Related Experiment Video
Updated: Aug 29, 2026

Induction and Assessment of Exertional Skeletal Muscle Damage in Humans
Published on: December 11, 2016
Regulatory light chain phosphorylation increases eccentric contraction-induced injury in skinned fast-twitch fibers
Martin K Childers1, Kerry S McDonald
1Department of Physical Medicine and Rehabilitation, DCO 46.00, One Hospital Drive, University of Missouri-Columbia, Columbia, Missouri 65212, USA. childersmk@health.missouri.edu
Abstract:
During contraction, activation of Ca(2+)/calmodulin-dependent myosin light chain kinase (MLCK) results in phosphorylation of myosin's regulatory light chain (RLC), which potentiates force and increases speed of force development over a wide range of [Ca(2+)]. We tested the hypothesis that RLC phosphorylation by MLCK mediates the extent of eccentric contraction-induced injury as measured by force deficit in skinned fast-twitch skeletal muscle fibers. Results indicated that RLC phosphorylation in single skinned rat psoas fibers significantly increased Ca(2+) sensitivity of isometric force; isometric force from 50 +/- 16 to 59 +/- 18 kN/m(2) during maximal Ca(2+) activation; peak absolute power output from 38 +/- 15 to 48 +/- 14 nW during maximal Ca(2+) activation; and the magnitude of contraction-induced force deficit during maximal (pCa 4.5) activation from 26 +/- 9.8 to 35 +/- 9.6%. We conclude that RLC phosphorylation increases force deficits following eccentric contractions, perhaps by increasing the number of force-generating cross-bridges.
Related Concept Videos
Cross-bridge Cycle
Excitation-Contraction Coupling in Skeletal Muscles
When an action potential...
Smooth Muscle Contraction
The onset of contraction is triggered by an increase in calcium ions within the sarcoplasm, similar to the process in striated muscle. However, smooth muscles have a relatively smaller reservoir of the sarcoplasmic...
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...
Energy Supply for Muscle Contraction
Muscle Recovery and Fatigue

