Related Experiment Video

Updated: Aug 14, 2026

Ex Vivo Assessment of Contractility, Fatigability and Alternans in Isolated Skeletal Muscles
14:02

Ex Vivo Assessment of Contractility, Fatigability and Alternans in Isolated Skeletal Muscles

Published on: November 1, 2012

Intracellular action potential generation and extinction strongly affect the sensitivity of M-wave characteristic

T I Arabadzhiev1, G V Dimitrov, N A Dimitrova

  • 1Centre of Biomedical Engineering, Bulgarian Academy of Sciences, Acad. G. Bonchev Str. B1 105, Sofia 1113, Bulgaria.

Journal of Electromyography and Kinesiology : Official Journal of the International Society of Electrophysiological Kinesiology
|January 25, 2005
PubMed

Insights

Mathematical simulations reveal that changes in muscle fiber propagation velocity (MFPV) and intracellular action potentials (IAPs) affect M-wave spectral frequencies. IAP changes significantly influence mean frequency (fmean) more than median frequency (fmed) during muscle fatigue.

Area of Science:

  • * Biophysics
  • * Neuroscience
  • * Exercise Physiology

Background:

  • * Peripheral muscle fatigue is associated with alterations in muscle fiber propagation velocity (MFPV) and intracellular action potentials (IAPs).
  • * M-wave power spectra analysis is used to assess muscle electrophysiology, with mean (fmean) and median (fmed) frequencies being key characteristic frequencies.

Purpose of the Study:

  • * To investigate the impact of combined changes in MFPV and IAP shape on M-wave characteristic frequencies (fmean and fmed) using mathematical simulations.
  • * To determine how IAP generation and extinction influence the sensitivity of spectral frequencies to MFPV variations.

Main Methods:

  • * Mathematical modeling and computer simulations were employed to analyze M-wave power spectra.
  • * Simulations focused on the effects of altered IAP generation/extinction and MFPV on spectral components and characteristic frequencies.

Main Results:

  • * IAP generation and extinction effects reduced the sensitivity of fmean and fmed to individual MFPV changes.
  • * Higher spectral components, linked to IAP depolarization, more significantly affected fmean than fmed.
  • * Under combined IAP and MFPV changes, fmean and fmed showed similar relative reductions, with fmean being more sensitive to IAP depolarization phase changes.

Conclusions:

  • * The study elucidates the complex interplay between MFPV and IAP dynamics in shaping M-wave spectral characteristics during fatigue.
  • * IAP changes, particularly during depolarization, have a pronounced effect on fmean, influencing its sensitivity to MFPV.
  • * Electrode configuration and muscle fiber length are additional factors influencing the sensitivity of M-wave frequencies.

More Related Videos

Assessment of Neuromuscular Function Using Percutaneous Electrical Nerve Stimulation07:53

Assessment of Neuromuscular Function Using Percutaneous Electrical Nerve Stimulation

Published on: September 13, 2015

Measuring Neuromuscular Junction Functionality10:40

Measuring Neuromuscular Junction Functionality

Published on: August 6, 2017

Related Concept Videos

Cross-bridge Cycle01:26

Cross-bridge Cycle

As muscle contracts, the overlap between the thin and thick filaments increases, decreasing the length of the sarcomere—the contractile unit of the muscle—using energy in the form of ATP. At the molecular level, this is a cyclic, multistep process that involves binding and hydrolysis of ATP, and movement of actin by myosin.
Generation of Action Potential in Skeletal Muscles01:24

Generation of Action Potential in Skeletal Muscles

Every cell in the body maintains a membrane potential due to an uneven distribution of positive and negative charges across its plasma membrane. The membrane potential is measured in millivolts and quantifies the difference in charge across the membrane.
Like neurons, muscle cells are also regarded as excitable due to their capacity to change in response to stimuli, primarily due to voltage-gated ion channels embedded in their plasma membranes, which get activated by alterations in the cell's...
Relaxation of Skeletal Muscles01:29

Relaxation of Skeletal Muscles

The period of muscle contraction primarily influences the duration of stimulation at the neuromuscular junction (NMJ), the presence of free calcium ions in the sarcoplasm, and the availability of energy or ATP to support contractions.
When an action potential reaches the axon terminal, it depolarizes the membrane and opens voltage-gated sodium channels. Sodium ions enter the cell, further depolarizing the presynaptic membrane. This depolarization causes voltage-gated calcium channels to open.
Motor Unit Stimulation01:20

Motor Unit Stimulation

When the neuron of a motor unit fires an action potential, it triggers a series of events, leading to a twitch contraction in the muscle fibers. The process of excitation-contraction coupling is crucial in relaying the action potential to the muscle fibers.
The latent period of contraction marks the onset of excitation-contraction coupling, when the action potential propagates across the sarcolemma, preparing the muscle fibers for contraction. As the fibers enter the contraction phase, the...
Muscle Stimulation Frequency01:22

Muscle Stimulation Frequency

The contraction strength of muscles is regulated by motor neurons, which modulate the frequency of action potentials dispatched to the motor units based on the body's requirements. This process of varying the muscle stimulation frequency allows muscles to contract with a force that is precisely tailored to the needs of the moment, whether lifting a feather or a heavy box.
Wave summation
At low firing rates, motor neurons induce individual twitch contractions in muscle fibers. These twitches...
Alterations in Muscle Tone lll01:11

Alterations in Muscle Tone lll

Rigidity and myotonia are distinct abnormalities of muscle tone that affect resistance and relaxation during movement. Although both involve altered muscle contraction, they arise from different neurological and muscular mechanisms.CharacteristicsRigidity is characterized by uniform resistance to passive movement across the entire range, independent of speed, affecting flexors and extensors equally. It may appear as lead-pipe rigidity (smooth, constant resistance) or cogwheel rigidity...