdesLaineFallaetal.2016,
  author    = {Martinez-Valdes, Eduardo Andr{\´e}s and Laine, C. M. and Falla, D. and Mayer, Frank and Farina, D.},
  title     = {High-density surface electromyography provides reliable estimates of motor unit behavior},
  series = {Clinical neurophysiology},
  volume    = {127},
  journal   = {Clinical neurophysiology},
  publisher = {Elsevier},
  address   = {Clare},
  issn      = {1388-2457},
  doi       = {10.1016/j.clinph.2015.10.065},
  pages     = {2534 -- 2541},
  year      = {2016},
  abstract  = {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.},
  language  = {en}
}
@article{MartinezValdesNegroLaineetal.2017,
  author    = {Martinez-Valdes, Eduardo Andr{\´e}s and Negro, F. and Laine, C. M. and Falla, D. and Mayer, Frank and Farina, Dario},
  title     = {Tracking motor units longitudinally across experimental sessions with high-density surface electromyography},
  series = {The Journal of Physiology},
  volume    = {595},
  journal   = {The Journal of Physiology},
  publisher = {Wiley},
  address   = {Hoboken},
  issn      = {0022-3751},
  doi       = {10.1113/JP273662},
  pages     = {1479 -- 1496},
  year      = {2017},
  abstract  = {A new method is proposed for tracking individual motor units (MUs) across multiple experimental sessions on different days. The technique is based on a novel decomposition approach for high-density surface electromyography and was tested with two experimental studies for reliability and sensitivity. Experiment I (reliability): ten participants performed isometric knee extensions at 10, 30, 50 and 70\% of their maximum voluntary contraction (MVC) force in three sessions, each separated by 1 week. Experiment II (sensitivity): seven participants performed 2 weeks of endurance training (cycling) and were tested pre-post intervention during isometric knee extensions at 10 and 30\% MVC. The reliability (Experiment I) and sensitivity (Experiment II) of the measured MU properties were compared for the MUs tracked across sessions, with respect to all MUs identified in each session. In Experiment I, on average 38.3\% and 40.1\% of the identified MUs could be tracked across two sessions (1 and 2 weeks apart), for the vastus medialis and vastus lateralis, respectively. Moreover, the properties of the tracked MUs were more reliable across sessions than those of the full set of identified MUs (intra-class correlation coefficients ranged between 0.63-0.99 and 0.39-0.95, respectively). In Experiment II, similar to 40\% of the MUs could be tracked before and after the training intervention and training-induced changes in MU conduction velocity had an effect size of 2.1 (tracked MUs) and 1.5 (group of all identified motor units). These results show the possibility of monitoring MU properties longitudinally to document the effect of interventions or the progression of neuromuscular disorders.},
  language  = {en}
}