Concentric needle jitter on voluntary activated frontalis in 20 healthy subjects.

INTRODUCTION Normative data for jitter parameters using a disposable concentric needle have been described in a few studies. METHODS Jitter, expressed as the mean consecutive difference (MCD), was measured in the frontalis muscle in 20 subjects by voluntary contraction. RESULTS Mean MCD for individual studies (20, gaussian), all potentials (400, non-gaussian), and 18th highest value (20, gaussian) were 19.9 ± 2.9 μs, 19.9 ± 6.6 μs, and 26.9 ± 4.4 μs, respectively. CONCLUSION The suggested upper normal limit for mean MCD is 26 μs and for outliers is 36 μs.