Load-dependence of fatigue related changes in tremor around 10 Hz.
OBJECTIVE
The aim of the study was to investigate the effects of different loads on tremor around 10 Hz during fatiguing contractions.


METHODS
Eighteen healthy volunteers performed sustained isometric knee extensions at 30%, 50% and 70% maximum voluntary contraction (MVC). During the fatiguing contractions, mechanical recordings were made with a high-resolution force sensor. Tremor-power was calculated for the 6-20 Hz frequency window as a function of time normalized to endurance time.


RESULTS
Initial tremor power was different between the high and low load tasks. Changes of tremor with contraction time differed between the three tasks, in that tremor of the 30% MVC contraction showed the least decrease throughout the sustained contraction, whilst that of the 50% and 70% MVC showed progressively higher decreases. At failure, all 3 contractions merged to the same tremor level.


CONCLUSIONS
Load-dependent, fatigue-related 6-20 Hz tremor changes during sustained submaximum voluntary contractions seem mainly the consequence of recruitment of new units and fatigue-related properties of the high threshold motor units of muscles.
Ebenbichler
G R
GR
Department of Physical Medicine and Rehabilitation, University of Vienna, Austria. gerold.ebenbichler@akh-wien.ac.at
Kollmitzer
J
J
Erim
Z
Z
Löscher
W N
WN
Kerschan
K
K
Posch
M
M
Nowotny
T
T
Kranzl
A
A
Wöber
C
C
Bochdansky
T
T
D000328:Adult; D005260:Female; D007839:Functional Laterality; D006801:Humans; D007537:Isometric Contraction / Q000502:physiology*; D007719:Knee Joint; D008297:Male; D009043:Motor Activity; D018763:Muscle Fatigue / Q000502:physiology*; D010807:Physical Endurance; D011597:Psychomotor Performance / Q000502:physiology*; D012016:Reference Values; D012146:Rest; D014202:Tremor; D016474:Weight-Bearing