F Response Frequency for the Median and Ulnar Nerves in a Normal Population

Date of Award

Summer 8-1992

Document Type


Degree Name

Master of Science (MS)


Rehabilitation Sciences


Physical Therapy

Committee Director

John L. Echternach

Committee Member

George A. Maihafer

Committee Member

R. P. Nielsen

Call Number for Print

Special Collections LD4331.P45K55


The F wave or F response results form the recurrent discharge of antidromically activated anterior horn cells. F response latency represents an impulse which travels to and from the spinal cord through the central segment of a nerve. Study of the F wave is commonly done to assess proximal conduction in motor nerves, to measure motor nerve conduction velocity over a longer pathway than in orthodromic motor studies, and to assess motor neuron excitability. F response characteristics less commonly studied include duration, chronodispersion, shape, amplitude, and frequency. The primary purpose of this study was to determine F response frequencies of the median and ulnar nerves in healthy subjects. Second, two different approaches to stimulation of the nerves were studied and compared. 21 healthy subjects were tested under similar circumstances, using a train of 50 stimuli at a rate of 1 Hz. F response frequency arising from all median nerves (n=42) ranged from 1 to 50 with a mean of 27.5 ± 13.3. F response frequency arising from all ulnar nerves ranged from 0 to 50 with a mean of 32.4 + 14.1. No significant difference was found between the mean frequencies for the bar and prong electrodes with median nerve stimulation. Median nerve mean frequencies for the bar and prong electrodes were 26.0 + 14.7 and 29.5 + 11.1, respectively. There was a significant difference between electrodes for the ulnar nerve (p < 0.05). Ulnar nerve mean frequencies for the bar and prong electrodes were 37.9 + 9.0 and 28.3 + 15.9, respectively. The distribution of frequencies for the median and ulnar nerves widely varied in this study. It is not clear determination of F response frequency for the median and ulnar nerves would be helpful in the evaluation of disease processes as there is much variability among subjects. This study suggests that the bar electrode provides a more consistent method of ulnar nerve stimulation. Results from this study highlight the need for more thorough investigation of all clinically relevant characteristics of the F response.


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