Muscle function measurements contribute to the evaluation of potential therapeutics for muscle pathology, as well as to the determination of mechanisms underlying physiology of this tissue. We will demonstrate the preparation of the extensor digitorum longus and diaphragm muscles for functional testing. Protocols for isometric and eccentric contractions will be shown, as well as differences in results between dystrophic muscles, representing a pathological state, and wildtype muscles.
Total time
~2–3 hours per mouse (dissection through data collection)
Model organism
Mouse (C57BL/6J wildtype and mdx dystrophic strains implied)
Steps
1
Dissect and prepare extensor digitorum longus muscle
Remove the EDL muscle from the murine hind limb under a dissecting microscope, carefully isolating the tissue and removing excess connective tissue. This preparation is essential for accurate force measurements.
▶ 02:07
2
Dissect and prepare diaphragm muscle tissue
Isolate the diaphragm muscle from the thoracic cavity and prepare it for mounting. This respiratory muscle serves as a functionally distinct comparison to limb muscles.
▶ 04:21
3
Mount isolated muscles in mechanics bath apparatus
Secure the prepared muscle between electrodes and force transducers in a temperature-controlled bath containing physiological saline. Proper mounting is critical for accurate force measurement.
▶ 05:57
4
Measure isometric muscle force contractions
Stimulate the muscle electrically to generate maximum isometric (fixed-length) contractions. Record peak force values to assess baseline muscle strength.
▶ 06:51
5
Measure eccentric muscle force during lengthening
Apply electrical stimulation while passively stretching the muscle to measure eccentric (lengthening) contractions. This protocol reveals force generation under load conditions.
▶ 08:52
6
Remove muscle from testing apparatus
Carefully detach the muscle tissue from the mechanics bath and electrodes following contraction testing to conclude the experimental procedure.
▶ 09:40
7
Compare wildtype and dystrophic muscle force profiles
Analyze and interpret differences in isometric and eccentric force generation between healthy wildtype and mdx dystrophic muscles to demonstrate pathological changes in muscle function.
▶ 10:59