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Related Concept Videos

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.
Somatic Spinal Reflexes01:22

Somatic Spinal Reflexes

Somatic spinal reflexes are rapid, involuntary muscular responses to external stimuli that involve the somatic musculature and the spinal cord.
One of the most well-known somatic spinal reflexes is the stretch reflex, which is activated by the sudden stretching of a muscle. This reflex involves the activation of specialized sensory receptors called muscle spindles, which are located in the muscle tissue and detect changes in the length and speed of muscle contractions. When a muscle is suddenly...
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...
Exercise Stress Test01:26

Exercise Stress Test

Introduction
Exercise stress testing, commonly known as a treadmill test, is a noninvasive procedure used to evaluate cardiovascular function and diagnose heart conditions.
Definition
An exercise stress test measures the heart's response to exertion using a treadmill or stationary bicycle. Chest electrodes record the heart's electrical activity through an ECG, and blood pressure is monitored regularly.
Purposes
Classification of Skeletal Muscle Relaxants01:28

Classification of Skeletal Muscle Relaxants

Skeletal muscle relaxants are a group of drugs that can reduce muscle stiffness and induce temporary paralysis to relieve pain. These agents can act centrally to reduce muscle tone or spasms in painful conditions such as multiple sclerosis (MS), amyotrophic lateral sclerosis (ALS), or spinal injuries; they are called antispasmodics or spasmolytics.
Peripherally acting skeletal muscle relaxants interfere with the neurotransmission at the neuromuscular end plate to induce paralysis during...

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Mechanical Control of Relaxation Using Intact Cardiac Trabeculae
07:51

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Published on: February 17, 2023

Changes in the flexion relaxation response following an exercise intervention.

Paul Marshall1, Bernadette Murphy

  • 1Department of Sport and Exercise Science, University of Auckland, New Zealand. p.marshall@auckland.ac.nz

Spine
|November 2, 2006
PubMed
Summary

Exercise intervention improved low back pain (LBP) by decreasing muscle activity during trunk flexion relaxation. This suggests changes in afferent feedback may explain improved electrical relaxation post-training.

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Area of Science:

  • Neuromuscular physiology
  • Rehabilitation science
  • Biomedical engineering

Background:

  • Chronic nonspecific low back pain (LBP) is often associated with impaired neuromuscular activation.
  • The flexion relaxation phenomenon is a key measure in LBP, but intervention-related changes are not well-documented.

Purpose of the Study:

  • To investigate changes in the active and passive phases of the flexion relaxation response after a 12-week exercise intervention in chronic LBP patients.
  • To assess the impact of exercise on neuromuscular activation patterns during trunk flexion.

Main Methods:

  • A pre- and post-intervention study design was employed.
  • Fifteen chronic LBP patients underwent a 12-week training program.
  • Surface electromyography (EMG) measured the flexion relaxation response, alongside Oswestry Disability Index and Visual Analog Scale.

Main Results:

  • Significant improvements in Oswestry Disability Index and Visual Analog Scale scores were observed.
  • No significant changes were noted in the active components of the flexion relaxation measurement.
  • A notable ~67% reduction in EMG activity during the relaxation phase at full trunk flexion was recorded.

Conclusions:

  • Exercise interventions can significantly alter the flexion relaxation phenomenon in LBP patients.
  • The observed decrease in activity during the relaxation phase suggests improved neuromuscular control.
  • Changes in afferent feedback mechanisms are hypothesized to underlie the observed improvements in electrical relaxation.