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Motor unit number index examination in dominant and non-dominant hand muscles. Laterality 2015;20(6):699-710 PMID: 26227495 PMCID: PMC4549196

Pubmed ID





This study investigated the effect of handedness on motor unit number index (MUNIX). Maximal hand strength, compound muscle action potential (CMAP) and voluntary surface electromyography (EMG) signals were measured bilaterally for the first dorsal interosseous (FDI) and thenar muscles in 24 right-handed and 2 left-handed healthy subjects. Mean (±standard error) grip and pinch forces in the dominant hand were 43.99 ± 2.36 kg and 9.36 ± 0.52 kg respectively, significantly larger than those in the non-dominant hand (grip: 41.37 ± 2.29 kg, p < .001; pinch: 8.79 ± 0.46 kg, p < .01). Examination of myoelectric parameters did not show a significant difference among the CMAP area, the MUNIX or motor unit size index (MUSIX) between the two sides in the FDI and thenar muscles. In addition, there was a lack of correlation between the strength and myoelectric parameters in regression analysis. However, strong correlations were observed between dominant and non-dominant hand muscles in both strength and myoelectric measures. Our results indicate that the population of motor units or spinal motor neurons as estimated from MUNIX may not be associated with handedness. Such findings help understand and interpret the MUNIX during its application for clinical or laboratory investigations.

Author List

Li X, He W, Li C, Wang YC, Slavens BA, Zhou P


Brooke Slavens BS,MS,PhD Assistant Professor in the Occupational Science & Technology department at University of Wisconsin - Milwaukee


2-s2.0-84940460093   1 Citations

MESH terms used to index this publication - Major topics in bold

Functional Laterality
Hand Strength
Middle Aged
Muscle Contraction
Muscle, Skeletal
Regression Analysis
Signal Processing, Computer-Assisted
Young Adult
jenkins-FCD Prod-331 a335b1a6d1e9c32173c9534e6f6ff51494143916