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Related Concept Videos

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...
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...
Neuroplasticity01:01

Neuroplasticity

Neuroplasticity reflects the brain's remarkable capacity to adapt and evolve, responding dynamically to learning, experiences, or injury by reorganizing its neural circuitry. This reorganization involves creating new neural connections and refining old ones through a series of biological processes that contribute to the brain's lifelong development and adaptability.
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.
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...

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Spinal reflex plasticity during maximal dynamic contractions after eccentric training.

Julien Duclay1, Alain Martin, Alice Robbe

  • 11INSERM U887, Dijon, France. julien.duclay@u-bourgogne.fr

Medicine and Science in Sports and Exercise
|March 5, 2008
PubMed
Summary

Eccentric strength training enhances spinal reflexes, particularly in the medial gastrocnemius, suggesting neural adaptations contribute to increased voluntary torque. This plasticity influences the balance of excitation and inhibition in motoneurons.

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Area of Science:

  • Neuroscience
  • Exercise Physiology
  • Motor Control

Background:

  • Eccentric strength training is known to increase muscle force production.
  • The neural mechanisms underlying these adaptations, especially concerning spinal reflex plasticity, require further elucidation.
  • Understanding spinal reflex modulation is crucial for optimizing training protocols and rehabilitation.

Purpose of the Study:

  • To investigate the plasticity of spinal reflexes in plantar flexor muscles following eccentric strength training.
  • To examine changes in H-reflex and V-wave responses during maximal voluntary contractions (MVC) of different types (isometric, concentric, eccentric).

Main Methods:

  • Eighteen healthy males participated, divided into an eccentric training group (N=10) and a control group (N=8).
  • The training group underwent 18 sessions of eccentric exercise over 7 weeks.
  • Spinal reflexes (H-reflex, V-wave) and M-waves were measured during passive and maximal voluntary contractions (isometric, concentric, eccentric) before, during, and after training.

Main Results:

  • H-reflex (Hmax/Mmax) and V-wave (V/Msup) responses showed significant changes in specific conditions after training.
  • The H-reflex ratio (Hsup/Msup) increased during eccentric MVC for soleus and all contraction types for medial gastrocnemius.
  • V/Msup ratios increased during isometric and eccentric contractions for soleus and all contraction types for medial gastrocnemius.

Conclusions:

  • Eccentric training induces neural adaptations, potentially involving increased supraspinal drive, contributing to enhanced voluntary torque.
  • Plasticity in spinal reflexes, specifically alterations in the excitation-inhibition balance within the motoneuron pool, underlies these training-induced changes.
  • These findings highlight the role of neural adaptations in response to eccentric exercise, offering insights into motor control and muscle plasticity.