Reproducibility of kinetics of electromyogram spectrum parameters during dynamic exercise

Abstract

During incremental exercise on a cycle ergometer a study was made of the reproducibility of changes in electromyographic activity (EMG) of human quadriceps muscles. Seven subjects performed three periods of incremental exercise either every 2 weeks (G1: four subjects) or 6 weeks (G2: three subjects). Each test was normalized with respect to the maximal aerobic power (MAP) of the subject. It consisted of a quasilinear increase in mechanical power (from 20% to 100% MAP) during 8 min. For rectus femoris muscle activity, changes in total power spectrum (PEMG) and in mean power frequency (MPF) were fitted by a 3rd order polynomial function (named profile) and normalized with respect to the maximal value for PEMG and to the mean value for MPF. A curvilinear increase was found for PEMG. The MPF kinetics varied from one subject to another. These changes were either a continuous increase, or a continuous decrease, or an increase followed by a decrease. Only for G2, was MAP determined before each test in order to update the limits of the test. A good reproducibility of PEMG was shown by its mean magnitude [95.88%, (SD 3.92)] and by computing a mean correlation coefficient between profiles two by two [r2 = 0.948 (SD 0.028) n = 21]. Intraclass coefficient correlation (ICC) calculated for each subject indicated a high level of reproducibility for five of the seven subjects (ICC > 0.80). No clear effect of MAP updating on PEMG and MPF profile reproducibility was observed. Thus it is suggested that MPF kinetics may characterize a subject at a given moment while PEMG kinetics may illustrate a normal profile, and they may both characterize EMG changes for a population during incremental exercise.

Reproducibility of eight lower limb muscles activity level in the course of an incremental pedaling exercise

“…On the other hand, standardization with respect to EMG changes recorded at 0 W could lead to overestimation of end-of-exercise activity when a given muscle was not activated at all at the onset of exercise. In order to avoid such misinterpretations of EMG data, RMS values were normalized with respect to the RMS max value recorded during the incremental exercise as previously reported [8,13]. Surface electromyography is commonly used for assessment of muscular function during different types of dynamic exercise such as cycling, running or isokinetic repeated contractions.…”

“…Indeed, to the best of our knowledge, only few studies showed the reproducibility of the EMG parameters during isokinetic repeated contractions [16,17] or throughout an incremental cycling exercise performed until exhaustion [8]. However, in the former, only few muscles (vastus medialis, vastus lateralis and rectus femoris) were recorded.…”

Heterogeneity of muscle recruitment pattern during pedaling in professional road cyclists: a magnetic resonance imaging and electromyography study

“…On the other hand, standardization with respect to EMG changes recorded at 0 W could lead to overestimation of end-of-exercise activity when a given muscle is not activated at all at the onset of exercise. In order to avoid such misinterpretations of EMG data, we normalized RMS values with respect to the RMS max value recorded during the incremental exercise as previously reported (Gamet et al 1996).…”

Alternative methods of normalising EMG during cycling

“…Since muscle activity has been shown to be repeatable during incremental cycling (Laplaud et al, 2006;Gamet et al, 1996), it could be assumed that the changes found in muscle activity during each cycling load was highlighted more by the type of method of normalisation used and not entirely due to the variation in muscle activity caused by fatigue or from the intrinsic and extrinsic influences on the EMG signal. In this study the aim was to measure the ability of each method to detect changes in muscle activity over five stages of the PPO test and also during the final stage of the PPO trial.…”