PMID- 16435342
OWN - NLM
STAT- MEDLINE
DCOM- 20060412
LR  - 20061115
IS  - 0148-639X (Print)
IS  - 0148-639X (Linking)
VI  - 33
IP  - 3
DP  - 2006 Mar
TI  - Augmentation of the contraction force of human thenar muscles by and during brief 
      discharge trains.
PG  - 384-92
AB  - We investigated the influence of the history of activity on the contractile 
      properties of abductor pollicis brevis (APB) to define how the forces produced by 
      individual stimuli change within a stimulus train, with a view to clarifying the 
      optimal discharge frequency for force production in brief trains. Supramaximal 
      electrical stimuli were delivered to the median nerve at the wrist singly or in 
      trains of 2-5 at various interstimulus intervals (ISIs). The force and 
      electromyographic (EMG) responses to trains of n stimuli were defined by online 
      subtraction of the responses to n - 1 stimuli. The force attributable to the nth 
      stimulus was normalized to that produced by a single stimulus. The contraction 
      force produced by 2 stimuli exceeded the force expected with linear summation of 
      2 single twitches by 30-40% at ISIs of 2-100 ms. Increasing the number of stimuli 
      resulted in less augmentation of the force produced by the last stimulus in the 
      train for ISIs up to 20 ms, but greater augmentation for ISIs of 50-100 ms. At 
      ISIs of less than 10 ms, the time to peak force produced by the last stimulus in 
      a 5-pulse train was delayed by approximately 100 ms, the peak force produced by 
      that stimulus was less than that produced by a single stimulus, and it occurred 
      on the falling phase of the overall contraction. These properties are best 
      explained by the catchlike property of muscle. This implies that the augmentation 
      of contraction force due to this property can increase throughout a stimulus 
      train, and is not restricted to the doublet discharges that have conventionally 
      been studied. We conclude that, with brief discharge trains, maximal forces occur 
      at ISIs of 56-75 ms, intervals that are longer than those conventionally 
      associated with the catchlike property. Discharge rates of 15-20 HZ appear to be 
      optimal for force generation by APB during steady contractions.
CI  - Muscle Nerve, 2006.
FAU - Howells, James
AU  - Howells J
AD  - Institute of Clinical Neurosciences, University of Sydney and Royal Prince Alfred 
      Hospital, Sydney, NSW 2006, Australia.
FAU - Trevillion, Louise
AU  - Trevillion L
FAU - Jankelowitz, Stacey
AU  - Jankelowitz S
FAU - Burke, David
AU  - Burke D
LA  - eng
PT  - Clinical Trial
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  - Adult
MH  - Electric Stimulation
MH  - Electromyography
MH  - Electrophysiology
MH  - Female
MH  - Humans
MH  - Male
MH  - Middle Aged
MH  - Muscle Contraction/physiology
MH  - Muscle, Skeletal/*pathology
MH  - Wrist/innervation/physiology
EDAT- 2006/01/26 09:00
MHDA- 2006/04/13 09:00
CRDT- 2006/01/26 09:00
PHST- 2006/01/26 09:00 [pubmed]
PHST- 2006/04/13 09:00 [medline]
PHST- 2006/01/26 09:00 [entrez]
AID - 10.1002/mus.20469 [doi]
PST - ppublish
SO  - Muscle Nerve. 2006 Mar;33(3):384-92. doi: 10.1002/mus.20469.