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Effect of activation force on knee extensor torques.

J F Kramer1, M D Vaz, D Hakansson

  • 1Department of Physical Therapy, Faculty of Applied Health Sciences, University of Western Ontario, London, Canada.

Medicine and Science in Sports and Exercise
|February 1, 1991
PubMed
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Increasing activation force on an isokinetic dynamometer significantly impacts knee extensor torques, particularly eccentric and average measures. This highlights the importance of consistent activation force in resistance training protocols.

Area of Science:

  • Biomechanics
  • Exercise Physiology

Background:

  • Isokinetic dynamometers are crucial tools for assessing muscle strength and performance.
  • Understanding factors influencing torque production is essential for accurate strength testing and training program design.

Purpose of the Study:

  • To investigate the effect of varying activation force magnitudes on knee extensor torques.
  • To determine if activation force influences peak, average, and range-specific torques during knee extension.

Main Methods:

  • Twenty-four healthy females performed knee extensions using an isokinetic dynamometer.
  • Subjects were tested with three activation forces (20, 50, 100 N) and two angular velocities (45, 135 degrees/s).
  • Torque data (peak, average, range-specific) were collected during concentric and eccentric muscle actions.

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Main Results:

  • Peak knee extensor torques were not significantly affected by activation force.
  • Average torques, eccentric torques at mid-range, and initial portion torques increased with higher activation forces.
  • The influence of activation force was more pronounced during eccentric actions and at faster angular velocities.

Conclusions:

  • Activation force magnitude is a critical variable that influences specific measures of knee extensor torque.
  • Standardized activation force protocols are necessary for reliable and comparable isokinetic testing.
  • Future research should consider activation force when designing resistance training and testing protocols.