HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS		QUICK SEARCH:   [advanced] Author: Keyword(s): Year:  Vol:  Page:

This Article Full Text Full Text (PDF) All Versions of this Article: 543/1/289    most recent 2002.023861v2 2002.023861v1 Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Kilbreath, S. L. Articles by Gandevia, S. C. Search for Related Content PubMed PubMed Citation Articles by Kilbreath, S. L. Articles by Gandevia, S. C.

Distribution of the forces produced by motor unit activity in the human flexor digitorum profundus

S. L. Kilbreath, R. B. Gorman *, J. Raymond † and S. C. Gandevia †

In humans, the flexor digitorum profundus (FDP), which is a multi-tendoned muscle, produces forces that flex the four distal interphalangeal joints of the fingers. We determined whether the force associated with activity in a single motor unit in the FDP was confined to a single finger or distributed to more than one finger during a natural grasp. The discharge of single low-threshold motor units (n = 69) was recorded at sites across the muscle during weak voluntary grasping involving all fingers and spike-triggered averaging of the forces under each of the finger pads was used to assess the distribution pattern. Spike-triggered averaging revealed that time-locked changes in force occurred under the 'test' finger (that finger on which the unit principally acted) as well as under the 'non-test' fingers. However, for the index-, middle- and ring-finger units, the changes in force under non-test fingers were typically small (< 20 % of those under the test finger). For little-finger units, the mean changes in force under the adjacent ring finger were large (>50 % of those under the test finger). The distribution of forces by little-finger units differed significantly from that for each of the other three fingers. Apart from increases in force under non-test fingers, there was occasional unloading of adjacent fingers (22/267 combinations), usually affecting the index finger. The increases in force under the test finger correlated significantly with the background force for units acting on the middle, ring and little fingers. During a functional grasp, the activity of single units in the FDP allows for a relatively selective control of forces at the tips of the index, middle and ring fingers, but this is limited for little-finger units.

This article has been cited by other articles:

				W. S. Yu, S. L. Kilbreath, R. C. Fitzpatrick, and S. C. Gandevia Thumb and finger forces produced by motor units in the long flexor of the human thumb J. Physiol., September 15, 2007; 583(3): 1145 - 1154. [Abstract] [Full Text] [PDF]

				T. J Butler, S. L Kilbreath, R. B Gorman, and S. C Gandevia Selective recruitment of single motor units in human flexor digitorum superficialis muscle during flexion of individual fingers J. Physiol., August 15, 2005; 567(1): 301 - 309. [Abstract] [Full Text] [PDF]

				S. A. Winges and M. Santello Common Input to Motor Units of Digit Flexors During Multi-Digit Grasping J Neurophysiol, December 1, 2004; 92(6): 3210 - 3220. [Abstract] [Full Text] [PDF]

				K. T. Reilly, M. A. Nordstrom, and M. H. Schieber Short-Term Synchronization Between Motor Units in Different Functional Subdivisions of the Human Flexor Digitorum Profundus Muscle J Neurophysiol, August 1, 2004; 92(2): 734 - 742. [Abstract] [Full Text] [PDF]

				M. H. Schieber and M. Santello Hand function: peripheral and central constraints on performance J Appl Physiol, June 1, 2004; 96(6): 2293 - 2300. [Abstract] [Full Text] [PDF]

				C. E. Lang and M. H. Schieber Reduced Muscle Selectivity During Individuated Finger Movements in Humans After Damage to the Motor Cortex or Corticospinal Tract J Neurophysiol, April 1, 2004; 91(4): 1722 - 1733. [Abstract] [Full Text] [PDF]

				H. Maas, R. T. Jaspers, G. C. Baan, and P. A. Huijing Myofascial force transmission between a single muscle head and adjacent tissues: length effects of head III of rat EDL J Appl Physiol, November 1, 2003; 95(5): 2004 - 2013. [Abstract] [Full Text] [PDF]

				K. T. Reilly and M. H. Schieber Incomplete Functional Subdivision of the Human Multitendoned Finger Muscle Flexor Digitorum Profundus: An Electromyographic Study J Neurophysiol, October 1, 2003; 90(4): 2560 - 2570. [Abstract] [Full Text] [PDF]

				C. E. Lang and M. H. Schieber Differential Impairment of Individuated Finger Movements in Humans After Damage to the Motor Cortex or the Corticospinal Tract J Neurophysiol, August 1, 2003; 90(2): 1160 - 1170. [Abstract] [Full Text] [PDF]