Affiliations: [a] Department of Electrical Engineering, University of
Brasília, Brasília, Brazil | [b] National Police Academy, Brazil | [c] College of Physical Education, University of Brasilia,
Brasilia, Brazil | [d] Federal Institute of Sudeste of Minas Gerais, Rio
Pomba, Brazil | [e] California State University, Fullerton, CA, USA
Abstract: BACKGROUND: Normalization in surface electromyography (SEMG) has
been the object of numerous investigations. OBJECTIVE: The purpose of this study was to evaluate the reliability
of normalized SEMG amplitude, as well as the reliability of different
normalization coefficients during isokinetic upper-body strength assessment.
METHODS: Thirteen male subjects performed a maximal isokinetic elbow
flexion test and test-retest separated by 5 to 7 days. Three normalization
coefficients were extracted from the tests: 1) mean value of the rectified SEMG
signal (Mean_{Task}); 2) peak value of the rectified SEMG
signal (Peak_{Task}); 3) maximal value of the rectified SEMG
signal of the peak torque repetition
(Isokinetic-spec_{MVC}). These normalization coefficients,
as well as the root mean square value (RMS) of the signal before and after
normalization by described coefficients (RMS-Mean_{Task};
RMS-Peak_{Task};
RMS-Isokinetic-spec_{MVC) were evaluated in terms of
absolute and relative reliability. RESULTS: None of the normalization coefficients presented acceptable
levels of absolute reliability (bias range in limits of agreement greater than
27%). However Mean_{Task} and
Isokinetic-spec_{MVC} presented good levels of relative
reliability (ICC > 0.80). RMS-Mean_{Task} was the only
amplitude parameter that demonstrated satisfactory indices of absolute (bias
range lower than 5% and CV < 1.50%) and relative (ICC > 0.80)
reliability. CONCLUSIONS: Normalizing SEMG amplitude by
Mean_{Task} is a reasonable strategy to reduce day-to-day
amplitude discrepancies during isokinetic upper-body strength assessment.
