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Updated: Jul 11, 2026
09:41
In Vivo Measurement of Hindlimb Dorsiflexor Isometric Torque from Pig
Published on: September 3, 2021
Joint angle and contraction mode influence quadriceps motor neuron pool excitability
Brian G Pietrosimone1, Robert R Hammill, Ethan N Saliba
1Exercise & Sport Injury Laboratory, University of Virginia, Charlottesville, Virginia, USA.
American Journal of Physical Medicine & Rehabilitation
|October 4, 2007
Summary
Central activation ratio (CAR) differs between isometric and eccentric contractions based on knee flexion angle. Isometric contractions show higher CAR at 30 degrees, while eccentric contractions show higher CAR at 70 degrees.
Area of Science:
- Biomechanics
- Neuromuscular Physiology
Background:
- Muscle activation assessment is crucial for understanding muscle function.
- Central Activation Ratio (CAR) quantifies voluntary muscle activation.
- Joint angle and contraction type influence muscle activation patterns.
Purpose of the Study:
- To compare the Central Activation Ratio (CAR) between eccentric and isometric contractions.
- To investigate the effect of knee flexion angle (30 and 70 degrees) on CAR.
Main Methods:
- Repeated-measures design with 16 healthy participants.
- CAR measured using the superimposed burst technique.
- Evaluated contractions at 30 and 70 degrees of knee flexion in both isometric and eccentric modes.
Main Results:
- Isometric CAR was significantly higher at 30° (0.88) than 70° (0.77) knee flexion.
- Eccentric CAR was significantly higher at 70° (0.87) than 30° (0.80) knee flexion.
- At 30°, isometric CAR > eccentric CAR; at 70°, eccentric CAR > isometric CAR.
Conclusions:
- CAR is significantly influenced by both joint angle and contraction mode.
- Isometric measures at a single joint angle may not generalize muscle activation for dynamic movements.
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