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. 2022 Feb 22:13:854385.
doi: 10.3389/fphys.2022.854385. eCollection 2022.

Motor Unit Number Estimation of the Second Lumbrical Muscle in Human Hand

Ya Zong  1 , Zhiyuan Lu  2 , Maoqi Chen  2 , Lianfu Deng  3 , Qin Xie  1 , Ping Zhou  2
Affiliations

Motor Unit Number Estimation of the Second Lumbrical Muscle in Human Hand

Ya Zong et al. Front Physiol. .

Abstract

The number of motor units of the lumbrical muscles in human hand has not been explored. The objective of this study was to fill this gap by estimating the number of motor units in the second lumbrical muscle. Compound muscle action potential scan of the second lumbrical muscle was performed in 12 healthy subjects, with 10 of them being tested on two separate occasions. Motor unit number estimation (MUNE) was derived from the MScanFit program. The average MUNE of the second lumbrical muscle was 41.6 ± 2.1 (mean ± standard error) from 12 subjects in the first test, and 42.0 ± 2.2 from 10 of the 12 subjects in the retest, demonstrating excellent measurement reliability. Findings of the study provide novel information about the motor unit number of the second lumbrical muscle in human hand. The relatively low motor unit number in the muscle can facilitate motor unit investigations, especially at high level muscle activation.

Keywords: CMAP scan; MScanFit; compound muscle action potential; motor unit number estimation; second lumbrical muscle.

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Conflict of interest statement

The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.

Figures

Figure 1
Figure 1
Electrode placement for CMAP scan recording of the second lumbrical muscle. Hand muscle anatomy showing the lumbricals can be found in https://learnmuscles.com/glossary/lumbricals-manus/.
Figure 2
Figure 2
Examples of CMAP scans from the same participant on two different testings. Stimulating range: 3.5–15 mA (testing #1), 3.5–16 mA (testing #2); CMAP amplitude: 2.31 mV (testing #1), 2.27 mV (testing #2); and MUNE: 40 (testing #1), 40 (testing #2).
Figure 3
Figure 3
Radar plot of the MUNE distribution of the 10 subjects for both visits. The numbers around the outside of the plot represent the individual subject number (1–10), and the numbers (0–60) are on contours of equal MUNE.
See this image and copyright information in PMC

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