Surface electromyogram power spectrum in human quadriceps muscle during incremental exercise

Abstract

Spectral electromyographic (EMG) changes in human quadriceps muscles were studied to reinvestigate discrepant results concerning mean power frequency (MPF) changes during dynamic exercise. An incremental test consisting of a quasi-linear increase in mechanical power on a bicycle ergometer (for 20-100% of maximal aerobic power) was performed by forty subjects. During this test, surface EMGs from the quadriceps muscles showed that EMG total power (PEMG) increased with a curvilinear pattern for every subject, whereas MPF kinetics varied from one subject to another. PEMG changes had the same shape, which would lead to disappointing results in terms of discrimination between subjects. The ability of normalized MPF kinetics to define significant clusters of subjects was tested using a principal component analysis. This analysis led to the projection of all experiments onto a plane and revealed a relevant grouping of MPF profiles. Differences in MPF kinetics between clusters are interpreted in terms of various possibilities of balance between physiological events leading to an increase or a decrease in MPF.

Median power frequency of the surface electromyogram and blood lactate concentration in incremental cycle ergometry

“…Present findings concerning the relationship between changes in f med and blood lactate concentration in dynamic exercise are in agreement with Gamet et al (1993). They have studied changes in MPF in human quadriceps muscle in 40 subjects.…”

Correlation between muscle metabolism and changes in M-wave and surface electromyogram: Dynamic constant load leg exercise in untrained subjects

“…Increased MF value during suprathreshold exercise and its persistence for 10 min during the recovery period where [LA] = 4.0 ± 0.3 mmol/L (vs. 2.0 ± 0.3 mmol/L after subthreshold exercise) cannot be explained by the changes in M wave, which should increase and not decrease the low-frequency FFT component. 1 As already shown, 2,6 no EMG signs of ''central'' muscle fatigue, i.e., decreased MF value, were found in the two situations. Increased MF value may result from the enhanced recruitment of the smaller motor units and/or an overall increase in the firing rate of all motor units.…”

Electromyographic changes in vastus lateralis during dynamic exercise

“…4,7,9,11 Some studies 4,9 reported a decrease in mean spectral frequency (MF), not confirmed by others. 7,11 The neuromuscular transmission and the sarcolemmal excitability do not appear to be altered during sustained maximal voluntary contraction 2 and M-wave changes during dynamic exercise are not documented. Data on correlative changes in SEMG and muscle metabolism are also rather sparse.…”