Related Experiment Video
Updated: Jun 25, 2026

Application of Chronic Stimulation to Study Contractile Activity-induced Rat Skeletal Muscle Phenotypic Adaptations
Published on: January 25, 2018
Effect of age on muscle activation and twitch properties during static and dynamic actions
Melissa R Wilder1, Jack Cannon
1Exercise and Sports Science Laboratories, School of Human Movement Studies, Charles Sturt University, Building N1, Panorama Avenue, Bathurst, New South Wales 2795, Australia.
Abstract:
In this investigation we examined age-associated changes in peak torque, voluntary activation levels, and potentiated twitch properties of the knee extensors during isometric (ISO), shortening (SHO), and lengthening (LEN) actions in 18 young subjects (19-27 years) and 12 elderly subjects (64-77 years). Peak torque was lower for the elderly subjects under the ISO (-31%) and SHO (-28%) conditions (P < 0.05); however, the loss in LEN peak torque in the elderly was less marked (-17%) (P > 0.05). Voluntary activation levels within and between groups were not significantly different and ranged between 96.8% and 98.9% (P > 0.05). Peak twitch torque and some temporal twitch characteristics were altered with age (P < 0.05), but such changes were similar across all muscle actions (P > 0.05). These data suggest that the attenuated reduction in LEN muscle strength associated with age is probably not related to contraction-specific changes in voluntary activation levels or potentiated twitch properties. Muscle Nerve, 2009.
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 Stimulation Frequency
Wave summation
At low firing rates, motor neurons induce individual twitch contractions in muscle fibers. These twitches...
Alterations in Muscle Tone ll
Alterations in Muscle Tone lll
Generation of Action Potential in Skeletal Muscles
Like neurons, muscle cells are also regarded as excitable due to their capacity to change in response to stimuli, primarily due to voltage-gated ion channels embedded in their plasma membranes, which get activated by alterations in the cell's...
Relaxation of Skeletal Muscles
When an action potential reaches the axon terminal, it depolarizes the membrane and opens voltage-gated sodium channels. Sodium ions enter the cell, further depolarizing the presynaptic membrane. This depolarization causes voltage-gated calcium channels to open.

