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Related Concept Videos

Isotonic and Isometric Muscle Contractions01:22

Isotonic and Isometric Muscle Contractions

Two primary types of muscle contractions are isotonic and isometric, each serving unique functions and involving distinct mechanisms. Both isotonic and isometric contractions are integral to the body's complex system of movement and stability. Isotonic exercises contribute significantly to functional strength and movement, while isometric contractions are crucial for maintaining posture and joint stability.
Isotonic contractions
Isotonic contractions occur when a muscle changes length while the...
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...
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...
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.
Alterations in Muscle Tone ll01:12

Alterations in Muscle Tone ll

Alterations in muscle tone are common manifestations of neurological disorders and reflect dysfunction within different nervous system regions. Spasticity, paratonia, and dystonia represent distinct forms of hypertonia, each with unique mechanisms, clinical features, and diagnostic importance.CharacteristicsSpasticity happens from upper motor neuron lesions and is characterized by velocity-dependent resistance to passive movement. Clinical features include:Exaggerated deep tendon reflexesClonus...

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Application of Chronic Stimulation to Study Contractile Activity-induced Rat Skeletal Muscle Phenotypic Adaptations
09:50

Application of Chronic Stimulation to Study Contractile Activity-induced Rat Skeletal Muscle Phenotypic Adaptations

Published on: January 25, 2018

Age-associated changes in muscle activity during isometric contraction.

Sridhar P Arjunan1, Dinesh K Kumar

  • 1Biosignals Laboratory, School of Electrical and Computing Engineering, Royal Melbourne Institute of Technology University, GPO Box 2476, Melbourne, 3001, Australia. sridhar.arjunan@rmit.edu.au

Muscle & Nerve
|December 4, 2012
PubMed
Summary

Aging reduces muscle activity complexity and increases force variability. These changes in muscle contraction are linked, potentially due to increased motor unit density with age.

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Area of Science:

  • Physiology
  • Biomedical Engineering
  • Gerontology

Background:

  • Aging impacts neuromuscular function, affecting muscle activity complexity and force control.
  • Understanding age-related changes in muscle contraction is crucial for maintaining physical function.

Purpose of the Study:

  • To investigate the effects of aging on the complexity of muscle activity.
  • To examine age-related changes in the force variance during isometric contractions.
  • To explore the relationship between muscle activity complexity and force variability.

Main Methods:

  • Surface electromyography (sEMG) of the biceps brachii and isometric contraction force were recorded.
  • 96 participants aged 20-70 years were included in the study.
  • Data analysis involved assessing sEMG complexity and force variability (coefficient of variation).

Main Results:

  • A decrease in sEMG complexity was observed with increasing age, with a significant change around 45 years.
  • The coefficient of variation (CoV) of muscle contraction force increased with age.
  • Reduced sEMG complexity strongly correlated with increased force CoV (r² = 0.76).

Conclusions:

  • Aging is associated with reduced muscle activity complexity and increased force variability.
  • The observed relationship suggests that age-related changes in motor unit density may underlie these neuromuscular alterations.