Effect of agonist load on fastest muscle contractions in human elbow flexors
Related Experiment Video
Updated: Oct 28, 2026

In Vivo Measurement of Hindlimb Dorsiflexor Isometric Torque from Pig
Published on: September 3, 2021
M M Wierzbicka1, D P Cros, E L Logigian
1Spinal Cord Injury Service, West Roxbury VA Medical Center, MA, USA.
Abstract:
The purpose of this study was to investigate whether the central nervous system (CNS) motor program subserving most-rapid voluntary force pulse generation is modified according to the level of agonist muscle load maintained prior to the pulse. Five normal subjects produced most-rapid force pulses to a target of 20% maximum voluntary force (MVF) above different levels of steady tonic contraction. Time to reach peak force, the first agonist burst duration and area were relatively constant for loads up to approximately 40% of MVF and then increased substantially with larger loads. These results indicate that the CNS adjusts agonist burst amplitude and duration in order to accomplish the same rapid motor task depending on the load. It is argued that these adjustments are necessary to compensate for physiological limitations of motor unit behavior and non-linearity between EMG activity and phasic force output.
Related Concept Videos
Motor Unit Stimulation
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...
Muscle Coordination and Action
Agonists
Agonist muscles, often called prime movers, are the primary muscles responsible for producing a specific movement.
Muscle Stimulation Frequency
Wave summation
At low firing rates, motor neurons induce individual twitch contractions in muscle fibers. These twitches...
Isotonic and Isometric Muscle Contractions
Isotonic contractions
Isotonic contractions occur when a muscle changes length while the...
Muscle Contraction
Muscle Contraction

