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. Author manuscript; available in PMC: 2020 Jun 18.
Published in final edited form as: Curr Opin Physiol. 2018 Dec 1;8:23–29. doi: 10.1016/j.cophys.2018.11.008

Figure 2. Functional characterization of mouse motor units in vivo.

Figure 2.

A–C. Procedure for type-identification of mouse MUs in vivo and examples of three MUs: FF (A), FR (B) and S (C). Individual twitch response allow measurement of twitch amplitudes and contraction time (A1, B1, C1). Series of unfused tetani allow to test the fatigability of the muscle fibers (A2–3, B2–3, C2–3). Motor units were classified as S-type if contraction time ≥20 ms; FR if contraction time <20 ms and twitch amplitude <8 mN; FF if contraction time <20 ms and twitch force ≥8 mN. See [22] for details. Figure from [22], licensed under CC-BY.