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Related Experiment Videos

Muscle activation differences between eccentric and concentric isokinetic exercise

E Kellis1, V Baltzopoulos

  • 1Division of Sport Science, University of Northumbria, Newcastle upon Tyne, United Kingdom.

Medicine and Science in Sports and Exercise
|November 14, 1998
PubMed
Summary
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Eccentric knee muscle actions generate greater joint moments but lower neural activation compared to concentric actions. Antagonist muscle activity significantly influences joint moments during isokinetic movements, especially at faster speeds.

Area of Science:

  • Biomechanics
  • Human Physiology
  • Kinesiology

Background:

  • Understanding the differences in muscle activation and joint moments between eccentric and concentric contractions is crucial for optimizing training and rehabilitation strategies.
  • Isokinetic testing allows for controlled assessment of muscle function across a range of speeds.

Purpose of the Study:

  • To compare electromyographic (EMG) activity and joint moments of agonists and antagonists during isokinetic eccentric and concentric knee muscle actions.
  • To investigate the influence of angular velocity on these parameters.

Main Methods:

  • Twelve healthy females performed maximal knee extension and flexion on a Biodex dynamometer at various angular velocities (30-150 degrees/s).
  • Electromyographic (EMG) activity of key knee muscles (vastus lateralis, rectus femoris, vastus medialis, hamstrings) was recorded.

Related Experiment Videos

  • Muscle moments and EMG data were normalized to maximum isometric values for comparison.

    • Main Results:

    • Normalized eccentric moments were significantly greater than concentric moments (P < 0.05).
    • Normalized integrated EMG (IEMG) for both agonists and antagonists was significantly lower during eccentric compared to concentric actions (P < 0.05).
    • These differences were more pronounced at higher angular velocities.

    Conclusions:

    • Neural activation and muscular action differ significantly between isokinetic eccentric and concentric tests, varying with angular velocity.
    • Antagonist EMG activity is muscle-dependent and plays a critical role in determining resultant joint moments during maximal voluntary movements.