Influence of needle electrode depth on DE‐STA motor unit number estimation

Abstract

To assess a potential source of technique-associated error, we evaluated the influence of needle electrode depth on decomposition-enhanced spike-triggered averaging (DE-STA) motor unit number estimation (MUNE) and quantitative motor unit analysis in the upper trapezius (UT). The DE-STA MUNE protocol was performed at superficial, intermediate, and deep needle electrode depths in 18 control subjects. Mean surface-detected motor unit potential amplitudes were significantly smaller for intermediate versus superficial (P<0.05), deep versus superficial (P<0.001), and deep versus intermediate (P<0.05). MUNE was significantly larger for deep versus superficial (P<0.001), with statistical trends toward larger MUNE values at greater depths for the remaining comparisons. No significant differences were found among needle electrode depths for quantitative motor unit potential parameters. These results demonstrate the important influence of needle electrode depth on DE-STA MUNE in the UT. Suggestions are made for improved standardization of the protocol.