"Avatar", a Modified Ex vivo Work Loop Experiments Using In vivo Strain and Activation
August 18th, 2023
This article details the methodology for emulating in vivo muscle force production during ex vivo work loop experiments using an "avatar" muscle from a laboratory rodent to assess the contributions of strain transients and activation to the muscle force response.
The goal of my laboratory is to understand in vivo muscle function by developing new experimental paradigms for ex vivo experiments and models that really relate to in vivo muscle function. The kind of experiments and models that we've been using over the past 20 years, it's become more and more obvious that they really don't relate to in vivo muscle function. Currently, there is a knowledge gap between top-down approaches that measure muscle function in vivo during dynamic movements of humans and animals, and bottom-up approaches that use controlled ex vivo and/or in situ experiments that measure muscle mechanics under isometric and/or isotonic conditions.
We are trying to design physiologically relevant ex vivo and in situ experiments that inform in vivo muscle mechanics. The most commonly used technique in our field is the sinusoidal work loop technique developed by Bob Josephson in the mid 1980s. This technique uses sinusoidal or sometimes satu strain trajectories at in vivo frequencies with in vivo stimulation patterns to emulate in vivo muscle function.
However, our Avatar technique demonstrates that deviations from purely sinusoidal strain trajectories resulting from foot contact during terrestrial locomotion are important determinants of muscle force and work.
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Overview
This article discusses the development of experimental paradigms for ex vivo muscle function that closely relate to in vivo conditions. It highlights the importance of bridging the knowledge gap between in vivo and ex vivo muscle mechanics.
Key Study Components
Area of Science
- Muscle physiology
- Experimental biology
- Biomechanics
Background
- Existing models often fail to replicate in vivo muscle function.
- There is a need for physiologically relevant experimental designs.
- The sinusoidal work loop technique is a commonly used method in this field.
- Understanding muscle mechanics is crucial for various applications in biology and medicine.
Purpose of Study
- To develop experimental models that accurately reflect in vivo muscle function.
- To assess the contributions of strain transients and activation to muscle force response.
- To improve the understanding of muscle mechanics during dynamic movements.
Methods Used
- Sinusoidal work loop technique for muscle force production.
- Use of laboratory rodent muscle as an avatar for experiments.
- Assessment of muscle response under controlled conditions.
- Comparison of ex vivo and in vivo muscle mechanics.
Main Results
- Demonstrated the effectiveness of the sinusoidal work loop technique.
- Identified key factors influencing muscle force response.
- Provided insights into the relationship between strain transients and activation.
- Highlighted the relevance of ex vivo models for understanding in vivo function.
Conclusions
- Ex vivo experiments can inform in vivo muscle mechanics.
- Bridging the gap between experimental approaches is essential.
- Future research should continue to refine these experimental paradigms.
