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Specific joint angle dependency of voluntary activation during eccentric knee extensions.

Valentin Doguet1, Valentin Rivière1, Arnaud Guével1

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Summary

Maximal muscle activation is reduced during eccentric contractions at longer knee angles (75° and 100°), but not at shorter angles (50°). This finding highlights differences in voluntary muscle activation across contraction types.

Keywords:
central activation ratioisometricmaximal contractionsmuscle lengthnegative workpositive work

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Area of Science:

  • Biomechanics
  • Human Physiology
  • Neuromuscular Function

Background:

  • Voluntary muscle activation is crucial for maximal force production.
  • Understanding activation differences across contraction types informs training and rehabilitation.

Purpose of the Study:

  • To compare voluntary muscle activation during isometric, concentric, and eccentric knee extensions.
  • To investigate the influence of joint angle on muscle activation.

Main Methods:

  • Fifteen participants underwent isometric, concentric, and eccentric knee extension protocols.
  • Central Activation Ratio (CAR) was measured at 50°, 75°, and 100° using nerve stimulation.

Main Results:

  • CAR increased with joint angle for all contraction types.
  • Eccentric contractions showed lower CAR than isometric and concentric at 75° and 100°.
  • CAR was similar across contraction types at 50°.

Conclusions:

  • Maximal voluntary muscle activation is impaired during eccentric contractions at longer joint angles.
  • Joint angle significantly modulates muscle activation capacity depending on contraction type.