PMID- 18642354
OWN - NLM
STAT- MEDLINE
DCOM- 20081105
LR  - 20080828
IS  - 0148-639X (Print)
IS  - 0148-639X (Linking)
VI  - 38
IP  - 3
DP  - 2008 Sep
TI  - Age-related reductions in the estimated numbers of motor units are minimal in the 
      human soleus.
PG  - 1108-15
LID - 10.1002/mus.20984 [doi]
AB  - The documented impact of contractile level on decomposition-enhanced 
      spike-triggered averaging motor unit number estimates (MUNEs) in young adults 
      demonstrates the importance of selecting an objective contraction intensity that 
      yields the most representative MUNE for a given muscle. Whether the same 
      contraction intensity would be ideal in an altered system (e.g., by aging or 
      disease) has yet to be examined. Thus, the main purpose of this study was to 
      compare the effects of contraction intensity on MUNEs from the soleus muscle in 
      young ( approximately 27 years) and old ( approximately 75 years) men. Using 
      decomposition-enhanced spike-triggered averaging, surface and intramuscular 
      electromyographic signals were collected from the soleus during a range of 
      submaximal isometric plantar-flexion contractions (threshold, 10%, 20%, and 30% 
      of maximum voluntary contraction; MVC). Five MUNEs were calculated, one for each 
      of the four contraction intensities and an ensemble MUNE was derived from all MUs 
      collected. Although MUNE decreased similarly with increased effort in both 
      groups, MUNEs were not significantly reduced in the old men compared to the young 
      men. Consequently, the ensemble MUNE was extrapolated to an intensity of 
      approximately 15% MVC in both young and old. The results suggest that, in the 
      soleus, the use of the same contraction intensity across age groups is a valid 
      comparison.
FAU - Dalton, Brian H
AU  - Dalton BH
AD  - Canadian Centre for Activity and Aging, School of Kinesiology, University of 
      Western Ontario, London, Ontario, N6A 5B9, Canada.
FAU - McNeil, Chris J
AU  - McNeil CJ
FAU - Doherty, Timothy J
AU  - Doherty TJ
FAU - Rice, Charles L
AU  - Rice CL
LA  - eng
PT  - Journal Article
PT  - Research Support, Non-U.S. Gov't
PL  - United States
TA  - Muscle Nerve
JT  - Muscle & nerve
JID - 7803146
SB  - IM
MH  - Action Potentials/physiology
MH  - Adult
MH  - Aged
MH  - *Aging
MH  - Analysis of Variance
MH  - Electric Stimulation
MH  - Electromyography/methods
MH  - Humans
MH  - Male
MH  - Motor Neurons/*physiology
MH  - Muscle Contraction/physiology
MH  - Muscle Strength Dynamometer
MH  - Muscle, Skeletal/*cytology/*physiology
MH  - Weights and Measures
EDAT- 2008/07/22 09:00
MHDA- 2008/11/06 09:00
CRDT- 2008/07/22 09:00
PHST- 2008/07/22 09:00 [pubmed]
PHST- 2008/11/06 09:00 [medline]
PHST- 2008/07/22 09:00 [entrez]
AID - 10.1002/mus.20984 [doi]
PST - ppublish
SO  - Muscle Nerve. 2008 Sep;38(3):1108-15. doi: 10.1002/mus.20984.