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Related Concept Videos

Ankle Joint01:10

Ankle Joint

The ankle is formed by the talocrural joint (crural = leg). It consists of the articulations between the talus bone of the foot and the distal ends of the tibia and fibula of the leg. The superior aspect of the talus bone is square-shaped and has three areas of articulation. The top of the talus articulates with the inferior tibia. This is the portion of the ankle joint that carries the body weight between the leg and foot. The sides of the talus are firmly held in position by the articulations...
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...
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...
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...
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.

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Related Experiment Video

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Diagnosis of Musculus Gastrocnemius Tightness - Key Factors for the Clinical Examination
08:43

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Relationship between ankle stiffness structure and muscle activation.

Hyunglae Lee1, Shuo Wang, Neville Hogan

  • 1Mechanical Engineering Department, Massachusetts Institute of Technology, MA 02139, USA. hyunglae@mit.edu

Annual International Conference of the IEEE Engineering in Medicine and Biology Society. IEEE Engineering in Medicine and Biology Society. Annual International Conference
|February 1, 2013
PubMed
Summary

Ankle stiffness increases with muscle activation, forming a "peanut" shape due to directional differences. This relationship remained highly linear for tibialis anterior and triceps surae activation.

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Area of Science:

  • Biomechanics
  • Human Movement Science
  • Musculoskeletal Research

Background:

  • Understanding ankle joint mechanics is crucial for diagnosing and treating movement disorders.
  • Muscle activation significantly influences joint stiffness, but its precise structural effects are not fully elucidated.
  • Quantifying ankle stiffness under varying muscle activation levels is essential for developing targeted rehabilitation strategies.

Purpose of the Study:

  • To characterize the structure of ankle stiffness across multiple muscle activation levels.
  • To investigate the relationship between muscle activation and ankle stiffness in the sagittal and frontal planes.
  • To determine if this relationship is linear for different ankle movements and muscle groups.

Main Methods:

  • Utilized a wearable ankle robot for multi-variable impedance estimation.
  • Employed visual feedback to guide subjects in maintaining target muscle activation levels (5%-30% MVC).
  • Measured ankle stiffness in dorsiflexion-plantarflexion and inversion-eversion directions.

Main Results:

  • Ankle stiffness increased with muscle activation, exhibiting a distinct "peanut" shape.
  • The increase in stiffness was more pronounced in the dorsiflexion-plantarflexion direction compared to inversion-eversion.
  • A highly linear relationship was observed between muscle activation and ankle stiffness across all measured directions and for both tibialis anterior and triceps surae activation.

Conclusions:

  • Ankle stiffness structure is direction-dependent and non-uniform, influenced by muscle activation levels.
  • The linear relationship between muscle activation and ankle stiffness provides a predictable model for joint behavior.
  • Findings are consistent across major ankle muscles, suggesting a generalizable principle of ankle joint control.