Firing rate of individual motor units in voluntary contraction of abductor digiti minimi muscle in man.

Abstract The frequency and variability of discharges of motor units in abductor digiti minimi muscle of 11 human subjects were investigated. In the first series, contraction was performed so as to raise the tension as linearly as possible from 0 to maximum in 2, 3.2, 5, 8, and 10 sec. There was a rise in discharge frequency when the tension was raised; this rise was steeper when the contraction was faster. The frequency at the start of discharge was higher, and the peak value of frequency was also higher at contractions with greater speeds. Irregular fluctuations in the discharge frequency was greater and appeared at earlier stages during the more rapid contractions. In the second series of experiments, the tension was held constant at various levels covering the entire range of contraction. At contractions with larger steady tension the discharge frequency of units was found to be higher and irregularity of discharge was enhanced. The units recruited at smaller tension vary over a greater range of discharge frequencies than those recruited at larger tension.

[1]  H P Clamann,et al.  Activity of single motor units during isometric tension , 1970, Neurology.

[2]  Olive C. Smith,et al.  ACTION POTENTIALS FROM SINGLE MOTOR UNITS IN VOLUNTARY CONTRACTION , 1934 .

[3]  O. Lippold,et al.  Motor unit activity in the voluntary contraction of human muscle , 1954, The Journal of physiology.

[4]  J. Petajan,et al.  Frequency control of motor unit action potentials. , 1969, Electroencephalography and clinical neurophysiology.

[5]  E. Evarts,et al.  Relation of pyramidal tract activity to force exerted during voluntary movement. , 1968, Journal of neurophysiology.

[6]  C D Marsden,et al.  Isolated single motor units in human muscle and their rate of discharge during maximal voluntary effort. , 1971, The Journal of physiology.

[7]  D. M. Lewis,et al.  The rate of tension development in isometric tetanic contractions of mammalian fast and slow skeletal muscle , 1965, The Journal of physiology.

[8]  D. Lindsley,et al.  ELECTRICAL ACTIVITY OF HUMAN MOTOR UNITS DURING VOLUNTARY CONTRACTION , 1935 .

[9]  R. Miledi,et al.  Presynaptic failure of neuromuscular propagation in rats , 1959, The Journal of physiology.

[10]  C. G. Phillips,et al.  THE PYRAMIDAL PROJECTION TO MOTONEURONES OF SOME MUSCLE GROUPS OF THE BABOON'S FORELIMB. , 1964, Progress in brain research.

[11]  F H NORRIS,et al.  Action potentials of single motor units in normal muscle. , 1955, Electroencephalography and clinical neurophysiology.

[12]  R. Person,et al.  Discharge frequency and discharge pattern of human motor units during voluntary contraction of muscle. , 1972, Electroencephalography and clinical neurophysiology.

[13]  J Tanji,et al.  Recruitment of motor units in voluntary contraction of a finger muscle in man. , 1973, Experimental neurology.

[14]  E. Adrian,et al.  The discharge of impulses in motor nerve fibres , 1929, The Journal of physiology.

[15]  F. Bracchi,et al.  Frequency stabilization in the motor centers of spinal cord and caudal brain stem. , 1966, The American journal of physiology.

[16]  J. Tanji,et al.  Discharges of single motor units at voluntary contraction of abductor digiti minimi muscle in man. , 1972, Brain research.