Discharge characteristics of motor units during long-duration contractions

被引:30
作者
Pascoe, Michael A. [1 ]
Holmes, Matthew R. [1 ]
Stuart, Douglas G. [2 ]
Enoka, Roger M. [1 ]
机构
[1] Univ Colorado, Dept Integrat Physiol, Boulder, CO 80309 USA
[2] Univ Arizona, Dept Physiol, Tucson, AZ USA
关键词
SPIKE FREQUENCY ADAPTATION; HUMAN BICEPS-BRACHII; VOLUNTARY CONTRACTION; HUMAN MOTONEURONS; SYNAPTIC NOISE; FIRING RATES; HAND MUSCLE; TIME-COURSE; LOAD TYPE; RECRUITMENT;
D O I
10.1113/expphysiol.2014.078584
中图分类号
Q4 [生理学];
学科分类号
071003 ;
摘要
The purpose of the study was to determine how long humans could sustain the discharge of single motor units during a voluntary contraction. The discharge of motor units in first dorsal interosseus of subjects (27.8 +/- 8.1 years old) was recorded for as long as possible. The task was terminated when the isolated motor unit stopped discharging action potentials, despite the ability of the individual to sustain the abduction force. Twenty-three single motor units were recorded. Task duration was 21.4 +/- 17.8 min. When analysed across discharge duration, mean discharge rate (10.6 +/- 1.8 pulses s(-1)) and mean abduction force (5.5 +/- 2.8% maximum) did not change significantly (discharge rate, P = 0.119; and abduction force, P = 0.235). In contrast, the coefficient of variation for interspike interval during the initial 30 s of the task was 22.2 +/- 6.0% and increased to 31.9 +/- 7.0% during the final 30 s (P < 0.001). All motor units were recruited again after 60 s of rest. Although subjects were able to sustain a relatively constant discharge rate, the cessation of discharge was preceded by a gradual increase in discharge variability. The findings also showed that the maximal duration of human motor unit discharge exceeds that previously reported for the discharge elicited in motor neurons by intracellular current injection in vitro.
引用
收藏
页码:1387 / 1398
页数:12
相关论文
共 59 条
[1]   Recruitment order of motor units in human vastus lateralis muscle is maintained during fatiguing contractions [J].
Adam, A ;
De Luca, CJ .
JOURNAL OF NEUROPHYSIOLOGY, 2003, 90 (05) :2919-2927
[2]   Rate coding is compressed but variability is unaltered for motor units in a hand muscle of old adults [J].
Barry, Benjamin K. ;
Pascoe, Michael A. ;
Jesunathadas, Mark ;
Enoka, Roger M. .
JOURNAL OF NEUROPHYSIOLOGY, 2007, 97 (05) :3206-3218
[3]   Load Type Influences Motor Unit Recruitment in Biceps Brachii During a Sustained Contraction [J].
Baudry, Stephane ;
Rudroff, Thorsten ;
Pierpoint, Lauren A. ;
Enoka, Roger M. .
JOURNAL OF NEUROPHYSIOLOGY, 2009, 102 (03) :1725-1735
[4]   Rotation of motoneurons during prolonged isometric contractions in humans [J].
Bawa, Parveen ;
Pang, Marco Y. ;
Olesen, Kari A. ;
Calancie, Blair .
JOURNAL OF NEUROPHYSIOLOGY, 2006, 96 (03) :1135-1140
[5]   Motor Unit Rotation in a Variety of Human Muscles [J].
Bawa, Parveen ;
Murnaghan, Chantelle .
JOURNAL OF NEUROPHYSIOLOGY, 2009, 102 (04) :2265-2272
[6]   Balanced inhibition and excitation drive spike activity in spinal half-centers [J].
Berg, Rune W. ;
Alaburda, Aidas ;
Hounsgaard, Jorn .
SCIENCE, 2007, 315 (5810) :390-393
[7]   Intense Synaptic Activity Enhances Temporal Resolution in Spinal Motoneurons [J].
Berg, Rune W. ;
Ditlevsen, Susanne ;
Hounsgaard, Jorn .
PLOS ONE, 2008, 3 (09)
[8]   MOTOR UNIT ACTIVITY IN THE VOLUNTARY CONTRACTION OF HUMAN MUSCLE [J].
BIGLAND, B ;
LIPPOLD, OCJ .
JOURNAL OF PHYSIOLOGY-LONDON, 1954, 125 (02) :322-335
[9]   FATIGUE OF INTERMITTENT SUBMAXIMAL VOLUNTARY CONTRACTIONS - CENTRAL AND PERIPHERAL FACTORS [J].
BIGLANDRITCHIE, B ;
FURBUSH, F ;
WOODS, JJ .
JOURNAL OF APPLIED PHYSIOLOGY, 1986, 61 (02) :421-429
[10]   CHANGES IN MOTONEURON FIRING RATES DURING SUSTAINED MAXIMAL VOLUNTARY CONTRACTIONS [J].
BIGLANDRITCHIE, B ;
JOHANSSON, R ;
LIPPOLD, OCJ ;
SMITH, S ;
WOODS, JJ .
JOURNAL OF PHYSIOLOGY-LONDON, 1983, 340 (JUL) :335-346