A Novel Noninvasive Method for Measuring Fatigability of the Quadriceps Muscle in Noncooperating Healthy Subjects.
BACKGROUND
Critical illness is associated with muscle weakness leading to long-term functional limitations.


OBJECTIVE
To assess the reliability of a novel method for evaluating fatigability of the quadriceps muscle in noncooperating healthy subjects.


METHODS
On two occasions, separated by seven days, nonvoluntary isometric contractions (twitch and tetanic) of the quadriceps femoris muscle evoked by transcutaneous electrical muscle stimulation were recorded in twelve healthy adults. For tetanic contractions, the Fatigue Index (ratio of peak torque values) and the slope of the regression line of peak torque values were primary outcome measures. For twitch contractions, maximum peak torque and rise time were calculated. Relative (intraclass correlation, ICC3.1) and absolute (standard error of measurement, SEM) reliability were assessed and minimum detectable change was calculated using a 95% confidence interval (MDC95%).


RESULTS
The Fatigue Index (ICC3.1, 0.84; MDC95%, 0.12) and the slope of the regression line (ICC3.1, 0.99; MDC95%, 0.03) showed substantial relative and absolute reliability during the first 15 and 30 contractions, respectively.


CONCLUSIONS
This method for assessing fatigability of the quadriceps muscle produces reliable results in healthy subjects and may provide valuable data on quantitative changes in muscle working capacity and treatment effects in patients who are incapable of producing voluntary muscle contractions.
Department of Intensive Care, Rigshospitalet, Copenhagen University Hospital, 2100 Copenhagen OE, Denmark.
Jesper B
JB
Poulsen
Section of Integrated Physiology, Department of Nutrition, Exercise and Sport, University of Copenhagen, 2200 Copenhagen N, Denmark.
Martin H
MH
Rose
Neurointensive Care Unit, Department of Neuroanaesthesiology, Rigshospitalet, Copenhagen University Hospital, 2100 Copenhagen OE, Denmark ; Centre of Inflammation and Metabolism, Rigshospitalet, Copenhagen University Hospital, 2100 Copenhagen OE, Denmark.
Kirsten
K
Møller
Department of Intensive Care, Rigshospitalet, Copenhagen University Hospital, 2100 Copenhagen OE, Denmark.
Anders
A
Perner
Section of Integrated Physiology, Department of Nutrition, Exercise and Sport, University of Copenhagen, 2200 Copenhagen N, Denmark.
Bente R
BR
Jensen
D000328:Adult; D005260:Female; D064368:Healthy Volunteers; D006801:Humans; D007537:Isometric Contraction / Q000502:physiology; D008297:Male; D009119:Muscle Contraction / Q000502:physiology; D018763:Muscle Fatigue / Q000502:physiology*; D018908:Muscle Weakness / Q000503:physiopathology*; D052097:Quadriceps Muscle / Q000503:physiopathology*; D004561:Transcutaneous Electric Nerve Stimulation