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Related Concept Videos

Motor Unit Stimulation01:20

Motor Unit Stimulation

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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.
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Muscles of the Vertebral Column01:27

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The back muscles that lie deep into the thoracolumbar fascia are called intrinsic or true back muscles. These muscles are divided into four layers: superficial, intermediate, deep, and deepest layers.
Superficial Layer:
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Excitation-Contraction Coupling in Skeletal Muscles01:20

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Excitation-contraction coupling is a series of events that occur between generating an action potential and initiating a muscle contraction. It occurs at the triad, a structure found in skeletal muscle fibers that comprise a T-tubule and terminal cisternae of the sarcoplasmic reticulum on each side. These triads are visible in longitudinally sectioned muscle fibers. They are typically located at the A-I junction — the junction between the A and I bands of the sarcomere.
When an action...
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Muscle Stimulation Frequency01:22

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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
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Updated: Nov 24, 2025

Muscle Function Obtained with Motion Mode Ultrasound and Surface Electromyography during Core Endurance Exercise
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Trunk Muscle Activation Patterns Differ Between Those With Low and High Back Extensor Strength During a Controlled

D Adam Quirk1,2, Raymond D Trudel3, Cheryl L Hubley-Kozey1,2

  • 1School of Biomedical Engineering, Dalhousie University, Halifax, NS, Canada.

Frontiers in Sports and Active Living
|December 21, 2020
PubMed
Summary
This summary is machine-generated.

Reduced active system function in the spine increases low back injury risk. Trunk muscles compensate with altered activation patterns, especially after injury recovery, highlighting the active system

Keywords:
biomechanicselectromyography (EMG)low back painmotor controlprincipal component analysis (PCA)spinal stabilitystrength

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Area of Science:

  • Biomechanics of the spine
  • Musculoskeletal health
  • Injury prevention and rehabilitation

Background:

  • Panjabi's spinal systems model suggests reduced function increases low back injury (LBI) risk.
  • Trunk muscle recruitment may compensate for deficits in spinal system function.

Purpose of the Study:

  • To investigate if reduced active system function (lower back extensor strength) alters trunk muscle activation patterns.
  • To determine if this relationship is modified after recovery from a LBI.

Main Methods:

  • Sixty men (30 recently recovered from LBI, 30 asymptomatic) were divided into STRONG and WEAK subgroups based on back extensor strength.
  • Trunk muscle electromyograms were recorded during a horizontal transfer task.
  • Principal component analysis and ANOVA analyzed muscle activation patterns (amplitude, temporal) for strength and group effects.

Main Results:

  • WEAK individuals generally exhibited higher abdominal and back extensor muscle activation amplitudes and greater temporal responsiveness than STRONG individuals.
  • Participants recently recovered from LBI showed more pronounced differences in muscle activation amplitudes between WEAK and STRONG subgroups.
  • These findings suggest compensatory strategies and modified motor control following LBI.

Conclusions:

  • Reduced active spinal system function necessitates compensatory trunk muscle activation.
  • Recent LBI experience amplifies these compensatory adjustments, potentially adapting to instability risks.
  • Understanding these motor control changes is crucial for LBI rehabilitation and prevention.