Potentiation of the first and second phases of the M wave after maximal voluntary contractions in the biceps brachii muscle

  • Javier Rodriguez-FalcesEmail author
  • Taian Vieira
  • Nicolas Place
  • Alberto Botter
Original Article


The study was undertaken to examine separately the potentiation of the first and second phases of the M wave in biceps brachii after conditioning maximal voluntary contractions (MVCs) of different durations. M waves were evoked in the biceps brachii muscle before and after isometric MVCs of 1, 3, 6, 10, 30, and 60 s. The amplitude, duration, and area of the first and second phases of monopolar M waves were measured during the 10-min period following each contraction. Our results indicated that the amplitude and area of the M-wave first phase increased after MVCs of long (≥ 30 s) duration (P < 0.05), while it decreased after MVCs of short (≤ 10 s) duration (P < 0.05). The enlargement after the long MVCs persisted for 5 min, whereas the depression after the short contractions lasted only for 15 s. The amplitude of the second phase increased immediately (1 s) after all MVCs tested (P < 0.05), regardless of their duration, and then returned rapidly (10 s) to control levels. Unexpectedly, the amplitude of the second phase decreased below control values between 15 s and 1 min after the MVCs lasting ≥ 6 s (P < 0.05). Our results reinforce the idea that the presence of fatigue is a necessary condition to induce an enlargement of the M-wave first phase and that this enlargement would be greater (and occur sooner) in muscles with a predominance of type II fibers (quadriceps and biceps brachii) compared to type-I predominant muscles (tibialis anterior). The unique findings observed for the M-wave second phase indicate that changes in this phase are highly muscle dependent.

Graphical abstract

Left panel—Representative examples of M waves recorded in one participant before (control) and at various times after conditioning maximal voluntary contractions (MVCs) of short (a1) and long (a2) duration. Left panel—Time course of recovery of the amplitude of the first (b1) and second (b2) phases of the M wave after conditioning MVCs of different durations.


M wave Brachial plexus stimulation Electromyography Biceps brachii Isometric contraction M-wave potentiation 



Amplitude of the first phase of the M wave


Amplitude of the second phase of the M wave


Amplitude resulting from the sum of AmpliFIRST and AmpliSECOND


Area of the first phase of the M wave


Area of the second phase of the M wave


Area resulting from the sum of AreaFIRST and AreaSECOND


Duration of the first phase of the M wave


Duration of the second phase of the M wave


Time interval between the first and second peaks of the M wave




Maximal voluntary contraction

M wave

Compound muscle action potential


Rectus femoris


Standard deviation


Standard error of the mean


Vastus lateralis


Vastus medialis



This work has been supported by the Spanish Ministerio de Economia y Competitividad (MINECO), under the TEC2014-58947-R project.

Author contributions

J.R-F, A. B, T. V, and N. P designed the experimental study; J.R-F, A. B, and T. V performed the experiments; J.R-F and A. B analyzed the data; J.R-F, A. B, T. V, and N. P interpreted the results of the experiments; J.R-F drafted the manuscript; J.R-F, A. B, T. V, and N. P edited and revised the manuscript; J.R-F, A. B, T. V, and N. P approved the final version of the manuscript.

Compliance with ethical standards

Approval for the project was obtained from the local Ethics Committee, and all procedures used in this study conformed to the Declaration of Helsinki.

Conflict of interest

The authors declare that they have no conflict of interest.


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Copyright information

© International Federation for Medical and Biological Engineering 2019

Authors and Affiliations

  • Javier Rodriguez-Falces
    • 1
    • 2
    Email author
  • Taian Vieira
    • 3
  • Nicolas Place
    • 4
  • Alberto Botter
    • 3
  1. 1.Department of Electrical and Electronical EngineeringPublic University of NavarraPamplonaSpain
  2. 2.Department of Electrical and Electronical EngineeringUniversidad Pública de Navarra D.I.E.EPamplonaSpain
  3. 3.Laboratory for Engineering of the Neuromuscular System (LISiN), Department of Electronics and TelecommunicationPolitecnico di TorinoTorinoItaly
  4. 4.Institute of Sport Sciences, Faculty of Biology MedicineUniversity of LausanneLausanneSwitzerland

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