PMID- 8913200
OWN - NLM
STAT- MEDLINE
DCOM- 19961220
LR  - 20080909
IS  - 0013-4694 (Print)
IS  - 0013-4694 (Linking)
VI  - 101
IP  - 5
DP  - 1996 Oct
TI  - Motor control and kinetics during low level concentric and eccentric contractions 
      in man.
PG  - 453-60
AB  - Motor unit (MU) recruitment patterns were studied in 6 female subjects during 
      dynamic contractions at relative workloads corresponding to 10% maximum voluntary 
      contraction. The contractions consisted of a 20 degree elbow flexion (concentric 
      contraction) and extension (eccentric contraction) and MU action potential trains 
      were recorded from the brachial biceps muscle. The mean angular velocity of the 
      dynamic contractions was 10 degrees/s, during which a total of 119 MUs were 
      identified. Additionally, a few contractions were studied at 20 degrees/s during 
      which 30 MUs were identified, and 9 MUs during the 40 degrees/s contraction. 
      About 60% of the identified MUs were active during the concentric as well as the 
      eccentric phase for each of the velocities. Mean firing rate decreased 
      significantly when the contraction changed from concentric to eccentric, whereas 
      the number and properties of identified active MUs were similar. This emphasizes 
      firing rate modulation as important during low level dynamic contractions rather 
      than selective recruitment of different types of MUs in the concentric versus the 
      eccentric phase. Similar kinetic demands occur frequently in occupational tasks, 
      especially during monotonous work. The present data indicate that only a limited 
      pool of MUs are being recruited during such tasks. Extensive recruitment of these 
      MUs may cause fatigue and start a potentially vicious circle leading to 
      work-related muscle disorders.
FAU - Sogaard, K
AU  - Sogaard K
AD  - National Institute of Occupational Health, Department of Physiology, Copenhagen 
      O, Denmark.
FAU - Christensen, H
AU  - Christensen H
FAU - Jensen, B R
AU  - Jensen BR
FAU - Finsen, L
AU  - Finsen L
FAU - Sjogaard, G
AU  - Sjogaard G
LA  - eng
PT  - Journal Article
PT  - Research Support, Non-U.S. Gov't
PL  - Ireland
TA  - Electroencephalogr Clin Neurophysiol
JT  - Electroencephalography and clinical neurophysiology
JID - 0375035
SB  - IM
MH  - Action Potentials/*physiology
MH  - Adult
MH  - Arm/*physiology
MH  - Elbow/*physiology
MH  - Female
MH  - Humans
MH  - Middle Aged
MH  - Motor Neurons/*physiology
MH  - Muscle Contraction/*physiology
EDAT- 1996/10/01 00:00
MHDA- 1996/10/01 00:01
CRDT- 1996/10/01 00:00
PHST- 1996/10/01 00:00 [pubmed]
PHST- 1996/10/01 00:01 [medline]
PHST- 1996/10/01 00:00 [entrez]
PST - ppublish
SO  - Electroencephalogr Clin Neurophysiol. 1996 Oct;101(5):453-60.