Measurement of contractile and electrical properties of single human thenar motor units in response to intraneural motor-axon stimulation

G. Westling, R. S. Johansson, Christine K Thomas, B. Bigland-Ritchie

Research output: Contribution to journalArticle

66 Citations (Scopus)

Abstract

1. A method is described for measuring contractile properties of single human motor units. Conventional human microneurographic techniques were adapted to stimulate individual motor axons in the median nerve, with the use of negative current pulses and a tungsten microelectrode, while recording motor-unit electromyographic activity (EMG) and isometric force responses from the thenar muscles. 2. EMG signals were recorded from both proximal and distal thenar muscle surfaces. Force was recorded in two directions (thumb flexion and abduction). This allowed calculation of the direction and magnitude of resultant force exerted by each unit. 3. Data accepted as originating from a single unit satisfied all the traditional 'all-or-none' criteria. Additional criteria also required the following: 1) a wide safety margin between the threshold for unit activation and the current intensity needed to elicit responses from other units; 2) that the characteristic direction in which each unit generated force did not change during the recording period; and 3) whenever F-responses were encountered, the second EMG waveform was identical to the first - a highly improbable event if more than one unit had been excited. 4. Respiration and blood pressure waves introduced baseline fluctuations that distorted the force measurements. These fluctuations were minimized by synchronizing stimuli to the pulse pressure cycle and resetting the baseline electronically just before stimulus onset. 5. Combining motor-axon stimulation at a site remote from the muscle with electronic resetting of the force baseline and delivery of stimuli at fixed intervals after the pulse pressure waves allowed the full time course of human motor-unit twitch and tetanic force and EMG signals to be recorded accurately without signal averaging.

Original languageEnglish
Pages (from-to)1331-1338
Number of pages8
JournalJournal of Neurophysiology
Volume64
Issue number4
StatePublished - Jan 1 1990

Fingerprint

Axons
Blood Pressure
Muscles
Tungsten
Median Nerve
Thumb
Microelectrodes
Respiration
Safety
Direction compound

ASJC Scopus subject areas

  • Physiology
  • Neuroscience(all)

Cite this

Measurement of contractile and electrical properties of single human thenar motor units in response to intraneural motor-axon stimulation. / Westling, G.; Johansson, R. S.; Thomas, Christine K; Bigland-Ritchie, B.

In: Journal of Neurophysiology, Vol. 64, No. 4, 01.01.1990, p. 1331-1338.

Research output: Contribution to journalArticle

Westling, G. ; Johansson, R. S. ; Thomas, Christine K ; Bigland-Ritchie, B. / Measurement of contractile and electrical properties of single human thenar motor units in response to intraneural motor-axon stimulation. In: Journal of Neurophysiology. 1990 ; Vol. 64, No. 4. pp. 1331-1338.
@article{d369957a24c542e9a7df7ee7037baacc,
title = "Measurement of contractile and electrical properties of single human thenar motor units in response to intraneural motor-axon stimulation",
abstract = "1. A method is described for measuring contractile properties of single human motor units. Conventional human microneurographic techniques were adapted to stimulate individual motor axons in the median nerve, with the use of negative current pulses and a tungsten microelectrode, while recording motor-unit electromyographic activity (EMG) and isometric force responses from the thenar muscles. 2. EMG signals were recorded from both proximal and distal thenar muscle surfaces. Force was recorded in two directions (thumb flexion and abduction). This allowed calculation of the direction and magnitude of resultant force exerted by each unit. 3. Data accepted as originating from a single unit satisfied all the traditional 'all-or-none' criteria. Additional criteria also required the following: 1) a wide safety margin between the threshold for unit activation and the current intensity needed to elicit responses from other units; 2) that the characteristic direction in which each unit generated force did not change during the recording period; and 3) whenever F-responses were encountered, the second EMG waveform was identical to the first - a highly improbable event if more than one unit had been excited. 4. Respiration and blood pressure waves introduced baseline fluctuations that distorted the force measurements. These fluctuations were minimized by synchronizing stimuli to the pulse pressure cycle and resetting the baseline electronically just before stimulus onset. 5. Combining motor-axon stimulation at a site remote from the muscle with electronic resetting of the force baseline and delivery of stimuli at fixed intervals after the pulse pressure waves allowed the full time course of human motor-unit twitch and tetanic force and EMG signals to be recorded accurately without signal averaging.",
author = "G. Westling and Johansson, {R. S.} and Thomas, {Christine K} and B. Bigland-Ritchie",
year = "1990",
month = "1",
day = "1",
language = "English",
volume = "64",
pages = "1331--1338",
journal = "Journal of Neurophysiology",
issn = "0022-3077",
publisher = "American Physiological Society",
number = "4",

}

TY - JOUR

T1 - Measurement of contractile and electrical properties of single human thenar motor units in response to intraneural motor-axon stimulation

AU - Westling, G.

AU - Johansson, R. S.

AU - Thomas, Christine K

AU - Bigland-Ritchie, B.

PY - 1990/1/1

Y1 - 1990/1/1

N2 - 1. A method is described for measuring contractile properties of single human motor units. Conventional human microneurographic techniques were adapted to stimulate individual motor axons in the median nerve, with the use of negative current pulses and a tungsten microelectrode, while recording motor-unit electromyographic activity (EMG) and isometric force responses from the thenar muscles. 2. EMG signals were recorded from both proximal and distal thenar muscle surfaces. Force was recorded in two directions (thumb flexion and abduction). This allowed calculation of the direction and magnitude of resultant force exerted by each unit. 3. Data accepted as originating from a single unit satisfied all the traditional 'all-or-none' criteria. Additional criteria also required the following: 1) a wide safety margin between the threshold for unit activation and the current intensity needed to elicit responses from other units; 2) that the characteristic direction in which each unit generated force did not change during the recording period; and 3) whenever F-responses were encountered, the second EMG waveform was identical to the first - a highly improbable event if more than one unit had been excited. 4. Respiration and blood pressure waves introduced baseline fluctuations that distorted the force measurements. These fluctuations were minimized by synchronizing stimuli to the pulse pressure cycle and resetting the baseline electronically just before stimulus onset. 5. Combining motor-axon stimulation at a site remote from the muscle with electronic resetting of the force baseline and delivery of stimuli at fixed intervals after the pulse pressure waves allowed the full time course of human motor-unit twitch and tetanic force and EMG signals to be recorded accurately without signal averaging.

AB - 1. A method is described for measuring contractile properties of single human motor units. Conventional human microneurographic techniques were adapted to stimulate individual motor axons in the median nerve, with the use of negative current pulses and a tungsten microelectrode, while recording motor-unit electromyographic activity (EMG) and isometric force responses from the thenar muscles. 2. EMG signals were recorded from both proximal and distal thenar muscle surfaces. Force was recorded in two directions (thumb flexion and abduction). This allowed calculation of the direction and magnitude of resultant force exerted by each unit. 3. Data accepted as originating from a single unit satisfied all the traditional 'all-or-none' criteria. Additional criteria also required the following: 1) a wide safety margin between the threshold for unit activation and the current intensity needed to elicit responses from other units; 2) that the characteristic direction in which each unit generated force did not change during the recording period; and 3) whenever F-responses were encountered, the second EMG waveform was identical to the first - a highly improbable event if more than one unit had been excited. 4. Respiration and blood pressure waves introduced baseline fluctuations that distorted the force measurements. These fluctuations were minimized by synchronizing stimuli to the pulse pressure cycle and resetting the baseline electronically just before stimulus onset. 5. Combining motor-axon stimulation at a site remote from the muscle with electronic resetting of the force baseline and delivery of stimuli at fixed intervals after the pulse pressure waves allowed the full time course of human motor-unit twitch and tetanic force and EMG signals to be recorded accurately without signal averaging.

UR - http://www.scopus.com/inward/record.url?scp=0025093854&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=0025093854&partnerID=8YFLogxK

M3 - Article

VL - 64

SP - 1331

EP - 1338

JO - Journal of Neurophysiology

JF - Journal of Neurophysiology

SN - 0022-3077

IS - 4

ER -